Bayer-Oglesby, Lucy
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Long-term exposure models for traffic related NO2 across geographically diverse areas over separate years
Although recent air pollution epidemiologic studies have embraced land-use regression models for estimating outdoor traffic exposure, few have examined the spatio-temporal variability of traffic related pollution over a long term period and the optimal methods to take these factors into account for exposure estimates. We used home outdoor NO2 measurements taken from eight geographically diverse areas to examine spatio-temporal variations, construct, and evaluate models that could best predict the within-city contrasts in observations. Passive NO2 measurements were taken outside of up to 100 residences per area over three seasons in 1993 and 2003 as part of the Swiss cohort study on air pollution and lung and heart disease in adults (SAPALDIA). The spatio-temporal variation of NO2 differed by area and year. Regression models constructed using the annual NO2 means from central monitoring stations and geographic parameters predicted home outdoor NO2 levels better than a dispersion model. However, both the regression and dispersion models underestimated the within-city contrasts of NO2 levels. Our results indicated that the best models should be constructed for individual areas and years, and would use the dispersion estimates as the urban background, geographic information system (GIS) parameters to enhance local characteristics, and temporal and meteorological variables to capture changing local dynamics. Such models would be powerful tools for assessing health effects from long-term exposure to air pollution in a large cohort
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 μm 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 μg 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 μg 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.
Long-term Source-Specific Air Pollution Exposure Characterization for a Large Population-Based Swiss Cohort (SAPALDIA)
Although evidence on acute health effects related to traffic exhaust is accumulating, there is less information regarding long-term exposure of source-specific air pollution in the general population. The SAPALDIA study is a long-term air pollution study that included 7990 subjects from 8 areas in Switzerland with the first health examination in 1991 and the second examination in 2002. Each area was monitored with up to 3 monitoring sites for PM, NO2, and other gaseous pollutants. In 1999–2000, a sampling campaign was conducted for PM10, PM2.5, and black smoke at 16 Swiss sites. In 2002–2003, passive NO2 measurements were collected strategically over the year outside and inside approximately 60 homes per area. Annual average concentrations of source-specific and total PM2.5, PM10, and NOx were estimated using a Gaussian dispersion model with GIS to match individual residences of the SAPALDIA subjects. This paper examines the performance of the dispersion model, variation of source-specific air pollution exposures, and the implications of these findings to long-term air pollution epidemiologic studies. For PM10 in 2000, modeled values predicted 68% of the variability in the measurements. For NO2 in 2000, the model predicted the measured values with an R2 over 0.80. The R2 for traffic-specific pollutant predictions ranged between 0.44 (P = 0.08) for traffic-related PM2.5 and 0.81 (P < 0.01) for traffic-related NO2 for sites with low traffic impacts. However, when traffic sites were included in the comparisons, the R2 was lower, ranging between 0.41 for traffic-originated PM10 and 0.51 for traffic-originated NO2. Nevertheless, our preliminary results indicated that variance in traffic-originated pollutants accounted for up to 45% of the variance in total PM10, 69% of that in total PM2.5, and 91% of that in NOx. In addition, we smoothed actual NO2 measurements outside individual residences and correlated the resulting smoothed estimates at these sites with NO2 estimates from the dispersion model. To obtain good agreement between the measured and modeled surfaces (r > 0.60), the minimal spatial smoothing window was found to range between 200 m in rural Davos and 1.75 km for urban Basel. Our results indicate that sites affected largely by regional and urban background pollution are properly presented by the model. Locations impacted by local traffic, however, may not be adequately predicted by the model and need either fine-tuning of the model or additional parameters to reflect local conditions. Predictions of exposures to source-specific air pollution are being examined against a series of respiratory and cardiovascular health effects in other papers.
Validity of Annoyance Scores for Estimation of Long Term Air Pollution Exposure in Epidemiologic Studies. The Swiss Study on Air Pollution and Lung Diseases in Adults (SAPALDIA)
In air pollution epidemiology, estimates of long term exposure are often based on measurements made at one fixed site monitor per area. This may lead to exposure misclassification. The present paper validates a questionnaire-based indicator of ambient air pollution levels and its applicability to assess their within-area variability. Within the framework of the SAPALDIA (Swiss Study on Air Pollution and Lung Diseases in Adults) cross-sectional study (1991), 9,651 participants reported their level of annoyance caused by air pollution on an 11-point scale. This subjective measure was compared with annual mean concentrations of particulate matter less than 10 μm in diameter (PM10) and nitrogen dioxide. The impact of individual factors on reported scores was evaluated. Nitrogen dioxide concentrations at home outdoors (measured in 1993), smoking, workplace dust exposure, and respiratory symptoms were found to be predictors of individual annoyance scores. Regression of population mean annoyance scores against annual mean PM10 and nitrogen dioxide concentrations (measured in 1993 and 1991, respectively) across areas showed a linear relation and strong correlations (r > 0.85). Analysis within areas yielded consistent results. The observed associations between subjective and objective air pollution exposure estimates suggest that population mean scores, but not individual scores, may serve as a simple tool for grading air quality within areas. Reported annoyance due to air pollution should be considered an indicator for a complex environmental condition and thus might be used for evaluating the implementation of environmental policies.
Improvements in PM10 Exposure and Reduced Rates of Respiratory Symptoms in a Cohort of Swiss Adults (SAPALDIA)
Rationale: Reductions in mortality following improvements in air quality were documented by several studies, and our group found, in an earlier analysis, that decreasing particulate levels attenuate lung function decline in adults. Objectives: We investigated whether decreases in particulates with an aerodynamic diameter of less than 10 microm (PM10) were associated with lower rates of reporting respiratory symptoms (i.e., decreased morbidity) on follow-up. