Journal of the Air & Waste Management Association
ISSN: 1096-2247 (Print) 2162-2906 (Online) Journal homepage: http://www.tandfonline.com/loi/uawm20
Ambient Air Concentrations Exceeded HealthBased Standards for PM2.5 and Benzene During the Deepwater Horizon Oil Spill Earthea Nance, Denae King, Beverly Wright & Robert D. Bullard To cite this article: Earthea Nance, Denae King, Beverly Wright & Robert D. Bullard (2015): Ambient Air Concentrations Exceeded Health-Based Standards for PM2.5 and Benzene During the Deepwater Horizon Oil Spill, Journal of the Air & Waste Management Association, DOI: 10.1080/10962247.2015.1114044 To link to this article: http://dx.doi.org/10.1080/10962247.2015.1114044
Accepted author version posted online: 13 Nov 2015.
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Date: 30 November 2015, At: 09:18
Ambient Air Concentrations Exceeded Health-Based Standards for PM 2.5 and Benzene During the Deepwater Horizon Oil Spill
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Earthea Nance1, Denae King1, Beverly Wright2, and Robert D. Bullard1
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Texas Southern University, 3100 Cleburne Street, Houston, TX 77004, USA
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Dillard University, 2601 Gentilly Boulevard, New Orleans, LA 70122, USA
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Implications
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Benzene and particulate matter monitoring during the Deepwater Horizon oil spill revealed that ambient air quality was a likely threat to public health and that residents in coastal Louisiana experienced significantly greater exposures than urban residents. Threshold air pollution levels established for the oil spill apparently were not used as a basis for informing the public about these potential health impacts. Also, despite carrying out the most comprehensive air monitoring ever conducted in the region, none of the agencies involved provided integrated analysis of the data or conclusive statements about public health risk. Better information about real-time risk is needed in future environmental disasters.
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Earthea Nance is an Associate Dean and an Associate Professor in the Barbara Jordan-Mickey Leland School of Public Affairs at Texas Southern University in Houston, Texas. Denae King is the Interim Associate Director of the Mickey Leland Center for Environment, Justice and Sustainability in the Barbara Jordan-Mickey Leland School of Public Affairs at Texas Southern University in Houston, Texas. Beverly Wright is the Executive Director of the Deep South Center for Environmental Justice at Dillard University in New Orleans, Louisiana. Robert D. Bullard is the Dean of the Barbara Jordan-Mickey Leland School of Public Affairs at Texas Southern University in Houston, Texas. For this paper we analyzed data from BP and EPA that were available to the public during the disaster. These data are available for download at http://works.bepress.com/nanceea/.
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Authors:
Introduction The Deepwater Horizon Oil Spill was the largest marine oil spill in the history of the United States (EPA, 2015a) and some scholars and news media argue that it was one of the worst
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environmental disasters (Houck, 2010; Silverleib, 2010; British Broadcasting Corporation, 2010). The disaster began on April 20, 2010 when an explosion and fire occurred on a drilling rig in the Gulf of Mexico approximately 50 miles offshore of Venice, Louisiana (EPA, 2010a;
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Middlebrook et al, 2012). With the uncapped well spewing an estimated 50,000–70,000 barrels
began controlled burns to keep the oil from reaching and damaging the coastline (Mufson, 2010).
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The explosion, evaporating oil, controlled surface oil burns, emissions from the ships used for cleanup and recovery, and secondary aerosols combined to create unknown air quality conditions
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in the Southeast Louisiana region. Middlebrook et al (2012) made new scientific discoveries related to oil spill emission particle size, secondary aerosol formation, and advection/dispersion in the atmosphere, and concluded that “it was likely that secondary organic aerosols from the Deepwater Horizon site impacted aerosol levels in populated areas near the Gulf Coast” (pp.
studied.
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20285). The impact of oil spill emissions on people on the ground, however, has been less To address this gap in knowledge, we evaluated urban, coastal, and regional
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concentrations of fine particulate matter (PM 2.5 ) and benzene in ground level ambient air. Our
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study offers new results about the possible public health implications of the oil spill. Prior to the Deepwater Horizon Oil Spill, the Southeast Louisiana region was considered an area with moderate air quality in terms of primary air pollutants (except for St. Bernard Parish);
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of oil a day (McNutt et al, 2012), the United States Coast Guard and British Petroleum (BP)
however, the region had a high risk of cancer from toxic air pollutant exposure, primarily benzene (EPA, 2013a; EPA, 2011a). A limited set of permanent stationary air monitoring
devices monitored compliance with Clean Air Act standards in the region. Recognizing the inadequacy of this network to monitor public environmental exposures during the oil spill, an
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extensive emergency air monitoring effort—led by the Environmental Protection Agency (EPA), the Centers for Disease Control (CDC), the National Oceanic and Atmospheric Administration (NOAA), and BP—quickly emerged to fill the gaps in air monitoring (Wright and Nance, 2014).
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The emergency network utilized mobile and stationary devices to take spatially- and temporally-
undertaken in the region. Over one million ambient air measurements were gathered during the
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oil spill; however, only the permanent stationary monitoring stations met the federal criteria for regulatory monitors (Wright and Nance, 2014). Worker exposure measurements were also
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gathered by the CDC, Occupational Safety and Health Administration (OSHA), USCG, BP, as well as atmospheric measurements gathered by NOAA but were not the subject of this study. By law (Protection of Environment, 40 CFR Part 50 Appendix N), regulatory monitors are
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usually located in highly populated urban areas to ensure that standards are being met in areas most likely to exhibit public health impacts (EPA, 2011b). Yet, the areas most likely impacted
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by oil spill emissions were along the sparsely populated coast where no regulatory monitors were available. The EPA worked to address this gap by installing thirteen emergency stationary
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monitors along the Louisiana coast. These emergency stationary monitors measured hydrogen sulfide (H 2 S), carbon monoxide (CO), particulate matter (PM), and volatile organic compounds (VOCs) (EPA, 2010; EPA, 2013). For the purposes of this study, we chose to examine ambient
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integrated samples and readings. This was perhaps the most extensive sampling regime ever
air concentrations of PM and the VOC benzene, both of which were prevalent during the oil rig
explosion, oil spill, and subsequent clean up. We also chose to compare the data gathered during the disaster to health-based levels under the federal provision that recognizes comparison to
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NAAQS when ambient air concentrations are high enough to cause concern (40 CFR Part 50 Section 50.14). According to the EPA, PM is one of two pollutants that pose the greatest threat to human health
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in the US—the other is ground-level ozone (Air Now, 2015; EPA, 2015b). PM is a complex
sulfates), organic chemicals, metals, and soil or dust particles (EPA, 2013b). The size of PM
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determines the potential health impact. Consequently, the EPA separates PM into two groups: inhalable coarse particles (PM 10 ) and fine particles (PM 2.5 ) . PM 10 is often found near roadways
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and dusty industries, while PM 2.5 particles are emitted from fires or can form when gases released from industrial sources and fossil fuel combustion react in the air. PM 2.5 is of greater concern because its small particle size allows for deep penetration into the lungs and possibly Adverse health effects include nonfatal heart attacks,
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into the bloodstream (EPA, 2013b).
aggravated asthma, and impaired lung function. Because of the known health effects of PM,
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residents of Southeast Louisiana were rightly concerned about possible health threats from the
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oil spill (IOM, 2010).
The Clean Air Act National Ambient Air Quality Standards (NAAQS) take into account the public health impacts of exposure to PM in the short term (hours to days) and in the long term
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mixture of extremely small particles and liquid droplets made up of acids (such as nitrates and
(weeks to months). The annual (long-term) PM 2.5 standard of 12 μg/m3 is less than the 24-hour (short-term) standard of 35 μg/m3 because a healthy human body has the capacity to recover
from a higher short-term dose. Exposure to continual doses over time are difficult for the body to absorb, hence a lower long term standard is required to protect public health (EPA, 2014a).
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Presently, the Clean Air Act requires hourly continuous monitoring of PM using specified monitoring equipment at targeted locations based on population density. These data are used to calculate short-term and long-term concentrations for comparison to the standards.
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Benzene is a component of petroleum and is listed as one of the top 20 chemicals produced in the
Common sources of benzene include tobacco smoke, gas stations, and motor vehicle exhaust
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(CDC, 2013; ATSDR, 2007). The most common route of exposure is inhalation, and benzene exposure has been shown to result in leukemia and blood-related diseases following long-term
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exposure (ATSDR, 2007; ACS, 2013). The Environmental Protection Agency (EPA) estimates an increased lifetime cancer risk of 2.2 x 10-6 to 7.8 x 10-6 for an individual who is continuously exposed to 1 µg/m3 of benzene in the air over their lifetime (EPA, 2012). More than 100 studies
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show there is no safe level of benzene; all concentrations contribute to cancer risk (Baan et al, 2009).
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Regulatory air monitors located in the urban centers of Southeast Louisiana showed no exceedances of Clean Air Act standards during the oil spill (LDEQ, 2010). This finding implies
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there were no public health impacts of concern. However, not addressed are the potential public health impacts not measured by the formal regulatory monitoring network. During the spill, an enormous number of independent samples of urban, coastal, and mixed regional air were taken
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U.S. It is a colorless, volatile and highly flammable liquid found in the natural environment.
using stationary and mobile monitors, and these data were recently made available to the public. These unique datasets make the Southeast Louisiana region a relatively well-constrained case for evaluating potential public health impacts from the spill. The Southeast Louisiana coastal region in question is a poorly sampled area (in terms of air monitoring), with large variations in
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background cancer risk, household income, and population density (EPA, 2011a; LDEQ, 2010; U.S. Census Bureau, 2010).
