Journal of Exposure Science and Environmental Epidemiology (2014) 24, 253–259 & 2014 Nature America, Inc. All rights reserved 1559-0631/14
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ORIGINAL ARTICLE
Proximity of US schools to major roadways: a nationwide assessment Samantha L. Kingsley1, Melissa N. Eliot1, Lynn Carlson2, Jennifer Finn3, David L. MacIntosh3, Helen H. Suh4 and Gregory A. Wellenius1 Long-term exposure to traffic pollution has been associated with adverse health outcomes in children and adolescents. A significant number of schools may be located near major roadways, potentially exposing millions of children to high levels of traffic pollution, but this hypothesis has not been evaluated nationally. We obtained data on the location and characteristics of 114,644 US public and private schools, grades prekindergarten through 12, and calculated their distance to the nearest major roadway. In 2005–2006, 3.2 million students (6.2%) attended 8,424 schools (7.3%) located within 100 m of a major roadway, and an additional 3.2 million (6.3%) students attended 8,555 (7.5%) schools located 100–250 m from a major roadway. Schools serving predominantly Black students were 18% (95% CI, 13–23%) more likely to be located within 250 m of a major roadway. Public schools eligible for Title I programs and those with a majority of students eligible for free/reduced price meals were also more likely to be near major roadways. In conclusion, 6.4 million US children attended schools within 250 m of a major roadway and were likely exposed to high levels of traffic pollution. Minority and underprivileged children were disproportionately affected, although some results varied regionally. Journal of Exposure Science and Environmental Epidemiology (2014) 24, 253–259; doi:10.1038/jes.2014.5; published online 5 February 2014 Keywords: air pollution; children; schools; socioeconomic status; traffic
INTRODUCTION Long-term exposure to pollution from traffic has been associated with adverse health effects among children and adolescents, especially in regards to respiratory health. Specifically, long-term exposure to traffic-related air pollution has been associated with an increased risk of developing asthma1–5 and increased incidence rate of acute asthma exacerbations among children with preexisting asthma.6,7 Young children may be particularly affected because their lungs are still developing, and because their smaller airways and higher breathing rates result in greater exposure to air pollutants relative to their size as compared with adults.8,9 Importantly, children who have underdeveloped lungs may have reduced lung function for the rest of their lives.9,10 Lung development, in turn, has been found to be associated with cognitive development.11 In addition to respiratory health, long-term exposure to air pollution may have adverse effects on children’s neurobehavioral function12,13 and cardiovascular health.14 Previous studies have found associations between socioeconomic factors and levels of traffic-related air pollutant exposure. For example, Gunier et al.15 found that Hispanic, African-American, and Asian children were more likely to live in areas of high traffic density compared with White children, and that children with the lowest versus highest income were five times more likely to live in areas with high traffic density. Houston et al.9 also found that Californian childcare facilities in minority and low-income areas were more likely to be near a major roadway compared with facilities in areas with fewer minority and higher-income residents. Studies have found that traffic-related air pollutants decrease approximately exponentially with increasing distance to major roadway.4,16,17 Children spend over 1,200 h at school each year 1
and often during peak traffic hours, and therefore may be exposed to higher levels of traffic-related air pollution at school than at home.9,18,19 Previous studies in specific locations have found associations between school proximity to major roadways and the percent of Hispanic and non-Hispanic Black children, the percent of children enrolled in free or reduced price meal programs, the percent of students whose primary language was not English, the percent of students below the poverty line, the percent without a high school diploma, and the percent of students born abroad.4,9,17,20,21 Appatova et al.22 examined the proximity to major roadways among B9% sample of US public schools within nine US metropolitan areas and found that a substantial percentage of students attended schools located near or very near major roadways with White students more likely than Hispanic students to attend such schools. However, whether similar patterns are observed nationally and among private schools has not been previously evaluated. Accordingly, the goal of this study was to examine the proximity of all US public and private schools to the nearest major roadway nationwide and identify segments of the population potentially at the greatest risk of high exposure to traffic pollution at school.
METHODS School Data We obtained school data through the National Center for Education Statistic (NCES) website. We downloaded public school data on 9 June 2010 through the NCES Common Core of Data (CCD; http://nces.ed.gov/ ccd/aboutCCD.asp), a comprehensive national statistical database of all public elementary and secondary schools and school districts. Statistical
Department of Epidemiology, Brown University, Providence, Rhode Island, USA; 2Department of Geological Sciences, Brown University, Providence, Rhode Island, USA; Environmental Health and Engineering, Needham, Massachusetts, USA and 4Department of Health Sciences, Northeastern University, Boston, Massachusetts, USA. Correspondence to: Dr. Gregory A. Wellenius, Brown University, Box G-S121-2, Providence, Rhode Island 02912, USA. Tel.: þ 401 365 4734. Fax: þ 1 401 863 3713. E-mail: [email protected] Received 11 September 2013; accepted 20 December 2013; published online 5 February 2014 3
Proximity of US schools to major roadways Kingsley et al
254 information is collected annually through five different surveys distributed to B100,000 public elementary and secondary schools in the United States. We downloaded private school data through the NCES Private School Universe Survey (PSS; http://nces.ed.gov/surveys/pss/index.asp) on 7 June 2010. The PSS is similar to the CCD in which it regularly collects data throughout the country that can be used to compare across all states, countries, and so on. Data files containing school data used in the analysis were downloaded from the CCD and PSS websites for the 2005–2006 school years. The school database included school location (both address, and latitude and longitude), urban-centric location (city, suburb, or rural), school type (public or private), school level (primary, middle, high, or other), public school eligibility for Title I programs (eligibility for financial assistance due to high percentage of poor students in public schools only), number of students enrolled, overall and by race, ethnicity, gender, and total number of students eligible for free or reduced price lunch (public schools only). NCES uses urban-centric locations and defines ‘‘city’’ as an area inside a principal city, ‘‘suburb’’ as a territory outside a principal city but inside an urbanized area, ‘‘town’’ as a territory inside an urban cluster, and ‘‘rural’’ as a census-defined rural territory. We combined urban-centric locations of suburb and town as one category, suburb, for this study. Race/ethnicity was defined as White, non-Hispanic; Black, non-Hispanic; Asian/Pacific Islander; American Indian/Alaskan Native; and Hispanic. We calculated the straight-line distance between each school and the nearest major roadway using ArcGIS 10.1 (ESRI, Redlands, CA, USA) and road spatial data, including US Census Feature Class Code (CFCC) data, from Tele Atlas North America. We defined major roadways as those with a CFCC classification of A1 (primary road with limited access or interstate highway) or A2 (primary road without limited access).
Statistical Analyses After excluding 120 electronic schools without physical campuses, data on 114,644 schools were available for analyses. We considered five categories of distance to the nearest major roadway (r100 m, 4100– 250 m, 4250–500 m, 4500–1,000 m, and 41,000 m) selected on the basis of the scientific literature, and calculated the total number of students enrolled by school level for each of these categories. Also based on scientific literature, in subsequent analyses we dichotomized distance so that schools r250 m from a major roadway are defined as being near a major roadway, whereas schools 4250 m are considered not near a major roadway. Socioeconomic status indicators of schools were defined as the majority of students in the school that are minority (Black, non-Hispanic, Hispanic, Asian/Pacific Islander, or American Indian/Alaskan Native), Black, Hispanic, or eligible for free/reduced price lunch. We also used school eligibility for Title I programs, which offer financial assistance to public schools with a high percentage of poor students, as an indicator of socioeconomic status. We performed analyses in the country as a whole and then stratified by region or state. We estimated prevalence ratios and 95% confidence intervals (CI) to assess the association between school-level indicators of socioeconomic status and the probability of a school being near a major roadway. Within each region, we calculated the association between school proximity to major roadways and school type (public or private), urban-centric location (rural, city, or suburban), schools predominantly (that is, 450%) serving minority students, schools predominantly serving Black students, schools predominantly serving Hispanic students, majority of students eligible for free or reduced price lunch, and eligibility for Title I programs. In addition, we calculated associations between school proximity to major roadways and the following student-level variables: Black students, Hispanic students, and public school students eligible for free or reduced price lunch. Analyses were carried out using STATA 11 (StataCorp, College Station, TX, USA).
RESULTS During the 2005–2006 school year, B50.7 million students attended 114,644 schools across the United States. The number of students and schools varied considerably across states, with California having the most schools (10,111) and students (5.55 million) and Wyoming having the fewest schools (388 schools and 87,860 students). Among public schools, 55,557 (65.1%) schools
serving 27.3 million students were eligible for Title I programs and 18.8 million students (40.7%) were eligible for free or reduced price lunch (Table 1). The median distance of schools to the nearest major roadway ranged from 1.0 km in the Northeast to 1.2 km in the West, with an overall median of 1.1 km. Nationally, 3.2 million students (6.2%) attended 8,424 schools (7.3%) located within 100 m of a major roadway, and an additional 3.2 million (6.3%) students attended 8,555 (7.5%) schools located between 100 and 250 m (Table 1). Nationwide, 2.8 million primary school students (11.7%), 1.2 million middle school students (11.9%), and 2.1 million high school students (13.9%) attended schools located within 250 m of a major roadway (see Supplementary Table 1). Race/Ethnicity and Socioeconomic Status The proportion of schools near a major roadway varied depending on the student population served, but not in a consistent manner. For example, schools serving predominantly Black students were 18% (95% CI, 13–23%) more likely to be located within 250 m of a major roadway compared with schools with more heterogeneous student populations (Table 2). However, schools serving predominantly minority students were 6% (95% CI, 3–8%) less likely to be within 250 m of a major roadway than schools serving predominantly White students. Schools serving predominantly Hispanic students were also less likely to be within 250 m of a major roadway compared with more heterogeneous schools. Proximity of schools to major roadways also varied by markers of school-wide socioeconomic status. For example, public schools with a majority of students eligible for free or reduced price lunches were 18% (95% CI, 14–22%) more likely to be within 250 m of a major roadway compared with public schools with less than 50% students eligible. Public schools that were eligible for Title I programs were 17% (95% CI, 13–21%) more likely to be near a major roadway compared with public schools not eligible for Title I. Results were very similar when we performed analyses on the student level. Black students were 7.3% (95% CI, 7.1–7.5%) more likely and Hispanic students were 19.6% (95% CI, 19.5–19.8%) less likely to attend school within 250 m of a major roadway compared with White students. Public school students eligible for free or reduced price lunches were 17.0% (16.8%, 17.2%) more likely to attend school within 250 m of a major roadway compared with students who were not eligible. Geographic Variability The proportion of schools located near major roadways differed across geographic locations. Figure 1 and Supplementary Table 2 show the absolute number and percent of students enrolled in schools within 250 m of a major roadway by state. Almost 30% students in Kentucky attended schools located within 250 m of a major roadway, the highest of any state. The Northeast had the highest proportion of schools and students within 250 m of a major roadway, and the West had the lowest proportion of school and students within 250 m of a major roadway (see Supplementary Table 1). Schools in rural areas were 11% (95% CI, 7–15%) more likely to be located within 250 m of a major roadway compared with schools in suburban areas (Table 2). Results varied by region for many of the variables (Table 3). Public schools were less likely to be within 250 m of a major roadway compared with private schools nationwide and within each region. In the Northeast, city schools had a 34% (95% CI, 25–43%) increased likelihood of being near a major roadway compared with suburban schools, but no significant associations were found in other regions of the country. In the West and South, rural schools were more likely to be within 250 m of a major
Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
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Proximity of US schools to major roadways Kingsley et al
255 Table 1.
Demographics of schools (A) and students (B) by distance to nearest major roadway.
(A) Schools, N (%) Distance
r100 m N ¼ 8,424 (7.3)
4100–250 m N ¼ 8,555 (7.5)
4250–500 m N ¼ 14,044 (12.3)
4500–1000 m N ¼ 22,090 (19.3)
41000 m N ¼ 61,531 (53.7)
School type Private Public Title I eligible
2,763 (32.8) 5,661 (67.2) 3,781 (67.3)
2,470 (28.9) 6,085 (71.1) 4,211 (69.7)
3,409 (24.3) 10,635 (75.7) 7,331 (69.6)
5,221 (23.6) 16,869 (76.4) 11,318 (67.8)
14,497 (23.6) 47,034 (76.4) 28,916 (62.2)
School level Primary Middle High Other
4,399 1,304 2,334 387
(52.2) (15.5) (27.7) (4.6)
5,022 1,264 1,892 377
(58.7) (14.8) (22.1) (4.4)
8,322 2,182 2,979 561
(59.3) (15.5) (21.2) (4.0)
13,423 3,582 4,292 793
(60.8) (16.2) (19.4) (3.6)
36,780 9,810 12,577 2,364
(59.8) (15.9) (20.4) (3.8)
Region West Midwest South Northeast
1,092 1,926 3,498 1,908
(13.0) (22.9) (41.5) (22.7)
1,676 2,236 2,795 1,848
(19.6) (26.1) (32.7) (21.6)
2,809 3,708 4,563 2,964
(20.0) (26.4) (32.5) (21.1)
4,740 5,728 7,142 4,480
(21.5) (25.9) (32.3) (20.3)
13,708 16,054 20,975 10,794
(22.3) (26.1) (34.1) (17.5)
Urban-centric location City Suburb Rural
1,894 (22.5) 3,424 (40.7) 3,106 (36.9)
2,819 (33.0) 3,713 (43.4) 2,023 (23.7)
4,518 (32.2) 6,548 (46.6) 2,978 (21.2)
7,792 (35.3) 10,504 (47.6) 3,794 (17.2)
14,698 (23.9) 26,122 (42.5) 20,711 (33.7)
Predominantly minority schoolsa Predominantly Black schools Predominantly Hispanic schools
2,210 (26.2) 962 (11.4) 509 (6.0)
2,952 (34.5) 1,116 (13.1) 938 (11.0)
5,066 (36.1) 1,810 (12.9) 1,638 (11.7)
8,392 (38.0) 2,908 (13.2) 2,782 (12.6)
17,647 (28.7) 5,317 (8.6) 5,811 (9.4)
(B) Students (in 1,000’s), N (%) Distance Race/ethnicity White Black Asian/Pacific Islander American Indian/Alaskan Native Hispanic Minority Students eligible for free or reduced price lunch
r100 m N ¼ 3,152 (6.2) 2,049 551 111 34 407 1,103 1,149
4100–250 m N ¼ 3,205 (6.3)
(65.0) (17.5) (3.5) (1.1) (12.9) (35.0) (41.8)
1,779 600 160 39 627 1,426 1,312
(55.5) (18.7) (5.0) (1.2) (19.6) (44.5) (46.5)
4250–500 m N ¼ 5,923 (11.7) 3,252 1,075 309 72 1,215 2,671 2,396
(54.9) (18.2) (5.2) (1.2) (20.5) (45.1) (44.7)
4500–1000 m N ¼ 10,118 (20.0) 5,418 1,849 522 110 2,219 4,700 4,107
(53.5) (18.3) (5.2) (1.1) (21.9) (46.5) (44.4)
41000 m N ¼ 28,260 (55.8) 16,958 4,179 1,351 337 5,433 11,301 9,858
(60.0) (14.8) (4.8) (1.2) (19.2) (40.0) (37.9)
a
Defined as schools with more than 50% students who are Black, African-American, Hispanic, Asian/Pacific Islander, or American Indian/Alaskan Native.
