Environ Monit Assess (2015) 187:250 DOI 10.1007/s10661-015-4500-z
Evaluation of air quality in Chengdu, Sichuan Basin, China: are China’s air quality standards sufficient yet? Xue Qiao & Daniel Jaffe & Ya Tang & Meaghan Bresnahan & Jie Song
Received: 10 October 2014 / Accepted: 1 April 2015 # Springer International Publishing Switzerland 2015
Abstract Air quality evaluation is important in order to inform the public about the risk level of air pollution to human health. To better assess air quality, China released its new national ambient air quality standards (NAAQS2012) and the new method to classify air quality level (AQL) in 2012. In this study, we examined the performance of China’s NAAQS-2012 and AQL classification method through applying them, the World Health Organization (WHO) guidelines, and the US AQL classification method to evaluate air quality in Chengdu, the largest city in southwestern China. The results show that annual mean concentrations of PM10, PM2.5, SO2, NO2, and O3 at the seven urban sites were in the ranges of 138– 161, 87–98, 18–32, 54–70, and 42–57 μg/m3, respectively, and the annual mean concentrations of CO were in the range of 1.09–1.28 mg/m3. Chengdu is located in one Electronic supplementary material The online version of this article (doi:10.1007/s10661-015-4500-z) contains supplementary material, which is available to authorized users. X. Qiao : Y. Tang (*) Department of Environment, College of Architecture and Environment, Sichuan University, Chengdu 610065, China e-mail: [email protected] D. Jaffe Department of Atmospheric Sciences, University of Washington-Seattle, Seattle, WA 98195, USA M. Bresnahan Georgetown College, Georgetown University, 37th and O Streets, N.W., Washington, D.C. 20057, USA J. Song Taomee Holdings LTD, Shanghai 200233, China
of the four largest regions affected by haze in China, and PM10 and PM2.5 were the top air pollutants, with annual concentrations over 2 times of their standards in NAAQ S-2012 and over 7 times of the WHO guidelines. Annual mean concentrations of the pollutants were much lower at the background site (LYS) than at the urban sites, but the annual mean concentrations of PM10 and PM2.5 at LYS were 3.5 and 5.7 times of the WHO guidelines, respectively. These suggest that severe air pollution in Chengdu was largely associated with local emissions but also related to regional air pollution. The compliance rates of PM10, PM2.5, SO2, and O3 met China’s NAAQ S-2012 standards four times more frequently than they met the WHO guidelines, as NAAQS-2012 uses the loosest interim target (IT) standards of WHO for these four pollutants. Air pollution in Chengdu was estimated and stated to be less severe using China’s classification than using the US classification, as China uses weaker concentration breakpoints and benign descriptions of AQL. Furthermore, China’s AQL classification method does not capture the cumulative effects of multiple pollutants, and the risk assessment is mainly based on the exposure-response relationship between air pollutant and human health quantified in the North America and West Europe; these can bring some uncertainties into evaluating the risk to human health in China. In summary, although China greatly improved its NAAQS and AQL classification method in 2012, further improvements are still needed. Keywords National Ambient Air Quality Standards . Air quality level . Air pollution . Haze
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Introduction Since the 1979 economic reforms, China has achieved spectacular economic growth, leading to improved average living standards, decreased poverty, and longer life expectancy. However, this economic development has also caused significant environmental degradation, particularly urban air pollution (He et al. 2002; Chan and Yao 2008; Kan et al. 2012; Zhang et al. 2012a; Alcorn 2013). In the 1970s, industrialized Chinese cities began to suffer from smog (He et al. 2002). In the 1980s, acid rain and SO2 pollution caused by coal combustion became a serious problem in the country (He et al. 2002), and south China became one of the three largest acid rain affected regions in the world following the two regions in West Europe and North America (Wang and Wang 1995). Although China’s SO2 emissions started to decrease in 2006 (National Bureau of Statistics of China (NBSC) 2013), some regions of China still have the highest SO2 emissions in the world (Kurokawal et al. 2013). While acid rain and SO2 pollution continue to be severe (Ministry of Environment Protection (MEP) 2014), haze has intensified, shrouding one fourth of China’s land territory and affecting 600 million people (National Development and Reform Commission (NDRC) 2013). Owing to its basin landform (Fig. 1a) and high air pollutant emissions (Kurokawal et al. 2013), Sichuan Basin is one of the four regions that have suffered the most from haze in China, and the other three are as follows: (1) Hua Bei Plain in North China and the Guanzhong Plain, (2) East China with the main body in the Yangtze River Delta area, and (3) South China with most areas of Guangdong and the Pearl River Delta area (Zhang et al. 2012b). Sichuan Basin is also recognized as one of the world’s regions that is most polluted by PM2.5 (Battele Memorial Institute and Center for International Earth Science Information Network (BMICIESIN) 2013), which is the major pollutant that causes haze. Chengdu is the largest city in Sichuan Basin, with a population of 11.7 million and an area of 12.1 thousand km2 in 2012 (Chengdu Statistics Bureau (CSB) 2013). Although haze has long been recognized as a severe problem in Chengdu, PM2.5 was not regularly measured until March 30, 2012, and hourly and daily concentrations of other pollutants (e.g., SO2, NO2, CO, O3, and PM10) were not released to the public until January 2013. To preliminarily study the haze problem in Chengdu, we used a nephelometer (Radiance
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Research M903, USA) to monitor hourly PM2.5 concentrations in the Wangjiang campus of Sichuan University (SCU) from November 16, 2011 to November 16, 2012 (Fig. 1). During this period, the Chengdu Environmental Monitoring Station (CDEMS) started to release daily PM2.5 concentrations at two sites, namely, Da Shi Xi Road (DSXR) and Jun Ping Street (JPS) (Fig. 1). Based on these PM2.5 data collected at SCU, DSXR, and JPS, we noticed the discrepancy of air quality between residents’ perceptions of air quality and the governmental report (Fig. 2), and this discrepancy was believed to be largely related to the exclusion of PM2.5 in air quality level (AQL) classification then. For example, daily PM2.5 concentration was 71 μg/m3 at SCU on 9 March 2012 (about three times of the WHO guideline) and local residents perceived poor visibility, but the government reported an air quality level of “moderate.” In 2012, China released the new National Ambient Air Quality Standards (NAAQS-2012) (MEP 2012a, b) and the new AQL classification method (MEP 2012c), both of which for the first time included PM2.5, making air quality evaluation more stringent. However, we still question: are these new standards sufficient enough to inform the public about the risk level from air pollution to human health? The objectives of this study are as follows: (1) to apply NAAQS-2012 and the new AQL classification method to evaluate air quality in Chengdu and (2) to discuss the performance of these new standards based on the evaluation of Chengdu’s air quality.