A rich body of research definitively concludes that
socioeconomically disadvantaged groups in general are more likely to be at risk of
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environmental hazards (Bullard, 2000; Bullard et. al., 2007; James et al., 2012). The oil spill
long-term effects (Solomon and Janssen, 2010).
People living and working in the area,
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especially people along the coast were apprehensive about their exposures. Therefore, the objectives of this study were: 1) to determine if health-based standards were exceeded during the
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oil spill; and 2) to assess the possibility of disparities in environmental exposures between the urban centers and the more rural coastal region of Southeast Louisiana.
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Experimental Methods
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Study area and timeframe
Six parishes in Southeast Louisiana were selected as the study area: Jefferson, La Fourche,
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Orleans, Plaquemines, St. Bernard, and Terrebonne. This 4,138 square-mile (10,717 square kilometer) region was selected because it was located closest to the oil spill, had the largest potentially exposed population, and was well sampled throughout the disaster. The time frame
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represented a potentially catastrophic environmental health hazard with both immediate and
for the study was May 1, 2010 to September 30, 2010. Although additional data were partly available three days before and three months after this period, the selected months represent the core period of oil spill emissions and burning and account for residual effects after the well was temporarily capped in July, and later permanently capped in early September.
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Oil spill air monitoring data Over one million measurements of ambient air were gathered during the oil spill. The EPA and BP established independent ambient air monitoring and air sampling programs. Monitoring
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made use of either stationary or mobile (i.e., mounted on a vehicle) direct-read equipment
air and sending it to a laboratory for analysis.
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BP and EPA deployed stationary and mobile monitoring devices that took random grab samples and time-weighted samples. For the purposes of this study, air monitoring was divided into three The urban category encompassed permanent and
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categories: urban, coastal, and regional.
emergency stationary monitors located in the major cities of each parish. The coastal category was comprised of emergency stationary monitors installed along the coastline in response to the spill. The regional category consisted of emergency mobile monitors installed on vehicles that
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traversed the parishes (e.g., coastal and urban) during the disaster. As shown in Figures 1(a) and 1(b), BP conducted more regional air monitoring over a larger study area than the EPA, while
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locations.
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much of the EPA’s efforts were focused on emergency stationary monitoring at discrete coastal
It is important to distinguish emergency monitoring from permanent monitoring not only because of location differences. The data collected from emergency monitors (both coastal and regional)
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(British Petroleum, 2010; British Petroleum, 2015). Air sampling involved taking a volume of
are considered “unofficial” because the equipment used did not meet formal Clean Air Act requirements.
Only the permanent monitors (urban only) maintained by the Louisiana
Department of Environmental Quality (LDEQ) met the strict Clean Air Act regulatory criteria for monitoring equipment. Consequently, only results from official permanent monitors have to
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be reported to the public. There are no reporting requirements for environmental data gathered during an emergency. In this study, data gathered during the oil spill via emergency monitors were compared to Clean Air Act standards and to regulatory data gathered at permanent monitors
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to assess potential public health impacts. The paper therefore presents findings that to our
Selected pollutants
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Particulate matter and benzene were assessed in this study because of the potential for significant ambient air emissions, the availability of data across the parishes, and clear health-based
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guidelines/standards. EPA installed stationary filter samplers to take 24-hour particulate matter readings and installed stationary Met One E-BAM monitors to take 1-hour PM readings. BP deployed a TSI Sidepack Personal Aerosol Monitor (AM510) instrument with cyclone to take continuous mobile PM readings. For benzene, EPA installed stationary 24-hour samplers and
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brought in its Trace Atmospheric Gas Analyzer (TAGA) for continuous mobile monitoring. Detection limits ranged from 0.127-16.00 μg/m3. BP outfitted its mobile monitoring vehicle
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with a GASTEC gas detection instrument to take continuous benzene readings, with a detection
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limit of 0.05-0.50 ppm. Taken together, these instruments gathered a total of 106,569 data points within the study area for the duration of the study period. Particulate matter (PM). Particulate matter (PM) was a significant contaminant released during
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knowledge have not been reported.
the oil spill. Two days of aircraft measurements were taken by scientists from the National Oceanic and Atmospheric Administration above the oil spill. With these data, Middlebrook et al (2012: Figure 7) estimated that over 1,000 metric tons of soot particles were emitted from
controlled burns and over 10,000 metric tons of secondary aerosol particles were created from
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evaporating hydrocarbons as cumulative emissions between April 20 and July 20, 2010. Daily and hourly PM data were gathered by the EPA via emergency stationary coastal monitors. When pooled across monitors, this sampling period produced 1,144 hourly PM 2.5 data points (August
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21, 2010 to September 6, 2010) in coastal areas only. BP’s emergency mobile monitors gathered
coastal areas. Daily PM 2.5 data consisting of 277 24-hour averages (from an estimated 63,200
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hourly PM 2.5 data points) were simultaneously gathered at six permanent stationary monitors operating continuously in the urban areas of the region in accordance with Clean Air Act
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requirements (May 1, 2010 to September 30, 2010). Total raw sample size was 102,682 data points.
Benzene. Benzene was a significant contaminant in the oil released in massive quantities during the oil spill, and a large quantity of benzene data was collected across the six parishes. The EPA
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also identified benzene as one of the leading air toxics that drives national cancer risk in the United States via the National Scale Air Toxics Assessment (NATA) (EPA, 2010b). Only EPA
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ambient benzene concentration data was examined in this study because BP’s benzene data did
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not meet instrument sensitivity criteria. The benzene data consisted of 1,053 daily stationary data points (April 28, 2010 to September 18, 2010) and 2,834 continuous mobile data points (April 28, 2010 to September 21, 2010). Total raw sample size for benzene was 3,887 data
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101,261 continuous PM 2.5 data points (May 14, 2010 to December 21, 2010) in both urban and
points.
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Data preparation Raw data obtained from EPA and BP were sorted by pollutant, parish, and monitoring station,
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and truncated to the study period. The data were then averaged to the appropriate time interval
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to examine short-term and long-term concentrations of PM and long-term concentrations of
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obtained by boat and other data gathered from locations outside of the study area were not used.
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Long-Term and Short-Term Comparisons
For our study, the time period of analysis was five months (April 20, 2010 to September 19, 2010), which corresponded to the primary period of potential exposure.
While potential
exposure continued as long as oil was floating and burning on the ocean surface and as long as
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disaster vehicles and equipment were active, there likely was a tapering off of air pollution after the well was permanently capped in September 2010. It is certainly possible that exposure
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continued beyond the five-month active oil spill. BP continued gathering ambient air data into
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December 2010, perhaps to document the rate at which air pollution levels tapered off after the spill. But because the EPA did not extend their data gathering efforts that far and because we wanted to have more than one data source for the purposes of triangulation and validity, we set
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benzene (Tables 1 and 2). Non-detect data points were eliminated. In addition, coastal data
the study period to five months. Our study therefore addresses both short-term (hours to days) and medium-term (weeks to months) ambient air concentrations. National Ambient Air Quality, Standards (NAAQS) for particulate matter are based on 24-hour and annual means. These short-term and long-term NAAQS standards were derived from many
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epidemiological studies that investigated exposure-dose-response as a function of PM concentration. Schwartz (2000), Krewski et al (2009), and Krewski et al (2000) showed that short-term exposure studies failed to characterize the full impact of exposure to PM in the
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presence of days or months of prior exposure. Their findings demonstrated that mortality due to
concentration (EPA 2010b). Consequently, a short-term standard alone is not sufficient to
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understand health impact. Studies by Beverland et al (2012) and Alexeeff et al (2011) confirmed that medium-term (1-3 month) exposures produced larger health effects than short-term (1-3 day)
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exposures, and that long-term (up to 10 years) effects were stronger still. Given these findings from the literature, we concluded that five months of data better approximated the health impacts associated with an annual exposure than a 24-hour exposure and that, lacking a medium-term standard, applying the NAAQS annual standard was reasonable for the exploratory and
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comparative purposes of our study.
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Stationary data captured a single data point on every first, second, third, or fourth day, and the mobile data were nearly continuous for 24 hours each day. Each dataset contained a sufficient
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number and frequency of measurements (i.e., the proportion of hours or days with available data to the total hours or days in the period) to allow direct comparisons to short-term and long-term standards or guidelines, and all valid data points were used in the analysis. Because the data
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PM exposure is a function of both the concentration as well as the number of days at a given
were taken in varying locations, it was possible to make generalized comparisons of overall air quality at different locations during the spill. We used the Kruskal-Wallis H-test to assess the distributions of regional, coastal, and urban data
because two of the datasets were non-normally distributed and all had large variations in sample
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size (Ghasemi and Zahediasl, 2012). Only the urban PM data were normally distributed and the Kruskal-Wallis H-test results demonstrated that the urban, coastal, and regional datasets were statistically different and could therefore be treated separately.