roadway compared with suburban schools, but the opposite was observed in the Midwest and Northeast. Supplementary Table 3 show results stratified by urban-centric location. In the West and South, schools serving predominantly minority students were less likely to be close to a major roadway compared with schools serving predominantly White students, but the opposite pattern was observed in the Northeast and Midwest. Schools serving predominantly Hispanic students were less likely to be within 250 m of a major roadway in all regions except the Northeast where they were 34% (95% CI, 21–48%) more likely to be within 250 m of a major roadway compared with schools with fewer Hispanic students. On the student level, this same regional effect in the Northeast was observed for Hispanic students. Schools serving predominantly Black students were more likely to be within 250 m of a major roadway in all regions of the country. However, on the student-level Black students, compared with White students, were more likely to attend schools within 250 m of a major roadway in the Northeast (PR ¼ 1.260; 95% CI, 1.255– 1.265) and Midwest (PR ¼ 1.060; 95% CI, 1.055–1.065) but less likely in the West (PR ¼ 0.843; 95% CI, 0.835–0.850) and South (PR ¼ 0.928; 95% CI, 0.925–0.930). In all regions, public schools with more than 50% students eligible for free or reduced price lunch and public schools eligible for Title I programs were more likely to be located near a major & 2014 Nature America, Inc.
roadway. Similarly, on the student level, students eligible for free or reduced price lunch were more likely to attend schools close to a major roadway in all regions of the country, ranging from 12.3% more likely in the West to 32.0% more likely in the Northeast. DISCUSSION A number of studies indicate that long-term exposure to traffic pollution may be detrimental to the health of children and adolescents.1–14 Traffic-related air pollution is highest immediately adjacent to major roadways, and decreases with increasing distance from roadways, such that beyond 250 m, levels of many pollutants are indistinguishable from background levels.4,7,16,17 We found that nationally in 2005–2006, 3.2 million (6.5%) students attended 8,424 (7.8%) schools located within 100 m of a major roadway and are therefore potentially exposed to very high levels of traffic-related air pollution on a daily basis, and a total of 6.4 million students attended schools located within 250 m of a major roadway and were therefore likely exposed to elevated levels of traffic pollution. In addition, we found significant associations between school proximity to major roadways and both race/ethnicity and indicators of socioeconomic status. Notably, schools predominantly serving Black students were 18% more likely to be located near a major roadway, and Black
Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
Proximity of US schools to major roadways Kingsley et al
256 Table 2.
Number of schools and students within 250 m of a major roadway and prevalence ratios of schools being within 250 m of a major roadway. Schools r250 m N (%)
Students in schools r250 m N (%)
PR (95% CI) for schools
11,746 (13.6) 5,233 (18.5)
5,570,049 (12.1) 786,702 (17.7)
0.74 (0.72, 0.76) 1.00 (ref)
5,129 (15.7) 4,713 (14.9) 7,137 (14.2)
1,706,420 (15.1) 1,891,273 (12.4) 2,759,058 (11.4)
1.11 (1.07, 1.15) 1.05 (1.01, 1.08) 1.00 (ref)
Predominantly minority schools 450% minority students r50% minority students
5,162 (14.2) 11,817 (15.1)
2,222,342 (11.9) 4,134,409 (12.9)
0.94 (0.92, 0.97) 1.00 (ref)
Predominantly Black schools 450% Black students r50% Black students
2,078 (17.2) 14,901 (14.5)
763,595 (15.5) 5,593,156 (12.2)
1.18 (1.13, 1.23) 1.00 (ref)
Predominantly Hispanic schools 450% Hispanic students r50% Hispanic students
1,447 (12.4) 15,532 (15.1)
728,345 (10.2) 5,628,406 (12.9)
0.82 (0.78, 0.86) 1.00 (ref)
Students at public schools eligible for free/reduced price lunch 450% r50%
5,974 (14.8) 5,736 (12.5)
2,284,998 (13.5) 2,934,965 (11.1)
1.18 (1.14, 1.22) 1.00 (ref)
Public schools eligible for Title I Yes No
7,992 (14.4) 3,664 (12.3)
3,573,108 (13.1) 1,955,074 (10.6)
1.17 (1.13, 1.21) 1.00 (ref)
School type Public Private Urban-centric location Rural City Suburban
Abbreviation: CI, confidence interval.
students were 7% more likely to attend a school located near a major roadway. In addition, schools eligible for Title 1 programs were 17% more likely to be near a major roadway, and students eligible for free or reduced price lunches were l7% more likely to attend a school located near a major roadway. The proportion of schools located within 250 m of a major roadway varied by state, region, and urban-centralized location. New York State had the largest absolute number of students (625,161) attending schools within 250 m of a major roadway, whereas the Northeast region and rural areas had the largest proportions of students attending school near a major roadway. Our findings are consistent with those from a study of schools in California that found an association between the median percent of children enrolled in free or reduced price meal programs and proximity to a major roadway.20 That same study also found that Hispanic students were more likely to attend a school within 150 m of a roadway carrying more than 50,000 vehicles per day versus non-Hispanic White children.20 Although direct comparison of our results is not possible, it is of interest that we found Hispanic students to be less likely to attend schools near major roadways in all regions except the Northeast. Previous studies have also found associations among lowincome, minority communities, and an increased risk of higher exposure to traffic-related air pollution.9,15,20 Our study lacked socioeconomic measures from the communities where students lived, but included school-wide indicators of socioeconomic status such as Title I eligibility and percent of students enrolled in free or reduced price meals. We found that public schools eligible for Title I programs and public schools with a majority of students eligible for free or reduced price meals were more likely to be near a major roadway, suggesting that poorer students may be more likely to be exposed to high levels of traffic-related air pollution. These findings were observed overall and within each region of the country.
