Wood smoke risk assessment: defining the questions.

Risk assessment provides a framework for combining and evaluating scientific data on source-to-health effects for contaminants that could potentially affect the health of human populations. It utilizes an integrated approach to hazard identification, dose response, exposure assessment, and risk characterization. Since the range of potential exposure scenarios is considerable, given the complexity of wood-smoke sources and emissions, there is a need for defining the critical characteristics for the key parameters leading to adverse health outcomes. During the International Biomass Smoke and Health Effects (IBSHE) conference at the University of Montana (August 2007), the breakout group entitled "Risk Assessment: Defining the Questions" was tasked with evaluating the current state of the science in regard to risk assessment involving biomass smoke exposure. As a result of these discussions, important data gaps and future research questions were identified that are reported in this article.

Evaluation of the use of diffusive air samplers for determining temporal and spatial variation of volatile organic compounds in the ambient air of urban communities.

The Houston-Galveston metropolitan area has a relatively high density of point and mobile sources of air toxics, and determining and understanding the relationship between emissions and ambient air concentrations of air toxics is important for evaluating potential impacts on public health and formulating effective regulatory policies to control this impact, both in this region and elsewhere. However, conventional ambient air monitoring approaches are limited with regard to expense, siting limitations, and representative sampling necessary for adequate exposure assessment. The overall goal of this multiphase study is to evaluate the use of simple passive air samplers to determine temporal and spatial variability of the ambient air concentrations of selected volatile organic compounds (VOCs) in urban areas. Phase 1 of this study, reported here, was a field evaluation of 3M organic vapor monitors (OVMs) involving limited comparisons with commonly used active sampling methods, an assessment of sampler precision, a determination of optimal sampling duration, and an investigation of the utility of a simple modification of the commercial sampler. The results indicated that a sampling duration of 72 hr exhibited generally low bias relative to automated continuous gas chromatography measurements, good overall precision, and an acceptable number of measurements above detection limits. The modified sampler showed good correlation with the commercial sampler, with higher sampling rates, although lower than expected.

Estimating volatile organic compound concentrations in selected microenvironments using time-activity and personal exposure data.

Repeated measures of personal exposure to 14 volatile organic compounds (VOC) were obtained over 3 seasons for 70 healthy, nonsmoking adults living in Minneapolis-St. Paul. Matched data were also available for participants' time-activity patterns, and measured VOC concentrations outdoors in the community and indoors in residences. A novel modeling approach employing hierarchical Bayesian techniques was used to estimate VOC concentrations (posterior mode) and variability (credible intervals) in five microenvironments: (1) indoors at home; (2) indoors at work/school; (3) indoors in other locations; (4) outdoors in any location; and (5) in transit. Estimated concentrations tended to be highest in "other" indoor microenvironments (e.g., grocery stores, restaurants, shopping malls), intermediate in the indoor work/school and residential microenvironments, and lowest in the outside and in-transit microenvironments. Model estimates for all 14 VOC were reasonable approximations of measured median concentrations in the indoor residential microenvironment. The largest predicted contributor to cumulative (2-day) personal exposure for all 14 VOC was the indoor residential environment. Model-based results suggest that indoors-at-work/school and indoors-at-other-location microenvironments were the second or third largest contributors for all VOC, while the outside-in-any-location and in-transit microenvironments appeared to contribute negligibly to cumulative personal exposure. Results from a mixed-effects model indicate that being in or near a garage increased personal exposure to o-xylene, m/p-xylene, benzene, ethylbenzene, and toluene, and leaving windows and doors at home open for 6 h or more decreased personal exposure to 13 of 14 VOC, all except trichloroethylene.

Source proximity and meteorological effects on residential outdoor VOCs in urban areas: Results from the Houston and Los Angeles RIOPA studies.

