Concentrations Of Hazardous Air Pollutants Research Articles

Geographic information system-based determination of priority monitoring areas for hazardous air pollutants in an industrial city.

Industrial cities are hotspots for many hazardous air pollutants (HAPs), which are detrimental to human health. We devised an identification method to determine priority HAP monitoring areas using a comprehensive approach involving monitoring, modeling, and demographics. The methodology to identify the priority HAP monitoring area consists of two parts: (1) mapping the spatial distribution of selected categories relevant to the target pollutant and (2) integrating the distribution maps of various categories and subsequent scoring. The identification method was applied in Ulsan, the largest industrial city in South Korea, to identify priority HAP monitoring areas. Four categories related to HAPs were used in the method: (1) concentrations of HAPs, (2) amount of HAP emissions, (3) the contribution of industrial activities, and (4) population density in the city. This method can be used to select priority HAP monitoring areas for intensive monitoring campaigns, cohort studies, and epidemiological studies.

Wildfires Increase Concentrations of Hazardous Air Pollutants in Downwind Communities.

Due in part to climate change, wildfire activity is increasing, with the potential for greater public health impact from smoke in downwind communities. Studies examining the health effects of wildfire smoke have focused primarily on fine particulate matter (PM2.5), but there is a need to better characterize other constituents, such as hazardous air pollutants (HAPs). HAPs are chemicals known or suspected to cause cancer or other serious health effects that are regulated by the United States (US) Environmental Protection Agency. Here, we analyzed concentrations of 21 HAPs in wildfire smoke from 2006 to 2020 at 309 monitors across the western US. Additionally, we examined HAP concentrations measured in a major population center (San Jose, CA) affected by multiple fires from 2017 to 2020. We found that concentrations of select HAPs, namely acetaldehyde, acrolein, chloroform, formaldehyde, manganese, and tetrachloroethylene, were all significantly elevated on smoke-impacted versus nonsmoke days (P < 0.05). The largest median increase on smoke-impacted days was observed for formaldehyde, 1.3 μg/m3 (43%) higher than that on nonsmoke days. Acetaldehyde increased 0.73 μg/m3 (36%), and acrolein increased 0.14 μg/m3 (34%). By better characterizing these chemicals in wildfire smoke, we anticipate that this research will aid efforts to reduce exposures in downwind communities.

Hazardous air pollutants in transmission pipeline natural gas: an analytic assessment

Natural gas production occurs in specific regions of the US, after which it is processed and transported via an interconnected network of high-pressure interstate pipelines. While the presence of hazardous air pollutants (HAPs) in unprocessed, upstream natural gas has been documented, little has been published on their presence in the midstream natural gas supply. We systematically evaluated publicly available, industry-disclosed HAP composition data sourced from Federal Energy Regulatory Commission (FERC) natural gas infrastructure applications submitted between 2017 and 2020. Natural gas composition data from these filings represent approximately 45% of the US onshore natural gas transmission system by pipeline mileage. Given that reporting natural gas HAP composition data is not required by FERC, only 49% of approved expansion projects disclosed natural gas HAP composition data. Of those applications that disclosed composition data, HAP concentrations were typically reported as higher for separator flash gas and condensate tank vapor compared to liquefied natural gas and transmission-grade natural gas, with mean benzene concentrations of 1106, 7050, 77, and 37 ppm respectively. We also identified one pipeline operator that reports real-time HAP concentrations for its natural gas at five pipeline interconnection points. Similar to the FERC applications, this operator reported benzene, toluene, ethylbenzene, xylenes and hydrogen sulfide as present in transmission pipeline natural gas. Notably, mercury was also reported as detectable in 14% of real-time natural gas measurements but was not reported in any FERC applications. Given that transmission infrastructure releases natural gas during uncontrolled leaks and loss of containment events as well as during routine operations (e.g. blowouts and compressor station blowdowns), these gas composition data may serve as a critical component of air quality and health-focused evaluations of natural gas releases.