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To examine the potential health concerns associated with air quality prior to and during the oil
100 in each parish. When an AQI value exceeds 100, air quality is considered unhealthy for
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certain sensitive groups and as AQI values continue to rise the general public is then affected. The number of AQI exceedances in each parish was calculated and recorded as exceedance days
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(EPA, 2013a; LDEQ, 2010; EPA, 2014b). The AQI is reported throughout the day to inform the public of the health effects of their local air. Currently, the AQI is calculated for five air pollutants: ground level ozone, PM, carbon monoxide, nitrogen dioxide, and sulfur dioxide (EPA, 2014b). The reported AQI typically represents the worst of the five pollutants. For this
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study, we focused only on PM 2.5 contributions to the AQI during the spill. To examine benzene-associated cancer risk and conduct a comparison to long-term standards for
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benzene, we analyzed benzene data available by parish from April 28, 2010 to September 18,
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2010. The resulting means were converted to cancer risk based on a benzene unit risk factor of 7.8 x 10-6. We then compared per parish cancer risk from benzene during the spill to the EPA’s low, high, and unacceptable cancer risk levels. These levels correspond to 1, 10, and 100 x 10-6,
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spill, we counted the number of times the EPA’s Air Quality Index (AQI) for PM 2.5 exceeded
respectively.
Although cancer risk from benzene exposure was calculated using benzene
exposure data from the 6-month time oil spill period, the cancer risk estimation was conducted to allow for comparison with lifetime risk of benzene exposure. Study Results
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Figure 1(a) shows the location of EPA’s emergency monitors and mobile routes, and LDEQ’s permanent monitoring stations. Terrebonne, La Fourche, St. Bernard, and Orleans Parishes each had one permanent station located in the main city.
Jefferson Parish had two permanent
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monitoring stations; however, Plaquemines Parish did not have a monitoring station. BP’s
to determine the oil spill’s potential impact on public health. First, the oil spill data were
background concentrations.
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compared to health-based or Clean Air Act standards. Second, the data were compared to Concentrations that exceeded background or Clean Air Act
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standards by at least a factor of two, and concentrations that increased cancer risk by at least an order of magnitude (i.e., a factor of 10) suggested cause for concern.
Particulate Matter: Before and During the Disaster
during the oil spill.
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Table 1 provides descriptive statistics for the regional, urban, and coastal PM 2.5 data collected The mean PM 2.5 concentrations observed from regional monitoring,
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stationary urban and coastal monitoring were 22.30 μg/m3, 9.68 μg/m3, and 17.33 μg/m3,
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respectively. The current primary annual PM 2.5 NAAQS used for enforcement of the Clean Air Act is 12 μg/m3 (EPA, 2014a). Therefore, PM 2.5 concentrations detected via regional and coastal monitoring during the oil spill both exceeded the NAAQS’ safe and acceptable limit designed to
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mobile monitoring routes used during the oil spill are shown in Figure 1(b). We used two tests
protect the general population against adverse health effects. Figure 2(a) shows background AQI levels for the Southeast Louisiana parishes. Three parishes exceeded the AQI limit for unhealthy air on at least one day in 2009, indicating that background air pollutants were too high. St. Bernard Parish was excessively high prior to the
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disaster, having exceeded an AQI of 100 on 93 days in 2009, driven primarily by high SO 2 levels for which the parish had been declared in non-attainment. Plaquemines Parish had no air monitoring station and thus background air quality data were unavailable. The remaining two
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parishes had no AQI exceedance days in the year prior to the spill.
these levels to the background AQI levels in Figure 2(a) reveals a sharp increase from zero to
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four AQI exceedance days in 2009 (before the oil spill) to 24 to 46 AQI exceedance days during the oil spill. This represents estimated increases in exceedance days ranging from 10 to 45 times
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higher and indicates an unequivocal escalation of ambient PM exposure consistent with oil spill emissions.
In addition to the frequency of exceedance days, we also looked for increased PM 2.5
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concentrations that clearly exceeded the Clean Air Act standards. As shown in Table 3, the estimated long term PM 2.5 concentrations detected during the oil spill were approximately two to
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three times higher than the concentrations observed prior to the disaster in Jefferson, St. Bernard,
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and Terrebonne parishes, thus indicating the possibility of public health impacts.
Benzene Levels Before and During the Disaster
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Figure 2(b) presents the results of the PM 2.5 data analysis during the oil spill. Comparing
Descriptive statistics for benzene concentrations detected via regional and stationary
coastal monitoring revealed mean benzene concentrations of 4.83 μg/m3 and 2.96 μg/m3,
respectively (Table 2). The EPA established a one-year oil spill screening level of 20 μg/m3. The State of Louisiana’s ambient standard is 12 μg/m3 and the Clean Air Act’s Unacceptable
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Risk Level is 13 μg/m3. All three standard levels exceed the regional and coastal mean benzene concentrations observed during the oil spill, suggesting no threat to public health. Figure 3(a) presents benzene-associated cancer risk per parish in 2005, the last year National Air
) were above the state mean of 6.8-in-a-million, although Orleans Parish had the highest risk.
The remaining parishes had a 3- to 5-in-a-million increased chance of developing cancer. The
92-in-a-million chance.
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State of Louisiana’s ambient air standard for benzene (12 μg/m3) corresponds to a cancer risk of Therefore, background benzene levels in all six parishes met the
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Louisiana standard as well as the EPA oil spill screening level (20 μg/m3 or 154 x 10-6). But according to the EPA and the City of Houston, slightly more benzene (13 μg/m3) would correspond to the “unacceptable risk” end of the Clean Air Act’s cancer risk range, which is 100-
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in-a-million (EPA, 2010c; Raun, 2008). This means that Louisiana’s standard and the EPA’s screening level are about two orders of magnitude above the health protective low risk limit of 1-
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in-a-million (0.13 μg/m3) established by the Clean Air Act.
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Background benzene risk levels exceeded the Clean Air Act health-protective low risk cancer level in all six parishes, with Orleans and Jefferson exceeding the standard by approximately one order of magnitude and the remaining parishes exceeding the standard by up to half an order of
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Toxic Assessment (NATA) data were available. Orleans Parish (18 x 10-6) and Jefferson (8 x 10-
magnitude. The existing background levels were unhealthy and presented an increased cancer risk. To determine excess public health impacts beyond background due to benzene released during the oil spill, we also looked for sharp increases in cancer risk at much higher levels than background. Because the EPA’s oil spill screening level for benzene and the State’s ambient
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benzene standard were not health protective, they could not be used to assess potential health impacts. Figure 3(b) presents the benzene data analysis during the oil spill. Comparing these
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levels to the background cancer risk in Figure 3(a) reveals a sharp increase from a range of 3- to
an estimated one order of magnitude increase in risk and a 2- to 19-fold increase above
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background concentration, which indicates an unequivocal escalation of ambient benzene. These results provide a basis for concluding that benzene concentrations went from the low end of the
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cancer risk range (1 to 10 x 10-6) to the high end of that range (10 to 100 x 10-6) in each parish (Figure 4).
EPA’s one-year benzene screening level (20 μg/m3 or 154 x 10-6) for the Deepwater
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Horizon Oil Spill was defined as a level above which action would be taken. Despite significant increases in ambient air benzene concentrations measured via emergency monitoring equipment
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during the spill, all of the parishes still met the EPA screening level. Unfortunately, this
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screening level is not considered protective of health and could not be used to assess the potential health impacts of increased benzene. Lacking an effective benzene standard or guideline directly applicable to public health during the oil spill, we used the unit low risk level for benzene (0.13
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18-in-a-million before the oil spill to 20- to 57-in-a-million during the oil spill. This represents
μg/m3 or 1 x 10-6) to evaluate potential health impacts (Table 3). With this standard, the results indicate that ambient levels of fine PM and benzene during the Deepwater Horizon Oil Spill
were high enough to cause public health impacts.
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Analysis of Urban versus Coastal Exposure Disparities In Table 4, PM 2.5 and benzene results are presented for urban and coastal areas. Overall, coastal
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(Jefferson, La Fourche, Plaquemines, and St. Bernard parishes) concentrations of PM 2.5 and
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benzene were higher than urban (Jefferson, La Fourche, Plaquemines, St. Bernard and
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was increased along the coast compared to the urban centers.
Table 5 shows that the coastal, urban, and regional PM data sets are statistically different. Air
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quality in the urban centers, measured by permanent stationary urban monitors, was relatively normal and exhibited far less variance than the coastal and regional data sets. The coastal data showed increased variation and higher absolute values that exceeded air quality standards. These findings suggest there were at least two separate airsheds during the oil spill, and the populations
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within each airshed possibly encountered different exposures. The regional data, which included urban and coastal areas, reflect the wide variability of pollutant levels present in the six parishes
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during the disaster. These geographic exposure disparities were measurable in real time; and
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therefore could have been used to issue region-specific preventive health announcements and precautions.
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Terrebonne) concentrations. This observation confirms that exposure to hazardous air pollutants
Discussion
Ambient concentrations of known air pollutants that exceed health-based Clean Air Act standards and guidelines are indeed an environmental health concern. Government agencies face extremely challenging circumstances during environmental disasters, and potentially
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controversial decisions have to be made in real time. Such decisions would benefit from having plans already in place that include thresholds for informing the public about potential health threats during a disaster. For the Deepwater Horizon Oil Spill, the EPA established that existing
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Clean Air Act standards were the appropriate threshold for primary air pollutants, including PM,
and there is no threshold below which exposure to PM would be harmless (Brook et al, 2010).
