Validity of ambient levels of fine particles as surrogate for personal exposure to outdoor air pollution--results of the European EXPOLIS-EAS Study (Swiss Center Basel)

Comparing human exposure to fine particulate matter in low and high-income countries: A systematic review of studies measuring personal PM2.5 exposure

BACKGROUND

Due to the adverse health effects of air pollution, researchers have advocated for personal exposure measurements whereby individuals carry portable monitors in order to better characterise and understand the sources of people's pollution exposure.

OBJECTIVES

The aim of this systematic review is to assess the differences in the magnitude and sources of personal PM2.5 exposures experienced between countries at contrasting levels of income.

METHODS

This review summarised studies that measured participants personal exposure by carrying a PM2.5 monitor throughout their typical day. Personal PM2.5 exposures were summarised to indicate the distribution of exposures measured within each country income category (based on low (LIC), lower-middle (LMIC), upper-middle (UMIC), and high (HIC) income countries) and between different groups (i.e. gender, age, urban or rural residents).

RESULTS

From the 2259 search results, there were 140 studies that met our criteria. Overall, personal PM2.5 exposures in HICs were lower compared to other countries, with UMICs exposures being slightly lower than exposures measured in LMICs or LICs. 34% of measured groups in HICs reported below the ambient World Health Organisation 24-h PM2.5 guideline of 15 μg/m3, compared to only 1% of UMICs and 0% of LMICs and LICs. There was no difference between rural and urban participant exposures in HICs, but there were noticeably higher exposures recorded in rural areas compared to urban areas in non-HICs, due to significant household sources of PM2.5 in rural locations. In HICs, studies reported that secondhand smoke, ambient pollution infiltrating indoors, and traffic emissions were the dominant contributors to personal exposures. While, in non-HICs, household cooking and heating with biomass and coal were reported as the most important sources.

CONCLUSION

This review revealed a growing literature of personal PM2.5 exposure studies, which highlighted a large variability in exposures recorded and severe inequalities in geographical and social population subgroups.

Deconstruction of annoyance due to air pollution by multiple correspondence analyses

Annoyance caused by air pollution is a matter of public health as it can cause stress and ill-health and affect quality of life, among other burdens. The aim of this study is to apply the multiple correspondence analyses (MCA) technique as a differential tooling to explore relationships between variables that can influence peoples' behaviour concerning annoyance caused by air pollution. Data were collected through a survey on air pollution, environmental issues and quality of life. Face-to-face survey studies were conducted in two industrialized urban areas (Vitoria in Brazil and Dunkirk in France). These two regions were chosen as their inhabitants often report feeling annoyed by air pollution, and both regions have similar industrial characteristics. The results showed a progressive correspondence between levels of annoyance and other active variables in the "air pollution" factor group: as the levels of annoyance increased, the levels of the other qualitative variables (importance of air quality, perceived exposure to industrial risk, assessment of air quality, perceived air pollution) also increased. Respondents who reported feeling annoyed by air pollution also thought that air quality was very important and were very concerned about exposure to industrial risks. Furthermore, they often assessed air quality as horrible, and they could frequently perceive air pollution by dust, odours and decreased visibility. The results also showed a statistically significant association between occurrence of allergies and high levels of annoyance.

Effects of Asian dust-derived particulate matter on ST-elevation myocardial infarction: retrospective, time series study

Background

Dust storms affect human health by impairing visibility and promoting interactions with microscopic organisms, such as bacteria and fungi. Although ST-elevation MI (STEMI) and non-ST-elevation MI (NSTEMI) differ mechanistically, few studies have investigated the incidence of cardiovascular diseases according to infarction type; these studies have yielded inconsistent findings. This study aimed to examine whether PM size (< 2.5 μm (PM_2.5) and < 10 μm (PM₁₀)) modifies the effect of Asian dust on acute myocardial infarction (AMI), with separate analyses for STEMI and NSTEMI.

Methods

MI-related data from 9934 emergency visits were collected from the Korea AMI Registry from 2005 to 2017. Asian dust events were defined as days with visibility of ≤10 km. Generalized linear models were used to analyze data with natural cubic splines. To examine potential modifiers, analyses were stratified by age, smoking status, and body mass index (BMI).

Results

No significant associations were observed between Asian dust and AMI. By adjusting for different lag structures, a significant effect was exclusively observed in STEMI. For moving average lags, the largest value at lag 5 (relative risk [RR] 1.083; 95% confidence interval [CI], 1.007–1.166) for single and lags 0–7 (RR 1.067; 95% CI: 1.002–1.136) was observed for PM_2.5; for PM₁₀, the largest significant effect was observed at lag 4 (RR 1.075; 95% CI: 1.010–1.144) for single and lags 0–7 (RR 1.067; 95% CI: 1.002–1.136). RRs were significantly higher in < 65-year-olds than in ≥65-year-olds. Additionally, RRs between the BMI < 25 and BMI ≥ 25 groups were not different; statistically significant effects were observed for concentration at lags 0–5 (RR: 1.073; 95% CI: 1.002–1.150) and lags 0–6 (RR: 1.071; 95% CI: 1.001–1.146) in the BMI < 25 group. A negative exposure-response association was observed between daily average visibility-adjusted PM and STEMI and daily average visibility-adjusted PM in < 65-year-olds.

Conclusions

Reducing PM_2.5 and PM₁₀ emissions, particularly during the days of Asian dust, may be crucial and reduce STEMI and AMI incidence among < 65-year-olds. These results indicate that the Asian dust alarm system needs revision to protect vulnerable populations.

Indoor, outdoor, and personal exposure to PM2.5 and their bioreactivity among healthy residents of Hong Kong

Direct evidence about associations between fine particles (PM_2.5) components and the corresponding PM_2.5 bioreactivity at the individual level is limited. We conducted a panel study with repeated personal measurements involving 56 healthy residents in Hong Kong. Fractional exhaled nitric oxide (FeNO) levels were measured from these subjects. Out of 56 subjects, 27 (48.2%) participated in concurrent outdoor, indoor, and personal PM_2.5 monitoring. Organic carbon (OC), elemental carbon (EC), particle bound-polycyclic aromatic hydrocarbons (PAHs), and phthalates were analyzed. Alteration in cell viability, lactic dehydrogenase (LDH), interleukin-6 (IL-6), and 8-isoprostane by 50 μg/mL PM_2.5 extracts was determined in A549 cells in vitro. Moderate heterogeneities were shown in PM_2.5 exposures and the corresponding PM_2.5 bioreactivity across different sample types. Associations between the analyzed components and PM_2.5 bioreactivity were assessed using the multiple regression models. Toxicological results revealed that indoor and personal exposure to OC as well as PAH compounds and their derivatives (e.g., Alkyl-PAHs, Oxy-PAHs) induced cell viability reduction and increase in levels of LDH, IL-6, and 8-isoprostane. Overall, OC in personal exposure played a dominant role in PM_2.5-induced bioreactivity. Subsequently, we examined the associations of FeNO with IL-6 and 8-isoprostane levels using mixed-effects models. The results showed that per interquartile change in IL-6 and 8-isoprostane were associated with a 6.4% (p < 0.01) and 11.1% (p < 0.01) increase in FeNO levels, respectively. Our study explored the toxicological properties of chemical components in PM_2.5 exposure, which suggested that residential indoors and personal OC and PAHs should be of great concern for human health. These findings indicated that further studies in inflammation and oxidative stress-related illnesses due to particle exposure would benefit from the assessment of in vitro PM_2.5 bioreactivity.

PM2.5 and NO2 exposure errors using proxy measures, including derived personal exposure from outdoor sources: A systematic review and meta-analysis

BACKGROUND

The use of proxy exposure estimates for PM_2.5 and NO₂ in air pollution studies instead of personal exposures, introduces measurement error, which can produce biased epidemiological effect estimates. Most studies consider total personal exposure as the gold standard. However, when studying the effects of ambient air pollution, personal exposure from outdoor sources is the exposure of interest.

OBJECTIVES

We assessed the magnitude and variability of exposure measurement error by conducting a systematic review of the differences between personal exposures from outdoor sources and the corresponding measurements for ambient concentrations in order to increase understanding of the measurement error structures of the pollutants.

DATA SOURCES AND ELIGIBILITY CRITERIA

We reviewed the literature (ISI Web of Science, Medline, 2000-2016) for English language studies (in any age group in any location (NO₂) or Europe and North America (PM_2.5)) that reported repeated measurements over time both for personal and ambient PM_2.5 or NO₂ concentrations. Only a few studies reported personal exposure from outdoor sources. We also collected data for infiltration factors and time-activity patterns of the individuals in order to estimate personal exposures from outdoor sources in every study.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies using modelled rather than monitored exposures were excluded. Type of personal exposure monitor was assessed. Random effects meta-analysis was conducted to quantify exposure error as the mean difference between "true" and proxy measures.