Concentrations, health risks, and sources of hazardous air pollutants in Seoul-Incheon, a megacity area in Korea

We conducted ambient monitoring of various hazardous air pollutants (HAPs) for 2 years (2013-2015) in two adjacent Korean cities in a megacity area: Seoul and Incheon. Measured HAPs included volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals (HMs). The objectives of this study were to evaluate the spatiotemporal variations of HAPs, to prioritize HAPs based on health risks, to identify sources using a receptor-based model, and to estimate source-specific risks. Overall, the HAP levels in Incheon were higher than those in Seoul. The concentrations of combustion-origin HAPs, such as PAHs and some HMs, were significantly higher during the heating period than during the non-heating period. However, most VOCs exhibited an opposite trend. Benzo[a]pyrene showed the highest cancer risk in both cities, followed by formaldehyde, arsenic, and benzene; trichloroethylene was the only species that exceeded the hazard quotient of 1. Cumulative cancer risks were 2.0 × 10-4 in Seoul and 2.7 × 10-4 in Incheon. Major sources and their contributions to each HAP concentration were estimated by positive matrix factorization modeling. Based on source-specific risk assessments, we suggest that both cities should give high priority to the control of traffic pollution and the supply of cleaner fuels in non-residential sectors. Reducing carbonyl concentrations in Seoul and industrial emissions in Incheon is also necessary. Establishing new ambient standards for benzo[a]pyrene and formaldehyde is worth considering as a long-term measure. This study provides scientific information on the occurrence, health risks, and sources of various HAPs in large urban areas.

Characterization and health impact assessment of hazardous air pollutants in residential areas near a large iron-steel industrial complex in Korea

Comprehensive air monitoring of hazardous air pollutants (HAPs) was conducted at four residential sites (three in the town and one in a suburb) in Pohang, where Korea's largest iron-steel industrial complex is located. The objectives of this study were to evaluate the occurrence and spatiotemporal distributions of HAPs and to identify important HAPs based on a health risk assessment. The 130 HAPs that were measured simultaneously included volatile organic compounds (VOCs), carbonyls, polycyclic aromatic hydrocarbons (PAHs), phthalates, and heavy metals (HMs). The impact of industrial emissions on the ambient levels of HAPs in Pohang appeared to be significant, because the concentrations of multiple HAPs at residential sites near the industrial complex were considerably higher than those at the suburban site. The concentrations of VOCs (except formaldehyde) and HMs did not exhibit a specific seasonal pattern, but PAH levels were generally 4–5 times higher in winter than in summer. The cumulative cancer risks posed by 28 HAPs averaged over the three residential sites and the suburban site were 2.3 × 10−4 and 1.6 × 10−4, respectively, both of which exceeded the tolerable risk criterion of 1 × 10−4. Benzo[a]pyrene posed the highest risk, followed by As, formaldehyde, benzene, and dibenz[a,h]pyrene. However, no single HAP exceeded the non-cancer risk criterion of 1. These results support the need for stricter controls on emissions of PAHs, VOCs, and HMs in Pohang, particularly for sources in the iron-steel industrial complex.

A Model-to-Monitor Evaluation of 2011 National-Scale Air Toxics Assessment (NATA).

Environmental research has widely utilized the ambient concentrations of hazardous air pollutants (HAPs) modeled by the National-Scale Air Toxics Assessment (NATA) program; however, limited studies have evaluated the model’s performance. This study aims to evaluate the model-to-monitor agreement of the 2011 NATA data with the monitoring data reported to the U.S. Environmental Protection Agency’s (EPA) Air Quality System (AQS). Concentrations of 27 representative HAPs measured at 274 sites in the U.S. in 2011 were merged with NATA data by census tract. The comparison consisted of two steps for each HAP: first, the model-monitor difference at each site was compared with the limit of quantitation (LOQ); second, the modeled annual average was compared to the 95% confidence interval of the monitored annual average. Nationally, NATA could predict national medians of most HAPs well; however, it was unable to capture high concentrations. At individual sites, a large portion of model-monitor differences was below the LOQs, indicating they were unquantifiable. Model-to-monitor agreement displayed inconsistent patterns in terms of chemical groups or EPA regions and was strongly impacted by the comparison methods. The substantial non-agreements of NATA predictions with monitoring data require caution in environmental epidemiology and justice studies that are based on NATA data.