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Rather than using an existing health-based guideline for benzene, EPA established a relatively high “one-year screening level.” There is no federal ambient benzene standard; neither is there a
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threshold concentration below which there is no benzene cancer risk (Baan et al, 2009). The EPA’s level of concern for one-year benzene exposure (20 μg/m3) significantly exceeded other similar guidelines, such as the State of Louisiana’s ambient benzene standard (12 μg/m3), the State of Texas’ one-year benzene screening level (4.5 μg/m3), EPA’s regional cancer
The EPA’s level of concern for benzene exposure during the oil spill also
pt
(0.02 μg/m3).
ed
screening level (0.312 μg/m3), and the World Health Organization’s ambient benzene guideline
exceeded the Clean Air Act’s high-risk cancer level (1.3 μg/m3). We concluded that the benzene
ce
screening level was not protective of public health and therefore was not an effective threshold for use during the spill.
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during the disaster. However, there is no federal PM standard for a 5-month exposure period,
Even though health-based air pollution thresholds were already established for short and long term PM 2.5 , they apparently were not used as a basis for informing the public about potential health impacts, especially with regard to more susceptible and/or more exposed population segments.
Comprehensive air monitoring was conducted by numerous agencies, but none
18
provided integrated analysis or conclusive statements about public health risk.
People in
Southeast Louisiana were exposed to higher PM levels for a minimum of five months in a row during the study period. Because in our view these concentration levels were high enough to
cr ip
t
cause concern, we compared them to the NAAQS PM annual standard. We also compared the
observational, not experimental; therefore, we had no control over the duration of possible
us
exposure. But no matter how one looks at these data, we conclude there should have been cause for concern. Better information about real-time risk is needed in future disasters.
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Given the results of this study, we recommend that government agencies involve local officials and the public in discussions about the health-based and regulatory air quality levels that should apply during an environmental disaster.
These discussions could also cover the types of
ed
emergency monitoring equipment that would be acceptable so that as much data as possible would be recognized as valid in the context of a disaster. Similar plans could be developed for
pt
“fenceline” communities who may have to shelter in place during industrial accidents and whose sensitive populations may need to be temporarily evacuated. Adopting health-based disaster
ce
thresholds would facilitate decision-making, enhance public awareness, and reduce potential public health impact during an environmental crisis.
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hourly and daily PM concentrations to the NAAQS PM 24-hour standard. Our study was
Conclusion All available ambient air quality data gathered during the Deepwater Horizon Oil Spill were reviewed, and a total of 106,569 measurements of fine PM and benzene were evaluated.
19
Ambient air concentrations of PM 2.5 were generally higher during the oil spill than the previous year and exceeded the Clean Air Act’s 12 μg/m3 annual and 35 μg/m3 hourly standards in the parishes studied. Daily AQI exceedances for PM 2.5 were 24 to 45 times higher than air quality All parishes also exceeded the annual 12 μg/m3
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t
standards in all of the parishes studied.
benzene were generally higher during the oil spill than during previous years. Benzene cancer
us
risk reached 20 to 57 times higher than the Clean Air Act’s 1-in-a-million low risk guideline in all of the parishes studied. All parishes studied also exceeded the high-risk guideline of 10-in-a-
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million. These findings provide a basis for concluding that ambient air quality—for PM 2.5 and benzene—was a likely threat to public health during the oil spill.
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26
Urban Data
Coastal Data
(μg/m3)
(μg/m3)
(μg/m3)
Standard
Long Term Mean
Standard 10.65
3.86
Long Term Mean
17.32
Standard Deviation 7.025
Sample Variance
113.58
Sample Variance
14.91
Sample Variance
49.36
Minimum
3.70
Minimum
2.00
Minimum
6.35
Maximum
ed
M an
Deviation
Deviation
9.68
cr ip
22.29
us
Long Term Mean
t
Regional Data
21.40
Maximum
37.82
3133
277
Count
51
Maximum
pt
ce
Count
89.16
Count
Notes: Data from all parishes are combined. Regional statistics are a 24-point moving average
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Table 1. Descriptive Statistics for Oil Spill Particulate Matter 2.5 Data
of continuous data gathered with mobile monitors. Urban and coastal statistics are averages of daily data gathered with stationary monitors.
27
Table 2. Descriptive Statistics for Oil Spill Benzene Data
Coastal Data
Regional Data
cr ip
t
(μg/m3)
4.83
Long Term Mean
Standard Error
0.12
Standard Error
1.81
6.76
Standard Deviation
22.95
45.81
Sample Variance
527.05
Minimum
0.12
Minimum
0.14
pt
ed
Sample Variance
M an
Standard Deviation
2.96
us
Long Term Mean
81.89
Maximum
290.00
Count
2791
Count
160
ce
Maximum
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(μg/m3)
Notes: Data from all parishes are combined.
28
Table 3. Summary of Potential Public Health Impacts from Gulf Oil Spill Air Emissions During the Disaster
Backgroun
Backgroun
Estimated
AQI
d
d
AQI
(Exceedance
Long Term
Benzene
(Exceedance
Days)
PM 2.5
Estimated
d Long
Benzene
Term
Cancer
PM 2.5
(μg/m )
Risk
8.61
8.6x10-6∗
43+
22.63w
20.5x10-6∗∗
La 0
3.1x10-6∗
45+
23.35w
38.3x10-6∗∗
1+
ce
Orleans
24+
23.84w
31.4x10-6∗∗
M an
-
pt
Fourche
ed
4+
Risk
(μg/m3)
3
Jefferson
us
Days)
Cancer
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Parish
Estimate
cr ip
Background
t
Prior to the Disaster
18.0x10-
-
6
∗∗
57.2x10-
Plaquemin
-a
-
3.0x10-6∗
25+
19.79w 6
e
29
∗∗∗
St. 93+ b
10.98
5.1x10-6∗
32+ c
23.73w
0
8.26
3.9x10-6∗
34+
23.10w
32.5x10-6∗∗
e
us
Notes: The + symbol indicates a level exceeding the Clean Air Act standard of zero exceedance days. The ∗ symbol indicates a level exceeding the Clean Air Act low risk cancer guideline of
M an
1x10-6; ∗∗ exceeds the high-risk guideline of 10x10-6; ∗∗∗ approaching the unacceptable risk guideline of 100x10-6; and w exceeds the Clean Air Act annual PM limit of 12 μg/m3. Predisaster benzene associated cancer risk estimates are from 2005 NATA risk assessment results,
ed
the latest available information. No data available.
b.
Before the disaster, the high number of AQI exceedances in St. Bernard Parish was not
pt
a.
c.
ce
the result of particulate matter alone. It was primarily caused by excess SO 2 emissions. During the disaster, exceedances in St. Bernard were estimated from particulate matter
Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
-
cr ip
Terrebonn
t
Bernard
alone, without including the traditionally high SO 2 emissions.
30
Table 4. Comparison of Urban and Coastal Air Quality During the Oil Spill Benzene
(μg/m3)
(μg/m3)
cr ip
t
PM 2.5
10.7
M an
Jefferson
ce
pt
Plaquemines
St. Bernard
Terrebonne
Overall Urban Mean
1.11
10.0
0.41
10.0
2.33
8.9
0.39
8.8
0.66
-
0.51
9.68
0.86b
ed
La Fourche
Orleans
us
Urban
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5-Month Mean Concentration 5-Month Mean Concentration
31
Coastal
13.13
0.997
15.73
-
13.91
5.076
M an
Plaquemines
-
us
Orleans
4.978
St. Bernard
0.767
-
-
ed
Terrebonne
16.00
14.50a
2.96c
pt
Overall Coastal Mean
ce
Notes:a. Exceeds annual standard of 12 μg/m3. b. Exceeds low risk guideline of 0.13 μg/m3.
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Downloaded by [Florida International University] at 09:18 30 November 2015
La Fourche
cr ip
t
Jefferson
c. Exceeds high risk guideline of 1.3 μg/m3.
32
Table 5. Results of Kruskal-Wallis H-Tests of Statistical Similarity H o : Distributions Particulate Matter
X2
df
H
p
9.21 150.24 2.38E-33
1.Between Coastal & Urban
1
6.63
4.96E-15
reject
2.Between Regional & Urban
1
6.63 114.91 8.26E-27
reject
3.Between Regional & Coastal
1
6.63
32.28
1.33E-8
reject
Benzene
df
X2
H
p
1
6.63
37.09
1.13E-9
61.28
ce
pt
ed
M an
Post Hoc Tests:
Coastal-Regional
reject
us
2
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Regional-Coastal-Urban
cr ip
t
are the same.
reject
Note: Alpha = 0.01. H was adjusted for ties. Bonferroni adjustment was applied to the post hoc tests.
33
cr ip us M an ed pt ce Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
t
Figure 1. (a) EPA Permanent and Emergency Monitoring Sites and Mobile Monitoring Routes. (b) BP Mobile Monitoring Routes.
34
cr ip us M an ed pt ce Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
t
Figure 2. (a) AQI Exceedances Prior to the Gulf Oil Spill. (b) AQI Exceedances During the Gulf Oil Spill.
35
cr ip us M an ed pt ce Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
t
Figure 3. (a) Benzene Cancer Risk Prior to the Gulf Oil Spill. (b) Benzene Cancer Risk During the Gulf Oil Spill.
36
ed
pt
ce
Ac
t
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us
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Downloaded by [Florida International University] at 09:18 30 November 2015
Figure 4. Estimated Cancer Risk Before and During the Gulf Oil Spill by Parish.