Concentrations of volatile organic compounds (VOCs) measured outside homes in Houston, TX and Los Angeles, CA were characterized by the effects of source proximity and meteorological factors. Benzene, toluene, ethylbenzene, m,p-xylene, o-xylene (BTEX), methyl tert butyl ether (MTBE), tetrachloroethylene (perchloroethylene, PCE), and carbon tetrachloride (CCl4) were examined. Multiple stepwise regression analysis converged the best-fit models with predictors from meteorological conditions and the proximity to specific point, area, and mobile sources on the residential outdoor VOC concentrations. Negative associations of wind speed with concentrations demonstrated the effect of dilution by high wind speed. Atmospheric stability increase was associated with concentration increase. Petrochemical source proximity was a significant predictor for BTEX and MTBE concentrations in Houston. Ethylbenzene and xylene source proximity was a significant predictor in Los Angeles. Close proximity to area sources such as scrap metal recycling or dry cleaning facilities increased the MTBE, PCE, and CCl4 concentrations in Houston and Los Angeles. Models for ethylbenzene, m,p-xylene, and MTBE in Houston, and benzene in Los Angeles explained that for the median values of the meteorological factors, homes closest to influential highways would have concentrations that were 1.7-2.2 fold higher than those furthest from these mobile emission sources. If the median distance to sources were used in the models, the VOC concentrations varied 1.7 to 6.6 fold as the meteorological conditions varied over the observed range. These results highlight that each urban area is unique and localized sources need to be carefully evaluated to understand potential contributions to VOC air concentrations near residences, which influence baseline indoor air concentrations and personal exposures. Results of this study could assist in the appropriate design of monitoring networks for community-level sampling. They may also improve the accuracy of exposure models linking emission sources with estimated pollutant concentrations at the residential level.

Relationship of Indoor, Outdoor and Personal Air (RIOPA) study: study design, methods and quality assurance/control results.

The Relationship of Indoor, Outdoor and Personal Air (RIOPA) Study was undertaken to evaluate the contribution of outdoor sources of air toxics, as defined in the 1990 Clean Air Act Amendments, to indoor concentrations and personal exposures. The concentrations of 18 volatile organic compounds (VOCs), 17 carbonyl compounds, and fine particulate matter mass (PM(2.5)) were measured using 48-h outdoor, indoor and personal air samples collected simultaneously. PM2.5 mass, as well as several component species (elemental carbon, organic carbon, polyaromatic hydrocarbons and elemental analysis) were also measured; only PM(2.5) mass is reported here. Questionnaires were administered to characterize homes, neighborhoods and personal activities that might affect exposures. The air exchange rate was also measured in each home. Homes in close proximity (<0.5 km) to sources of air toxics were preferentially (2:1) selected for sampling. Approximately 100 non-smoking households in each of Elizabeth, NJ, Houston, TX, and Los Angeles, CA were sampled (100, 105, and 105 respectively) with second visits performed at 84, 93, and 81 homes in each city, respectively. VOC samples were collected at all homes, carbonyls at 90% and PM(2.5) at 60% of the homes. Personal samples were collected from nonsmoking adults and a portion of children living in the target homes. This manuscript provides the RIOPA study design and quality control and assurance data. The results from the RIOPA study can potentially provide information on the influence of ambient sources on indoor air concentrations and exposure for many air toxics and will furnish an opportunity to evaluate exposure models for these compounds.

Relationships of Indoor, Outdoor, and Personal Air (RIOPA). Part I. Collection methods and descriptive analyses.

This study on the relationships of indoor, outdoor, and personal air (RIOPA) was undertaken to collect data for use in evaluating the contribution of outdoor sources of air toxics and particulate matter (PM) to personal exposure. The study was not designed to obtain a population-based sample, but rather to provide matched indoor, outdoor, and personal concentrations in homes that varied in their proximity to outdoor pollution sources and had a wide range of air exchange rates (AERs). This design allowed examination of relations among indoor, outdoor, and personal concentrations of air toxics and PM across a wide range of environmental conditions; the resulting data set obtained for a wide range of environmental pollutants and AERs can be used to evaluate exposure models. Approximately 100 households with residents who do not smoke participated in each of three cities in distinct locations expected to have different climates and housing characteristics: Elizabeth, New Jersey; Houston, Texas; and Los Angeles County, California. Questionnaires were administered to characterize homes, neighborhoods, and personal activities that might affect exposures. The concentrations of a suite of volatile organic compounds (VOCs) and carbonyl compounds, as well as the fraction of airborne particulate matter with a mass median aerodynamic diameter < or = 2.5 microm (PM2.5), were measured during continuous 48-hour sessions in which indoor, outdoor, and personal air samples were collected simultaneously. During the same 48-hour period, the AER (exchanges/hr; x hr(-1)) was determined in each home, and carbonyl compounds were measured inside vehicle cabins driven by a subset of the participants. In most of the homes, measurements were made twice, during two different seasons, to obtain a wide distribution of AERs. This report presents in detail the data collection methods, quality control measures, and initial analyses of data distributions and relations among indoor, outdoor, and personal concentrations. The results show that indoor sources dominated personal and indoor air concentrations of many measured VOCs and carbonyl compounds. For several measured species, personal concentrations were higher than either indoor or outdoor concentrations, indicating the presence of some sources closely related to personal activities. For some species there were no significant indoor sources in the majority of the homes; thus indoor concentrations were mainly determined by outdoor concentrations in these homes. The range of distributions of air concentrations for the measured VOCs, formaldehyde and acetaldehyde, PM2.5, and AERs were generally consistent with values reported previously in the literature. Thus associations derived from or models based on this data set that may link the influence of outdoor sources with indoor air concentrations of air toxics and PM2.5 can be relevant to other urban settings. The simultaneous measurements of indoor concentrations, outdoor concentrations, AERs, and room volumes allowed the use of a mass balance model, under the steady-state approximation, to mechanistically examine the relative contributions of indoor and outdoor sources to measured indoor concentrations on a home-by-home basis. Estimated indoor source strengths for VOCs and carbonyl compounds varied widely from home to home, consistent with the indoor-outdoor concentration patterns, as shown in scatter plots. The indoor source estimations agreed with published values for PM2.5 and with the general understanding of sources of VOCs and carbonyl compounds. The source strengths reported here, derived from hundreds of homes, are an important contribution to the literature on exposure to air toxics. For the first time for many compounds, these estimates present a cohesive set of measurements across a range of air toxics in paired indoor, outdoor, and personal samples along with AER and questionnaire results that can be used for future analyses of indoor air quality. The estimation of outdoor contributions to measured indoor concentrations provides insights about the relative importance of indoor and outdoor sources in determining indoor concentrations, the main determinant of personal exposure for most of the measured compounds. In this report simple statistical tests mainly of the pooled data were used to analyze differences by sampling site, emission source type, season, home type, and home age. Paired adult-child personal concentrations within the same home were also compared using the pooled data set. These analyses generated some intriguing results that warrant more in-depth investigation in the future.

A global survey of occupational health competencies and curriculum.

The World Health Organization has identified a worldwide shortage of occupational health professionals, but evidence suggests that the work and education of these professionals vary across countries. This survey examined the professional development of occupational physicians, occupational nurses, industrial hygienists, and ergonomists in terms of practice competencies and academic curriculum. Of 89 countries that received the survey, 48 (54%) responded. Important differences in competencies and curricula were identified for all groups. More competencies were identified more frequently in developed countries. Academic programs existed more often in developed countries, but curriculum contents varied. The study provides a concrete reference point for discussion and development of competencies and curriculum.

Outdoor, indoor, and personal exposure to VOCs in children.

We measured volatile organic compound (VOC) exposures in multiple locations for a diverse population of children who attended two inner-city schools in Minneapolis, Minnesota. Fifteen common VOCs were measured at four locations: outdoors (O), indoors at school (S), indoors at home (H), and in personal samples (P). Concentrations of most VOCs followed the general pattern O approximately equal to S < P less than or equal to H across the measured microenvironments. The S and O environments had the smallest and H the largest influence on personal exposure to most compounds. A time-weighted model of P exposure using all measured microenvironments and time-activity data provided little additional explanatory power beyond that provided by using the H measurement alone. Although H and P concentrations of most VOCs measured in this study were similar to or lower than levels measured in recent personal monitoring studies of adults and children in the United States, p-dichlorobenzene was the notable exception to this pattern, with upper-bound exposures more than 100 times greater than those found in other studies of children. Median and upper-bound H and P exposures were well above health benchmarks for several compounds, so outdoor measurements likely underestimate long-term health risks from children's exposure to these compounds.

Field method comparison between passive air samplers and continuous monitors for Vocs and NO2 in El Paso, Texas.