Methods and materials Hourly concentrations of PM10, PM2.5, SO2, NO2, O3, and CO collected at eight sites between April 11, 2013 and April 10, 2014 were used to evaluate air quality for Chengdu. These eight sites include one background site (Lin Yanshan: LYS) and seven sites in the urban area (Fig. 1). The seven urban sites were DSXR, JPS, Jin Quan Liang He (JQLH), Liang Jia Xiang (LJX), Shi Li Dian (SLD), Sha He Pu (SHP), and San Wa Yao (SWY). Real-time hourly concentrations of air pollutants at these sites were derived from the Web site of CDEMS (www.cdemc.org/PM25. aspx). Since a considerable amount of hourly data were unavailable at each site (published as “NA” on the website) and air pollutant concentrations at the seven urban sites were generally similar (as shown in
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Fig. 1 Locations of Sichuan Basin (a), Chengdu (a), and the air quality monitoring sites (b)
Fig. 3), we averaged hourly concentrations at the seven urban sites for each pollutant to represent air quality in the entire urban area.
Compliance rate of each pollutant (compliance rate is the percent of air pollutant concentrations found to meet an environmental standard) and AQL were also
Fig. 2 Daily concentrations of PM2.5 at SCU, JPS, and DSXR and the air quality levels (AQLs) reported by the Chengdu government between November 2011 and January 2013
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Fig. 3 Hourly concentrations of PM10, PM2.5, NO2, SO2, O3, and CO at eight sites in Chengdu between April 2013 and April 2014
calculated for LYS and the urban area. To evaluate the performance of China’s NAAQS-2012, we compared the compliance rates calculated using the NAAQS2012 to those calculated using the WHO guidelines (Table 1). To assess the performance of China’s AQL classification method, we compared the AQLs classified using the Chinese method (MEP 2012c) to those classified using the US method (US Environment Protection Agency (USEPA) 2012), as the Chinese method is mainly based on the US method (Andrews 2009). To classify AQL for a given site, individual air quality index (IAQI) for each air pollutant is calculated first. To calculate IAQI for a given pollutant, the pollutant concentration between the concentration breakpoints is linearly interpolated using the Eq. (1) below. Although China and the USA both use the same equation, the two countries use different concentration breakpoints (Table S1). The highest IAQI among all the measured pollutants is identified as the
air quality index (AQI) for the given site. Based on AQI, AQL is classified into six levels (Table 2). The six levels are “good,” “moderate,” “lightly polluted,” “moderately polluted,” “heavily polluted,” and “severely polluted” in China, while they are “good,” “moderate,” “unhealthy for sensitive groups,” “unhealthy,” “very unhealthy,” and “hazardous” in the USA. IAQI ¼ Ilow þ Ihigh −Ilow ðCi −Clow Þ= Chigh −Clow
ð1Þ Definitions: Ci Clow Chigh Ilow Ihigh
concentration of i pollutant concentration breakpoint that is lower than Ci concentration breakpoint that is higher than Ci index breakpoint corresponding to Clow index breakpoint corresponding to Chigh.
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Table 1 Selected air pollutant standards for urban areas set by China and the World Health Organization (WHO) Items
TSP (μg/m3) PM10 (μg/m3) 3
PM2.5 (μg/m ) NOx (μg/m3)
3
NO2 (μg/m )
SO2 (μg/m3)
O3 (μg/m3) CO (mg/m3)
a
China’s
WHOb
NAAQS-2012a
Guideline
IT-3
IT-2
IT-1
High levelc
daily
300
-
-
-
-
-
Annual
200
-
-
-
-
-
daily
150
50
75
100
150
-
Annual
70
20
30
50
70
-
daily
75
25
37.5
50
75
-
Annual
35
10
15
25
35
-
Hourly
250
-
-
-
-
-
daily
100
-
-
-
-
-
Annual
50
-
-
-
-
-
Hourly
200
200
-
-
-
-
daily
80
-
-
-
-
-
Annual
40
40
-
-
-
-
10-minute
-
500
-
-
-
-
Hourly
500
-
-
-
-
-
3-hour
-
-
-
-
-
-
daily
150
20
-
50
125
-
Annual
60
-
-
-
-
-
Hourly
200
-
-
-
-
-
8-hour
160
100
-
-
160
240
Hourly
10
-
-
-
-
-
8-hour
-
-
-
-
-
-
daily
4
-
-
-
-
-
MEP (2012a)
b
WHO (2005)
c
Significant health effect
Results Air pollutant concentrations Hourly concentrations of each pollutant at each site are summarized in Fig. 3. Annual mean concentrations of PM10 and PM2.5 at the urban sites were in the ranges of 138–161 and 87–98 μg/m3, respectively, about 2–3 times of the NAAQS-2012 standards (70 and 35 μg/m3, respectively) and about 7–10 times of the WHO guidelines (20 and 10 μg/m3, respectively). Annual mean concentrations of SO2 at the urban sites were in the range of 18–32 μg/m3, lower than the NAAQS-2012 standard (60 μg/m3). Annual mean concentrations of NO2 at the urban sites were in the range of 54–70 μg/m3, about 1.2–1.9 times of 40 μg/m3, which is
the NAAQS-2012 standard and also the WHO guideline. Annual mean concentrations of O3 and CO at the urban sites were in the range of 42–57 μg/m3 and 1.09– 1.28 mg/m3, respectively, and NAAQS-2012 and WHO do not set annual standards for these two pollutants. Compared to those observations at the urban sites, annual mean concentrations of PM10, PM2.5, SO2, NO2, O3, and CO at LYS were much lower (69, 57, 17, 21, and 31 μg/m3 and 0.65 mg/m3, respectively). However, the annual mean concentrations of PM10 and PM2.5 at LYS also exceeded the WHO guidelines (2.5–4.7 times higher), and the annual mean concentration of PM2.5 at LYS was 1.6 times of the NAAQS-2012 standard, reflecting the impacts from long-range transport of air pollutants on Chengdu’s air quality. The above analyses suggest that local emissions led to severe air pollution in
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Table 2 Air quality level (AQL) classification in China and in the USA Chinaa
USAb
When the AQI is in this range
…Air quality conditions are:
When the AQI is in this range
…Air quality conditions are:
0–50
Good
0–50
Good
51–100
Moderate
51–100
Moderate
101–150
Lightly polluted
101–150
Unhealthy for sensitive groups
151–200
Moderately polluted
151–200
Unhealthy
201–300
Heavily polluted
201–300
Very unhealthy
>300
Severely polluted
>300
Hazardous
a
MEP (2012c)
b
USEPA (2012)
the urban area, but air pollution in Chengdu was also related to regional air pollution. Daily or the maximum daily 8-h average (MDA8) concentrations of each pollutant at LYS (285–328 days valid) and in the urban area (332 days valid) are presented in Fig. 4. At LYS, the daily concentrations (mean±S.D.) of PM10, PM2.5, SO2, and NO2 were 72±42, 55±39, 17± 8, and 21±8 μg/m3, respectively, daily CO concentrations were 0.63±0.27 mg/m3, and MDA8 O3 concentrations were 55±39 μg/m3. Compared to the observations at LYS, the daily concentrations of PM10, PM2.5, SO2, and NO2 in the urban area were much higher (139±83,
90±61, 26±13, and 61±21 μg/m3, respectively). Daily concentrations of CO (1.20±0.52 mg/m3) and MDA8 concentrations of O3 in the urban area (113±58 μg/m3) were also much higher. Using these daily and MDA8 concentrations, we then calculated the compliance rates for each pollutant and classified AQL, and the results are presented in the following two sections. Compliance rates of air pollutants Compliance rates of each pollutant at LYS and in the urban area are presented in Fig. 5. The compliance rates
Fig. 4 Daily or MDA8 concentrations of PM10, PM2.5, NO2, SO2, O3, and CO at the background site (LYS) and in the urban areas of Chengdu between April 2013 and April 2014
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Fig. 5 Compliance rates of air pollutants at the background site (LYS) and in the urban area of Chengdu between April 2013 and April 2014
of PM10, PM2.5, SO2, and O3 were lower under the WHO guidelines than under the NAAQS-2012. Specifically, daily PM10 in the urban area met NAAQ S-2012 64 % of the time but met the WHO guideline only 7 % of the time. Daily PM2.5 in the urban area met NAAQS-2012 50 % of the time but met the WHO guideline only 3 % of the time. Daily concentrations of PM10 and PM2.5 at LYS met NAAQS-2012 (95 and 78 %, respectively), about two times more frequently than they met the WHO guidelines (35 and 24 %, respectively). Although daily SO2 at LYS and the urban area met China’s NAAQS-2012 all the time, only 68 % of days at LYS and 42 % of days in the urban area met the WHO guideline. MDA8 concentrations of O3 at LYS and the urban area met NAAQS-2012 (98 and 78 %, respectively) more frequently than they met the WHO guideline (89 and 54 %, respectively). The daily concentrations of NO2 and CO met NAAQS-2012 82–100 % of days, and WHO does not set daily guidelines for these two pollutants. As China uses weaker standards for PM10, PM2.5, SO2, and O3 compared to the WHO guidelines (Table 1), compliance rates of these four pollutants were higher based on the NAAQS-2012 (Fig. 5).
quality using the Chinese classification, and considerably fewer days were identified with a “good” level using the US classification (13 % of days at LYS and 1 day in the urban area). There were more days identified with a “moderate” air quality using China’s classification (45 % at LYS and 47 % in the urban area) than using the US classification (17 % at LYS and 32 % in the urban area). In contrast, there were fewer days having an air quality worse than “moderate” under China’s classification (23 % at LYS and 50 % in the urban area) than under the US classification (56 % at LYS and 83 % in the urban area). The top three polluted levels are “unhealthy,” “very unhealthy,” and “hazardous” in the USA and are “moderately polluted,” “heavily polluted,” and “severely polluted” in China. In the urban area, considerably more days were identified with the top three polluted levels using the US classification (unhealthy, 43 %; very unhealthy, 12 %; and hazardous, 2 %) than using the Chinese classification (moderately polluted, 10 %; heavily polluted, 12 %; and severely polluted, 2 %). The above analyses suggest that air pollution in Chengdu was estimated and stated to be less severe using China’s method compared to that using the US method.
AQLs Discussion The AQLs estimated using the Chinese and US classification methods are presented in Fig. 6. Using either the Chinese or the US classification, LYS and the urban area were polluted to a certain degree most of the time (>70 %). Only 30 % of days at LYS and 5 % of days in the urban area were identified with a “good” air
High risk from air pollution to human health in Chengdu As air pollution has high risk to human health in Chengdu, the municipal government has implemented
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Fig. 6 Air quality levels at the background site (LYS) and in the urban area of Chengdu between April 2013 and April 2014
a number of strategies to mitigate the pollution, and these strategies are presented at the Chengdu governmental Web site (http://www.chengdu.gov.cn/). For example, all industrial factories should have been relocated out of the urban area by the end of 2007, and coal combustion has been banned in the urban area. However, air pollution is still severe in Chengdu (Fig. 6), partially because most of the industrial factories in urban Chengdu were relocated to the Qingbaijiang industrial zone and Jintang county, both of which are in the region about 20 km upwind of urban Chengdu (Tao et al. 2014). PM10 and PM2.5 were the top air pollutants in urban Chengdu, which had annual mean concentrations 7–10 times of the WHO guidelines (Fig. 3), and they were influenced by similar source categories, including crustal dust, vehicular exhaust, secondary sulfate, secondary nitrate, and cement dust (Tian et al. 2013). The other pollutants were less important compared to PM, but compliance rates of daily SO2 and MDA8 O3 in urban Chengdu were only 42 and 54 % under the WHO guidelines, respectively (Fig. 5), and the annual mean concentrations of NO2 in urban Chengdu were about 1.5 times of the WHO guideline. It is well known that SO2 in China is mainly from coal combustion. Over 66 % of NO2 in urban Chengdu was from vehicle exhaust (Zhang et al. 2010) , as Chengdu has the third largest amount of private vehicles (~3.36 million in 2014) in China, following Beijing and Chongqing. O3 in urban Chengdu is mainly from photochemical oxidation of volatile organic compounds (VOCs) and CO in the presence of
NOx (Yan 2013). Although Chengdu is located in one of the four largest regions affected by haze in China (Zhang et al. 2012b), there is no epidemiological study to investigate the correlation of long- and short-term exposure to air pollutants with mortality, heart failure, and/or respiratory mortality. However, there are some epidemiological studies for the other three regions most affected by haze in China (Chen et al. 2011, 2012, 2013a; Wang et al. 2013; Zhou et al. 2013, 2014; Cai et al. 2014; Yang et al. 2014). As air pollutants in Chengdu are from miscellaneous sources and there is a lack of a relevant epidemiological study, joint efforts exerted by all walks of life, such as government, medical institutions, and academies, are needed to further understand and reduce air pollution impacts on human health. Limitations of China’s air quality standards When comparing China’s air quality standards to the WHO and US standards, it should be kept in mind that the WHO guidelines and the US AQL classification method also have their own limitations. NAAQS-2012 NAAQS was developed to assess the health threat of air pollution and to manage air quality, and the sufficiency of NAAQS influences the performance of air quality assessment and impacts the reactions of individuals and governmental managers to air pollution. Compared to the WHO guidelines, the standards of PM10, PM2.5,
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SO2, and O3 in China’s NAAQS-2012 are weaker, resulting in higher compliance rates (Fig. 3). Human health would still be at high risk if air pollutant concentrations meet the NAAQS-2012 but exceed the WHO guidelines. For example, China’s daily PM2.5 standard is 75 μg/m3, three times the WHO guideline (25 μg/m3), a concentration at which cardiopulmonary and lung cancer-related mortality have been shown to increase in response to long-term exposure with more than 95 % confidence (WHO 2005). Besides the guidelines, WHO also sets interim target (IT) values, which are proposed as incremental steps in a progressive reduction of air pollution and are intended for use in areas where pollution is high (WHO 2005) (Table 1). Taken PM2.5 for example, the WHO IT-1 value is 75 μg/m3, a concentration at which approximately a 5 % increase in shortterm mortality results compared to the WHO guideline; further, the WHO IT-2 and IT-3 values are 50 and 37.5 μg/m3, respectively (WHO 2005). At the early stage to mitigate air pollution, China presently uses the loosest IT standards of PM2.5, PM10, and O3. Although using the loosest IT values would be useful for China to achieve its incremental goals of air quality improvement, the compliance rate of each air pollutant under stricter standards should also be released to the public, since one of the most important goals of air quality assessment is to protect human health. AQL classification method The risk level of air pollution to human health can be underestimated and understated due to weak concentration breakpoints to calculate IAQI (Andrews 2009), vague and benign descriptions of AQL (Andrews 2009), the exclusion of certain pollutants (Andrews 2008, 2009), and ignoring the cumulative effect of multiple pollutants (Stieb et al. 2008; Chen et al. 2013b). Although China’s AQL classification method is mainly based on the US method, the concentration breakpoints are weaker in China (Table S1). For example, to reach a “good” AQL, daily PM2.5 concentration should be below 35 μg/m3 in China but below 15.4 μg/m3 in the USA. Due to weaker concentration breakpoints, there were more days in urban Chengdu identified having “good” and “moderate” air quality using China’s classification (5 and 45 %, respectively) than using the US classification (only 1 day and 17 %, respectively) (Fig. 6). The descriptions of AQL are supposed to clearly inform the public about the extent that air
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pollution threatens their health, but the descriptions used in China are vague and benign (Andrews 2009), and it would be hard for individuals to comprehend the threat extent directly from the terms “moderate,” “lightly polluted,” “moderately polluted,” “heavily polluted,” and “severely polluted.” In the USA, the descriptions are “good,” “moderate,” “unhealthy for sensitive groups,” “unhealthy,” “very unhealthy,” and “hazardous,” all of which more clearly describe the threat extent. Furthermore, both the Chinese and US methods do not capture the cumulative effects of multiple pollutants or reflect the apparent no-threshold concentration-response relationship which characterizes the association between air pollution and health (Stieb et al. 2008; Chen et al. 2013b). There is still much room to further improve China’s AQL classification method. Further improving air quality evaluation in China As discussed in sections “High risk from air pollution to human health in Chengdu” and “Limitations of China’s air quality standards,” to further improve China’s air quality evaluation, NAAQS needs to include stricter standards in addition to the loosest IT standards of WHO, the descriptions of AQL should be made more clear to clarify the extent that air pollution threatens human health, the concentration breakpoints to classify AQL need to be more stringent, and the cumulative effects of multiple pollutants on human health should also be considered in AQL classification. Besides the above, another effort is needed. Air quality standards for urban areas are developed based on quantitative studies of the relationship between air pollutant concentrations and human health. Environmental risk assessments typically include four steps: hazard identification, quantifying exposure-response relationship, exposure assessment, and risk estimation (US National Research Council (USNRC) 1983). Hazard identification is to identify if a negative health effect is caused by a given pollutant, the exposure-response relationship is to determine the relationship between the magnitude of exposure and the probability of occurrence of the health effects, exposure assessment is to determine the extent of human exposure, and risk estimation is to combine the information from the above three processes with the aim of determining the health risk for a given group of people (USNRC 1983). The exposure-response relationship differs among populations and is a function of not just exposure but also of the anatomic and
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physiological characteristics of the exposed population (Baldauf et al. 2001). The current risk assessment of air pollution in the developing countries of Asia is mainly based on the exposure-response relationship quantified in the North America and West Europe, bringing considerable uncertainties in the developing countries (Aunan and Pan 2004). More epidemiological studies are needed to well quantify the exposure-response relationship in China.
Conclusion In this study, we evaluated air quality in Chengdu using hourly concentrations of PM10, PM2.5, SO2, NO2, O3, and CO collected at one background site (LYS) and seven urban sites in Chengdu between April 11, 2013 and April 10, 2014. Air pollution is severe in Chengdu, and PM10 and PM2.5 were the top air pollutants at the seven urban sites, with annual mean concentrations 2–3 times of China’s NAAQS-2012 and 7–10 times of the WHO guideline. Compared to that of the urban area, annual mean concentrations of PM10, PM2.5, SO2, NO2, O3, and CO at the background site LYS were lower, but the annual mean concentrations of PM10 and PM2.5 at LYS also exceeded the WHO guidelines (2.5–4.7 times higher), and the annual mean concentration of PM2.5 at LYS was 1.6 times of the NAAQS-2012 standard, reflecting that long-range transport of air pollutants was also a considerable cause of air pollution in Chengdu. Compared to that calculated using the WHO guidelines, daily PM10, daily PM2.5, daily SO2, and MDA8 O3 in the urban area met China’s NAAQS2012 (64, 50, 100, and 78 %, respectively) much more frequently than they met the WHO guidelines (7, 3, 42, and 54 %, respectively). Compared to that classified using the US method, AQL in Chengdu was estimated and stated less severe using China’s method, due to weaker concentration breakpoints and benign descriptions of AQL. Furthermore, China’s AQL classification method does not capture the cumulative effects of multiple pollutants and was developed based on the exposure-response relationship between air pollution and human health quantified in the North America and West Europe, and these may lead to considerable uncertainties in evaluating the risk from air pollution to human health in China. In summary, although China greatly improved its NAAQS and AQL classification method in 2012, further improvements are still needed.
Environ Monit Assess (2015) 187:250 Acknowledgments This study is sponsored by the Program of Introducing Talents of Discipline to Universities (B08037), the International Program of the Ministry of Science and Technology of China (2010DFA91280), and the National Science Foundation of China (21407110). The authors would also like to thank the two anonymous reviewers for their valuable comments and suggestions.