RESULTS

Thirty-two papers for PM_2.5 and 24 for NO₂ were identified. Outdoor sources were found to contribute 44% (range: 33-55%) of total personal exposure to PM_2.5 and 74% (range: 57-88%) to NO₂. Overall estimates of personal exposure (24-hour averages) from outdoor sources were 9.3 μg/m³ and 12.0 ppb for PM_2.5 and NO₂ respectively, while the corresponding difference between these exposures and the ambient concentrations (i.e. the measurement error) was 5.72 μg/m³ and 7.17 ppb. Our findings indicated also higher error variability for NO₂ than PM_2.5. Large heterogeneity was observed which was not explained sufficiently by geographical location or age group of the study sample.

LIMITATIONS, CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Relying only on information available in published studies led to some limitations: the contribution of outdoor sources to total personal exposure for NO₂ had to be inferred, individual variation in exposure misclassification was unavailable and instrument error could not be addressed. The larger magnitude and variability of errors for NO₂ compared with PM_2.5 has implications for biases in the health effect estimates of multi-pollutant epidemiological models. Results suggest that further research is needed regarding personal exposure studies and measurement error bias in epidemiological models.

Reduction of personal PM2.5 exposure via indoor air filtration systems in Detroit: an intervention study

The adverse health effects of fine particulate matter (PM < 2.5 μm in diameter [PM_2.5]) air pollution are well-documented. There is a growing body of evidence that high-efficiency particulate arrestance (HEPA) filtration can reduce indoor PM_2.5 concentrations and deliver some health benefits via the reduction of exposure to PM. However, few studies have tested the ability of portable air filtration systems to lower overall personal-level PM_2.5 exposures. The Reducing Air Pollution in Detroit Intervention Study (RAPIDS) was designed to evaluate cardiovascular health benefits and personal PM_2.5 exposure reductions via indoor portable air filtration systems among senior citizens in Detroit, Michigan. We evaluated the utility of two commercially available high-efficiency (HE: true-HEPA) and low-efficiency (LE: HEPA-type) indoor air filtration to reduce indoor PM_2.5 concentrations and personal PM_2.5 exposures for 40 participants in a double-blinded randomized crossover intervention. Each participant was subjected to three intervention scenarios: HE, LE, or no filter (control) of three consecutive days each, during which personal, indoor, and outdoor PM_2.5 concentrations were measured daily. For mean indoor PM_2.5 concentrations, we observed 60 and 52% reductions using HE and LE filters, respectively, relative to no filtration. Personal PM_2.5 exposures were reduced by 53 and 31% using HE and LE filters, respectively, when compared with the control scenario. To our knowledge, this is the first indoor air filtration intervention study to examine the effectiveness of both HE and LE filters in reducing personal PM_2.5 exposures.

Wood stove use and other determinants of personal and indoor exposures to particulate air pollution and ozone among elderly persons in a Northern Suburb

A six-month winter-spring study was conducted in a suburb of the northern European city of Kuopio, Finland, to identify and quantify factors determining daily personal exposure and home indoor levels of fine particulate matter (PM_2.5 , diameter <2.5 µm) and its light absorption coefficient (PM_2.5abs ), a proxy for combustion-derived black carbon. Moreover, determinants of home indoor ozone (O₃ ) concentration were examined. Local central site outdoor, home indoor, and personal daily levels of pollutants were monitored in this suburb among 37 elderly residents. Outdoor concentrations of the pollutants were significant determinants of their levels in home indoor air and personal exposures. Natural ventilation in the detached and row houses increased personal exposure to PM_2.5 , but not to PM_2.5abs , when compared with mechanical ventilation. Only cooking out of the recorded household activities increased indoor PM_2.5 . The use of a wood stove room heater or wood-fired sauna stove was associated with elevated concentrations of personal PM_2.5 and PM_2.5abs , and indoor PM_2.5abs . Candle burning increased daily indoor and personal PM_2.5abs , and it was also a determinant of indoor ozone level. In conclusion, relatively short-lasting wood and candle burning of a few hours increased residents' daily exposure to potentially hazardous, combustion-derived carbonaceous particulate matter.

Estimation of personal exposure to fine particles (PM2.5) of ambient origin for healthy adults in Hong Kong

Personal exposure and ambient fine particles (PM_2.5) measurements for 13 adult subjects (ages 19-57) were conducted in Hong Kong between April 2014 and June 2015. Six to 21 personal samples (mean = 19) per subject were obtained throughout the study period. Samples were analyzed for mass by gravimetric analysis, and 19 elements (from Na to Pb) were analyzed using X-Ray Fluorescence. Higher subject-specific correlations between personal and ambient sulfur (r_s = 0.92; p < 0.001) were found as compared to PM_2.5 mass (r_s = 0.79; p < 0.001) and other elements (0.06 < r_s < 0.86). Personal vs. ambient sulfur regression yielded an average exposure factor (F_pex) of 0.73 ± 0.02, supporting the use of sulfur as a surrogate to estimate personal exposure to PM_2.5 of ambient origin (E_a). E_a accounted for 41-82% and 57-73% of total personal PM_2.5 exposures (P) by season and by subject, respectively. The importance of both E_a and non-ambient exposures (E_na, 11.2 ± 5.6 μg/m³; 32.5 ± 10.9%) are noted. Mixed-effects models were applied to estimate the relationships between ambient PM_2.5 concentrations and their corresponding exposure variables (E_a, P). Higher correlations for E_a (0.90; p < 0.001) than for P (0.58; p < 0.01) were found. A calibration coefficient < 1 suggests an attenuation of 22% (ranging 16-28%) of the true effect estimates when using average ambient concentrations at central monitoring stations as surrogates for E_a. Stationary ambient data can be used to assess population exposure only if PM exposure is dominated by E_a.

Estimation of personal PM2.5 and BC exposure by a modeling approach - Results of a panel study in Shanghai, China

BACKGROUND

Epidemiologic studies of PM_2.5 (particulate matter with aerodynamic diameter ≤2.5 μm) and black carbon (BC) typically use ambient measurements as exposure proxies given that individual measurement is infeasible among large populations. Failure to account for variation in exposure will bias epidemiologic study results. The ability of ambient measurement as a proxy of exposure in regions with heavy pollution is untested.

OBJECTIVE

We aimed to investigate effects of potential determinants and to estimate PM_2.5 and BC exposure by a modeling approach.

METHODS

We collected 417 24 h personal PM_2.5 and 130 72 h personal BC measurements from a panel of 36 nonsmoking college students in Shanghai, China. Each participant underwent 4 rounds of three consecutive 24-h sampling sessions through December 2014 to July 2015. We applied backwards regression to construct mixed effect models incorporating all accessible variables of ambient pollution, climate and time-location information for exposure prediction. All models were evaluated by marginal R² and root mean square error (RMSE) from a leave-one-out-cross-validation (LOOCV) and a 10-fold cross-validation (10-fold CV).

RESULTS

Personal PM_2.5 was 47.6% lower than ambient level, with mean (±Standard Deviation, SD) level of 39.9 (±32.1) μg/m³; whereas personal BC (6.1 (±2.8) μg/m³) was about one-fold higher than the corresponding ambient concentrations. Ambient levels were the most significant determinants of PM_2.5 and BC exposure. Meteorological and season indicators were also important predictors. Our final models predicted 75% of the variance in 24 h personal PM_2.5 and 72 h personal BC. LOOCV analysis showed an R² (RMSE) of 0.73 (0.40) for PM_2.5 and 0.66 (0.27) for BC. Ten-fold CV analysis showed a R² (RMSE) of 0.73 (0.41) for PM_2.5 and 0.68 (0.26) for BC.

CONCLUSION

We used readily accessible data and established intuitive models that can predict PM_2.5 and BC exposure. This modeling approach can be a feasible solution for PM exposure estimation in epidemiological studies.

Maternal exposure to PM2.5 in south Texas, a pilot study

In this study, we characterized personal exposure to fine particulate matter (PM_2.5), black carbon (BC), and nicotine in pregnant women in Hidalgo County, where the hospitalization rates of childhood asthma are the highest in the state of Texas. The measurements were conducted over three non-consecutive sampling days for 17 participants in their third trimester. Measurements were partitioned into four microenvironments, i.e., Residential, Vehicular, Commercial, and Other, on the basis of GPS coordinates and temperature and humidity measurements. The daily average PM_2.5 mass concentration was 24.2 (standard deviation=22.0) μg/m³, with the highest daily mass concentration reaching 126.0μg/m³. The daily average BC concentration was 1.44 (SD=0.82) μg/m³, ranging from 0.5 to 5.4μg/m³. Hair nicotine concentrations were all near the detection level (i.e., 49.2pg/mg), indicating that the participants were not routinely exposed to tobacco smoke. The Residential microenvironment contributed dominantly to the mass concentration since the participants chiefly remained at home and cooking activities contributed significantly to the total PM_2.5. When compared to an ambient monitoring station, the person-specific PM_2.5 was frequently more than double the ambient measurement (10.4μg/m³ overall), revealing that even in regions where ambient concentrations are below national standards, individuals may be still be exposed to elevated PM_2.5 mass concentrations.