37
ISSN: 1096-2247 (Print) 2162-2906 (Online) Journal homepage: http://www.tandfonline.com/loi/uawm20
Ambient Air Concentrations Exceeded HealthBased Standards for PM2.5 and Benzene During the Deepwater Horizon Oil Spill Earthea Nance, Denae King, Beverly Wright & Robert D. Bullard To cite this article: Earthea Nance, Denae King, Beverly Wright & Robert D. Bullard (2015): Ambient Air Concentrations Exceeded Health-Based Standards for PM2.5 and Benzene During the Deepwater Horizon Oil Spill, Journal of the Air & Waste Management Association, DOI: 10.1080/10962247.2015.1114044 To link to this article: http://dx.doi.org/10.1080/10962247.2015.1114044
Accepted author version posted online: 13 Nov 2015.
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Date: 30 November 2015, At: 09:18
Ambient Air Concentrations Exceeded Health-Based Standards for PM 2.5 and Benzene During the Deepwater Horizon Oil Spill
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t
Earthea Nance1, Denae King1, Beverly Wright2, and Robert D. Bullard1
1
Texas Southern University, 3100 Cleburne Street, Houston, TX 77004, USA
2
Dillard University, 2601 Gentilly Boulevard, New Orleans, LA 70122, USA
us
Implications
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Benzene and particulate matter monitoring during the Deepwater Horizon oil spill revealed that ambient air quality was a likely threat to public health and that residents in coastal Louisiana experienced significantly greater exposures than urban residents. Threshold air pollution levels established for the oil spill apparently were not used as a basis for informing the public about these potential health impacts. Also, despite carrying out the most comprehensive air monitoring ever conducted in the region, none of the agencies involved provided integrated analysis of the data or conclusive statements about public health risk. Better information about real-time risk is needed in future environmental disasters.
ce
pt
ed
Earthea Nance is an Associate Dean and an Associate Professor in the Barbara Jordan-Mickey Leland School of Public Affairs at Texas Southern University in Houston, Texas. Denae King is the Interim Associate Director of the Mickey Leland Center for Environment, Justice and Sustainability in the Barbara Jordan-Mickey Leland School of Public Affairs at Texas Southern University in Houston, Texas. Beverly Wright is the Executive Director of the Deep South Center for Environmental Justice at Dillard University in New Orleans, Louisiana. Robert D. Bullard is the Dean of the Barbara Jordan-Mickey Leland School of Public Affairs at Texas Southern University in Houston, Texas. For this paper we analyzed data from BP and EPA that were available to the public during the disaster. These data are available for download at http://works.bepress.com/nanceea/.
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Authors:
Introduction The Deepwater Horizon Oil Spill was the largest marine oil spill in the history of the United States (EPA, 2015a) and some scholars and news media argue that it was one of the worst
1
environmental disasters (Houck, 2010; Silverleib, 2010; British Broadcasting Corporation, 2010). The disaster began on April 20, 2010 when an explosion and fire occurred on a drilling rig in the Gulf of Mexico approximately 50 miles offshore of Venice, Louisiana (EPA, 2010a;
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t
Middlebrook et al, 2012). With the uncapped well spewing an estimated 50,000–70,000 barrels
began controlled burns to keep the oil from reaching and damaging the coastline (Mufson, 2010).
us
The explosion, evaporating oil, controlled surface oil burns, emissions from the ships used for cleanup and recovery, and secondary aerosols combined to create unknown air quality conditions
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in the Southeast Louisiana region. Middlebrook et al (2012) made new scientific discoveries related to oil spill emission particle size, secondary aerosol formation, and advection/dispersion in the atmosphere, and concluded that “it was likely that secondary organic aerosols from the Deepwater Horizon site impacted aerosol levels in populated areas near the Gulf Coast” (pp.
studied.
ed
20285). The impact of oil spill emissions on people on the ground, however, has been less To address this gap in knowledge, we evaluated urban, coastal, and regional
pt
concentrations of fine particulate matter (PM 2.5 ) and benzene in ground level ambient air. Our
ce
study offers new results about the possible public health implications of the oil spill. Prior to the Deepwater Horizon Oil Spill, the Southeast Louisiana region was considered an area with moderate air quality in terms of primary air pollutants (except for St. Bernard Parish);
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of oil a day (McNutt et al, 2012), the United States Coast Guard and British Petroleum (BP)
however, the region had a high risk of cancer from toxic air pollutant exposure, primarily benzene (EPA, 2013a; EPA, 2011a). A limited set of permanent stationary air monitoring
devices monitored compliance with Clean Air Act standards in the region. Recognizing the inadequacy of this network to monitor public environmental exposures during the oil spill, an
2
extensive emergency air monitoring effort—led by the Environmental Protection Agency (EPA), the Centers for Disease Control (CDC), the National Oceanic and Atmospheric Administration (NOAA), and BP—quickly emerged to fill the gaps in air monitoring (Wright and Nance, 2014).
cr ip
t
The emergency network utilized mobile and stationary devices to take spatially- and temporally-
undertaken in the region. Over one million ambient air measurements were gathered during the
us
oil spill; however, only the permanent stationary monitoring stations met the federal criteria for regulatory monitors (Wright and Nance, 2014). Worker exposure measurements were also
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gathered by the CDC, Occupational Safety and Health Administration (OSHA), USCG, BP, as well as atmospheric measurements gathered by NOAA but were not the subject of this study. By law (Protection of Environment, 40 CFR Part 50 Appendix N), regulatory monitors are
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usually located in highly populated urban areas to ensure that standards are being met in areas most likely to exhibit public health impacts (EPA, 2011b). Yet, the areas most likely impacted
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by oil spill emissions were along the sparsely populated coast where no regulatory monitors were available. The EPA worked to address this gap by installing thirteen emergency stationary
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monitors along the Louisiana coast. These emergency stationary monitors measured hydrogen sulfide (H 2 S), carbon monoxide (CO), particulate matter (PM), and volatile organic compounds (VOCs) (EPA, 2010; EPA, 2013). For the purposes of this study, we chose to examine ambient
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integrated samples and readings. This was perhaps the most extensive sampling regime ever
air concentrations of PM and the VOC benzene, both of which were prevalent during the oil rig
explosion, oil spill, and subsequent clean up. We also chose to compare the data gathered during the disaster to health-based levels under the federal provision that recognizes comparison to
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NAAQS when ambient air concentrations are high enough to cause concern (40 CFR Part 50 Section 50.14). According to the EPA, PM is one of two pollutants that pose the greatest threat to human health
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in the US—the other is ground-level ozone (Air Now, 2015; EPA, 2015b). PM is a complex
sulfates), organic chemicals, metals, and soil or dust particles (EPA, 2013b). The size of PM
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determines the potential health impact. Consequently, the EPA separates PM into two groups: inhalable coarse particles (PM 10 ) and fine particles (PM 2.5 ) . PM 10 is often found near roadways
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and dusty industries, while PM 2.5 particles are emitted from fires or can form when gases released from industrial sources and fossil fuel combustion react in the air. PM 2.5 is of greater concern because its small particle size allows for deep penetration into the lungs and possibly Adverse health effects include nonfatal heart attacks,
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into the bloodstream (EPA, 2013b).
aggravated asthma, and impaired lung function. Because of the known health effects of PM,
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residents of Southeast Louisiana were rightly concerned about possible health threats from the
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oil spill (IOM, 2010).
The Clean Air Act National Ambient Air Quality Standards (NAAQS) take into account the public health impacts of exposure to PM in the short term (hours to days) and in the long term
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mixture of extremely small particles and liquid droplets made up of acids (such as nitrates and
(weeks to months). The annual (long-term) PM 2.5 standard of 12 μg/m3 is less than the 24-hour (short-term) standard of 35 μg/m3 because a healthy human body has the capacity to recover
from a higher short-term dose. Exposure to continual doses over time are difficult for the body to absorb, hence a lower long term standard is required to protect public health (EPA, 2014a).
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Presently, the Clean Air Act requires hourly continuous monitoring of PM using specified monitoring equipment at targeted locations based on population density. These data are used to calculate short-term and long-term concentrations for comparison to the standards.
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Benzene is a component of petroleum and is listed as one of the top 20 chemicals produced in the
Common sources of benzene include tobacco smoke, gas stations, and motor vehicle exhaust
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(CDC, 2013; ATSDR, 2007). The most common route of exposure is inhalation, and benzene exposure has been shown to result in leukemia and blood-related diseases following long-term
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exposure (ATSDR, 2007; ACS, 2013). The Environmental Protection Agency (EPA) estimates an increased lifetime cancer risk of 2.2 x 10-6 to 7.8 x 10-6 for an individual who is continuously exposed to 1 µg/m3 of benzene in the air over their lifetime (EPA, 2012). More than 100 studies
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show there is no safe level of benzene; all concentrations contribute to cancer risk (Baan et al, 2009).
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Regulatory air monitors located in the urban centers of Southeast Louisiana showed no exceedances of Clean Air Act standards during the oil spill (LDEQ, 2010). This finding implies
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there were no public health impacts of concern. However, not addressed are the potential public health impacts not measured by the formal regulatory monitoring network. During the spill, an enormous number of independent samples of urban, coastal, and mixed regional air were taken
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U.S. It is a colorless, volatile and highly flammable liquid found in the natural environment.
using stationary and mobile monitors, and these data were recently made available to the public. These unique datasets make the Southeast Louisiana region a relatively well-constrained case for evaluating potential public health impacts from the spill. The Southeast Louisiana coastal region in question is a poorly sampled area (in terms of air monitoring), with large variations in
5
background cancer risk, household income, and population density (EPA, 2011a; LDEQ, 2010; U.S. Census Bureau, 2010).
A rich body of research definitively concludes that
socioeconomically disadvantaged groups in general are more likely to be at risk of
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environmental hazards (Bullard, 2000; Bullard et. al., 2007; James et al., 2012). The oil spill
long-term effects (Solomon and Janssen, 2010).
People living and working in the area,
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especially people along the coast were apprehensive about their exposures. Therefore, the objectives of this study were: 1) to determine if health-based standards were exceeded during the
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oil spill; and 2) to assess the possibility of disparities in environmental exposures between the urban centers and the more rural coastal region of Southeast Louisiana.
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Experimental Methods
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Study area and timeframe
Six parishes in Southeast Louisiana were selected as the study area: Jefferson, La Fourche,
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Orleans, Plaquemines, St. Bernard, and Terrebonne. This 4,138 square-mile (10,717 square kilometer) region was selected because it was located closest to the oil spill, had the largest potentially exposed population, and was well sampled throughout the disaster. The time frame
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represented a potentially catastrophic environmental health hazard with both immediate and
for the study was May 1, 2010 to September 30, 2010. Although additional data were partly available three days before and three months after this period, the selected months represent the core period of oil spill emissions and burning and account for residual effects after the well was temporarily capped in July, and later permanently capped in early September.
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Oil spill air monitoring data Over one million measurements of ambient air were gathered during the oil spill. The EPA and BP established independent ambient air monitoring and air sampling programs. Monitoring
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made use of either stationary or mobile (i.e., mounted on a vehicle) direct-read equipment
air and sending it to a laboratory for analysis.
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BP and EPA deployed stationary and mobile monitoring devices that took random grab samples and time-weighted samples. For the purposes of this study, air monitoring was divided into three The urban category encompassed permanent and
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categories: urban, coastal, and regional.
emergency stationary monitors located in the major cities of each parish. The coastal category was comprised of emergency stationary monitors installed along the coastline in response to the spill. The regional category consisted of emergency mobile monitors installed on vehicles that
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traversed the parishes (e.g., coastal and urban) during the disaster. As shown in Figures 1(a) and 1(b), BP conducted more regional air monitoring over a larger study area than the EPA, while
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locations.
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much of the EPA’s efforts were focused on emergency stationary monitoring at discrete coastal
It is important to distinguish emergency monitoring from permanent monitoring not only because of location differences. The data collected from emergency monitors (both coastal and regional)
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(British Petroleum, 2010; British Petroleum, 2015). Air sampling involved taking a volume of
are considered “unofficial” because the equipment used did not meet formal Clean Air Act requirements.
Only the permanent monitors (urban only) maintained by the Louisiana
Department of Environmental Quality (LDEQ) met the strict Clean Air Act regulatory criteria for monitoring equipment. Consequently, only results from official permanent monitors have to
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be reported to the public. There are no reporting requirements for environmental data gathered during an emergency. In this study, data gathered during the oil spill via emergency monitors were compared to Clean Air Act standards and to regulatory data gathered at permanent monitors
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to assess potential public health impacts. The paper therefore presents findings that to our
Selected pollutants
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Particulate matter and benzene were assessed in this study because of the potential for significant ambient air emissions, the availability of data across the parishes, and clear health-based
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guidelines/standards. EPA installed stationary filter samplers to take 24-hour particulate matter readings and installed stationary Met One E-BAM monitors to take 1-hour PM readings. BP deployed a TSI Sidepack Personal Aerosol Monitor (AM510) instrument with cyclone to take continuous mobile PM readings. For benzene, EPA installed stationary 24-hour samplers and
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brought in its Trace Atmospheric Gas Analyzer (TAGA) for continuous mobile monitoring. Detection limits ranged from 0.127-16.00 μg/m3. BP outfitted its mobile monitoring vehicle
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with a GASTEC gas detection instrument to take continuous benzene readings, with a detection
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limit of 0.05-0.50 ppm. Taken together, these instruments gathered a total of 106,569 data points within the study area for the duration of the study period. Particulate matter (PM). Particulate matter (PM) was a significant contaminant released during
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knowledge have not been reported.
the oil spill. Two days of aircraft measurements were taken by scientists from the National Oceanic and Atmospheric Administration above the oil spill. With these data, Middlebrook et al (2012: Figure 7) estimated that over 1,000 metric tons of soot particles were emitted from
controlled burns and over 10,000 metric tons of secondary aerosol particles were created from
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evaporating hydrocarbons as cumulative emissions between April 20 and July 20, 2010. Daily and hourly PM data were gathered by the EPA via emergency stationary coastal monitors. When pooled across monitors, this sampling period produced 1,144 hourly PM 2.5 data points (August
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21, 2010 to September 6, 2010) in coastal areas only. BP’s emergency mobile monitors gathered
coastal areas. Daily PM 2.5 data consisting of 277 24-hour averages (from an estimated 63,200
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hourly PM 2.5 data points) were simultaneously gathered at six permanent stationary monitors operating continuously in the urban areas of the region in accordance with Clean Air Act
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requirements (May 1, 2010 to September 30, 2010). Total raw sample size was 102,682 data points.
Benzene. Benzene was a significant contaminant in the oil released in massive quantities during the oil spill, and a large quantity of benzene data was collected across the six parishes. The EPA
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also identified benzene as one of the leading air toxics that drives national cancer risk in the United States via the National Scale Air Toxics Assessment (NATA) (EPA, 2010b). Only EPA
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ambient benzene concentration data was examined in this study because BP’s benzene data did
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not meet instrument sensitivity criteria. The benzene data consisted of 1,053 daily stationary data points (April 28, 2010 to September 18, 2010) and 2,834 continuous mobile data points (April 28, 2010 to September 21, 2010). Total raw sample size for benzene was 3,887 data
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101,261 continuous PM 2.5 data points (May 14, 2010 to December 21, 2010) in both urban and
points.
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Data preparation Raw data obtained from EPA and BP were sorted by pollutant, parish, and monitoring station,
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and truncated to the study period. The data were then averaged to the appropriate time interval
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to examine short-term and long-term concentrations of PM and long-term concentrations of
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obtained by boat and other data gathered from locations outside of the study area were not used.
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Long-Term and Short-Term Comparisons
For our study, the time period of analysis was five months (April 20, 2010 to September 19, 2010), which corresponded to the primary period of potential exposure.
While potential
exposure continued as long as oil was floating and burning on the ocean surface and as long as
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disaster vehicles and equipment were active, there likely was a tapering off of air pollution after the well was permanently capped in September 2010. It is certainly possible that exposure
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continued beyond the five-month active oil spill. BP continued gathering ambient air data into
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December 2010, perhaps to document the rate at which air pollution levels tapered off after the spill. But because the EPA did not extend their data gathering efforts that far and because we wanted to have more than one data source for the purposes of triangulation and validity, we set
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benzene (Tables 1 and 2). Non-detect data points were eliminated. In addition, coastal data
the study period to five months. Our study therefore addresses both short-term (hours to days) and medium-term (weeks to months) ambient air concentrations. National Ambient Air Quality, Standards (NAAQS) for particulate matter are based on 24-hour and annual means. These short-term and long-term NAAQS standards were derived from many
10
epidemiological studies that investigated exposure-dose-response as a function of PM concentration. Schwartz (2000), Krewski et al (2009), and Krewski et al (2000) showed that short-term exposure studies failed to characterize the full impact of exposure to PM in the
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presence of days or months of prior exposure. Their findings demonstrated that mortality due to
concentration (EPA 2010b). Consequently, a short-term standard alone is not sufficient to
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understand health impact. Studies by Beverland et al (2012) and Alexeeff et al (2011) confirmed that medium-term (1-3 month) exposures produced larger health effects than short-term (1-3 day)
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exposures, and that long-term (up to 10 years) effects were stronger still. Given these findings from the literature, we concluded that five months of data better approximated the health impacts associated with an annual exposure than a 24-hour exposure and that, lacking a medium-term standard, applying the NAAQS annual standard was reasonable for the exploratory and
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comparative purposes of our study.
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Stationary data captured a single data point on every first, second, third, or fourth day, and the mobile data were nearly continuous for 24 hours each day. Each dataset contained a sufficient
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number and frequency of measurements (i.e., the proportion of hours or days with available data to the total hours or days in the period) to allow direct comparisons to short-term and long-term standards or guidelines, and all valid data points were used in the analysis. Because the data
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PM exposure is a function of both the concentration as well as the number of days at a given
were taken in varying locations, it was possible to make generalized comparisons of overall air quality at different locations during the spill. We used the Kruskal-Wallis H-test to assess the distributions of regional, coastal, and urban data
because two of the datasets were non-normally distributed and all had large variations in sample
11
size (Ghasemi and Zahediasl, 2012). Only the urban PM data were normally distributed and the Kruskal-Wallis H-test results demonstrated that the urban, coastal, and regional datasets were statistically different and could therefore be treated separately.