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Evaluation of air quality in Chengdu, Sichuan Basin, China: are China’s air quality standards sufficient yet? Xue Qiao & Daniel Jaffe & Ya Tang & Meaghan Bresnahan & Jie Song
Received: 10 October 2014 / Accepted: 1 April 2015 # Springer International Publishing Switzerland 2015
Abstract Air quality evaluation is important in order to inform the public about the risk level of air pollution to human health. To better assess air quality, China released its new national ambient air quality standards (NAAQS2012) and the new method to classify air quality level (AQL) in 2012. In this study, we examined the performance of China’s NAAQS-2012 and AQL classification method through applying them, the World Health Organization (WHO) guidelines, and the US AQL classification method to evaluate air quality in Chengdu, the largest city in southwestern China. The results show that annual mean concentrations of PM10, PM2.5, SO2, NO2, and O3 at the seven urban sites were in the ranges of 138– 161, 87–98, 18–32, 54–70, and 42–57 μg/m3, respectively, and the annual mean concentrations of CO were in the range of 1.09–1.28 mg/m3. Chengdu is located in one Electronic supplementary material The online version of this article (doi:10.1007/s10661-015-4500-z) contains supplementary material, which is available to authorized users. X. Qiao : Y. Tang (*) Department of Environment, College of Architecture and Environment, Sichuan University, Chengdu 610065, China e-mail: [email protected] D. Jaffe Department of Atmospheric Sciences, University of Washington-Seattle, Seattle, WA 98195, USA M. Bresnahan Georgetown College, Georgetown University, 37th and O Streets, N.W., Washington, D.C. 20057, USA J. Song Taomee Holdings LTD, Shanghai 200233, China
of the four largest regions affected by haze in China, and PM10 and PM2.5 were the top air pollutants, with annual concentrations over 2 times of their standards in NAAQ S-2012 and over 7 times of the WHO guidelines. Annual mean concentrations of the pollutants were much lower at the background site (LYS) than at the urban sites, but the annual mean concentrations of PM10 and PM2.5 at LYS were 3.5 and 5.7 times of the WHO guidelines, respectively. These suggest that severe air pollution in Chengdu was largely associated with local emissions but also related to regional air pollution. The compliance rates of PM10, PM2.5, SO2, and O3 met China’s NAAQ S-2012 standards four times more frequently than they met the WHO guidelines, as NAAQS-2012 uses the loosest interim target (IT) standards of WHO for these four pollutants. Air pollution in Chengdu was estimated and stated to be less severe using China’s classification than using the US classification, as China uses weaker concentration breakpoints and benign descriptions of AQL. Furthermore, China’s AQL classification method does not capture the cumulative effects of multiple pollutants, and the risk assessment is mainly based on the exposure-response relationship between air pollutant and human health quantified in the North America and West Europe; these can bring some uncertainties into evaluating the risk to human health in China. In summary, although China greatly improved its NAAQS and AQL classification method in 2012, further improvements are still needed. Keywords National Ambient Air Quality Standards . Air quality level . Air pollution . Haze
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Introduction Since the 1979 economic reforms, China has achieved spectacular economic growth, leading to improved average living standards, decreased poverty, and longer life expectancy. However, this economic development has also caused significant environmental degradation, particularly urban air pollution (He et al. 2002; Chan and Yao 2008; Kan et al. 2012; Zhang et al. 2012a; Alcorn 2013). In the 1970s, industrialized Chinese cities began to suffer from smog (He et al. 2002). In the 1980s, acid rain and SO2 pollution caused by coal combustion became a serious problem in the country (He et al. 2002), and south China became one of the three largest acid rain affected regions in the world following the two regions in West Europe and North America (Wang and Wang 1995). Although China’s SO2 emissions started to decrease in 2006 (National Bureau of Statistics of China (NBSC) 2013), some regions of China still have the highest SO2 emissions in the world (Kurokawal et al. 2013). While acid rain and SO2 pollution continue to be severe (Ministry of Environment Protection (MEP) 2014), haze has intensified, shrouding one fourth of China’s land territory and affecting 600 million people (National Development and Reform Commission (NDRC) 2013). Owing to its basin landform (Fig. 1a) and high air pollutant emissions (Kurokawal et al. 2013), Sichuan Basin is one of the four regions that have suffered the most from haze in China, and the other three are as follows: (1) Hua Bei Plain in North China and the Guanzhong Plain, (2) East China with the main body in the Yangtze River Delta area, and (3) South China with most areas of Guangdong and the Pearl River Delta area (Zhang et al. 2012b). Sichuan Basin is also recognized as one of the world’s regions that is most polluted by PM2.5 (Battele Memorial Institute and Center for International Earth Science Information Network (BMICIESIN) 2013), which is the major pollutant that causes haze. Chengdu is the largest city in Sichuan Basin, with a population of 11.7 million and an area of 12.1 thousand km2 in 2012 (Chengdu Statistics Bureau (CSB) 2013). Although haze has long been recognized as a severe problem in Chengdu, PM2.5 was not regularly measured until March 30, 2012, and hourly and daily concentrations of other pollutants (e.g., SO2, NO2, CO, O3, and PM10) were not released to the public until January 2013. To preliminarily study the haze problem in Chengdu, we used a nephelometer (Radiance
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Research M903, USA) to monitor hourly PM2.5 concentrations in the Wangjiang campus of Sichuan University (SCU) from November 16, 2011 to November 16, 2012 (Fig. 1). During this period, the Chengdu Environmental Monitoring Station (CDEMS) started to release daily PM2.5 concentrations at two sites, namely, Da Shi Xi Road (DSXR) and Jun Ping Street (JPS) (Fig. 1). Based on these PM2.5 data collected at SCU, DSXR, and JPS, we noticed the discrepancy of air quality between residents’ perceptions of air quality and the governmental report (Fig. 2), and this discrepancy was believed to be largely related to the exclusion of PM2.5 in air quality level (AQL) classification then. For example, daily PM2.5 concentration was 71 μg/m3 at SCU on 9 March 2012 (about three times of the WHO guideline) and local residents perceived poor visibility, but the government reported an air quality level of “moderate.” In 2012, China released the new National Ambient Air Quality Standards (NAAQS-2012) (MEP 2012a, b) and the new AQL classification method (MEP 2012c), both of which for the first time included PM2.5, making air quality evaluation more stringent. However, we still question: are these new standards sufficient enough to inform the public about the risk level from air pollution to human health? The objectives of this study are as follows: (1) to apply NAAQS-2012 and the new AQL classification method to evaluate air quality in Chengdu and (2) to discuss the performance of these new standards based on the evaluation of Chengdu’s air quality.