Concentrations, sources and human health risk of inhalation exposure to air toxics in Edmonton, Canada

With concern about levels of air pollutants in recent years in the Capital Region of Alberta, an investigation of ambient concentrations, sources and potential human health risk of hazardous air pollutants (HAPs) or air toxics was undertaken in the City of Edmonton over a 5-year period (2009–2013). Mean concentrations of individual HAPs in ambient air including volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs) and trace metals ranged from 0.04 to 1.73 μg/m3, 0.01–0.54 ng/m3, and 0.05–3.58 ng/m3, respectively. Concentrations of benzene, naphthalene, benzo(a)pyrene (BaP), arsenic, manganese and nickel were far below respective annual Alberta Ambient Air Quality Objectives. Carcinogenic and non-carcinogenic risk of air toxics were also compared with risk levels recommended by regulatory agencies. Positive matrix factorization identified six air toxics sources with traffic as the dominant contributor to total HAPs (4.33 μg/m3, 42%), followed by background/secondary organic aerosol (SOA) (1.92 μg/m3, 25%), fossil fuel combustion (0.92 μg/m3, 11%). On high particulate air pollution event days, local traffic was identified as the major contributor to total HAPs compared to background/SOA and fossil fuel combustion. Carcinogenic risk values of traffic, background/SOA and metals industry emissions were above the USEPA acceptable level (1 × 10−6), but below a tolerable risk (1 × 10−4) and Alberta benchmark (1 × 10−5). These findings offer useful preliminary information about current ambient air toxics levels, dominant sources and their potential risk to public health; and this information can support policy makers in the development of appropriate control strategies if required.

Assessment of volatile organic compound and hazardous air pollutant emissions from oil and natural gas well pads using mobile remote and on-site direct measurements

Emissions of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) from oil and natural gas production were investigated using direct measurements of component-level emissions on pads in the Denver-Julesburg (DJ) Basin and remote measurements of production pad-level emissions in the Barnett, DJ, and Pinedale basins. Results from the 2011 DJ on-site study indicate that emissions from condensate storage tanks are highly variable and can be an important source of VOCs and HAPs, even when control measures are present. Comparison of the measured condensate tank emissions with potentially emitted concentrations modeled using E&P TANKS (American Petroleum Institute [API] Publication 4697) suggested that some of the tanks were likely effectively controlled (emissions less than 95% of potential), whereas others were not. Results also indicate that the use of a commercial high-volume sampler (HVS) without corresponding canister measurements may result in severe underestimates of emissions from condensate tanks. Instantaneous VOC and HAP emissions measured on-site on controlled systems in the DJ Basin were significantly higher than VOC and HAP emission results from the study conducted by Eastern Research Group (ERG) for the City of Fort Worth (2011) using the same method in the Barnett on pads with low or no condensate production. The measured VOC emissions were either lower or not significantly different from the results of studies of uncontrolled emissions from condensate tanks measured by routing all emissions through a single port monitored by a flow measurement device for 24 hr. VOC and HAP concentrations measured remotely using the U.S. Environmental Protection Agency (EPA) Other Test Method (OTM) 33A in the DJ Basin were not significantly different from the on-site measurements, although significant differences between basins were observed.Implications: VOC and HAP emissions from upstream production operations are important due to their potential impact on regional ozone levels and proximate populations. This study provides information on the sources and variability of VOC and HAP emissions from production pads as well as a comparison between different measurement techniques and laboratory analysis protocols. On-site and remote measurements of VOC and HAP emissions from oil and gas production pads indicate that measurable emissions can occur despite the presence of control measures, often as a result of leaking thief hatch seals on condensate tanks. Furthermore, results from the remote measurement method OTM 33A indicate that it can be used effectively as an inspection technique for identifying oil and gas well pads with large fugitive emissions.

Overview of the Benzene and Other Toxics Exposure (BEE-TEX) Field Study.

The Benzene and other Toxics Exposure (BEE-TEX) field study was an experimental campaign designed to demonstrate novel methods for measuring ambient concentrations of hazardous air pollutants (HAPs) in real time and to attribute these concentrations to quantified releases from specific emission points in industrial facilities while operating outside facility fence lines. BEE-TEX was conducted in February 2015 at three neighboring communities in the Houston Ship Channel of Texas, where a large number of petrochemical facilities are concentrated. The novel technologies deployed during BEE-TEX included: (1) tomographic remote sensing based on differential optical absorption spectroscopy; (2) real-time broadcasting of ambient air monitoring data over the World Wide Web; (3) real-time source attribution and quantification of HAP emissions based on either tomographic or mobile measurement platforms; and (4) the use of cultured human lung cells in vitro as portable indicators of HAP exposure.