Appatova et al.22 considered a sample of B9,000 public schools (B9% of all US schools and representing B12% of all US students) in nine metropolitan statistical areas and reported associations between students’ race and school proximity to major roadways. Interestingly, there was no race consistently found to attend schools closer to major roadways across all the metropolitan areas considered. Our results also show significant associations between race and the likelihood of schools being near major roadways when stratified by region, such as schools serving predominantly minority students that were more likely to be within 250 m of a major roadway in the Northeast and Midwest, but less likely to be close to a major roadway in the West and South. We also found that the Northeast and South had the highest percent of schools located within 250 m of a major roadway, whereas the West had the smallest percent, consistent with the finding by Appatova et al.22 that schools’ proximity to major roadways decreased monotonically from East to West. Our study builds on this previous work by including a full census of both public and private schools across the country rather than focusing on a sample of public schools within specific metropolitan areas. In addition, our study includes additional school-based measures of socioeconomic status such as eligibility for Title I programs and percent of students eligible for free or reduced price lunch. Our study has some potential limitations. First, we used school distance to nearest major roadway as a marker of long-term exposure to traffic pollution. However, actual exposure to traffic pollution depends on many additional factors including time spent indoors, building air exchange rates, and local topography, meteorology and land-use characteristics. For example, A1 and A2 Census Feature Class Codes do not necessarily correspond to traffic volumes or emissions. In addition, schools are not single points but are campuses that encompass buildings, fields, and parking lots. Thus, proximity to major roadway represents a misclassified marker of student exposure to traffic pollution.
Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
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Proximity of US schools to major roadways Kingsley et al
257
Figure 1. Number of students attending a school within 250 m of a major roadway (a) and percent of students attending a school within 250 m of a major roadway (b).
Nonetheless, distance to nearest major roadway is easy to measure, easy to understand by both policymakers and the public, and therefore a common school siting criterion used by policymakers. Our study is also limited because indicators of socioeconomic status (Title I eligibility and free or reduced lunch price eligibility) were only available for public schools. Thus, some of our results may not be generalizable to private schools. On the other hand, our analyses included over 114,000 schools nationwide and most of the results are generalizable to the United States. & 2014 Nature America, Inc.
Due to the number of students regularly exposed to trafficrelated air pollution at school, several recommendations have been made to update the building and siting policies for new schools. Existing schools located near major roadways may consider holding outdoor activities in areas farthest from major roadways, and/or installing efficient air filters with the air intake as far from roadways and parking lots as possible.9,20 In summary, during the 2005–2006 school year, more than 6 million children attended schools within 250 m of a major roadway, nationwide, and were likely to be exposed to high
Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
Proximity of US schools to major roadways Kingsley et al
258 Table 3.
Prevalence of schools being within 250 m of a major roadway stratified by region. West PR (95% CI)
Midwest PR (95% CI)
South PR (95% CI)
Northeast PR (95% CI)
School type Public Private
0.68 (0.63, 0.73) 1.00 (ref )
0.72 (0.68, 0.77) 1.00 (ref )
0.76 (0.72, 0.80) 1.00 (ref)
0.77 (0.73, 0.82) 1.00 (ref)
Urban-centric location Rural City Suburban
1.23 (1.13, 1.34) 0.95 (0.87, 1.00) 1.00 (ref )
0.95 (0.89, 1.02) 1.03 (0.96, 1.10) 1.00 (ref )
1.24 (1.17, 1.30) 1.02 (0.96, 1.08) 1.00 (ref)
0.96 (0.89, 1.04) 1.34 (1.25, 1.43) 1.00 (ref)
Predominantly minority schools 450% minority students r50% minority students
0.87 (0.81, 0.94) 1.00 (ref )
1.08 (1.00, 1.16) 1.00 (ref )
0.80 (0.76, 0.84) 1.00 (ref)
1.28 (1.20, 1.36) 1.00 (ref)
Predominantly Black schools 450% Black students r50% Black students
1.29 (1.00, 1.65) 1.00 (ref )
1.14 (1.04, 1.25) 1.00 (ref )
1.06 (1.00, 1.12) 1.00 (ref)
1.21 (1.10, 1.32) 1.00 (ref)
Predominantly Hispanic schools 450% Hispanic students r50% Hispanic students
0.86 (0.78, 0.94) 1.00 (ref )
0.91 (0.76, 1.09) 1.00 (ref )
0.67 (0.62, 0.73) 1.00 (ref)
1.34 (1.21, 1.48) 1.00 (ref)
Students at public schools eligible for free/reduced lunch price 450% r50%
1.11 (1.01, 1.21) 1.00 (ref )
1.20 (1.00, 1.16) 1.00 (ref )
1.12 (1.06, 1.18) 1.00 (ref)
1.36 (1.17, 1.38) 1.00 (ref)
Public schools eligible for Title I Yes No
1.14 (1.04, 1.25) 1.00 (ref )
1.08 (1.00, 1.16) 1.00 (ref )
1.18 (1.12, 1.25) 1.00 (ref)
1.27 (1.17, 1.38) 1.00 (ref)
Abbreviation: CI, confidence interval.
levels of air pollution from traffic. Black and underprivileged children were disproportionately affected, but some results varied by region. Additional research is needed to identify interventions that may minimize potentially harmful environmental exposures at schools and improve the health, safety, and performance of students. CONFLICT OF INTEREST The authors declare no conflict of interest.
ACKNOWLEDGEMENTS The project described was supported by grant R00-ES015774 from the National Institute of Environmental Health Sciences (NIEHS), NIH, and a seed grant from Brown University. The contents of this report are solely the responsibility of the authors and do not necessarily represent the official views of the sponsoring institutions.
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5 Kim JJ, Huen K, Adams S, Smorodinsky S, Hoats A, Malig B et al. Residential traffic and children’s respiratory health. Environ Health Perspect 2008; 116: 1274–1279. 6 English P, Neutra R, Scaif R, Sullivan M, Waller L, Zhu L. Examining associations between childhood asthma and traffic flow using a geographic information system. Environ Health Perspect 1999; 107: 761–767. 7 Spira-Cohen A, Chen LC, Kendall M, Lall R, Thurston GD. Personal exposures to traffic-related air pollution and acute respiratory health among Bronx schoolchildren with asthma. Environ Health Perspect 2011; 119: 559–565. 8 Schwartz J. Air pollution and children’s health. Pediatrics 2004; 113: 1037–1043. 9 Houston D, Ong P, Wu J, Winer A. Proximity of licensed child care facilities to near-roadway vehicle pollution. Am J Public Health 2006; 96: 1611–1617. 10 Gauderman WJ, Vora H, McConnell R, Berhane K, Gilliland F, Thomas D et al. Effect of exposure to traffic on lung development from 10 to 18 years of age: a cohort study. Lancet 2007; 369: 571–577. 11 Suglia SF, Wright RO, Schwartz J, Wright RJ. Association between lung function and cognition among children in a prospective birth cohort study. Psychosom Med 2008; 70: 356–362. 12 Suglia SF, Gryparis A, Wright RO, Schwartz J, Wright RJ. Association of black carbon with cognition among children in a prospective birth cohort study. Am J Epidemiol 2008; 167: 280–286. 13 Wang S, Zhang J, Zeng X, Zeng Y, Chen S. Association of traffic-related air pollution with children’s neurobehavioral functions in Quanzhou, China. Environ Health Perspect 2009; 117: 1612–1618. 14 Breton CV, Wang X, Mack WJ, Berhane K, Lopez M, Islam TS et al. Childhood air pollutant exposure and carotid artery intima-media thickness in young adults. Circulation 2012; 126: 1614–1620. 15 Gunier RB, Hertz A, Von Behren J, Reynolds P. Traffic density in California: socioeconomic and ethnic differences among potentially exposed children. J Expo Anal Environ Epidemiol 2003; 13: 240–246. 16 Zhu Y, Hinds WC, Kim S, Sioutas C. Concentration and size distribution of ultrafine particles near a major highway. J Air Waste Manage Assoc 2002; 52: 1032–1042. 17 Rundell KW, Caviston R, Hollenbach AM, Murphy K. Vehicular air pollution, playgrounds, and youth athletic fields. Inhal Toxicol 2006; 18: 541–547.
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259 18 Juster FT, Ono H, Stafford FP. Changing times of American youth: 1981-2003. Institute for Social Research, University of Michigan, Ann Arbor, Michigan 2004, pp 1–15. 19 Korenstein S, Piazza B. An exposure assessment of PM10 from a major highway interchange: are children in nearby schools at risk? J Environ Health 2002; 65: 9–17. 20 Green RS, Smorodinsky S, Kim JJ, McLaughlin R, Ostro B. Proximity of California public schools to busy roads. Environ Health Perspect 2003; 112: 61–66.
21 Wu YC, Batterman SA. Proximity of schools in Detroit, Michigan to automobile and truck traffic. J Expo Sci Environ Epidemiol 2006; 16: 457–470. 22 Appatova AS, Ryan PH, LeMasters GK, Grinshpun SA. Proximal exposure of public schools and students to major roadways: a nationwide US survey. J Environ Plann Manage 2008; 51: 631–646.
Supplementary Information accompanies the paper on the Journal of Exposure Science and Environmental Epidemiology website (http:// www.nature.com/jes)
& 2014 Nature America, Inc.
Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
www.nature.com/jes
ORIGINAL ARTICLE
Proximity of US schools to major roadways: a nationwide assessment Samantha L. Kingsley1, Melissa N. Eliot1, Lynn Carlson2, Jennifer Finn3, David L. MacIntosh3, Helen H. Suh4 and Gregory A. Wellenius1 Long-term exposure to traffic pollution has been associated with adverse health outcomes in children and adolescents. A significant number of schools may be located near major roadways, potentially exposing millions of children to high levels of traffic pollution, but this hypothesis has not been evaluated nationally. We obtained data on the location and characteristics of 114,644 US public and private schools, grades prekindergarten through 12, and calculated their distance to the nearest major roadway. In 2005–2006, 3.2 million students (6.2%) attended 8,424 schools (7.3%) located within 100 m of a major roadway, and an additional 3.2 million (6.3%) students attended 8,555 (7.5%) schools located 100–250 m from a major roadway. Schools serving predominantly Black students were 18% (95% CI, 13–23%) more likely to be located within 250 m of a major roadway. Public schools eligible for Title I programs and those with a majority of students eligible for free/reduced price meals were also more likely to be near major roadways. In conclusion, 6.4 million US children attended schools within 250 m of a major roadway and were likely exposed to high levels of traffic pollution. Minority and underprivileged children were disproportionately affected, although some results varied regionally. Journal of Exposure Science and Environmental Epidemiology (2014) 24, 253–259; doi:10.1038/jes.2014.5; published online 5 February 2014 Keywords: air pollution; children; schools; socioeconomic status; traffic
INTRODUCTION Long-term exposure to pollution from traffic has been associated with adverse health effects among children and adolescents, especially in regards to respiratory health. Specifically, long-term exposure to traffic-related air pollution has been associated with an increased risk of developing asthma1–5 and increased incidence rate of acute asthma exacerbations among children with preexisting asthma.6,7 Young children may be particularly affected because their lungs are still developing, and because their smaller airways and higher breathing rates result in greater exposure to air pollutants relative to their size as compared with adults.8,9 Importantly, children who have underdeveloped lungs may have reduced lung function for the rest of their lives.9,10 Lung development, in turn, has been found to be associated with cognitive development.11 In addition to respiratory health, long-term exposure to air pollution may have adverse effects on children’s neurobehavioral function12,13 and cardiovascular health.14 Previous studies have found associations between socioeconomic factors and levels of traffic-related air pollutant exposure. For example, Gunier et al.15 found that Hispanic, African-American, and Asian children were more likely to live in areas of high traffic density compared with White children, and that children with the lowest versus highest income were five times more likely to live in areas with high traffic density. Houston et al.9 also found that Californian childcare facilities in minority and low-income areas were more likely to be near a major roadway compared with facilities in areas with fewer minority and higher-income residents. Studies have found that traffic-related air pollutants decrease approximately exponentially with increasing distance to major roadway.4,16,17 Children spend over 1,200 h at school each year 1
and often during peak traffic hours, and therefore may be exposed to higher levels of traffic-related air pollution at school than at home.9,18,19 Previous studies in specific locations have found associations between school proximity to major roadways and the percent of Hispanic and non-Hispanic Black children, the percent of children enrolled in free or reduced price meal programs, the percent of students whose primary language was not English, the percent of students below the poverty line, the percent without a high school diploma, and the percent of students born abroad.4,9,17,20,21 Appatova et al.22 examined the proximity to major roadways among B9% sample of US public schools within nine US metropolitan areas and found that a substantial percentage of students attended schools located near or very near major roadways with White students more likely than Hispanic students to attend such schools. However, whether similar patterns are observed nationally and among private schools has not been previously evaluated. Accordingly, the goal of this study was to examine the proximity of all US public and private schools to the nearest major roadway nationwide and identify segments of the population potentially at the greatest risk of high exposure to traffic pollution at school.
METHODS School Data We obtained school data through the National Center for Education Statistic (NCES) website. We downloaded public school data on 9 June 2010 through the NCES Common Core of Data (CCD; http://nces.ed.gov/ ccd/aboutCCD.asp), a comprehensive national statistical database of all public elementary and secondary schools and school districts. Statistical
Department of Epidemiology, Brown University, Providence, Rhode Island, USA; 2Department of Geological Sciences, Brown University, Providence, Rhode Island, USA; Environmental Health and Engineering, Needham, Massachusetts, USA and 4Department of Health Sciences, Northeastern University, Boston, Massachusetts, USA. Correspondence to: Dr. Gregory A. Wellenius, Brown University, Box G-S121-2, Providence, Rhode Island 02912, USA. Tel.: þ 401 365 4734. Fax: þ 1 401 863 3713. E-mail: [email protected] Received 11 September 2013; accepted 20 December 2013; published online 5 February 2014 3
Proximity of US schools to major roadways Kingsley et al
254 information is collected annually through five different surveys distributed to B100,000 public elementary and secondary schools in the United States. We downloaded private school data through the NCES Private School Universe Survey (PSS; http://nces.ed.gov/surveys/pss/index.asp) on 7 June 2010. The PSS is similar to the CCD in which it regularly collects data throughout the country that can be used to compare across all states, countries, and so on. Data files containing school data used in the analysis were downloaded from the CCD and PSS websites for the 2005–2006 school years. The school database included school location (both address, and latitude and longitude), urban-centric location (city, suburb, or rural), school type (public or private), school level (primary, middle, high, or other), public school eligibility for Title I programs (eligibility for financial assistance due to high percentage of poor students in public schools only), number of students enrolled, overall and by race, ethnicity, gender, and total number of students eligible for free or reduced price lunch (public schools only). NCES uses urban-centric locations and defines ‘‘city’’ as an area inside a principal city, ‘‘suburb’’ as a territory outside a principal city but inside an urbanized area, ‘‘town’’ as a territory inside an urban cluster, and ‘‘rural’’ as a census-defined rural territory. We combined urban-centric locations of suburb and town as one category, suburb, for this study. Race/ethnicity was defined as White, non-Hispanic; Black, non-Hispanic; Asian/Pacific Islander; American Indian/Alaskan Native; and Hispanic. We calculated the straight-line distance between each school and the nearest major roadway using ArcGIS 10.1 (ESRI, Redlands, CA, USA) and road spatial data, including US Census Feature Class Code (CFCC) data, from Tele Atlas North America. We defined major roadways as those with a CFCC classification of A1 (primary road with limited access or interstate highway) or A2 (primary road without limited access).
Statistical Analyses After excluding 120 electronic schools without physical campuses, data on 114,644 schools were available for analyses. We considered five categories of distance to the nearest major roadway (r100 m, 4100– 250 m, 4250–500 m, 4500–1,000 m, and 41,000 m) selected on the basis of the scientific literature, and calculated the total number of students enrolled by school level for each of these categories. Also based on scientific literature, in subsequent analyses we dichotomized distance so that schools r250 m from a major roadway are defined as being near a major roadway, whereas schools 4250 m are considered not near a major roadway. Socioeconomic status indicators of schools were defined as the majority of students in the school that are minority (Black, non-Hispanic, Hispanic, Asian/Pacific Islander, or American Indian/Alaskan Native), Black, Hispanic, or eligible for free/reduced price lunch. We also used school eligibility for Title I programs, which offer financial assistance to public schools with a high percentage of poor students, as an indicator of socioeconomic status. We performed analyses in the country as a whole and then stratified by region or state. We estimated prevalence ratios and 95% confidence intervals (CI) to assess the association between school-level indicators of socioeconomic status and the probability of a school being near a major roadway. Within each region, we calculated the association between school proximity to major roadways and school type (public or private), urban-centric location (rural, city, or suburban), schools predominantly (that is, 450%) serving minority students, schools predominantly serving Black students, schools predominantly serving Hispanic students, majority of students eligible for free or reduced price lunch, and eligibility for Title I programs. In addition, we calculated associations between school proximity to major roadways and the following student-level variables: Black students, Hispanic students, and public school students eligible for free or reduced price lunch. Analyses were carried out using STATA 11 (StataCorp, College Station, TX, USA).
RESULTS During the 2005–2006 school year, B50.7 million students attended 114,644 schools across the United States. The number of students and schools varied considerably across states, with California having the most schools (10,111) and students (5.55 million) and Wyoming having the fewest schools (388 schools and 87,860 students). Among public schools, 55,557 (65.1%) schools
serving 27.3 million students were eligible for Title I programs and 18.8 million students (40.7%) were eligible for free or reduced price lunch (Table 1). The median distance of schools to the nearest major roadway ranged from 1.0 km in the Northeast to 1.2 km in the West, with an overall median of 1.1 km. Nationally, 3.2 million students (6.2%) attended 8,424 schools (7.3%) located within 100 m of a major roadway, and an additional 3.2 million (6.3%) students attended 8,555 (7.5%) schools located between 100 and 250 m (Table 1). Nationwide, 2.8 million primary school students (11.7%), 1.2 million middle school students (11.9%), and 2.1 million high school students (13.9%) attended schools located within 250 m of a major roadway (see Supplementary Table 1). Race/Ethnicity and Socioeconomic Status The proportion of schools near a major roadway varied depending on the student population served, but not in a consistent manner. For example, schools serving predominantly Black students were 18% (95% CI, 13–23%) more likely to be located within 250 m of a major roadway compared with schools with more heterogeneous student populations (Table 2). However, schools serving predominantly minority students were 6% (95% CI, 3–8%) less likely to be within 250 m of a major roadway than schools serving predominantly White students. Schools serving predominantly Hispanic students were also less likely to be within 250 m of a major roadway compared with more heterogeneous schools. Proximity of schools to major roadways also varied by markers of school-wide socioeconomic status. For example, public schools with a majority of students eligible for free or reduced price lunches were 18% (95% CI, 14–22%) more likely to be within 250 m of a major roadway compared with public schools with less than 50% students eligible. Public schools that were eligible for Title I programs were 17% (95% CI, 13–21%) more likely to be near a major roadway compared with public schools not eligible for Title I. Results were very similar when we performed analyses on the student level. Black students were 7.3% (95% CI, 7.1–7.5%) more likely and Hispanic students were 19.6% (95% CI, 19.5–19.8%) less likely to attend school within 250 m of a major roadway compared with White students. Public school students eligible for free or reduced price lunches were 17.0% (16.8%, 17.2%) more likely to attend school within 250 m of a major roadway compared with students who were not eligible. Geographic Variability The proportion of schools located near major roadways differed across geographic locations. Figure 1 and Supplementary Table 2 show the absolute number and percent of students enrolled in schools within 250 m of a major roadway by state. Almost 30% students in Kentucky attended schools located within 250 m of a major roadway, the highest of any state. The Northeast had the highest proportion of schools and students within 250 m of a major roadway, and the West had the lowest proportion of school and students within 250 m of a major roadway (see Supplementary Table 1). Schools in rural areas were 11% (95% CI, 7–15%) more likely to be located within 250 m of a major roadway compared with schools in suburban areas (Table 2). Results varied by region for many of the variables (Table 3). Public schools were less likely to be within 250 m of a major roadway compared with private schools nationwide and within each region. In the Northeast, city schools had a 34% (95% CI, 25–43%) increased likelihood of being near a major roadway compared with suburban schools, but no significant associations were found in other regions of the country. In the West and South, rural schools were more likely to be within 250 m of a major
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Proximity of US schools to major roadways Kingsley et al
255 Table 1.
Demographics of schools (A) and students (B) by distance to nearest major roadway.