Methods and materials Hourly concentrations of PM10, PM2.5, SO2, NO2, O3, and CO collected at eight sites between April 11, 2013 and April 10, 2014 were used to evaluate air quality for Chengdu. These eight sites include one background site (Lin Yanshan: LYS) and seven sites in the urban area (Fig. 1). The seven urban sites were DSXR, JPS, Jin Quan Liang He (JQLH), Liang Jia Xiang (LJX), Shi Li Dian (SLD), Sha He Pu (SHP), and San Wa Yao (SWY). Real-time hourly concentrations of air pollutants at these sites were derived from the Web site of CDEMS (www.cdemc.org/PM25. aspx). Since a considerable amount of hourly data were unavailable at each site (published as “NA” on the website) and air pollutant concentrations at the seven urban sites were generally similar (as shown in
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Fig. 1 Locations of Sichuan Basin (a), Chengdu (a), and the air quality monitoring sites (b)
Fig. 3), we averaged hourly concentrations at the seven urban sites for each pollutant to represent air quality in the entire urban area.
Compliance rate of each pollutant (compliance rate is the percent of air pollutant concentrations found to meet an environmental standard) and AQL were also
Fig. 2 Daily concentrations of PM2.5 at SCU, JPS, and DSXR and the air quality levels (AQLs) reported by the Chengdu government between November 2011 and January 2013
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Fig. 3 Hourly concentrations of PM10, PM2.5, NO2, SO2, O3, and CO at eight sites in Chengdu between April 2013 and April 2014
calculated for LYS and the urban area. To evaluate the performance of China’s NAAQS-2012, we compared the compliance rates calculated using the NAAQS2012 to those calculated using the WHO guidelines (Table 1). To assess the performance of China’s AQL classification method, we compared the AQLs classified using the Chinese method (MEP 2012c) to those classified using the US method (US Environment Protection Agency (USEPA) 2012), as the Chinese method is mainly based on the US method (Andrews 2009). To classify AQL for a given site, individual air quality index (IAQI) for each air pollutant is calculated first. To calculate IAQI for a given pollutant, the pollutant concentration between the concentration breakpoints is linearly interpolated using the Eq. (1) below. Although China and the USA both use the same equation, the two countries use different concentration breakpoints (Table S1). The highest IAQI among all the measured pollutants is identified as the
air quality index (AQI) for the given site. Based on AQI, AQL is classified into six levels (Table 2). The six levels are “good,” “moderate,” “lightly polluted,” “moderately polluted,” “heavily polluted,” and “severely polluted” in China, while they are “good,” “moderate,” “unhealthy for sensitive groups,” “unhealthy,” “very unhealthy,” and “hazardous” in the USA. IAQI ¼ Ilow þ Ihigh −Ilow ðCi −Clow Þ= Chigh −Clow
ð1Þ Definitions: Ci Clow Chigh Ilow Ihigh
concentration of i pollutant concentration breakpoint that is lower than Ci concentration breakpoint that is higher than Ci index breakpoint corresponding to Clow index breakpoint corresponding to Chigh.
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Table 1 Selected air pollutant standards for urban areas set by China and the World Health Organization (WHO) Items
TSP (μg/m3) PM10 (μg/m3) 3
PM2.5 (μg/m ) NOx (μg/m3)
3
NO2 (μg/m )
SO2 (μg/m3)
O3 (μg/m3) CO (mg/m3)
a
China’s
WHOb
NAAQS-2012a
Guideline
IT-3
IT-2
IT-1
High levelc
daily
300
-
-
-
-
-
Annual
200
-
-
-
-
-
daily
150
50
75
100
150
-
Annual
70
20
30
50
70
-
daily
75
25
37.5
50
75
-
Annual
35
10
15
25
35
-
Hourly
250
-
-
-
-
-
daily
100
-
-
-
-
-
Annual
50
-
-
-
-
-
Hourly
200
200
-
-
-
-
daily
80
-
-
-
-
-
Annual
40
40
-
-
-
-
10-minute
-
500
-
-
-
-
Hourly
500
-
-
-
-
-
3-hour
-
-
-
-
-
-
daily
150
20
-
50
125
-
Annual
60
-
-
-
-
-
Hourly
200
-
-
-
-
-
8-hour
160
100
-
-
160
240
Hourly
10
-
-
-
-
-
8-hour
-
-
-
-
-
-
daily
4
-
-
-
-
-
MEP (2012a)
b
WHO (2005)
c
Significant health effect
Results Air pollutant concentrations Hourly concentrations of each pollutant at each site are summarized in Fig. 3. Annual mean concentrations of PM10 and PM2.5 at the urban sites were in the ranges of 138–161 and 87–98 μg/m3, respectively, about 2–3 times of the NAAQS-2012 standards (70 and 35 μg/m3, respectively) and about 7–10 times of the WHO guidelines (20 and 10 μg/m3, respectively). Annual mean concentrations of SO2 at the urban sites were in the range of 18–32 μg/m3, lower than the NAAQS-2012 standard (60 μg/m3). Annual mean concentrations of NO2 at the urban sites were in the range of 54–70 μg/m3, about 1.2–1.9 times of 40 μg/m3, which is
the NAAQS-2012 standard and also the WHO guideline. Annual mean concentrations of O3 and CO at the urban sites were in the range of 42–57 μg/m3 and 1.09– 1.28 mg/m3, respectively, and NAAQS-2012 and WHO do not set annual standards for these two pollutants. Compared to those observations at the urban sites, annual mean concentrations of PM10, PM2.5, SO2, NO2, O3, and CO at LYS were much lower (69, 57, 17, 21, and 31 μg/m3 and 0.65 mg/m3, respectively). However, the annual mean concentrations of PM10 and PM2.5 at LYS also exceeded the WHO guidelines (2.5–4.7 times higher), and the annual mean concentration of PM2.5 at LYS was 1.6 times of the NAAQS-2012 standard, reflecting the impacts from long-range transport of air pollutants on Chengdu’s air quality. The above analyses suggest that local emissions led to severe air pollution in
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Table 2 Air quality level (AQL) classification in China and in the USA Chinaa
USAb
When the AQI is in this range
…Air quality conditions are:
When the AQI is in this range
…Air quality conditions are:
0–50
Good
0–50
Good
51–100
Moderate
51–100
Moderate
101–150
Lightly polluted
101–150
Unhealthy for sensitive groups
151–200
Moderately polluted
151–200
Unhealthy
201–300
Heavily polluted
201–300
Very unhealthy
>300
Severely polluted
>300
Hazardous
a
MEP (2012c)
b
USEPA (2012)
the urban area, but air pollution in Chengdu was also related to regional air pollution. Daily or the maximum daily 8-h average (MDA8) concentrations of each pollutant at LYS (285–328 days valid) and in the urban area (332 days valid) are presented in Fig. 4. At LYS, the daily concentrations (mean±S.D.) of PM10, PM2.5, SO2, and NO2 were 72±42, 55±39, 17± 8, and 21±8 μg/m3, respectively, daily CO concentrations were 0.63±0.27 mg/m3, and MDA8 O3 concentrations were 55±39 μg/m3. Compared to the observations at LYS, the daily concentrations of PM10, PM2.5, SO2, and NO2 in the urban area were much higher (139±83,
90±61, 26±13, and 61±21 μg/m3, respectively). Daily concentrations of CO (1.20±0.52 mg/m3) and MDA8 concentrations of O3 in the urban area (113±58 μg/m3) were also much higher. Using these daily and MDA8 concentrations, we then calculated the compliance rates for each pollutant and classified AQL, and the results are presented in the following two sections. Compliance rates of air pollutants Compliance rates of each pollutant at LYS and in the urban area are presented in Fig. 5. The compliance rates