Risk assessment of population inhalation exposure to volatile organic compounds and carbonyls in urban China

Over the past three decades, China has experienced rapid urbanization. The risks to its urban population posed by inhalation exposure to hazardous air pollutants (HAPs) have not been well characterized. Here, we summarize recent measurements of 16 highly prevalent HAPs in urban China and compile their distribution inputs. Based on activity patterns of urban Chinese working adults, we derive personal exposures. Using a probabilistic risk assessment method, we determine cancer and non-cancer risks for working females and males. We also assess the uncertainty associated with risk estimates using Monte Carlo simulation, accounting for variations in HAP concentrations, cancer potency factors (CPFs) and inhalation rates. Average total lifetime cancer risks attributable to HAPs are 2.27×10−4 (2.27 additional cases per 10,000 people exposed) and 2.93×10−4 for Chinese urban working females and males, respectively. Formaldehyde, 1,4-dichlorobenzene, benzene and 1,3-butadiene are the major risk contributors yielding the highest median cancer risk estimates, >1×10−5. About 70% of the risk is due to exposures occurring in homes. Outdoor sources contribute most to the risk of benzene, ethylbenzene and carbon tetrachloride, while indoor sources dominate for all other compounds. Chronic exposure limits are not exceeded for non-carcinogenic effects, except for formaldehyde. Risks are overestimated if variation is not accounted for. Sensitivity analyses demonstrate that the major contributors to total variance are range of inhalation rates, CPFs of formaldehyde, 1,4-dichlorobenzene, benzene and 1,3-butadiene, and indoor home concentrations of formaldehyde and benzene. Despite uncertainty, risks exceeding the acceptable benchmark of 1×10−6 suggest actions to reduce exposures. Future efforts should be directed toward large-scale measurements of air pollutant concentrations, refinement of CPFs and investigation of population exposure parameters. The present study is a first effort to estimate carcinogenic and non-carcinogenic risks of inhalation exposure to HAPs for the large working populations of Chinese cites.

Evaluation of the agreement between modeled and monitored ambient hazardous air pollutants in California

Elevated breast cancer incidence rates in urban areas have led to speculation regarding the potential role of air pollution. In order to inform the exposure assessment for a subsequent breast cancer study, we evaluated agreement between modeled and monitored hazardous air pollutants (HAPs). Modeled annual ambient concentrations of HAPs in California came from the US Environmental Protection Agency’s National Air Toxics Assessment database for 1996, 1999, 2002, and 2005 and corresponding monitored data from the California Air Resources Board’s air quality monitoring program. We selected 12 compounds of interest for our study and focused on evaluating agreement between modeled and monitored data, and of temporal trends. Modeled data generally underestimated the monitored data, especially in 1996. For most compounds agreement between modeled and monitored concentrations improved over time. We concluded that 2002 and 2005 modeled data agree best with monitored data and are the most appropriate years for direct use in our subsequent epidemiologic analysis.

A Fatal Flaw in the Clean Air Act: How the Clean Air Act Fails to Adequately Regulate Ambient Concentrations of Hazardous Air Pollutants

The Clean Air Act mandates that the U.S. Environmental Protection Agency regulate emissions of over 180 Hazardous Air Pollutants (HAPs). These HAPs are commonly used industrial chemicals and compounds with the potential to cause either cancer or other serious non-cancer health effects. Although EPA estimates that “on average, approximately 1 in every 20,000 people have an increased likelihood of contracting cancer as a result of breathing air toxins from outdoor sources if they were exposed to 2005 emission levels over the course of their lifetime,” EPA does not regulate or restrict emissions of these HAPs based on the health risks posed by ambient-air concentrations or actual exposures to these toxic substances. EPA does regulate emissions of these HAPs, but the primary regulatory tool is to impose technology-based emission controls on sources of these HAPs. Years after those controls are installed, evaluates the health risks remaining (i.e., residual risks) from facilities that emit the HAPs. Unfortunately, EPA does not evaluate these risks based on actual ambient concentrations of these pollutants; instead EPA bases their assessment on engineering calculations. EPA’s own research indicates that air pollution is posing significant health risks, particularly in urban areas. EPA should revise their program so as to restrict ambient concentrations of HAPs to levels that will provide adequate protection of public health.

Estimating Cancer Risk Increment from Air Pollutant Exposure for Sewer Workers Working in an Industrial City

Sewer construction in Taiwan lags other developed nations, and the authorities are undertaking major sewerage system construction projects in several cities. In Kaohsiung City, sewerage networks pass through residential, commercial and industrial areas. The composition of sewage thus is highly complicated. Eight target monitoring positions are chosen to analyze the compounds and concentrations of hazardous air pollutants. Pollutant concentrations are used to evaluate the cancer risk increment based on inhalation intake for sewer workers under using exhaust ventilation and wearing personal gas filtering equipment. GC/MS analysis confirmed that concentrations of benzene and trichloromethane compounds in sewer air for all the monitoring positions exceeded the minimum risk levels (MRLs) of 0.009 ppm benzene and 0.1 ppm trichloromethane, and the maximum concentrations reached 148.4 and 327.3 ppm, respectively. The cancer risks of benzene and trichloromethane for workers without personal protection approached 2.77-3.98×10^(-3) and 29.74-42.70×10^(-3), respectively. Through ventilation for 15 minutes and the wearing of gas filtering equipment, the cancer risks for benzene and trichloromethane were reduced to 0.0003-0.0004×10^(-3) and 0.0029-0.0041×10^(-3), respectively. The authorities thus must order all workers to follow a strict code of practice for sewer entry before entering sewer systems. This code of practice should include a minimum time for general exhaust ventilation and the use of personal protection equipment.

Do brain cancer rates correlate with ambient exposure levels of criteria air pollutants or hazardous air pollutants (HAPs)?

Age-adjusted brain cancer rates vary more than fourfold among US counties, but risk factors underlying this variation have not been identified. The only known risk factor for brain cancer is ionizing radiation at therapeutic dose levels. Lifestyle factors are not known to affect brain cancer risk; hypothetical risks from environmental or occupational exposures to numerous chemicals have been suggested, but no consistent results have emerged in populations exposed to chemicals via oral intake or inhalation. We investigated whether county-by-county brain cancer incidence rates and mortality rates were correlated with patterns of local ambient air pollution. We utilized central-site ambient measurement data for criteria air pollutants, and inhalation exposure concentrations of hazardous air pollutants (HAPs) as predicted by the US EPA National Air Toxics Assessment. We selected 30 HAPs that had been variously hypothesized in the context of a link to brain cancer risk. We also included a regression on density of domestic cattle populations given that viruses have been implicated in brain cancer and cattle are a well-known reservoir for a variety of viruses. The analyses yielded correlations that were mostly null or negative, with similar results obtained for brain cancer incidence and mortality rates. The cattle density correlations were slightly positive and statistically significant. Given the limitations of this exploratory analysis, further research is needed to investigate the role of environmental chemical exposures in brain cancer risk. Our findings suggest that county-by-county differences in air pollution exposure concentrations are not likely to be explanatory factors for variations in brain cancer rates.

Modeling population exposures to outdoor sources of hazardous air pollutants

Accurate assessment of human exposures is an important part of environmental health effects research. However, most air pollution epidemiology studies rely upon imperfect surrogates of personal exposures, such as information based on available central-site outdoor concentration monitoring or modeling data. In this paper, we examine the limitations of using outdoor concentration predictions instead of modeled personal exposures for over 30 gaseous and particulate hazardous air pollutants (HAPs) in the US. The analysis uses the results from an air quality dispersion model (the ASPEN or Assessment System for Population Exposure Nationwide model) and an inhalation exposure model (the HAPEM or Hazardous Air Pollutant Exposure Model, Version 5), applied by the US. Environmental protection Agency during the 1999 National Air Toxic Assessment (NATA) in the US. Our results show that the total predicted chronic exposure concentrations of outdoor HAPs from all sources are lower than the modeled ambient concentrations by about 20% on average for most gaseous HAPs and by about 60% on average for most particulate HAPs (mainly, due to the exclusion of indoor sources from our modeling analysis and lower infiltration of particles indoors). On the other hand, the HAPEM/ASPEN concentration ratio averages for onroad mobile source exposures were found to be greater than 1 (around 1.20) for most mobile-source related HAPs (e.g. 1, 3-butadiene, acetaldehyde, benzene, formaldehyde) reflecting the importance of near-roadway and commuting environments on personal exposures to HAPs. The distribution of the ratios of personal to ambient concentrations was found to be skewed for a number of the VOCs and reactive HAPs associated with major source emissions, indicating the importance of personal mobility factors. We conclude that the increase in personal exposures from the corresponding predicted ambient levels tends to occur near locations where there are either major emission sources of HAPs or when individuals are exposed to either on- or nonroad sources of HAPs during their daily activities. These findings underscore the importance of applying exposure-modeling methods, which incorporate information on time-activity, commuting, and exposure factors data, for the purposes of assigning exposures in air pollution health studies.