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To examine the potential health concerns associated with air quality prior to and during the oil
100 in each parish. When an AQI value exceeds 100, air quality is considered unhealthy for
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certain sensitive groups and as AQI values continue to rise the general public is then affected. The number of AQI exceedances in each parish was calculated and recorded as exceedance days
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(EPA, 2013a; LDEQ, 2010; EPA, 2014b). The AQI is reported throughout the day to inform the public of the health effects of their local air. Currently, the AQI is calculated for five air pollutants: ground level ozone, PM, carbon monoxide, nitrogen dioxide, and sulfur dioxide (EPA, 2014b). The reported AQI typically represents the worst of the five pollutants. For this
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study, we focused only on PM 2.5 contributions to the AQI during the spill. To examine benzene-associated cancer risk and conduct a comparison to long-term standards for
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benzene, we analyzed benzene data available by parish from April 28, 2010 to September 18,
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2010. The resulting means were converted to cancer risk based on a benzene unit risk factor of 7.8 x 10-6. We then compared per parish cancer risk from benzene during the spill to the EPA’s low, high, and unacceptable cancer risk levels. These levels correspond to 1, 10, and 100 x 10-6,
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spill, we counted the number of times the EPA’s Air Quality Index (AQI) for PM 2.5 exceeded
respectively.
Although cancer risk from benzene exposure was calculated using benzene
exposure data from the 6-month time oil spill period, the cancer risk estimation was conducted to allow for comparison with lifetime risk of benzene exposure. Study Results
12
Figure 1(a) shows the location of EPA’s emergency monitors and mobile routes, and LDEQ’s permanent monitoring stations. Terrebonne, La Fourche, St. Bernard, and Orleans Parishes each had one permanent station located in the main city.
Jefferson Parish had two permanent
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monitoring stations; however, Plaquemines Parish did not have a monitoring station. BP’s
to determine the oil spill’s potential impact on public health. First, the oil spill data were
background concentrations.
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compared to health-based or Clean Air Act standards. Second, the data were compared to Concentrations that exceeded background or Clean Air Act
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standards by at least a factor of two, and concentrations that increased cancer risk by at least an order of magnitude (i.e., a factor of 10) suggested cause for concern.
Particulate Matter: Before and During the Disaster
during the oil spill.
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Table 1 provides descriptive statistics for the regional, urban, and coastal PM 2.5 data collected The mean PM 2.5 concentrations observed from regional monitoring,
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stationary urban and coastal monitoring were 22.30 μg/m3, 9.68 μg/m3, and 17.33 μg/m3,
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respectively. The current primary annual PM 2.5 NAAQS used for enforcement of the Clean Air Act is 12 μg/m3 (EPA, 2014a). Therefore, PM 2.5 concentrations detected via regional and coastal monitoring during the oil spill both exceeded the NAAQS’ safe and acceptable limit designed to
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mobile monitoring routes used during the oil spill are shown in Figure 1(b). We used two tests
protect the general population against adverse health effects. Figure 2(a) shows background AQI levels for the Southeast Louisiana parishes. Three parishes exceeded the AQI limit for unhealthy air on at least one day in 2009, indicating that background air pollutants were too high. St. Bernard Parish was excessively high prior to the
13
disaster, having exceeded an AQI of 100 on 93 days in 2009, driven primarily by high SO 2 levels for which the parish had been declared in non-attainment. Plaquemines Parish had no air monitoring station and thus background air quality data were unavailable. The remaining two
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parishes had no AQI exceedance days in the year prior to the spill.
these levels to the background AQI levels in Figure 2(a) reveals a sharp increase from zero to
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four AQI exceedance days in 2009 (before the oil spill) to 24 to 46 AQI exceedance days during the oil spill. This represents estimated increases in exceedance days ranging from 10 to 45 times
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higher and indicates an unequivocal escalation of ambient PM exposure consistent with oil spill emissions.
In addition to the frequency of exceedance days, we also looked for increased PM 2.5
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concentrations that clearly exceeded the Clean Air Act standards. As shown in Table 3, the estimated long term PM 2.5 concentrations detected during the oil spill were approximately two to
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three times higher than the concentrations observed prior to the disaster in Jefferson, St. Bernard,
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and Terrebonne parishes, thus indicating the possibility of public health impacts.
Benzene Levels Before and During the Disaster
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Figure 2(b) presents the results of the PM 2.5 data analysis during the oil spill. Comparing
Descriptive statistics for benzene concentrations detected via regional and stationary
coastal monitoring revealed mean benzene concentrations of 4.83 μg/m3 and 2.96 μg/m3,
respectively (Table 2). The EPA established a one-year oil spill screening level of 20 μg/m3. The State of Louisiana’s ambient standard is 12 μg/m3 and the Clean Air Act’s Unacceptable
14
Risk Level is 13 μg/m3. All three standard levels exceed the regional and coastal mean benzene concentrations observed during the oil spill, suggesting no threat to public health. Figure 3(a) presents benzene-associated cancer risk per parish in 2005, the last year National Air
) were above the state mean of 6.8-in-a-million, although Orleans Parish had the highest risk.
The remaining parishes had a 3- to 5-in-a-million increased chance of developing cancer. The
92-in-a-million chance.
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State of Louisiana’s ambient air standard for benzene (12 μg/m3) corresponds to a cancer risk of Therefore, background benzene levels in all six parishes met the
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Louisiana standard as well as the EPA oil spill screening level (20 μg/m3 or 154 x 10-6). But according to the EPA and the City of Houston, slightly more benzene (13 μg/m3) would correspond to the “unacceptable risk” end of the Clean Air Act’s cancer risk range, which is 100-
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in-a-million (EPA, 2010c; Raun, 2008). This means that Louisiana’s standard and the EPA’s screening level are about two orders of magnitude above the health protective low risk limit of 1-
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in-a-million (0.13 μg/m3) established by the Clean Air Act.
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Background benzene risk levels exceeded the Clean Air Act health-protective low risk cancer level in all six parishes, with Orleans and Jefferson exceeding the standard by approximately one order of magnitude and the remaining parishes exceeding the standard by up to half an order of
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Toxic Assessment (NATA) data were available. Orleans Parish (18 x 10-6) and Jefferson (8 x 10-
magnitude. The existing background levels were unhealthy and presented an increased cancer risk. To determine excess public health impacts beyond background due to benzene released during the oil spill, we also looked for sharp increases in cancer risk at much higher levels than background. Because the EPA’s oil spill screening level for benzene and the State’s ambient
15
benzene standard were not health protective, they could not be used to assess potential health impacts. Figure 3(b) presents the benzene data analysis during the oil spill. Comparing these
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levels to the background cancer risk in Figure 3(a) reveals a sharp increase from a range of 3- to
an estimated one order of magnitude increase in risk and a 2- to 19-fold increase above
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background concentration, which indicates an unequivocal escalation of ambient benzene. These results provide a basis for concluding that benzene concentrations went from the low end of the
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cancer risk range (1 to 10 x 10-6) to the high end of that range (10 to 100 x 10-6) in each parish (Figure 4).
EPA’s one-year benzene screening level (20 μg/m3 or 154 x 10-6) for the Deepwater
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Horizon Oil Spill was defined as a level above which action would be taken. Despite significant increases in ambient air benzene concentrations measured via emergency monitoring equipment
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during the spill, all of the parishes still met the EPA screening level. Unfortunately, this
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screening level is not considered protective of health and could not be used to assess the potential health impacts of increased benzene. Lacking an effective benzene standard or guideline directly applicable to public health during the oil spill, we used the unit low risk level for benzene (0.13
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18-in-a-million before the oil spill to 20- to 57-in-a-million during the oil spill. This represents
μg/m3 or 1 x 10-6) to evaluate potential health impacts (Table 3). With this standard, the results indicate that ambient levels of fine PM and benzene during the Deepwater Horizon Oil Spill
were high enough to cause public health impacts.
16
Analysis of Urban versus Coastal Exposure Disparities In Table 4, PM 2.5 and benzene results are presented for urban and coastal areas. Overall, coastal
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(Jefferson, La Fourche, Plaquemines, and St. Bernard parishes) concentrations of PM 2.5 and
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benzene were higher than urban (Jefferson, La Fourche, Plaquemines, St. Bernard and
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was increased along the coast compared to the urban centers.
Table 5 shows that the coastal, urban, and regional PM data sets are statistically different. Air
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quality in the urban centers, measured by permanent stationary urban monitors, was relatively normal and exhibited far less variance than the coastal and regional data sets. The coastal data showed increased variation and higher absolute values that exceeded air quality standards. These findings suggest there were at least two separate airsheds during the oil spill, and the populations
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within each airshed possibly encountered different exposures. The regional data, which included urban and coastal areas, reflect the wide variability of pollutant levels present in the six parishes
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during the disaster. These geographic exposure disparities were measurable in real time; and
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therefore could have been used to issue region-specific preventive health announcements and precautions.
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Terrebonne) concentrations. This observation confirms that exposure to hazardous air pollutants
Discussion
Ambient concentrations of known air pollutants that exceed health-based Clean Air Act standards and guidelines are indeed an environmental health concern. Government agencies face extremely challenging circumstances during environmental disasters, and potentially
17
controversial decisions have to be made in real time. Such decisions would benefit from having plans already in place that include thresholds for informing the public about potential health threats during a disaster. For the Deepwater Horizon Oil Spill, the EPA established that existing
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Clean Air Act standards were the appropriate threshold for primary air pollutants, including PM,
and there is no threshold below which exposure to PM would be harmless (Brook et al, 2010).