This study evaluates the performance of Model 3300 Ogawa Passive Nitrogen Dioxide (NO2) Samplers and 3M 3520 Organic Vapor Monitors (OVMs) by comparing integrated passive sampling concentrations to averaged hourly NO2 and volatile organic compound (VOC) measurements at two sites in El Paso, TX. Sampling periods were three time intervals (3-day weekend, 4-day weekday, and 7-day weekly) for three consecutive weeks. OVM concentrations were corrected for ambient pressure to account for higher elevation. Precise results (< 5% relative standard deviation, RSD) were found for NO2 measurements from collocated Ogawa samplers. Reproducibility was lower from duplicate OVMs for BTEX (benzene, toluene, ethylbenzene, and xylene isomers) VOCs (> or = 77% RSD for 2-day samples) with better precision for longer sampling periods. Comparison of Ogawa NO2 samplers with chemiluminescence measurements averaged over the same time period suggested potential calibration problems with the chemiluminescence analyzer. For BTEX species, generally good agreement was obtained between OVMs and automated-gas chromatograph (auto-GC) measurements. The OVMs successfully tracked increasing levels of VOCs recorded by the auto-GCs. However, except for toluene, OVM BTEX measurements generally exceeded their continuous counterparts with a mean bias of 5-10%. Although interpretation of the study results was limited due to small sample sizes, diffusion barrier influences caused by shelters that housed OVMs and differences in sampling heights between OVMs and auto-GC inlet may explain the overestimation.

Cancer risk disparities between hispanic and non-hispanic white populations: the role of exposure to indoor air pollution.

BACKGROUND: Hispanics are the fastest growing minority group in the United States; however, minimal information is available on their cancer risks from exposures to hazardous air pollutants (HAPs) and how these risks compare to risks to non-Hispanic whites. METHODS: We estimated the personal exposure and cancer risk of Hispanic and white adults who participated in the Relationships of Indoor, Outdoor, and Personal Air (RIOPA) study. We evaluated 12 of the sampled volatile organic compounds and carbonyls and identified the HAPs of most concern and their possible sources. Furthermore, we examined sociodemographic factors and building characteristics. RESULTS: Cumulative cancer risks (CCRs) estimated for Hispanics (median = 519 x 10(-6), 90th percentile = 3,968 x 10(-6)) and for whites (median = 443 x 10(-6), 90th percentile = 751 x 10(-6)) were much greater than the U.S. Environmental Protection Agency (EPA) benchmark of 10(-6). Cumulative risks were dominated by formaldehyde and p-dichlorobenzene (p-DCB) and, to a lesser extent, by acetaldehyde, chloroform, and benzene. Exposure to all of these compounds except benzene was primarily due to indoor residential sources. Hispanics had statistically higher CCRs than did whites (p

Passive dosimeters for nitrogen dioxide in personal/indoor air sampling: a review.

Accurate measurement of nitrogen dioxide concentrations in both outdoor and indoor environments, including personal exposures, is a fundamental step for linking atmospheric nitrogen dioxide levels to potential health and ecological effects. The measurement has been conducted generally in two ways: active (pumped) sampling and passive (diffusive) sampling. Diffusion samplers, initially developed and used for workplace air monitoring, have been found to be useful and cost-effective alternatives to conventional pumped samplers for monitoring ambient, indoor and personal exposures at the lower concentrations found in environmental settings. Since the 1970s, passive samplers have been deployed for ambient air monitoring in urban and rural sites, and to determine personal and indoor exposure to NO2. This article reviews the development of NO2 passive samplers, the sampling characteristics of passive samplers currently available, and their application in ambient and indoor air monitoring and personal exposure studies. The limitations and advantages of the various passive sampler geometries (i.e., tube, badge, and radial type) are also discussed. This review provides researchers and risk assessors with practical information about NO2 passive samplers, especially useful when designing field sampling strategies for exposure and indoor/outdoor air sampling.

Source proximity and outdoor-residential VOC concentrations: results from the RIOPA study.

Ambient volatile organic compound concentrations outside residences were measured in Elizabeth, New Jersey as part of the Relationship of Indoor, Outdoor, and Personal A:r (RIOPA) study to assess the influence of proximity of the residences to known ambient emissions sources. The closest distances between the outdoor samplers and emission sources were determined using Geographic Information Systems (GIS)techniques. Multiple regression models were developed for residential ambient concentrations of aromatic hydrocarbons (BTEX), methyl tert butyl ether (MTBE), and tetrachloroethylene (PCE). The natural log transformed ambient concentrations of BTEX were inversely associated with distances to major roadways with high traffic densities and gasoline stations, atmospheric stability, temperature, and wind speed. Ambient MTBE levels were associated with inverse distance to gas stations and interstate highways. Residential ambient PCE concentration was inversely associated with distance to dry cleaning facilities, atmospheric stability, temperature, wind speed, and relative humidity. The linear regression models that include proximity to emission sources and meteorological variables explained 16-45% of the overall variation of ambient residential VOC concentrations. Meteorological conditions, especially atmospheric stability and temperature, explained 60-90% of the total variation in the regression models. The residential ambient air concentrations were 1.5-4 times higher than the urban background levels outside homes very close (<50 m) to ambient emission sources where approximately 7% of the population live. However, the relative increase of risk for disease is small and variations in air concentration in the background urban atmosphere are greater than those from the proximity to roadways.