Characteristics of major volatile organic hazardous air pollutants in the urban air of Kaohsiung city

The concentrations and characteristics of volatile organic hazardous air pollutants (HAPs) in the urban city of Kaohsiung from motor vehicles and dense pollutant sources has become a national concern. To continuously monitor volatile organic HAPs, sampling sites were selected near the four air-quality monitoring stations established by Ethe nvironmental Protection Administration of Taiwan ROC, namely Nan-tz, Tso-ying, San-min and Hsiao-kang, from north to south. An on-site automated online monitor of volatile organic compounds (VOCs) was used for continuous monitoring. This study performed two consecutive days of 24-h monitoring of five volatile organic HAPs form August to October 2005 at the four monitoring sites, which cover the northern, central, and southern areas of Kaohsiung city. The average monitored concentration was 2.78-4.84 ppb for benzene, 5.90-9.66 ppb for toluene, 3.62-5.90 ppb for ethylbenzene, 3.73-5.34 ppb for m,p-xylene, 3.38-4.22 ppb for o-xylene, and 4.48-7.00 ppb for styrene. The average monitored concentrations of the major volatile organic HAPs tended to follow the pattern San-min > Nan-tz > Hsiao-kang > Tso-ying. Among all the species monitored in this study, toluene had the highest ambient concentration, followed by styrene, m,p-xylene, ethylbenzene, o-xylene, and benzene. The results showed that the concentration at night was higher than that in the day for toluene at Nan-tz, San-min, Hsiao-kang, and for benzene at Nan-tz and Hsiao-kang.

Background Concentrations of 18 Air Toxics for North America

The U.S. Clean Air Act identifies 188 hazardous air pollutants (HAPs), or “air toxics,” associated with adverse human health effects. Of these air toxics, 18 were targeted as the most important in a 10–City Pilot Study conducted in 2001 and 2002 as part of the National Air Toxics Trend Sites Program. In the present analysis, measurements available from monitoring networks in North America were used to estimate boundary layer background concentrations and trends of these 18 HAPs. The background concentrations reported in this study are as much as 85% lower than those reported in recent studies of HAP concentrations. Background concentrations of some volatile organic compounds were analyzed for trends at the 95% confidence level; only carbon tetrachloride (CCI4) and tetrachloroethylene decreased significantly in recent years. Remote background concentrations were compared with the one-in–a-million (i.e., 10–6) cancer benchmarks to determine the possible causes of health risk in rural and remote areas; benzene, chloroform, formaldehyde, and chromium (Cr) fine particulate were higher than cancer benchmark values. In addition, remote background concentrations were found to contribute between 5% and 99% of median urban concentrations.

A human health assessment of hazardous air pollutants in Portland, OR

Ambient air samples collected from five monitoring sites in Portland, OR during July 1999 to August 2000 were analyzed for 43 hazardous air pollutants (HAP). HAP concentrations were compared to carcinogenic and non-carcinogenic benchmark levels. Carcinogenic benchmark concentrations were set at a risk level of one-in-one-million (1×10 −6). Hazard ratios of 1.0 were used when comparing HAP concentrations to non-carcinogenic benchmarks. Emission sources (point, area, and mobile) were identified and a cumulative cancer risk and total hazard index were calculated for HAPs exceeding these health benchmark levels. Seventeen HAPs exceeded a cancer risk level of 1×10 −6 at all five monitoring sites. Nineteen HAPs exceeded this level at one or more site. Carbon tetrachloride, 1,3-butadiene, formaldehyde, and 1,1,2,2-tetrachloroethane contributed more than 50% to the upper-bound lifetime cumulative cancer risk of 2.47×10 −4. Acrolein was the only non-carcinogenic HAP with hazard ratios that exceeded 1.0 at all five sites. Mobile sources contributed the greatest percentage (68%) of HAP emissions. Additional monitoring and health assessments for HAPs in Portland, OR are warranted, including addressing issues that may have overestimated or underestimated risks in this study. Abatement strategies for HAPs that exceeded health benchmarks should be implemented to reduce potential adverse health risks.