Fig. 4 Daily or MDA8 concentrations of PM10, PM2.5, NO2, SO2, O3, and CO at the background site (LYS) and in the urban areas of Chengdu between April 2013 and April 2014
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Fig. 5 Compliance rates of air pollutants at the background site (LYS) and in the urban area of Chengdu between April 2013 and April 2014
of PM10, PM2.5, SO2, and O3 were lower under the WHO guidelines than under the NAAQS-2012. Specifically, daily PM10 in the urban area met NAAQ S-2012 64 % of the time but met the WHO guideline only 7 % of the time. Daily PM2.5 in the urban area met NAAQS-2012 50 % of the time but met the WHO guideline only 3 % of the time. Daily concentrations of PM10 and PM2.5 at LYS met NAAQS-2012 (95 and 78 %, respectively), about two times more frequently than they met the WHO guidelines (35 and 24 %, respectively). Although daily SO2 at LYS and the urban area met China’s NAAQS-2012 all the time, only 68 % of days at LYS and 42 % of days in the urban area met the WHO guideline. MDA8 concentrations of O3 at LYS and the urban area met NAAQS-2012 (98 and 78 %, respectively) more frequently than they met the WHO guideline (89 and 54 %, respectively). The daily concentrations of NO2 and CO met NAAQS-2012 82–100 % of days, and WHO does not set daily guidelines for these two pollutants. As China uses weaker standards for PM10, PM2.5, SO2, and O3 compared to the WHO guidelines (Table 1), compliance rates of these four pollutants were higher based on the NAAQS-2012 (Fig. 5).
quality using the Chinese classification, and considerably fewer days were identified with a “good” level using the US classification (13 % of days at LYS and 1 day in the urban area). There were more days identified with a “moderate” air quality using China’s classification (45 % at LYS and 47 % in the urban area) than using the US classification (17 % at LYS and 32 % in the urban area). In contrast, there were fewer days having an air quality worse than “moderate” under China’s classification (23 % at LYS and 50 % in the urban area) than under the US classification (56 % at LYS and 83 % in the urban area). The top three polluted levels are “unhealthy,” “very unhealthy,” and “hazardous” in the USA and are “moderately polluted,” “heavily polluted,” and “severely polluted” in China. In the urban area, considerably more days were identified with the top three polluted levels using the US classification (unhealthy, 43 %; very unhealthy, 12 %; and hazardous, 2 %) than using the Chinese classification (moderately polluted, 10 %; heavily polluted, 12 %; and severely polluted, 2 %). The above analyses suggest that air pollution in Chengdu was estimated and stated to be less severe using China’s method compared to that using the US method.
AQLs Discussion The AQLs estimated using the Chinese and US classification methods are presented in Fig. 6. Using either the Chinese or the US classification, LYS and the urban area were polluted to a certain degree most of the time (>70 %). Only 30 % of days at LYS and 5 % of days in the urban area were identified with a “good” air
High risk from air pollution to human health in Chengdu As air pollution has high risk to human health in Chengdu, the municipal government has implemented
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Fig. 6 Air quality levels at the background site (LYS) and in the urban area of Chengdu between April 2013 and April 2014
a number of strategies to mitigate the pollution, and these strategies are presented at the Chengdu governmental Web site (http://www.chengdu.gov.cn/). For example, all industrial factories should have been relocated out of the urban area by the end of 2007, and coal combustion has been banned in the urban area. However, air pollution is still severe in Chengdu (Fig. 6), partially because most of the industrial factories in urban Chengdu were relocated to the Qingbaijiang industrial zone and Jintang county, both of which are in the region about 20 km upwind of urban Chengdu (Tao et al. 2014). PM10 and PM2.5 were the top air pollutants in urban Chengdu, which had annual mean concentrations 7–10 times of the WHO guidelines (Fig. 3), and they were influenced by similar source categories, including crustal dust, vehicular exhaust, secondary sulfate, secondary nitrate, and cement dust (Tian et al. 2013). The other pollutants were less important compared to PM, but compliance rates of daily SO2 and MDA8 O3 in urban Chengdu were only 42 and 54 % under the WHO guidelines, respectively (Fig. 5), and the annual mean concentrations of NO2 in urban Chengdu were about 1.5 times of the WHO guideline. It is well known that SO2 in China is mainly from coal combustion. Over 66 % of NO2 in urban Chengdu was from vehicle exhaust (Zhang et al. 2010) , as Chengdu has the third largest amount of private vehicles (~3.36 million in 2014) in China, following Beijing and Chongqing. O3 in urban Chengdu is mainly from photochemical oxidation of volatile organic compounds (VOCs) and CO in the presence of
NOx (Yan 2013). Although Chengdu is located in one of the four largest regions affected by haze in China (Zhang et al. 2012b), there is no epidemiological study to investigate the correlation of long- and short-term exposure to air pollutants with mortality, heart failure, and/or respiratory mortality. However, there are some epidemiological studies for the other three regions most affected by haze in China (Chen et al. 2011, 2012, 2013a; Wang et al. 2013; Zhou et al. 2013, 2014; Cai et al. 2014; Yang et al. 2014). As air pollutants in Chengdu are from miscellaneous sources and there is a lack of a relevant epidemiological study, joint efforts exerted by all walks of life, such as government, medical institutions, and academies, are needed to further understand and reduce air pollution impacts on human health. Limitations of China’s air quality standards When comparing China’s air quality standards to the WHO and US standards, it should be kept in mind that the WHO guidelines and the US AQL classification method also have their own limitations. NAAQS-2012 NAAQS was developed to assess the health threat of air pollution and to manage air quality, and the sufficiency of NAAQS influences the performance of air quality assessment and impacts the reactions of individuals and governmental managers to air pollution. Compared to the WHO guidelines, the standards of PM10, PM2.5,