A comparison of asbestos and urban particulate matter in the in vitro modification of human alveolar macrophage antigen-presenting cell function.

The mechanism for how inhaled particles cause or exacerbate human diseases is not known. It is clear, however, that some particles are more bioactive than others. One possible mechanism may involve a modification of antigen-presenting cell function. In this study, 2 forms of asbestos (crocidolite and Libby amphibole) and PM(2.5) (an urban particle) were cultured with human alveolar macrophages (HAMs) to determine whether antigen-presenting cell (APC) function was altered. HAMs were exposed to the bioactive particles, asbestos and PM(2.5), for 24 hours, then isolated free of extracellular particulates and nonviable cells. Isolated HAMs were then cultured with autologous lymphocytes in an 11-day APC assay using tetanous toxoid as the antigen and the resulting culture supernatants were assayed for lymphocyte-derived cytokines. Asbestos exposure, regardless of type, up-regulated a TH1 lymphocyte-derived cytokine, interferon gamma (IFNgamma), and the TH2 lymphocyte-derived cytokines interleukin-4 (IL-4) and interleukin-13 (IL-13). PM(2.5) exposure up-regulated all 3 cytokines also. Although cytokine production levels were significantly higher for the treatment compared to control cultures as a group, there was extreme variability in the responses between subjects. In addition, there was no correlation between an individual's cells' response to asbestos verses PM, suggesting that more than one possible mechanism exists for a particle-induced APC effect and individual differential sensitivities to inhaled bioactive particles. This work supports the hypothesis that some inhaled particles can modify immune function by directly affecting APCs thus up-regulating the normal lymphocyte response to antigens in the lung.

Particulate matter immunomodulatory effects on autoantibody development in New Zealand mixed mice.

Particulate matter exposures have been linked to increased mortality and morbidity that may be associated with immune dysfunction. Therefore, Lupus-prone New Zealand mixed mice (NZM) were intranasally instilled with either 30 microl saline or 30 microl saline suspensions of 500 microg acid-washed PM 1648, PM 1648 or PM(2.5) collected in Houston, TX, once a week for 4 weeks. Lung injury, mortality, and various immune dysfuntions were assessed. Accelerated mortality was observed in the PM 1648 and PM(2.5) instilled mice compared to the acid-washed PM 1648 and saline-instilled mice. PM 1648 and PM(2.5) significantly suppressed the natural development of anti-nuclear antibodies in NZM mice at 16 weeks. IgG serum levels were significantly increased in the acid-washed PM 1648 instilled mice at 8 weeks following PM instillation compared to the saline-instilled group. In contrast, IgG serum levels were significantly decreased in the PM 1648 and PM(2.5) instilled mice at 8 weeks post-PM instillation as compared to the acid-washed PM 1648 instilled group. There were increases in the amount of immune cell infiltration, fibrosis and collagen deposition within the lungs of PM 1648 and PM(2.5) groups in comparison within the saline- and acid-washed PM 1648 instilled mice. These results demonstrate that PM has an immunosuppressive effect on the development of anti-nuclear autoantibodies and modulates the IgG responses in this model of autoimmune disease.

A comparison of murine and human alveolar macrophage responses to urban particulate matter.