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Rather than using an existing health-based guideline for benzene, EPA established a relatively high “one-year screening level.” There is no federal ambient benzene standard; neither is there a
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threshold concentration below which there is no benzene cancer risk (Baan et al, 2009). The EPA’s level of concern for one-year benzene exposure (20 μg/m3) significantly exceeded other similar guidelines, such as the State of Louisiana’s ambient benzene standard (12 μg/m3), the State of Texas’ one-year benzene screening level (4.5 μg/m3), EPA’s regional cancer
The EPA’s level of concern for benzene exposure during the oil spill also
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(0.02 μg/m3).
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screening level (0.312 μg/m3), and the World Health Organization’s ambient benzene guideline
exceeded the Clean Air Act’s high-risk cancer level (1.3 μg/m3). We concluded that the benzene
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screening level was not protective of public health and therefore was not an effective threshold for use during the spill.
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during the disaster. However, there is no federal PM standard for a 5-month exposure period,
Even though health-based air pollution thresholds were already established for short and long term PM 2.5 , they apparently were not used as a basis for informing the public about potential health impacts, especially with regard to more susceptible and/or more exposed population segments.
Comprehensive air monitoring was conducted by numerous agencies, but none
18
provided integrated analysis or conclusive statements about public health risk.
People in
Southeast Louisiana were exposed to higher PM levels for a minimum of five months in a row during the study period. Because in our view these concentration levels were high enough to
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cause concern, we compared them to the NAAQS PM annual standard. We also compared the
observational, not experimental; therefore, we had no control over the duration of possible
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exposure. But no matter how one looks at these data, we conclude there should have been cause for concern. Better information about real-time risk is needed in future disasters.
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Given the results of this study, we recommend that government agencies involve local officials and the public in discussions about the health-based and regulatory air quality levels that should apply during an environmental disaster.
These discussions could also cover the types of
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emergency monitoring equipment that would be acceptable so that as much data as possible would be recognized as valid in the context of a disaster. Similar plans could be developed for
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“fenceline” communities who may have to shelter in place during industrial accidents and whose sensitive populations may need to be temporarily evacuated. Adopting health-based disaster
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thresholds would facilitate decision-making, enhance public awareness, and reduce potential public health impact during an environmental crisis.
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hourly and daily PM concentrations to the NAAQS PM 24-hour standard. Our study was
Conclusion All available ambient air quality data gathered during the Deepwater Horizon Oil Spill were reviewed, and a total of 106,569 measurements of fine PM and benzene were evaluated.
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Ambient air concentrations of PM 2.5 were generally higher during the oil spill than the previous year and exceeded the Clean Air Act’s 12 μg/m3 annual and 35 μg/m3 hourly standards in the parishes studied. Daily AQI exceedances for PM 2.5 were 24 to 45 times higher than air quality All parishes also exceeded the annual 12 μg/m3
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standards in all of the parishes studied.
benzene were generally higher during the oil spill than during previous years. Benzene cancer
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risk reached 20 to 57 times higher than the Clean Air Act’s 1-in-a-million low risk guideline in all of the parishes studied. All parishes studied also exceeded the high-risk guideline of 10-in-a-
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million. These findings provide a basis for concluding that ambient air quality—for PM 2.5 and benzene—was a likely threat to public health during the oil spill.
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Agency for Toxic Substances and Disease Registry (ATSDR). 2007. Public Health Statement Benzene. Division of Toxicology and Environmental Medicine. Atlanta.
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26
Urban Data
Coastal Data
(μg/m3)
(μg/m3)
(μg/m3)
Standard
Long Term Mean
Standard 10.65
3.86
Long Term Mean
17.32
Standard Deviation 7.025
Sample Variance
113.58
Sample Variance
14.91
Sample Variance
49.36
Minimum
3.70
Minimum
2.00
Minimum
6.35
Maximum
ed
M an
Deviation
Deviation
9.68
cr ip
22.29
us
Long Term Mean
t
Regional Data
21.40
Maximum
37.82
3133
277
Count
51
Maximum
pt
ce
Count
89.16
Count
Notes: Data from all parishes are combined. Regional statistics are a 24-point moving average
Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
Table 1. Descriptive Statistics for Oil Spill Particulate Matter 2.5 Data
of continuous data gathered with mobile monitors. Urban and coastal statistics are averages of daily data gathered with stationary monitors.
27
Table 2. Descriptive Statistics for Oil Spill Benzene Data
Coastal Data
Regional Data
cr ip
t
(μg/m3)
4.83
Long Term Mean
Standard Error
0.12
Standard Error
1.81
6.76
Standard Deviation
22.95
45.81
Sample Variance
527.05
Minimum
0.12
Minimum
0.14
pt
ed
Sample Variance
M an
Standard Deviation
2.96
us
Long Term Mean
81.89
Maximum
290.00
Count
2791
Count
160
ce
Maximum
Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
(μg/m3)
Notes: Data from all parishes are combined.
28
Table 3. Summary of Potential Public Health Impacts from Gulf Oil Spill Air Emissions During the Disaster
Backgroun
Backgroun
Estimated
AQI
d
d
AQI
(Exceedance
Long Term
Benzene
(Exceedance
Days)
PM 2.5
Estimated
d Long
Benzene
Term
Cancer
PM 2.5
(μg/m )
Risk
8.61
8.6x10-6∗
43+
22.63w
20.5x10-6∗∗
La 0
3.1x10-6∗
45+
23.35w
38.3x10-6∗∗
1+
ce
Orleans
24+
23.84w
31.4x10-6∗∗
M an
-
pt
Fourche
ed
4+
Risk
(μg/m3)
3
Jefferson
us
Days)
Cancer
Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
Parish
Estimate
cr ip
Background
t
Prior to the Disaster
18.0x10-
-
6
∗∗
57.2x10-
Plaquemin
-a
-
3.0x10-6∗
25+
19.79w 6
e
29
∗∗∗
St. 93+ b
10.98
5.1x10-6∗
32+ c
23.73w
0
8.26
3.9x10-6∗
34+
23.10w
32.5x10-6∗∗
e
us
Notes: The + symbol indicates a level exceeding the Clean Air Act standard of zero exceedance days. The ∗ symbol indicates a level exceeding the Clean Air Act low risk cancer guideline of
M an
1x10-6; ∗∗ exceeds the high-risk guideline of 10x10-6; ∗∗∗ approaching the unacceptable risk guideline of 100x10-6; and w exceeds the Clean Air Act annual PM limit of 12 μg/m3. Predisaster benzene associated cancer risk estimates are from 2005 NATA risk assessment results,
ed
the latest available information. No data available.
b.
Before the disaster, the high number of AQI exceedances in St. Bernard Parish was not
pt
a.
c.
ce
the result of particulate matter alone. It was primarily caused by excess SO 2 emissions. During the disaster, exceedances in St. Bernard were estimated from particulate matter
Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
-
cr ip
Terrebonn
t
Bernard
alone, without including the traditionally high SO 2 emissions.
30
Table 4. Comparison of Urban and Coastal Air Quality During the Oil Spill Benzene
(μg/m3)
(μg/m3)
cr ip
t
PM 2.5
10.7
M an
Jefferson
ce
pt
Plaquemines
St. Bernard
Terrebonne
Overall Urban Mean
1.11
10.0
0.41
10.0
2.33
8.9
0.39
8.8
0.66
-
0.51
9.68
0.86b
ed
La Fourche
Orleans
us
Urban
Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
5-Month Mean Concentration 5-Month Mean Concentration
31
Coastal
13.13
0.997
15.73
-
13.91
5.076
M an
Plaquemines
-
us
Orleans
4.978
St. Bernard
0.767
-
-
ed
Terrebonne
16.00
14.50a
2.96c
pt
Overall Coastal Mean
ce
Notes:a. Exceeds annual standard of 12 μg/m3. b. Exceeds low risk guideline of 0.13 μg/m3.
Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
La Fourche
cr ip
t
Jefferson
c. Exceeds high risk guideline of 1.3 μg/m3.
32
Table 5. Results of Kruskal-Wallis H-Tests of Statistical Similarity H o : Distributions Particulate Matter
X2
df
H
p
9.21 150.24 2.38E-33
1.Between Coastal & Urban
1
6.63
4.96E-15
reject
2.Between Regional & Urban
1
6.63 114.91 8.26E-27
reject
3.Between Regional & Coastal
1
6.63
32.28
1.33E-8
reject
Benzene
df
X2
H
p
1
6.63
37.09
1.13E-9
61.28
ce
pt
ed
M an
Post Hoc Tests:
Coastal-Regional
reject
us
2
Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
Regional-Coastal-Urban
cr ip
t
are the same.
reject
Note: Alpha = 0.01. H was adjusted for ties. Bonferroni adjustment was applied to the post hoc tests.
33
cr ip us M an ed pt ce Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
t
Figure 1. (a) EPA Permanent and Emergency Monitoring Sites and Mobile Monitoring Routes. (b) BP Mobile Monitoring Routes.
34
cr ip us M an ed pt ce Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
t
Figure 2. (a) AQI Exceedances Prior to the Gulf Oil Spill. (b) AQI Exceedances During the Gulf Oil Spill.
35
cr ip us M an ed pt ce Ac
Downloaded by [Florida International University] at 09:18 30 November 2015
t
Figure 3. (a) Benzene Cancer Risk Prior to the Gulf Oil Spill. (b) Benzene Cancer Risk During the Gulf Oil Spill.
36
ed
pt
ce
Ac
t
cr ip
us
M an
Downloaded by [Florida International University] at 09:18 30 November 2015
Figure 4. Estimated Cancer Risk Before and During the Gulf Oil Spill by Parish.
37