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SO2, and O3 in China’s NAAQS-2012 are weaker, resulting in higher compliance rates (Fig. 3). Human health would still be at high risk if air pollutant concentrations meet the NAAQS-2012 but exceed the WHO guidelines. For example, China’s daily PM2.5 standard is 75 μg/m3, three times the WHO guideline (25 μg/m3), a concentration at which cardiopulmonary and lung cancer-related mortality have been shown to increase in response to long-term exposure with more than 95 % confidence (WHO 2005). Besides the guidelines, WHO also sets interim target (IT) values, which are proposed as incremental steps in a progressive reduction of air pollution and are intended for use in areas where pollution is high (WHO 2005) (Table 1). Taken PM2.5 for example, the WHO IT-1 value is 75 μg/m3, a concentration at which approximately a 5 % increase in shortterm mortality results compared to the WHO guideline; further, the WHO IT-2 and IT-3 values are 50 and 37.5 μg/m3, respectively (WHO 2005). At the early stage to mitigate air pollution, China presently uses the loosest IT standards of PM2.5, PM10, and O3. Although using the loosest IT values would be useful for China to achieve its incremental goals of air quality improvement, the compliance rate of each air pollutant under stricter standards should also be released to the public, since one of the most important goals of air quality assessment is to protect human health. AQL classification method The risk level of air pollution to human health can be underestimated and understated due to weak concentration breakpoints to calculate IAQI (Andrews 2009), vague and benign descriptions of AQL (Andrews 2009), the exclusion of certain pollutants (Andrews 2008, 2009), and ignoring the cumulative effect of multiple pollutants (Stieb et al. 2008; Chen et al. 2013b). Although China’s AQL classification method is mainly based on the US method, the concentration breakpoints are weaker in China (Table S1). For example, to reach a “good” AQL, daily PM2.5 concentration should be below 35 μg/m3 in China but below 15.4 μg/m3 in the USA. Due to weaker concentration breakpoints, there were more days in urban Chengdu identified having “good” and “moderate” air quality using China’s classification (5 and 45 %, respectively) than using the US classification (only 1 day and 17 %, respectively) (Fig. 6). The descriptions of AQL are supposed to clearly inform the public about the extent that air
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pollution threatens their health, but the descriptions used in China are vague and benign (Andrews 2009), and it would be hard for individuals to comprehend the threat extent directly from the terms “moderate,” “lightly polluted,” “moderately polluted,” “heavily polluted,” and “severely polluted.” In the USA, the descriptions are “good,” “moderate,” “unhealthy for sensitive groups,” “unhealthy,” “very unhealthy,” and “hazardous,” all of which more clearly describe the threat extent. Furthermore, both the Chinese and US methods do not capture the cumulative effects of multiple pollutants or reflect the apparent no-threshold concentration-response relationship which characterizes the association between air pollution and health (Stieb et al. 2008; Chen et al. 2013b). There is still much room to further improve China’s AQL classification method. Further improving air quality evaluation in China As discussed in sections “High risk from air pollution to human health in Chengdu” and “Limitations of China’s air quality standards,” to further improve China’s air quality evaluation, NAAQS needs to include stricter standards in addition to the loosest IT standards of WHO, the descriptions of AQL should be made more clear to clarify the extent that air pollution threatens human health, the concentration breakpoints to classify AQL need to be more stringent, and the cumulative effects of multiple pollutants on human health should also be considered in AQL classification. Besides the above, another effort is needed. Air quality standards for urban areas are developed based on quantitative studies of the relationship between air pollutant concentrations and human health. Environmental risk assessments typically include four steps: hazard identification, quantifying exposure-response relationship, exposure assessment, and risk estimation (US National Research Council (USNRC) 1983). Hazard identification is to identify if a negative health effect is caused by a given pollutant, the exposure-response relationship is to determine the relationship between the magnitude of exposure and the probability of occurrence of the health effects, exposure assessment is to determine the extent of human exposure, and risk estimation is to combine the information from the above three processes with the aim of determining the health risk for a given group of people (USNRC 1983). The exposure-response relationship differs among populations and is a function of not just exposure but also of the anatomic and
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physiological characteristics of the exposed population (Baldauf et al. 2001). The current risk assessment of air pollution in the developing countries of Asia is mainly based on the exposure-response relationship quantified in the North America and West Europe, bringing considerable uncertainties in the developing countries (Aunan and Pan 2004). More epidemiological studies are needed to well quantify the exposure-response relationship in China.
Conclusion In this study, we evaluated air quality in Chengdu using hourly concentrations of PM10, PM2.5, SO2, NO2, O3, and CO collected at one background site (LYS) and seven urban sites in Chengdu between April 11, 2013 and April 10, 2014. Air pollution is severe in Chengdu, and PM10 and PM2.5 were the top air pollutants at the seven urban sites, with annual mean concentrations 2–3 times of China’s NAAQS-2012 and 7–10 times of the WHO guideline. Compared to that of the urban area, annual mean concentrations of PM10, PM2.5, SO2, NO2, O3, and CO at the background site LYS were lower, but the annual mean concentrations of PM10 and PM2.5 at LYS also exceeded the WHO guidelines (2.5–4.7 times higher), and the annual mean concentration of PM2.5 at LYS was 1.6 times of the NAAQS-2012 standard, reflecting that long-range transport of air pollutants was also a considerable cause of air pollution in Chengdu. Compared to that calculated using the WHO guidelines, daily PM10, daily PM2.5, daily SO2, and MDA8 O3 in the urban area met China’s NAAQS2012 (64, 50, 100, and 78 %, respectively) much more frequently than they met the WHO guidelines (7, 3, 42, and 54 %, respectively). Compared to that classified using the US method, AQL in Chengdu was estimated and stated less severe using China’s method, due to weaker concentration breakpoints and benign descriptions of AQL. Furthermore, China’s AQL classification method does not capture the cumulative effects of multiple pollutants and was developed based on the exposure-response relationship between air pollution and human health quantified in the North America and West Europe, and these may lead to considerable uncertainties in evaluating the risk from air pollution to human health in China. In summary, although China greatly improved its NAAQS and AQL classification method in 2012, further improvements are still needed.
Environ Monit Assess (2015) 187:250 Acknowledgments This study is sponsored by the Program of Introducing Talents of Discipline to Universities (B08037), the International Program of the Ministry of Science and Technology of China (2010DFA91280), and the National Science Foundation of China (21407110). The authors would also like to thank the two anonymous reviewers for their valuable comments and suggestions.
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