INVESTIGATING HAZARDOUS AIR POLLUTANTS IN RELATION TO AUTISM SPECTRUM DISORDERS

ISEE-554 Introduction: The number of cases of autism appears to be increasing dramatically, but the causes remain largely unknown, raising concern that environmental factors may play a role. Substances that are known or suspected to affect neurodevelopment may be important, as well as those that interfere with the endocrine system during fetal development. We are linking data compiled by the USEPA on hazardous air pollutants (HAPs) to our autism surveillance system data to investigate possible associations between autism and prenatal exposures. Methods: As part of a national CDC-sponsored network, we are conducting multi-source surveillance of autism spectrum disorders (ASD) among children born in 1994 in six counties. For this project we include initial cases ascertained from the state Department of Developmental Services and the Kaiser Permanente Medical Care Program. Liveborn controls are selected from linked birth-infant death vital records, frequency matched to cases by gender and month of birth, in a 2:1 ratio. Address at birth, as recorded on the birth certificate, is geo-coded to obtain census tract for linkage. The USEPA has estimated outdoor air concentrations of various HAPs by census tract nationwide, based on modeling emission inventory and meteorological data. We used the 1996 database, because it is closest to 1994, which includes 33 pollutants. Results: We ascertained about 350 ASD cases and selected appropriate controls, so over 1000 births are included. The cases were predominantly male (82%), as expected. By race, the sample includes 63% Whites, with cases slightly more likely to be Asian or Black than controls. Parents of cases were less likely to be young or to have only a high school education than control parents. We identified HAPs with known or suspected neurotoxicity or developmental toxicity, and assessed whether there was variation in concentration across the 1228 census tracts in the region. This yielded 16 compounds, including heavy metals, volatile organic compounds, and PAH’s. We will examine categorical levels of the pollutants, individually and grouped by type, by demographic factors from the birth certificate and case-control status. Odds ratios will be calculated, including adjustment for selected factors. Discussion: This study efficiently addresses issues of great concern, namely investigating the potential environmental risk factors associated with autism and the health effects of urban air pollution. We are using methodology consistent with environmental health tracking programs.

Childhood cancer incidence rates and hazardous air pollutants in California: an exploratory analysis.

Hazardous air pollutants (HAPs) are compounds shown to cause cancer or other adverse health effects. We analyzed population-based childhood cancer incidence rates in California (USA) from 1988 to 1994, by HAP exposure scores, for all California census tracts. For each census tract, we calculated exposure scores by combining cancer potency factors with outdoor HAP concentrations modeled by the U.S. Environmental Protection Agency. We evaluated the relationship between childhood cancer rates and exposure scores for 25 potentially carcinogenic HAPs emitted from mobile, area, and point sources and from all sources combined. Our study period saw 7,143 newly diagnosed cancer cases in California; of these, 6,989 (97.8%) could be assigned to census tracts and included in our analysis. Using Poisson regression, we estimated rate ratios (RRs) adjusted for age, race/ethnicity, and sex. We found little evidence for elevated cancer RRs for all sites or for gliomas among children living in high-ranking combined-source exposure areas. We found elevated RRs and a significant trend with increasing exposure level for childhood leukemia in tracts ranked highest for exposure to the combined group of 25 HAPs (RR = 1.21; 95% confidence interval, 1.03, 1.42) and in tracts ranked highest for point-source HAP exposure (RR = 1.32; 95% confidence interval, 1.11, 1.57). Our findings suggest an association between increased childhood leukemia rates and high HAP exposure, but studies involving more comprehensive exposure assessment and individual-level exposure data will be important for elucidating this relationship.