(A) Schools, N (%) Distance
r100 m N ¼ 8,424 (7.3)
4100–250 m N ¼ 8,555 (7.5)
4250–500 m N ¼ 14,044 (12.3)
4500–1000 m N ¼ 22,090 (19.3)
41000 m N ¼ 61,531 (53.7)
School type Private Public Title I eligible
2,763 (32.8) 5,661 (67.2) 3,781 (67.3)
2,470 (28.9) 6,085 (71.1) 4,211 (69.7)
3,409 (24.3) 10,635 (75.7) 7,331 (69.6)
5,221 (23.6) 16,869 (76.4) 11,318 (67.8)
14,497 (23.6) 47,034 (76.4) 28,916 (62.2)
School level Primary Middle High Other
4,399 1,304 2,334 387
(52.2) (15.5) (27.7) (4.6)
5,022 1,264 1,892 377
(58.7) (14.8) (22.1) (4.4)
8,322 2,182 2,979 561
(59.3) (15.5) (21.2) (4.0)
13,423 3,582 4,292 793
(60.8) (16.2) (19.4) (3.6)
36,780 9,810 12,577 2,364
(59.8) (15.9) (20.4) (3.8)
Region West Midwest South Northeast
1,092 1,926 3,498 1,908
(13.0) (22.9) (41.5) (22.7)
1,676 2,236 2,795 1,848
(19.6) (26.1) (32.7) (21.6)
2,809 3,708 4,563 2,964
(20.0) (26.4) (32.5) (21.1)
4,740 5,728 7,142 4,480
(21.5) (25.9) (32.3) (20.3)
13,708 16,054 20,975 10,794
(22.3) (26.1) (34.1) (17.5)
Urban-centric location City Suburb Rural
1,894 (22.5) 3,424 (40.7) 3,106 (36.9)
2,819 (33.0) 3,713 (43.4) 2,023 (23.7)
4,518 (32.2) 6,548 (46.6) 2,978 (21.2)
7,792 (35.3) 10,504 (47.6) 3,794 (17.2)
14,698 (23.9) 26,122 (42.5) 20,711 (33.7)
Predominantly minority schoolsa Predominantly Black schools Predominantly Hispanic schools
2,210 (26.2) 962 (11.4) 509 (6.0)
2,952 (34.5) 1,116 (13.1) 938 (11.0)
5,066 (36.1) 1,810 (12.9) 1,638 (11.7)
8,392 (38.0) 2,908 (13.2) 2,782 (12.6)
17,647 (28.7) 5,317 (8.6) 5,811 (9.4)
(B) Students (in 1,000’s), N (%) Distance Race/ethnicity White Black Asian/Pacific Islander American Indian/Alaskan Native Hispanic Minority Students eligible for free or reduced price lunch
r100 m N ¼ 3,152 (6.2) 2,049 551 111 34 407 1,103 1,149
4100–250 m N ¼ 3,205 (6.3)
(65.0) (17.5) (3.5) (1.1) (12.9) (35.0) (41.8)
1,779 600 160 39 627 1,426 1,312
(55.5) (18.7) (5.0) (1.2) (19.6) (44.5) (46.5)
4250–500 m N ¼ 5,923 (11.7) 3,252 1,075 309 72 1,215 2,671 2,396
(54.9) (18.2) (5.2) (1.2) (20.5) (45.1) (44.7)
4500–1000 m N ¼ 10,118 (20.0) 5,418 1,849 522 110 2,219 4,700 4,107
(53.5) (18.3) (5.2) (1.1) (21.9) (46.5) (44.4)
41000 m N ¼ 28,260 (55.8) 16,958 4,179 1,351 337 5,433 11,301 9,858
(60.0) (14.8) (4.8) (1.2) (19.2) (40.0) (37.9)
a
Defined as schools with more than 50% students who are Black, African-American, Hispanic, Asian/Pacific Islander, or American Indian/Alaskan Native.
roadway compared with suburban schools, but the opposite was observed in the Midwest and Northeast. Supplementary Table 3 show results stratified by urban-centric location. In the West and South, schools serving predominantly minority students were less likely to be close to a major roadway compared with schools serving predominantly White students, but the opposite pattern was observed in the Northeast and Midwest. Schools serving predominantly Hispanic students were less likely to be within 250 m of a major roadway in all regions except the Northeast where they were 34% (95% CI, 21–48%) more likely to be within 250 m of a major roadway compared with schools with fewer Hispanic students. On the student level, this same regional effect in the Northeast was observed for Hispanic students. Schools serving predominantly Black students were more likely to be within 250 m of a major roadway in all regions of the country. However, on the student-level Black students, compared with White students, were more likely to attend schools within 250 m of a major roadway in the Northeast (PR ¼ 1.260; 95% CI, 1.255– 1.265) and Midwest (PR ¼ 1.060; 95% CI, 1.055–1.065) but less likely in the West (PR ¼ 0.843; 95% CI, 0.835–0.850) and South (PR ¼ 0.928; 95% CI, 0.925–0.930). In all regions, public schools with more than 50% students eligible for free or reduced price lunch and public schools eligible for Title I programs were more likely to be located near a major & 2014 Nature America, Inc.
roadway. Similarly, on the student level, students eligible for free or reduced price lunch were more likely to attend schools close to a major roadway in all regions of the country, ranging from 12.3% more likely in the West to 32.0% more likely in the Northeast. DISCUSSION A number of studies indicate that long-term exposure to traffic pollution may be detrimental to the health of children and adolescents.1–14 Traffic-related air pollution is highest immediately adjacent to major roadways, and decreases with increasing distance from roadways, such that beyond 250 m, levels of many pollutants are indistinguishable from background levels.4,7,16,17 We found that nationally in 2005–2006, 3.2 million (6.5%) students attended 8,424 (7.8%) schools located within 100 m of a major roadway and are therefore potentially exposed to very high levels of traffic-related air pollution on a daily basis, and a total of 6.4 million students attended schools located within 250 m of a major roadway and were therefore likely exposed to elevated levels of traffic pollution. In addition, we found significant associations between school proximity to major roadways and both race/ethnicity and indicators of socioeconomic status. Notably, schools predominantly serving Black students were 18% more likely to be located near a major roadway, and Black
Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
Proximity of US schools to major roadways Kingsley et al
256 Table 2.
Number of schools and students within 250 m of a major roadway and prevalence ratios of schools being within 250 m of a major roadway. Schools r250 m N (%)
Students in schools r250 m N (%)
PR (95% CI) for schools
11,746 (13.6) 5,233 (18.5)
5,570,049 (12.1) 786,702 (17.7)
0.74 (0.72, 0.76) 1.00 (ref)
5,129 (15.7) 4,713 (14.9) 7,137 (14.2)
1,706,420 (15.1) 1,891,273 (12.4) 2,759,058 (11.4)
1.11 (1.07, 1.15) 1.05 (1.01, 1.08) 1.00 (ref)
Predominantly minority schools 450% minority students r50% minority students
5,162 (14.2) 11,817 (15.1)
2,222,342 (11.9) 4,134,409 (12.9)
0.94 (0.92, 0.97) 1.00 (ref)
Predominantly Black schools 450% Black students r50% Black students
2,078 (17.2) 14,901 (14.5)
763,595 (15.5) 5,593,156 (12.2)
1.18 (1.13, 1.23) 1.00 (ref)
Predominantly Hispanic schools 450% Hispanic students r50% Hispanic students
1,447 (12.4) 15,532 (15.1)
728,345 (10.2) 5,628,406 (12.9)
0.82 (0.78, 0.86) 1.00 (ref)
Students at public schools eligible for free/reduced price lunch 450% r50%
5,974 (14.8) 5,736 (12.5)
2,284,998 (13.5) 2,934,965 (11.1)
1.18 (1.14, 1.22) 1.00 (ref)
Public schools eligible for Title I Yes No
7,992 (14.4) 3,664 (12.3)
3,573,108 (13.1) 1,955,074 (10.6)
1.17 (1.13, 1.21) 1.00 (ref)
School type Public Private Urban-centric location Rural City Suburban
Abbreviation: CI, confidence interval.