There is increasing evidence linking mortality, increased asthma morbidity, and other respiratory disorders to increases in fine airborne particulate matter (PM) concentrations. However, there are only limited data dealing with the biological mechanisms that ultimately lead to the reported health effects. Rodents are frequently used as an animal model to help elucidate the mechanisms of toxicity that may provide clues for the understanding of PM toxicity in humans; however, the relationships between murine and human PM toxicity have not been established. PM is known to target the pulmonary epithelium and resident alveolar macrophages (AM). PM can initiate cytotoxic effects on the AM including apoptosis and necrosis, depending on the particle concentration, which may be central to the pathological effects just described. This study examined AM apoptosis and necrosis initiated by PM in AM from humans and BALB/c mice in an in vitro exposure model. Freshly isolated AM from human volunteers were incubated with seven different residual fractions of PM1648 derived from organic solvent extractions, high-temperature heating and acid digestions that change the surface characteristics of the original PM. These results were compared to the analogous murine experiments. The results suggested that, at the same concentration of PM, the trend of toxicity and the posttreatment effects observed in BALB/c and human AM have a similar pattern. Altering the surface chemistry by removal of one or more PM components, such as through the various treatments conducted in this study, is sufficient to alter PM bioactivity in both human and murine AM in a similar manner. In addition, the human and murine models were compared with regard to in vitro cytotoxicity using PM(2.5) particles. The cytotoxic PM(2.5) effects were identical in both human and mouse models. Regression analysis revealed that the BALB/c mouse is a suitable model for PM cytotoxicity of AM as it is a good predictive model for the human AM responses.

Surface components of airborne particulate matter induce macrophage apoptosis through scavenger receptors.

Epidemiology studies have linked mortality, increased asthma morbidity, and other respiratory disorders in urban areas to increases in fine airborne particulate matter (PM) concentrations. However, neither the bioactive components of PM nor the biological mechanisms of the reported health effects have been elucidated. A number of studies have implicated soluble metals, the strong acid fraction, and/or other components of PM as possible bioactive mediators. Alveolar macrophage (AM) apoptosis, mediated through scavenger receptors (SR), may be important in the response to inflammatory particles. Therefore, this study explores the hypothesis that organic and metallic components of PM induce apoptosis by interacting with SR. Freshly isolated AM from Balb/c mice were incubated with PM 1648 samples untreated or extracted with Milli-Q water, acetone, or cyclohexane, acid digested, or heated at 100 or 500 degrees C. Cell viability was assessed by trypan blue exclusion and apoptosis was demonstrated by examination of cell morphology and cell death ELISA. Untreated PM induced necrosis and apoptosis in AM. Treatment of PM by organic extraction, acid digestion, or high heat modified the particle surface composition and apoptosis was decreased. Apoptosis induced by untreated, acetone extracted, and high heat-treated PM was blocked by polyinosinic acid or 2F8 antibody. These results demonstrate that PM-induced apoptosis is mediated by Class A Type I/II SR. Altering the surface characteristics of PM interferes with recognition by SR, resulting in decreased apoptosis of AM. Therefore, altering the surface chemistry by removal of one or more PM components, such as the various treatments conducted in this study, is sufficient to alter PM bioactivity. These results may also help explain why PM from many different sources, with differences in composition, are all bioactive, since it is the overall matrix that is important, not just one component.

Inhalation exposures to acrylamide in biomedical laboratories.

This study evaluated airborne acrylamide exposures experienced by laboratory personnel using either crystalline or commercially available solutions of acrylamide to make polyacrylamide gels. Exposures were monitored for a short-term (15-min) sampling period, during the weighing of the crystalline acrylamide or the removal of the acrylamide solution from its original container, and a long-term period, during which a sample was collected for as long as the subject was potentially exposed to acrylamide. Mean air concentrations for the 15-min exposures were 7.20 +/- 5.64 micrograms/m3 and 5.81 +/- 4.53 micrograms/m3 for the users of crystalline and solution acrylamide, respectively, although this difference was not statistically significant (p > 0.05). Mean concentrations for the long-term exposures were 12.77 +/- 24.20 micrograms/m3 for workers employing crystalline acrylamide and 4.22 +/- 7.05 micrograms/m3 for personnel using acrylamide solutions. This difference was also not statistically significant. Although the results indicate that the research laboratory personnel were generally exposed to measurable concentrations of acrylamide, with several subjects exposed to elevated levels, the calculated 8-hour time-weighted average exposures were below current occupational exposure limits. However, because the neurotoxic effects of acrylamide are cumulative and it is a suspected carcinogen, all exposures should be kept as low as reasonably achievable.

Comparison of personal, indoor, and outdoor exposures to hazardous air pollutants in three urban communities.