Different relationships between personal exposure and ambient concentration by particle size

Ambient particulate matter (PM) concentrations at monitoring stations were often used as an indicator of population exposure to PM in epidemiological studies. The correlation between personal exposure and ambient concentrations of PM varied because of diverse time-activity patterns. The aim of this study was to determine the relationship between personal exposure and ambient concentrations of PM₁₀ and PM_2.5 with minimal impact of time-activity pattern on personal exposure. Performance of the MicroPEM, v3.2 was evaluated by collocation with central ambient air monitors for PM₁₀ and PM_2.5. A field technician repeatedly conducted measurement of 24 h personal exposures to PM₁₀ and PM_2.5 with a fixed time-activity pattern of office worker over 26 days in Seoul, Korea. The relationship between the MicroPEM and the ambient air monitor showed good linearity. Personal exposure and ambient concentrations of PM_2.5 were highly correlated with a fixed time-activity pattern compared with PM₁₀. The finding implied a high infiltration rate of PM_2.5 and low infiltration rate of PM₁₀. The relationship between personal exposure and ambient concentrations of PM₁₀ and PM_2.5 was different for high level episodes. In the Asian dust episode, staying indoors could reduce personal exposure to PM₁₀. However, personal exposure to PM_2.5 could not be reduced by staying indoors during the fine dust advisory episode.

Personal exposure to fine particulate matter concentrations in central business district of a tropical coastal city

In the present study, personal exposure to fine particulate matter (particulate matter with an aerodynamic diameter <2.5 μm [PM_2.5]) concentrations in an urban hotspot (central business district [CBD]) was investigated. The PM monitoring campaigns were carried out at an urban hotspot from June to October 2015. The personal exposure monitoring was performed during three different time periods, i.e., morning (8 a.m.-9 a.m.), afternoon (12.30 p.m.-1.30 p.m.), and evening (4 p.m.-5 p.m.), to cover both the peak and lean hour activities of the CBD. The median PM_2.5 concentrations were 38.1, 34.9, and 40.4 µg/m³ during the morning, afternoon, and evening hours on the weekends. During weekdays, the median PM_2.5 concentrations were 59.5, 29.6, and 36.6 µg/m³ in the morning, afternoon, and evening hours, respectively. It was observed that the combined effect of traffic emissions, complex land use, and micrometeorological conditions created localized air pollution hotspots. Furthermore, the total PM_2.5 lung dose levels for an exposure duration of 1 hr were 8.7 ± 5.7 and 12.3 ± 5.2 µg at CBD during weekends and weekdays, respectively, as compared with 2.5 ± 0.8 µg at the urban background (UB). This study emphasizes the need for mobile measurement for short-term personal exposure assessment complementing the fixed air quality monitoring.

IMPLICATIONS

Personal exposure monitoring at an urban hotspot indicated space and time variation in PM concentrations that is not captured by the fixed air quality monitoring networks. The short-term exposure to higher concentrations can have a significant impact on health that need to be considered for the health risk-based air quality management. The study emphasizes the need of hotspot-based monitoring complementing the already existing fixed air quality monitoring in urban areas. The personal exposure patterns at hotspots can provide additional insight into sustainable urban planning.

Integrating travel behavior with land use regression to estimate dynamic air pollution exposure in Hong Kong

BACKGROUND

Epidemiological studies typically use subjects' residential address to estimate individuals' air pollution exposure. However, in reality this exposure is rarely static as people move from home to work/study locations and commute during the day. Integrating mobility and time-activity data may reduce errors and biases, thereby improving estimates of health risks.

OBJECTIVES

To incorporate land use regression with movement and building infiltration data to estimate time-weighted air pollution exposures stratified by age, sex, and employment status for population subgroups in Hong Kong.

METHODS

A large population-representative survey (N = 89,385) was used to characterize travel behavior, and derive time-activity pattern for each subject. Infiltration factors calculated from indoor/outdoor monitoring campaigns were used to estimate micro-environmental concentrations. We evaluated dynamic and static (residential location-only) exposures in a staged modeling approach to quantify effects of each component.

RESULTS

Higher levels of exposures were found for working adults and students due to increased mobility. Compared to subjects aged 65 or older, exposures to PM_2.5, BC, and NO₂ were 13%, 39% and 14% higher, respectively for subjects aged below 18, and 3%, 18% and 11% higher, respectively for working adults. Exposures of females were approximately 4% lower than those of males. Dynamic exposures were around 20% lower than ambient exposures at residential addresses.

CONCLUSIONS

The incorporation of infiltration and mobility increased heterogeneity in population exposure and allowed identification of highly exposed groups. The use of ambient concentrations may lead to exposure misclassification which introduces bias, resulting in lower effect estimates than 'true' exposures.

Characterization of emissions from a desktop 3D printer and indoor air measurements in office settings

Emissions from a desktop 3D printer based on fused deposition modeling (FDM) technology were measured in a test chamber and indoor air was monitored in office settings. Ultrafine aerosol (UFA) emissions were higher while printing a standard object with polylactic acid (PLA) than with acrylonitrile butadiene styrene (ABS) polymer (2.1 × 10(9) vs. 2.4 × 10(8) particles/min). Prolonged use of the printer led to higher emission rates (factor 2 with PLA and 4 with ABS, measured after seven months of occasional use). UFA consisted mainly of volatile droplets, and some small (100-300 nm diameter) iron containing and soot-like particles were found. Emissions of inhalable and respirable dust were below the limit of detection (LOD) when measured gravimetrically, and only slightly higher than background when measured with an aerosol spectrometer. Emissions of volatile organic compounds (VOC) were in the range of 10 µg/min. Styrene accounted for more than 50% of total VOC emitted when printing with ABS; for PLA, methyl methacrylate (MMA, 37% of TVOC) was detected as the predominant compound. Two polycyclic aromatic hydrocarbons (PAH), fluoranthene and pyrene, were observed in very low amounts. All other analyzed PAH, as well as inorganic gases and metal emissions except iron (Fe) and zinc (Zn), were below the LOD or did not differ from background without printing. A single 3D print (165 min) in a large, well-ventilated office did not significantly increase the UFA and VOC concentrations, whereas these were readily detectable in a small, unventilated room, with UFA concentrations increasing by 2,000 particles/cm(3) and MMA reaching a peak of 21 µg/m(3) and still being detectable in the room even 20 hr after printing.

Sources of indoor air pollution in New York City residences of asthmatic children

Individuals spend ∼90% of their time indoors in proximity to sources of particulate and gaseous air pollutants. The sulfur tracer method was used to separate indoor concentrations of particulate matter (PM) PM2.5 mass, elements and thermally resolved carbon fractions by origin in New York City residences of asthmatic children. Enrichment factors relative to sulfur concentrations were used to rank species according to the importance of their indoor sources. Mixed effects models were used to identify building characteristics and resident activities that contributed to observed concentrations. Significant indoor sources were detected for OC1, Cl, K and most remaining OC fractions. We attributed 46% of indoor PM2.5 mass to indoor sources related to OC generation indoors. These sources include cooking (NO2, Si, Cl, K, OC4 and OP), cleaning (most OC fractions), candle/incense burning (black carbon, BC) and smoking (K, OC1, OC3 and EC1). Outdoor sources accounted for 28% of indoor PM2.5 mass, mainly photochemical reaction products, metals and combustion products (EC, EC2, Br, Mn, Pb, Ni, Ti, V and S). Other indoor sources accounted for 26% and included re-suspension of crustal elements (Al, Zn, Fe, Si and Ca). Indoor sources accounted for ∼72% of PM2.5 mass and likely contributed to differences in the composition of indoor and outdoor PM2.5 exposures.

Modelling of human exposure to air pollution in the urban environment: a GPS-based approach

The main objective of this work was the development of a new modelling tool for quantification of human exposure to traffic-related air pollution within distinct microenvironments by using a novel approach for trajectory analysis of the individuals. For this purpose, mobile phones with Global Positioning System technology have been used to collect daily trajectories of the individuals with higher temporal resolution and a trajectory data mining, and geo-spatial analysis algorithm was developed and implemented within a Geographical Information System to obtain time-activity patterns. These data were combined with air pollutant concentrations estimated for several microenvironments. In addition to outdoor, pollutant concentrations in distinct indoor microenvironments are characterised using a probabilistic approach. An example of the application for PM2.5 is presented and discussed. The results obtained for daily average individual exposure correspond to a mean value of 10.6 and 6.0-16.4 μg m(-3) in terms of 5th-95th percentiles. Analysis of the results shows that the use of point air quality measurements for exposure assessment will not explain the intra- and inter-variability of individuals' exposure levels. The methodology developed and implemented in this work provides time-sequence of the exposure events thus making possible association of the exposure with the individual activities and delivers main statistics on individual's air pollution exposure with high spatio-temporal resolution.