students were 7% more likely to attend a school located near a major roadway. In addition, schools eligible for Title 1 programs were 17% more likely to be near a major roadway, and students eligible for free or reduced price lunches were l7% more likely to attend a school located near a major roadway. The proportion of schools located within 250 m of a major roadway varied by state, region, and urban-centralized location. New York State had the largest absolute number of students (625,161) attending schools within 250 m of a major roadway, whereas the Northeast region and rural areas had the largest proportions of students attending school near a major roadway. Our findings are consistent with those from a study of schools in California that found an association between the median percent of children enrolled in free or reduced price meal programs and proximity to a major roadway.20 That same study also found that Hispanic students were more likely to attend a school within 150 m of a roadway carrying more than 50,000 vehicles per day versus non-Hispanic White children.20 Although direct comparison of our results is not possible, it is of interest that we found Hispanic students to be less likely to attend schools near major roadways in all regions except the Northeast. Previous studies have also found associations among lowincome, minority communities, and an increased risk of higher exposure to traffic-related air pollution.9,15,20 Our study lacked socioeconomic measures from the communities where students lived, but included school-wide indicators of socioeconomic status such as Title I eligibility and percent of students enrolled in free or reduced price meals. We found that public schools eligible for Title I programs and public schools with a majority of students eligible for free or reduced price meals were more likely to be near a major roadway, suggesting that poorer students may be more likely to be exposed to high levels of traffic-related air pollution. These findings were observed overall and within each region of the country.
Appatova et al.22 considered a sample of B9,000 public schools (B9% of all US schools and representing B12% of all US students) in nine metropolitan statistical areas and reported associations between students’ race and school proximity to major roadways. Interestingly, there was no race consistently found to attend schools closer to major roadways across all the metropolitan areas considered. Our results also show significant associations between race and the likelihood of schools being near major roadways when stratified by region, such as schools serving predominantly minority students that were more likely to be within 250 m of a major roadway in the Northeast and Midwest, but less likely to be close to a major roadway in the West and South. We also found that the Northeast and South had the highest percent of schools located within 250 m of a major roadway, whereas the West had the smallest percent, consistent with the finding by Appatova et al.22 that schools’ proximity to major roadways decreased monotonically from East to West. Our study builds on this previous work by including a full census of both public and private schools across the country rather than focusing on a sample of public schools within specific metropolitan areas. In addition, our study includes additional school-based measures of socioeconomic status such as eligibility for Title I programs and percent of students eligible for free or reduced price lunch. Our study has some potential limitations. First, we used school distance to nearest major roadway as a marker of long-term exposure to traffic pollution. However, actual exposure to traffic pollution depends on many additional factors including time spent indoors, building air exchange rates, and local topography, meteorology and land-use characteristics. For example, A1 and A2 Census Feature Class Codes do not necessarily correspond to traffic volumes or emissions. In addition, schools are not single points but are campuses that encompass buildings, fields, and parking lots. Thus, proximity to major roadway represents a misclassified marker of student exposure to traffic pollution.
Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
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Proximity of US schools to major roadways Kingsley et al
257
Figure 1. Number of students attending a school within 250 m of a major roadway (a) and percent of students attending a school within 250 m of a major roadway (b).
Nonetheless, distance to nearest major roadway is easy to measure, easy to understand by both policymakers and the public, and therefore a common school siting criterion used by policymakers. Our study is also limited because indicators of socioeconomic status (Title I eligibility and free or reduced lunch price eligibility) were only available for public schools. Thus, some of our results may not be generalizable to private schools. On the other hand, our analyses included over 114,000 schools nationwide and most of the results are generalizable to the United States. & 2014 Nature America, Inc.
Due to the number of students regularly exposed to trafficrelated air pollution at school, several recommendations have been made to update the building and siting policies for new schools. Existing schools located near major roadways may consider holding outdoor activities in areas farthest from major roadways, and/or installing efficient air filters with the air intake as far from roadways and parking lots as possible.9,20 In summary, during the 2005–2006 school year, more than 6 million children attended schools within 250 m of a major roadway, nationwide, and were likely to be exposed to high
Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
Proximity of US schools to major roadways Kingsley et al
258 Table 3.
Prevalence of schools being within 250 m of a major roadway stratified by region. West PR (95% CI)
Midwest PR (95% CI)
South PR (95% CI)
Northeast PR (95% CI)
School type Public Private
0.68 (0.63, 0.73) 1.00 (ref )
0.72 (0.68, 0.77) 1.00 (ref )
0.76 (0.72, 0.80) 1.00 (ref)
0.77 (0.73, 0.82) 1.00 (ref)
Urban-centric location Rural City Suburban
1.23 (1.13, 1.34) 0.95 (0.87, 1.00) 1.00 (ref )
0.95 (0.89, 1.02) 1.03 (0.96, 1.10) 1.00 (ref )
1.24 (1.17, 1.30) 1.02 (0.96, 1.08) 1.00 (ref)
0.96 (0.89, 1.04) 1.34 (1.25, 1.43) 1.00 (ref)
Predominantly minority schools 450% minority students r50% minority students
0.87 (0.81, 0.94) 1.00 (ref )
1.08 (1.00, 1.16) 1.00 (ref )
0.80 (0.76, 0.84) 1.00 (ref)
1.28 (1.20, 1.36) 1.00 (ref)
Predominantly Black schools 450% Black students r50% Black students
1.29 (1.00, 1.65) 1.00 (ref )
1.14 (1.04, 1.25) 1.00 (ref )
1.06 (1.00, 1.12) 1.00 (ref)
1.21 (1.10, 1.32) 1.00 (ref)
Predominantly Hispanic schools 450% Hispanic students r50% Hispanic students
0.86 (0.78, 0.94) 1.00 (ref )
0.91 (0.76, 1.09) 1.00 (ref )
0.67 (0.62, 0.73) 1.00 (ref)
1.34 (1.21, 1.48) 1.00 (ref)
Students at public schools eligible for free/reduced lunch price 450% r50%
1.11 (1.01, 1.21) 1.00 (ref )
1.20 (1.00, 1.16) 1.00 (ref )
1.12 (1.06, 1.18) 1.00 (ref)
1.36 (1.17, 1.38) 1.00 (ref)
Public schools eligible for Title I Yes No
1.14 (1.04, 1.25) 1.00 (ref )
1.08 (1.00, 1.16) 1.00 (ref )
1.18 (1.12, 1.25) 1.00 (ref)
1.27 (1.17, 1.38) 1.00 (ref)
Abbreviation: CI, confidence interval.
levels of air pollution from traffic. Black and underprivileged children were disproportionately affected, but some results varied by region. Additional research is needed to identify interventions that may minimize potentially harmful environmental exposures at schools and improve the health, safety, and performance of students. CONFLICT OF INTEREST The authors declare no conflict of interest.
ACKNOWLEDGEMENTS The project described was supported by grant R00-ES015774 from the National Institute of Environmental Health Sciences (NIEHS), NIH, and a seed grant from Brown University. The contents of this report are solely the responsibility of the authors and do not necessarily represent the official views of the sponsoring institutions.
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Journal of Exposure Science and Environmental Epidemiology (2014), 253 – 259