Two-day average concentrations of 15 individual volatile organic compounds (VOCs) were measured concurrently in (a) ambient air in three urban neighborhoods, (b) air inside residences of participants, and (c) personal air near the breathing zone of 71 healthy, nonsmoking adults. The outdoor (O), indoor (I), and personal (P) samples were collected in the Minneapolis/St. Paul metropolitan area over three seasons (spring, summer, and fall) in 1999 using charcoal-based passive air samplers (3M model 3500 organic vapor monitors). A hierarchical, mixed-effects statistical model was used to estimate the mutually adjusted effects of monitor location, community, and season while accounting for within-subject and within-time-index (monitoring period) correlation. Outdoor VOC concentrations were relatively low compared to many other urban areas, and only minor seasonal differences were observed. A consistent pattern of P > I > O was observed across both communities and seasons for 13 of 15 individual VOCs (exceptions were carbon tetrachloride and chloroform). Results indicate that ambient VOC measurements at central monitoring sites can seriously underestimate actual exposures for urban residents, even when the outdoor measurements are taken in their own neighborhoods.

Evaluating differences between measured personal exposures to volatile organic compounds and concentrations in outdoor and indoor air.

Accurate estimation of human exposures to volatile organic compounds (VOCs) is a key element of strategies designed to protect public health from the adverse effects of hazardous air pollutants. The focus here is on examining the capability of three different exposure metrics (outdoor community concentrations, indoor residential concentrations, and a simple time-weighted model) to estimate observed personal exposures to 14 VOCs. The analysis is based on 2-day average concentrations of individual VOCs measured concurrently in outdoor (O) air in three urban neighborhoods, indoor (I) air in participant's residences, and personal (P) air near the breathing zone of 71 healthy, nonsmoking adults. A median of four matched P-I-O samples was collected for each study participant in Minneapolis/St. Paul over three seasons (spring, summer, and fall) in 1999 using charcoal-based passive air samplers (3M model 3500 organic vapor monitors). Results show a clear pattern for the 14 VOCs, with P > I > O concentrations. Intra-individual variability typically spanned at least an order of magnitude, and inter-individual variability spanned 2 or more orders of magnitude for each of the 14 VOCs. Although both O and I concentrations generally underestimated personal exposures, I concentrations provided a substantially better estimate of measured P concentrations. Mean squared error (MSE) as well as correlation measures were used to assess estimator performance at the subject-specific level, and hierarchical, mixed effects models were used to estimate the bias and variance components of MSE by tertile of personal exposure. Bias and variance both tended to increase in the upper third of the P exposure distribution for O versus P and I versus P. A simple time-weighted model incorporating measured concentrations in both outdoor community air and indoor residential air provided no improvement over I concentration alone for the estimation of P exposure.

Chlordanes in the indoor and outdoor air of three U.S. cities.

Indoor and outdoor concentrations of six chlordane components (trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor, oxychlordane, and MC5) were measured at 157 residences, all of which were inhabited by nonsmoking individuals, in three urban areas during June 1999-May 2000. The analyses were conducted on a subset of 48 h integrated samples collected in Los Angeles County, CA, Houston, TX, and Elizabeth, NJ within the Relationship of Indoor, Outdoor, and Personal Air (RIOPA) study. Both particle-bound (PM2.5; quartz fiber filter) and vapor-phase (PUF sorbant) chlordane concentrations were separately measured by GC/EI MS after solvent extraction. The outdoor (gas + particle) total chlordane (trans-chlordane + cis-chlordane + trans-nonachlor + cis-nonachlor) concentrations ranged from 0.036 to 4.27 ng m(-3) in Los Angeles County, from 0.008 to 11.00 ng m(-3) in Elizabeth, and from 0.062 to 1.77 ng m(-3) in Houston. The corresponding indoor total chlordane concentrations ranged from 0.037 to 112.0 ng m(-3) in Los Angeles County, from 0.260 to 31.80 ng m(-3) in Elizabeth, and from 0.410 to 38.90 ng m(-3) in Houston study homes. Geometric mean concentrations were higher in indoor air than outdoor air (1.98 vs 0.58 ng m(-3) in CA; 1.30 vs 0.17 ng m(-3) in NJ; 4.18 vs 0.28 ng m(-3) in TX), which suggests there are significant indoor sources of chlordane species in a subset of homes in each of the three cities. Calculated source strengths relate to home age, with the highest apparent indoor source strengths occurring in unattached single-family homes built during the period from 1945 to 1959. Principle indoor sources of chlordanes likely include volatilization from residues of indoor application of chlordanes and infiltration from subsurface and foundation application of chlordane-containing termiticides during home construction.