Progress on understanding spatial and temporal variability of PM(2.5) and its components in the Detroit Exposure and Aerosol Research Study (DEARS)

The Detroit Exposure and Aerosol Research Study (DEARS) measured personal exposures, ambient, residential indoor and residential outdoor concentrations of select PM2.5 aerosol components (SO4, NO3, Fe, Si, Ca, K, Mn, Pb, Zn, EC and OC) over a three year period (2004-2007). These events represented approximately 190 calendar days of monitoring which was performed in seven residential neighborhoods throughout Wayne County, MI. The selection of neighborhoods and participants for study inclusion was based upon an a priori hypothesis that each neighborhood represented a potentially distinct air quality scenario being influenced by both regional as well as local pollution sources. Daily (24 h integrated) measurement data were used to evaluate the spatial and temporal PM2.5 compositional variability of the personal, indoor and outdoor spatial settings as they related to a central ambient monitoring site (Allen Park). Many of the PM2.5 components were observed to have spatially different outdoor mass concentrations in matched neighborhood by neighborhood comparisons, with sulfate, OC, and NO3 being noted exceptions. Coefficient of divergence (COD) comparisons involving outdoor measures for Ca, Si, Fe, Zn, Pb, and EC revealed significant spatial variability. While concentrations of most components were lower indoors as compared to outdoor measures, K and Si indoor concentrations often reflected aerosol enrichment (indoor/outdoor ratios ≥ 1.2). Even when personal exposures were adjusted for day to day changes in ambient concentrations, certain components (Ca, Fe, Mn, Zn, among others) revealed a high degree of location-specific spatial variability suggesting the influences of personal activities and/or local source influences on total personal PM2.5 exposures. As a whole, findings indicate that reliance on a central ambient monitor as a surrogate for total personal and potentially even residential outdoor estimates of PM2.5 aerosol composition may provide an undesirable degree of exposure uncertainty for health-based risk estimates. The focus of this paper is on the spatial variability and uncertainty in using a central monitoring site to estimate exposures. Additional information concerning the DEARS can be found at http://www.epa.gov/DEARS/.

Association between unemployment, income, education level, population size and air pollution in Czech cities: evidence for environmental inequality? A pilot national scale analysis

We analyzed differentials in exposure to SO(2), PM(10) and NO(2) among Czech urban populations categorized according to education level, unemployment rate, population size and average annual salary. Altogether 39 cities were included in the analysis. The principal component analysis revealed two factors explaining 72.8% of the data variability. The first factor explaining 44.7% of the data variability included SO(2), PM(10), low education level and high unemployment, documenting that inhabitants with unfavorable socioeconomic status mainly reside in smaller cities with higher concentration levels of combustion-related air pollutants. The second factor explaining 28.1% of the data variability included NO(2), high salary, high education level and large population, suggesting that large cities with residents with higher socioeconomic status are exposed to higher levels of traffic-related air pollution. We conclude that, after more than a decade of free-market economy, the Czech Republic, a former Soviet satellite with a centrally planned economy, displays signs of a certain kind of environmental inequality, since environmental hazards are unevenly distributed among the Czech urban populations.

Airborne particulate matter and gaseous air pollutants in residential structures in Lodi province, Italy

The province of Lodi is located in northern Italy on the Po River plain, where high background levels of air pollutants are prevalent. Lodi province is characterized by intensive agriculture, notably animal husbandry. This paper assesses indoor levels of selected airborne pollutants in 60 homes in the province, with special attention to size-fractionated particulate matter (PM). Indoor PM₂.₅ concentrations are frequently higher than current guidelines. PM₁₀ and nitrogen dioxide also exceed the respective guideline recommendations in some cases, noting that 24-h nitrogen dioxide levels were compared with an annual limit value. All other studied pollutant levels are below current international guidelines. Among indoor PM size fractions, PM₀.₅ is predominant in terms of mass concentrations corresponding to 57% of PM₁₀ in summer and 71% in winter. A strong seasonal trend is observed for all studied pollutants, with higher levels in winter corresponding to changes in ambient concentrations. The seasonal variation in PM₁₀ is largely due to PM₀.₅ increase from summer to winter. Summer indoor PM levels are mainly from indoor-generated particles, while particles of outdoor origin represent the main contribution to winter indoor PM levels. On average, indoor concentrations of coarse PM are mostly constituted by indoor-generated particles.

PRACTICAL IMPLICATIONS

This study presents a comparison between measured indoor concentrations in the study area and indoor air quality guideline criteria. Accordingly, particulate matter (PM) and NO₂ are identified as key pollutants that may pose health concerns. It is also found that indoor PM in residential units is mainly constituted by particles with aerodynamic diameters <0.5 μm, especially in winter. Risk mitigation strategies should be focused on the reduction in indoor levels of NO₂ and ultrafine and fine particles, both infiltrated from outdoors and generated by indoor sources.

Personal PM10 exposure in asthmatic adults in Padova, Italy: seasonal variability and factors affecting individual concentrations of particulate matter

Personal exposure to PM(10) measured in different seasons in a sample of asthmatic subjects living in Padova (Northern Italy) was compared with simultaneously measured outdoor PM(10) concentrations. The specific contribution of ambient PM(10) and other factors to individual exposure was evaluated in one of the areas of Europe with the worst air pollution. Thirty-one asthmatic subjects (21 non-smokers and 10 smokers) carried personal PM(10) monitors for six 24-hr sessions, in different seasons of the year. Concomitant daily 24-hr ambient PM(10) concentrations were measured by air quality monitoring networks. A multivariate analysis was performed to identify factors explaining personal exposure to PM(10), using a random effect model. The analysis on the 31 subjects referred to a total of 155 observations. The mean personal PM(10) exposure was higher (range 79.3-126.1microg/m(3)) than the outdoor concentrations (range 37.3-85.4microg/m(3)) in all seasons; and personal exposures varied less than outdoor PM(10) levels from one season to another. Smokers had significantly higher personal PM(10) concentrations than non-smokers (127.99 vs 78.8microg/m(3); T=-5.70; p<0.001). Moderate correlations emerged between outdoor and personal PM(10) concentrations. The correlation improved after excluding subjects exposed to active or passive smoking (median Pearson's R 0.41 vs 0.26). Considering all the subjects, smoking was the main factor affecting personal exposure, contributing to 41% of the variability. Outdoor PM(10) concentrations (25%), temperature (12%) and season (15%) also contributed to personal PM(10) exposure. Outdoor PM(10) (46%), temperature (20%), season (19%) and time spent indoors (6%) were significantly associated with personal exposure in non-smokers. We concluded that it is crucial to perform personal monitoring and to evaluate the complexity of factors that contribute to individual PM exposure. While tobacco smoke was the primary source of PM(10) in all subjects, the contribution of ambient components was particularly relevant for the personal exposure levels of our non-smokers living in a highly-polluted environment.

Modeling exposure to air pollution from the WTC disaster based on reports of perceived air pollution

We examined the utility of a newly developed perceived air pollution (PAP) scale and of a modeled air pollution (MAP) scale derived from it for predicting previously observed birth outcomes of pregnant women enrolled following September 11, 2001. Women reported their home and work locations in the four weeks after September 11, 2001 and the PAP at each site on a four-point scale designed for this purpose. Locations were geocoded and their distance from the World Trade Center (WTC) site determined. PAP values were used to develop a model of air pollution for a 20-mile radius from the WTC site. MAP values were assigned to each geocoded location. We examined the relationship of PAP and MAP values to maternal characteristics and to distance of home and work sites from the WTC site. Both PAP and MAP values were highly correlated with distance from the WTC. Maternal characteristics that were associated with PAP values reported for home or work sites (race, demoralization, material hardship, first trimester on September 11) were not associated with modeled MAP values. Relationships of several birth outcomes to proximity to the WTC, which we previously reported using this data set, were also seen when MAP values were used as the measure of exposure, instead of proximity. MAP developed from reports of PAP may be useful to identify high-risk areas and predict health outcomes when there are multiple sources of pollution and a "distance from source" analysis is impossible.

Elemental levels in tree-bark and epiphytic-lichen transplants at a mixed environment in mainland Portugal, and comparisons with an in situ lichen

Samples of Platanus hybrida Brot. bark and Flavoparmelia caperata (L.) Hale thalli, from a clean area in northern Portugal (Baião), were transplanted into an exposure location at the south-western Atlantic coast, impacted by urban-industrial emissions (Sines), for a 10-month long experiment. Bark pieces were confined into nylon bags (2-mm mesh), and lichen thalli kept with their bark substrate (Pinus pinaster (Ait.) Sol.). Every two months, a double set of transplants (one for bark, one for lichens) was brought back into the laboratory, together with native samples of Evernia prunastri (L.) Ach. Following suitable cleansing and preparation procedures, field samples were put through INAA for elemental assessment. The results indicate that, regardless of signal magnitude, (1) concentrations in bark and lichen transplants are significantly correlated with atmospheric deposition for an appreciable number of elements; (2) there are a number of significant correlations between transplanted and native samples, and again between the latter and the deposition; and (3) the elements with biological patterns that follow the deposition in either transplanted or native samples (Co, V) are the very ones whose bioaccumulation seems to benefit from an alternation of wet-dry periods, which fits the precipitation record of the test site during the exposure term.

Reduced exposure to PM10 and attenuated age-related decline in lung function

BACKGROUND

Air pollution has been associated with impaired health, including reduced lung function in adults. Moving to cleaner areas has been shown to attenuate adverse effects of air pollution on lung function in children but not in adults.

METHODS

We conducted a prospective study of 9651 adults (18 to 60 years of age) randomly selected from population registries in 1990 and assessed in 1991, with 8047 participants reassessed in 2002. There was complete information on lung volumes and flows (e.g., forced vital capacity [FVC], forced expiratory volume in 1 second [FEV1], FEV1 as a percentage of FVC, and forced expiratory flow between 25 and 75% of the FVC [FEF25-75]), smoking habits, and spatially resolved concentrations of particulate matter that was less than 10 microm in aerodynamic diameter (PM10) from a validated dispersion model assigned to residential addresses for 4742 participants at both the 1991 and the 2002 assessments and in the intervening years.

RESULTS

Overall exposure to individual home outdoor PM10 declined over the 11-year follow-up period (median, -5.3 mug per cubic meter; interquartile range, -7.5 to -4.2). In mixed-model regression analyses, with adjustment for confounders, PM10 concentrations at baseline, and clustering within areas, there were significant negative associations between the decrease in PM10 and the rate of decline in FEV1 (P=0.045), FEV1 as a percentage of FVC (P=0.02), and FEF25-75 (P=0.001). The net effect of a decline of 10 microg of PM10 per cubic meter over an 11-year period was to reduce the annual rate of decline in FEV1 by 9% and of FEF25-75 by 16%. Cumulative exposure in the interval between the two examinations showed similar associations.

CONCLUSIONS

Decreasing exposure to airborne particulates appears to attenuate the decline in lung function related to exposure to PM10. The effects are greater in tests reflecting small-airway function.

Urban background particulate matter and allergic sensitization in adults of ECRHS II

BACKGROUND

Epidemiological studies have shown weak or inconsistent associations between ambient air pollutants and allergic sensitization. The aim of this study was to evaluate whether regional urban air pollution may partly explain the large variation in the prevalence of allergic sensitization across cities of the European Community Respiratory Health Survey (ECRHS) II.

METHODS

ECRHS is a cross-sectional survey initiated in 29 countries across Europe in the 1990s (ECRHS I) with a follow-up conducted 10 years later (ECRHS II). Subject characteristics were measured by questionnaires and blood tests conducted for the measurement of specific immunoglobulin E. Fine particle mass (PM(2.5), <2.5 microm) and sulphur on PM(2.5) were measured in 21 centres and annual averages of urban regional background air pollution were calculated. Results were scaled by an interquartile range increase in ambient PM(2.5) (6.03 microg/m(3)) and sulphur (1336 ng/m(3)). Generalized estimating equations were applied to compute population average effect estimates with adjustment for age, gender, smoking habit, education and number of siblings.

RESULTS

A notable variation in pollution level and prevalence of allergic sensitization was observed. Moreover, exposure to urban regional background air pollution was not associated with allergic sensitization; adjusted odds ratios and 95% confidence interval were 1.02 (0.95-1.09) for PM(2.5) and 1.08 (0.86-1.31) for sulphur. These statistically non-significant associations were sensitive to model specification.

CONCLUSIONS

The study suggests that regional air pollution measured at fixed sites is not associated with allergic sensitization among adults in ECRHS II.

Exposure to fine particles (PM2.5 and PM1) and black smoke in the general population: personal, indoor, and outdoor levels

Personal exposure to PM(2.5) and PM(1), together with indoor and residential outdoor levels, was measured in the general adult population (30 subjects, 23-51 years of age) of Gothenburg, Sweden. Simultaneously, urban background concentrations of PM(2.5) were monitored with an EPA WINS impactor. The 24-h samples were gravimetrically analyzed for mass concentration and black smoke (BS) using a smokestain reflectometer. Median levels of PM(2.5) were 8.4 microg/m(3) (personal), 8.6 microg/m(3) (indoor), 6.4 microg/m(3) (residential outdoor), and 5.6 microg/m(3) (urban background). Personal exposure to PM(1) was 5.4 microg/m(3), while PM(1) indoor and outdoor levels were 6.2 and 5.2 microg/m(3), respectively. In non-smokers, personal exposure to PM(2.5) was significantly higher than were residential outdoor levels. BS absorption coefficients were fairly similar for all microenvironments (0.4-0.5 10(-5) m(-1)). Personal exposure to particulate matter (PM) and BS was well correlated with indoor levels, and there was an acceptable agreement between personal exposure and urban background concentrations for PM(2.5) and BS(2.5) (r(s)=0.61 and 0.65, respectively). PM(1) made up a considerable amount (70-80%) of PM(2.5) in all microenvironments. Levels of BS were higher outdoors than indoors and higher during the fall compared with spring. The correlations between particle mass and BS for both PM(2.5) vs. BS(2.5) and PM(1) versus BS(1) were weak for all microenvironments including personal exposure. The urban background station provided a good estimate of residential outdoor levels of PM(2.5) and BS(2.5) within the city (r(s)=0.90 and 0.77, respectively). Outdoor levels were considerably affected by long-range transported air pollution, which was not found for personal exposure or indoor levels. The within-individual (day-to-day) variability dominated for personal exposure to both PM(2.5) and BS(2.5) in non-smokers.

Results of an indoor size fractionated PM school sampling program in Libby, Montana

Libby, Montana is the only PM(2.5) non-attainment area in the western United States with the exceptions of parts of southern California. During January through March 2005, a particulate matter (PM) sampling program was conducted within Libby's elementary and middle schools to establish baseline indoor PM concentrations before a wood stove change-out program is implemented over the next several years. As part of this program, indoor concentrations of PM mass, organic carbon (OC), and elemental carbon (EC) in five different size fractions (>2.5, 1.0-2.5, 0.5-1.0, 0.25-0.5, and <0.25 microm) were measured. Total measured PM mass concentrations were much higher inside the elementary school, with particle size fraction (>2.5, 0.5-1.0, 0.25-0.5, and <0.25 microm) concentrations between 2 and 5 times higher when compared to the middle school. The 1.0-2.5 microm fraction had the largest difference between the two sites, with elementary school concentrations nearly 10 times higher than the middle school values. The carbon component for the schools' indoor PM was found to be predominantly composed of OC. Measured total OC and EC concentrations, as well as concentrations within individual size fractions, were an average of two to five times higher at the elementary school when compared to the middle school. For the ultrafine fraction (<0.25), EC concentrations were similar between each of the schools. Despite the differences in concentrations between the schools at the various fraction levels, the OC/EC ratio was determined to be similar.

The health relevance of ambient particulate matter characteristics: coherence of toxicological and epidemiological inferences

The aim of this article is to review progress toward integration of toxicological and epidemiological research results concerning the role of specific physicochemical properties, and associated sources, in the adverse impact of ambient particulate matter (PM) on public health. Contemporary knowledge about atmospheric aerosols indicates their complex and variable nature. This knowledge has influenced toxicological assessments, pointing to several possible properties of concern, including particle size and specific inorganic and organic chemical constituents. However, results from controlled exposure laboratory studies are difficult to relate to actual community health results because of ambiguities in simulated PM mixtures, inconsistent concentration measurements, and the wide range of different biological endpoints. The use of concentrated ambient particulates (CAPs) coupled with factor analysis has provided an improved understanding of biological effects from more realistic laboratory-based exposure studies. Epidemiological studies have provided information concerning sources of potentially toxic particles or components, adding insight into the significance of exposure to secondary particles, such as sulfate, compared with primary emissions, such as elemental and organic carbon from transportation sources. Recent epidemiological approaches incorporate experimental designs that take advantage of broadened speciation monitoring, multiple monitoring stations, source proximity designs, and emission intervention. However, there continue to be major gaps in knowledge about the relative toxicity of particles from various sources, and the relationship between toxicity and particle physicochemical properties. Advancing knowledge could be facilitated with cooperative toxicological and epidemiological study designs, with the support of findings from atmospheric chemistry.

Indoor and outdoor concentrations of PM2.5 trace elements at homes, preschools and schools in Stockholm, Sweden

Fine particles (PM2.5) were sampled indoors and outdoors at 40 sampling sites; in ten classrooms in five schools, at ten preschools and 20 non-smoking homes, in three communities in Stockholm, Sweden, during nine 2-week periods. Each sampling site was sampled twice, once during winter and once during spring. The samples were analysed for elemental concentrations using X-ray fluorescence (XRF) spectroscopy. In all locations significantly higher outdoor concentrations were found for elements that are related to long-range transported air masses (S, Ni, Br and Pb), while only Ti was higher indoors in all locations. Similar differences for S, Br and Pb were found in both seasons for homes and schools. In preschools different seasonal patterns were seen for the long-range transported elements S, Br and Pb and the crustal elements Ti, Mn and Fe. The indoor/outdoor ratios for S and Pb suggest an outdoor PM2.5 particle net infiltration of about 0.6 in these buildings. The community located 25 km from the city centre had significantly lower outdoor concentrations of elements of crustal or traffic origin compared with the two central communities, but had similar levels of long-range transported elements. Significant correlations were found between PM2.5 and most elements outdoors (rs = 0.45-0.90). Copper levels were found to correlate well (rs = 0.64-0.91) to the traffic marker NO2 during both winter and spring in all locations. Copper may be a suitable elemental marker for traffic-related aerosols in health studies in areas without other significant outdoor Cu sources.

Living near main streets and respiratory symptoms in adults: the Swiss Cohort Study on Air Pollution and Lung Diseases in Adults

The Swiss Cohort Study on Air Pollution and Lung Diseases in Adults (SAPALDIA), conducted in 1991 (SAPALDIA 1) in eight areas among 9,651 randomly selected adults aged 18-60 years, reported associations among the prevalence of respiratory symptoms, nitrogen dioxide, and particles with an aerodynamic diameter of less than 10 microg/m3. Later, 8,047 subjects reenrolled in 2002 (SAPALDIA 2). The effects of individually assigned traffic exposures on reported respiratory symptoms were estimated, while controlling for socioeconomic and exposure- and health-related factors. The risk of attacks of breathlessness increased for all subjects by 13% (95% confidence interval: 3, 24) per 500-m increment in the length of main street segments within 200 m of the home and decreased in never smokers by 12% (95% confidence interval: 0, 22) per 100-m increment in distance from home to a main street. Living within 20 m of a main street increased the risks of regular phlegm by 15% (95% confidence interval: 0, 31) and wheezing with breathing problems by 34% (95% confidence interval: 0, 79) in never smokers. In 2002, the effects related to road distance were different from those in 1991, which could be due to changes in the traffic pollution mixture. These findings among a general population provide strong confirmation that living near busy streets leads to adverse respiratory health effects.

Comparison of oxidative properties, light absorbance, total and elemental mass concentration of ambient PM2.5 collected at 20 European sites

OBJECTIVE

It has been proposed that the redox activity of particles may represent a major determinant of their toxicity. We measured the in vitro ability of ambient fine particles [particulate matter with aerodynamic diameters<or=2.5 microm (PM2.5)] to form hydroxyl radicals (.OH) in an oxidant environment, as well as to deplete physiologic antioxidants (ascorbic acid, glutathione) in the naturally reducing environment of the respiratory tract lining fluid (RTLF). The objective was to examine how these toxicologically relevant measures were related to other PM characteristics, such as total and elemental mass concentration and light absorbance.

DESIGN

Gravimetric PM2.5 samples (n=716) collected over 1 year from 20 centers participating in the European Community Respiratory Health Survey were available. Light absorbance of these filters was measured with reflectometry. PM suspensions were recovered from filters by vortexing and sonication before dilution to a standard concentration. The oxidative activity of these particle suspensions was then assessed by measuring their ability to generate .OH in the presence of hydrogen peroxide, using electron spin resonance and 5,5-dimethyl-1-pyrroline-N-oxide as spin trap, or by establishing their capacity to deplete antioxidants from a synthetic model of the RTLF.

RESULTS AND CONCLUSION

PM oxidative activity varied significantly among European sampling sites. Correlations between oxidative activity and all other characteristics of PM were low, both within centers (temporal correlation) and across communities (annual mean). Thus, no single surrogate measure of PM redox activity could be identified. Because these novel measures are suggested to reflect crucial biologic mechanisms of PM, their use may be pertinent in epidemiologic studies. Therefore, it is important to define the appropriate methods to determine oxidative activity of PM.

Personal exposures and indoor, residential outdoor, and urban background levels of fine particle trace elements in the general population

Personal exposures and indoor, residential outdoor, and urban background levels of PM(2.5) and PM(1) were measured simultaneously in Göteborg, Sweden. A total of 270 24 hour samples from 30 subjects were analyzed for elemental concentrations using X-ray fluorescence (XRF) spectroscopy. Personal exposures to PM(2.5) were significantly higher for Cl, Ca, Ti, and Fe compared with the other locations. For most elements, residential outdoor levels were significantly higher than urban background levels. Correlations between personal exposure and stationary measurements were moderate to high for Zn, Br, and Pb (r(s)= 0.47-0.81), while Ca and Cu showed low correlations. The penetration indoors from outdoors was 0.7, as calculated from S and Pb ratios. For the pairs of parallel PM(1) and PM(2.5) measurements, only Ca and Fe levels were significantly lower for PM(1) at all sites. Significant correlations were found between urban background mass concentrations and personal exposure levels for elements attributed to combustion processes (S, V, and Pb) and resuspended dust (Ti, Fe, and Zn), indicating that both sources could be relevant to health effects related to urban background mass. Air mass origin strongly affected the measured urban background concentrations of some elements (S, Cl, V, Ni, Br, and Pb). These findings were also seen for personal exposure (S, Cl, V, and Pb) and indoor levels (S, Cl, V, Ni, and Pb). No differences were seen for crustal elements. Air mass origin should be taken into account in the description and interpretation of time series studies of air pollution and health.

Associations between personal exposures and fixed-site ambient measurements of fine particulate matter, nitrogen dioxide, and carbon monoxide in Toronto, Canada

A longitudinal study investigating personal exposures to PM(2.5), nitrogen dioxide (NO(2)), and carbon monoxide (CO) for cardiac compromised individuals was conducted in Toronto, Canada. The aim of the study was (1) to examine the distribution of exposures to PM(2.5), NO(2), and CO; and (2) to investigate the relationship between personal exposures and fixed-site ambient measurements of PM(2.5), NO(2), and CO. In total, 28 subjects with coronary artery disease wore the Rupprecht & Patashnick ChemPass Personal Sampling System one day a week for a maximum of 10 weeks. The mean (SD) personal exposures were 22 microg m(-3) (42), 14 p.p.b. (6), and 1.4 p.p.m (0.5) for PM(2.5), NO(2), and CO, respectively. PM(2.5) and CO personal exposures were greater than central fixed-site ambient measurements, while the reverse pattern was observed for NO(2). Ambient PM(2.5) and NO(2) were correlated with personal exposures to PM(2.5) and NO(2) with median Spearman's correlation coefficients of 0.69 and 0.57, respectively. The correlations between personal exposures and ambient measurements made closest to the subjects' homes or the average of all stations within the study were not stronger than the correlation between personal exposures and central fixed-site measurements. Personal exposures to PM(2.5) were correlated with personal exposures to NO(2) (median Spearman's correlation coefficient of 0.43). This study suggests that central fixed-site measurements of PM(2.5) and NO(2) may be treated as surrogates for personal exposures to PM(2.5) and NO(2) in epidemiological studies, and that NO(2) is a potential confounder of PM(2.5).

Associations between ambient, personal, and indoor exposure to fine particulate matter constituents in Dutch and Finnish panels of cardiovascular patients

AIMS

To assess the relation between ambient, indoor, and personal levels of PM2.5 and its elemental composition for elderly subjects with cardiovascular disease.

METHODS

In the framework of a European Union funded study, panel studies were conducted in Amsterdam, the Netherlands and Helsinki, Finland. Outdoor PM2.5 concentrations were measured at a fixed site. Each subject's indoor and personal PM2.5 exposure was measured biweekly for six months, during the 24 hour period preceding intensive health measurements. The absorbance of PM2.5 filters was measured as a marker for diesel exhaust. The elemental content of more than 50% of the personal and indoor samples and all corresponding outdoor samples was measured using energy dispersive x ray fluorescence.

RESULTS

For Amsterdam and Helsinki respectively, a total of 225 and 238 personal, and 220 and 233 indoor measurements, were analysed from 36 and 46 subjects. For most elements, personal and indoor concentrations were lower than and highly correlated with outdoor concentrations. The highest correlations (median r>0.9) were found for sulfur and particle absorbance, which both represent fine mode particles from outdoor origin. Low correlations were observed for elements that represent the coarser part of the PM2.5 particles (Ca, Cu, Si, Cl).

CONCLUSIONS

The findings of this study provide support for using fixed site measurements as a measure of exposure to particulate matter in time series studies linking the day to day variation in particulate matter to the day to day variation in health endpoints, especially for components of particulate matter that are generally associated with fine particles and have few indoor sources. The high correlation for absorbance of PM2.5 documents that this applies to particulate matter from combustion sources, such as diesel vehicles, as well.

A case-crossover study of wintertime ambient air pollution and infant bronchiolitis

We examined the association of infant bronchiolitis with acute exposure to ambient air pollutants.

DESIGN

We employed a time-stratified case-crossover method and based the exposure windows on a priori, biologically based hypotheses.

PARTICIPANTS

We evaluated effects in 19,901 infants in the South Coast Air Basin of California in 1995-2000 with a hospital discharge record for bronchiolitis in the first year of life (International Classification of Diseases, 9th Revision, CM466.1).

EVALUATIONS/MEASUREMENTS

Study subjects' ZIP code was linked to ambient air pollution monitors to derive exposures. We estimated the risk of bronchiolitis hospitalization associated with increases in wintertime ambient air pollutants using conditional logistic regression.

RESULTS

We observed no increased risk after acute exposure to particulate matter < or = 2.5 microm in aerodynamic diameter (PM2.5), carbon monoxide, or nitrogen dioxide. PM2.5 exposure models suggested a 26-41% increased risk in the most premature infants born at gestational ages between 25 and 29 weeks; however, these findings were based on very small numbers.

CONCLUSIONS

We found little support for a link between acute increases in ambient air pollution and infant bronchiolitis except modestly increased risk for PM2.5 exposure among infants born very prematurely. In these infants, the periods of viral acquisition and incubation concurred with the time of increased risk. RELEVANCE TO PROFESSIONAL PRACTICE: We present novel data for the infant period and the key respiratory disease of infancy, bronchiolitis. Incompletely explained trends in rising bronchiolitis hospitalization rates and increasing number of infants born prematurely underscore the importance of evaluating the impact of ambient air pollution in this age group in other populations and studies.

Air pollution epidemiologic studies in South Africa--need for freshening up

The results of epidemiologic studies obtained in developed countries cannot be extrapolated with complete confidence to developing countries. The objectives of this review were to examine the evidence from local studies for associations between air pollution and adverse health along with a critical review for methodologic limitations. The literature search strategy and selection criteria involved a MEDLINE search up to June 2005. Of 267 journal articles found, 14 focused on air pollution epidemiology (excluding active smoking and internal dose as a proxy for health outcomes). Two studies were also located by word of mouth or through the references from the selected studies. The local studies provide some evidence of an association with a range of serious and common health problems. No study established an exposure-response curve for the criteria pollutants carbon monoxide, sulfur dioxide, nitrogen oxides, lead, and ozone. Therefore, using the results of such studies in risk-assessment is impossible. The studies were fraught with systematic and random errors, which limit their validity and precision. We recommend conducting a quantitative intervention study with an analytical study design in all major cities in the countries where residents are still using dirty fuels for cooking, lighting, and space heating. Future studies must involve national and international multidisciplinary stakeholders and must be planned well in advance.

PM2.5 of ambient origin: estimates and exposure errors relevant to PM epidemiology

Epidemiological studies routinely use central-site particulate matter (PM) as a surrogate for exposure to PM of ambient (outdoor) origin. Below we quantify exposure errors that arise from variations in particle infiltration to aid evaluation of the use of this surrogate, rather than actual exposure, in PM epidemiology. Measurements from 114 homes in three cities from the Relationship of Indoor, Outdoor and Personal Air (RIOPA) study were used. Indoor PM2.5 of outdoor origin was calculated as follows: (1) assuming a constant infiltration factor, as would be the case if central-site PM were a "perfect surrogate" for exposure to outdoor particles; (2) including variations in measured air exchange rates across homes; (3) also incorporating home-to-home variations in particle composition, and (4) calculating sample-specific infiltration factors. The final estimates of PM2.5 of outdoor origin take into account variations in building construction, ventilation practices, and particle properties that result in home-to-home and day-to-day variations in particle infiltration. As assumptions became more realistic (from the first, most constrained model to the fourth, least constrained model), the mean concentration of PM2.5 of outdoor origin increased. Perhaps more importantly, the bandwidth of the distribution increased. These results quantify several ways in which the use of central site PM results in underestimates of the ambient PM2.5 exposure distribution bandwidth. The result is larger uncertainties in relative risk factors for PM2.5 than would occur if epidemiological studies used more accurate exposure measures. In certain situations this can lead to bias.

Traffic related pollution and heart rate variability in a panel of elderly subjects

BACKGROUND

Particulate air pollution has been associated with increased cardiovascular deaths and hospital admissions. To help understand the mechanisms, the types of particles most involved, and the types of persons most susceptible, the association between exposure to summertime air pollution and heart rate variability (HRV) was examined in a panel study of 28 elderly subjects.

METHODS

Subjects were seen once a week for up to 12 weeks and HRV (SDNN, r-MSSD, PNN50, low frequency/high frequency ratio (LFHFR)) was measured for approximately 30 minutes at each session using a defined protocol. Temperature, day of the week, and hour of the day were controlled, and dummy variables for each subject were controlled for subject specific risk factors.

RESULTS

PM2.5 was associated with r-MSSD (-10.1% change for an interquartile range (IQR) increase in exposure (95% CI -2.8 to -16.9)) and PNN50, but stronger associations were seen with black carbon, an indicator of traffic particles, which was also associated with SDNN (-4.6% per IQR (95% CI -2.0 to -7.2)) and LFHFR. Secondary particles were more weakly associated with r-MSSD, as was ozone. No associations were seen with SO2 or NO2. CO had similar patterns of association to black carbon, which disappeared after controlling for black carbon. Black carbon had a substantially higher effect on SDNN in subjects who had had a previous myocardial infarction (-12.7%, 95% CI -5.7 to -19.25).

CONCLUSIONS

Particles, especially from traffic, are associated with disturbances of autonomic control of the heart.

Traffic related air pollution as a determinant of asthma among Taiwanese school children

BACKGROUND

There is evidence that long term exposure to ambient air pollution increases the risk of childhood asthma, but the role of different sources and components needs further elaboration. To assess the effect of air pollutants on the risk of asthma among school children, a nationwide cross sectional study of 32 672 Taiwanese school children was conducted in 2001.

METHODS

Routine air pollution monitoring data for sulphur dioxide (SO2), nitrogen oxides (NOx), ozone (O3), carbon monoxide (CO), and particles with an aerodynamic diameter of 10 microm or less (PM10) were used. Information on individual characteristics and indoor environments was from a parent administered questionnaire (response rate 93%). The exposure parameters were calculated using the mean of the 2000 monthly averages. The effect estimates were presented as odds ratios (ORs) per 10 ppb changes for SO2, NOx, and O3, 100 ppb changes for CO, and 10 microg/m3 changes for PM10.

RESULTS

In a two stage hierarchical model adjusting for confounding, the risk of childhood asthma was positively associated with O3 (adjusted OR 1.138, 95% confidence interval (CI) 1.001 to 1.293), CO (adjusted OR 1.045, 95% CI 1.017 to 1.074), and NOx (adjusted OR 1.005, 95% CI 0.954 to 1.117). Against our prior hypothesis, the risk of childhood asthma was weakly or not related to SO2 (adjusted OR 0.874, 95% CI 0.729 to 1.054) and PM10 (adjusted OR 0.934, 95% CI 0.909 to 0.960).

CONCLUSIONS

The results are consistent with the hypothesis that long term exposure to traffic related outdoor air pollutants such as NOx, CO, and O3 increases the risk of asthma in children.

Traffic at residential address, respiratory health, and atopy in adults: the National German Health Survey 1998

Motor vehicle traffic contributes to more than 50% of PM10 in Europe and might have far reaching impacts on human health. We investigated the relationship between residential street type as a surrogate for traffic intensity and the prevalence of respiratory symptoms, atopic diseases, and allergic sensitization in adults. Data from 6896 subjects of the German Health Survey 1998 with complete information on residential street type were used. Multiple logistic regression analyses were applied to model associations between street type categories, and respiratory and atopic outcomes were assessed by screening questionnaire of The European Respiratory Health Survey and specific IgE measurements. Living at extremely or considerably busy roads (23.9% of total study population) compared to roads with no or rare traffic (64.5%) was statistically significantly associated with chronic bronchitis (aOR 1.36 (95% CI) (1.01-1.83)) while nocturnal coughing attacks (past 12 months) (1.24 (0.98-1.57)), wheeze during the past 12 months (1.21 (0.93-57)), and hay fever (1.16 (0.94-1.42)) were marginally increased after adjustment for several potential confounders and for multiple testing. No increased risks were found for asthma (0.97 (0.67-1.42)) and allergic sensitization (1.05 (0.91-1.20)). We conclude that exposure to traffic-related air pollutants increases the risk of nonallergic respiratory symptoms and to a lesser degree the risk of hay fever and allergic sensitization but not the risk of asthma in adults.

Can we use fixed ambient air monitors to estimate population long-term exposure to air pollutants? The case of spatial variability in the Genotox ER study

Associations between average total personal exposures to PM2.5, PM10, and NO2 and concomitant outdoor concentrations were assessed within the framework of the Genotox ER study. It was carried out in four French metropolitan areas (Grenoble, Paris, Rouen, and Strasbourg) with the participation, in each site, of 60-90 nonsmoking volunteers composed of two groups of equal size (adults and children) who carried the personal Harvard Chempass multipollutant sampler during 48 h along two different seasons ("hot" and "cold"). In each center, volunteers were selected so as to live (home and work/school) in three different urban sectors contrasted in terms of air pollution (one highly exposed to traffic emissions, one influenced by local industrial sources, and a background urban environment). In parallel to personal exposure measurements, a fixed ambient air monitoring station surveyed the same pollutants in each local sector. A linear regression model was accommodated where the dependent pollutant-specific variable was the difference, for each subject, between the average ambient air concentrations over 48 h and the personal exposure over the same period. The explanatory variables were the metropolitan areas, the three urban sectors, season, and age group. While average exposures to particles were underestimated by outdoor monitors, in almost all cities, seasons, and age groups, differences were lower for NO2 and, in general, in the other direction. Relationships between average total personal exposures and ambient air levels varied across metropolitan areas and local urban sectors. These results suggest that using ambient air concentrations to assess average exposure of populations, in epidemiological studies of long-term effects or in a risk assessment setting, calls for some caution. Comparison of personal exposures to PM or NO2 with ambient air levels is inherently disturbed by indoor sources and activities patterns. Discrepancies between measurement devices and local and regional sources of pollution may also strongly influence how the ambient air concentrations relate to population exposure. Much attention should be given to the selection of the most appropriate monitoring sites according to the study objectives.

Influence of ambient (outdoor) sources on residential indoor and personal PM2.5 concentrations: analyses of RIOPA data

The Relationship of Indoor, Outdoor and Personal Air (RIOPA) study was designed to investigate residential indoor, outdoor and personal exposures to several classes of air pollutants, including volatile organic compounds, carbonyls and fine particles (PM2.5). Samples were collected from summer, 1999 to spring, 2001 in Houston (TX), Los Angeles (CA) and Elizabeth (NJ). Indoor, outdoor and personal PM2.5 samples were collected at 212 nonsmoking residences, 162 of which were sampled twice. Some homes were chosen due to close proximity to ambient sources of one or more target analytes, while others were farther from sources. Median indoor, outdoor and personal PM2.5 mass concentrations for these three sites were 14.4, 15.5 and 31.4 microg/m3, respectively. The contributions of ambient (outdoor) and nonambient sources to indoor and personal concentrations were quantified using a single compartment box model with measured air exchange rate and a random component superposition (RCS) statistical model. The median contribution of ambient sources to indoor PM2.5 concentrations using the mass balance approach was estimated to be 56% for all study homes (63%, 52% and 33% for California, New Jersey and Texas study homes, respectively). Reasonable variations in model assumptions alter median ambient contributions by less than 20%. The mean of the distribution of ambient contributions across study homes agreed well for the mass balance and RCS models, but the distribution was somewhat broader when calculated using the mass balance model with measured air exchange rates.

Time-space modeling of journey-time exposure to traffic-related air pollution using GIS

Journey-time exposures represent an important, though as yet little-studied, component of human exposure to traffic-related air pollution, potentially with important health effects. Methods for assessing journey-time exposures, either as part of epidemiological studies or for policy assessment, are, however, poorly developed. This paper describes the development and testing of a GIS-based system for modeling human journey-time exposures to traffic-related air pollution: STEMS (Space-Time Exposure Modeling System). The model integrates data on source activity, pollutant dispersion, and travel behavior to derive individual- or group-level exposure measures to atmospheric pollution. The model, which is designed to simulate exposures of people as they move through a changing air pollution field, was developed, validated, and trialed in Northampton, UK. The system currently uses ArcInfo to couple four separate submodels: a source activity/emission model (SATURN), a proprietary atmospheric dispersion model (ADMS-Urban), an empirically derived background air pollution model, and a purposely designed time-activity-based exposure model (TOTEM). This paper describes the structure of the modeling system; presents results of field calibration, validation, and sensitivity analysis; and illustrates the use of the model to analyze journey-time exposures of schoolchildren.

Air pollution and respiratory status in asthmatic children: hints for a locally based preventive strategy. AIRE study

Respiratory health effects of short-term exposure to ambient air pollution have been examined in 120 'asthma-like' school-aged children in some areas of Emilia-Romagna (urban-industrial and rural area). They kept a daily diary, through 12 weeks, for respiratory symptoms, PEF measurements, drug consumption and daily activity. The average daily concentrations of air pollutants in the same period (TSP, NO2, CO, PM2.5) were higher in the industrial than the rural area. Asthma was diagnosed in 77% of cases, 85% of subjects took medical treatments for respiratory disease in the last year and 90% used medicine for respiratory diseases. Significantly lower variations in PEF, between morning and evening, were observed in the rural area, considering only the asthmatic or cough subsets of children. Symptom prevalence was higher in the urban-industrial area than the rural area; the most frequent symptoms were cough, phlegm and stuffed nose. The two area populations are homogeneous in individual features, family susceptibility, passive smoking exposure and atopy. The differences observed in the frequency of daily reported symptoms could be attributed to external situations like the different reported exposures to pollutants. Although most analyses revealed non-significant associations, panel analysis showed a significant statistical risk for the cough and phlegm group by an increase of 10 microg of TSP (RR 1.0017, 95% CI: 1.0002-1.0033) in the entire group. In the urban-industrial panel we observed a significant association between cough and phlegm together and PM2.5 (RR 1.0044, 95% CI: 1.0011-1.0077). The results of this investigation should be used in orienting local political decisions.

The EXPOLIS study: implications for exposure research and environmental policy in Europe

Exposure analysis is a crucial part of effective management of public health risks caused by pollutants and chemicals in our environment. During the last decades, more data required for exposure analysis has become available, but the need for direct population based measurements of exposures is still clear. The current work (i) describes the European EXPOLIS study, designed to produce this kind of exposure data for major air pollutants in Europe, and the database created to make the collected data available for researchers (ii) reviews the exposure analysis conducted and results published so far using these data and (iii) discusses the implications of the results from the point of view of research and environmental policy in Europe. Fine particle (with 37 elements and black smoke), nitrogen dioxide, volatile organic compounds (30 compounds) and carbon monoxide inhalation exposures and exposure-related questionnaire data were measured in seven European cities during 1996-2000. The EXPOLIS database has been used for exposure analysis of these pollutants for 4 years now and results have been published in approximately 30 peer-reviewed journal papers, demonstrating the versatility, usability and scientific value of such a data set. The multipollutant exposure data from the same subjects in the random population samples allows for analyses of the determinants, microenvironments and sources of exposures to multipollutant mixtures and associations between the different air pollutants. This information is necessary and useful for developing effective policies and control strategies for healthier environment.

Use of real-time light scattering data to estimate the contribution of infiltrated and indoor-generated particles to indoor air

The contribution of outdoor particulate matter (PM) to residential indoor concentrations is currently not well understood. Most importantly, separating indoor PM into indoor- and outdoor-generated components will greatly enhance our knowledge of the outdoor contribution to total indoor and personal PM exposures. This paper examines continuous light scattering data at 44 residences in Seattle, WA. A newly adapted recursive model was used to model outdoor-originated PM entering indoor environments. After censoring the indoor time-series to remove the influence of indoor sources, nonlinear regression was used to estimate particle penetration (P, 0.94 +/- 0.10), air exchange rate (a, 0.54 +/- 0.60 h(-1)), particle decay rate (k, 0.20 +/- 0.16 h(-1)), and particle infiltration (F(inf), 0.65 +/- 0.21) for each of the 44 residences. All of these parameters showed seasonal differences. The F(inf) estimates agree well with those estimated from the sulfur-tracer method (R2 = 0.78). The F(inf) estimates also showed robust and expected behavior when compared against known influencing factors. Among our study residences, outdoor-generated particles accounted for an average of 79 +/- 17% of the indoor PM concentration, with a range of 40-100% at individual residences. Although estimates of P, a, and k were dependent on the modeling technique and constraints, we showed that a recursive mass balance model combined with our censoring algorithms can be used to attribute indoor PM into its outdoor and indoor components and to estimate an average P, a, k, and F(inf), for each residence.

Using sulfur as a tracer of outdoor fine particulate matter

Six homes in the metropolitan Boston area were sampled between 6 and 12 consecutive days for indoor and outdoor particle volume and mass concentrations, particle elemental concentrations, and air exchange rates (AERs). Indoor/outdoor (I/O) ratios of nighttime (i.e., particle nonindoor source periods) sulfur, PM2.5 and the specific particle size intervals were used to provide estimates of the effective penetration efficiency. Mixed models and graphical displays were used to assess the ability of the I/O ratios for sulfur to estimate corresponding I/O ratios for PM2.5 and the various particle sizes. Results from this analysis showed that particulate sulfur compounds were primarily of outdoor origin and behaved in a manner that was representative of total PM2.5 in Boston, MA. These findings support the conclusion that sulfur can be used as a suitable tracer of outdoor PM2.5 for the homes sampled in this study. Sulfur was more representative of particles of similar size (0.06-0.5 microm), providing evidence that the size composition of total PM2.5 is an important characteristic affecting the robustness of sulfur-based estimation methods.

Fine PM measurements: personal and indoor air monitoring

This review compiles personal and indoor microenvironment particulate matter (PM) monitoring needs from recently set research objectives, most importantly the NRC published "Research Priorities for Airborne Particulate Matter (1998)". Techniques and equipment used to monitor PM personal exposures and microenvironment concentrations and the constituents of the sampled PM during the last 20 years are then reviewed. Development objectives are set and discussed for personal and microenvironment PM samplers and monitors, for filter materials, and analytical laboratory techniques for equipment calibration, filter weighing and laboratory climate control. The progress is leading towards smaller sample flows, lighter, silent, independent (battery powered) monitors with data logging capacity to store microenvironment or activity relevant sensor data, advanced flow controls and continuous recording of the concentration. The best filters are non-hygroscopic, chemically pure and inert, and physically robust against mechanical wear. Semiautomatic and primary standard equivalent positive displacement flow meters are replacing the less accurate methods in flow calibration, and also personal sampling flow rates should become mass flow controlled (with or without volumetric compensation for pressure and temperature changes). In the weighing laboratory the alternatives are climatic control (set temperature and relative humidity), and mechanically simpler thermostatic heating, air conditioning and dehumidification systems combined with numerical control of temperature, humidity and pressure effects on flow calibration and filter weighing.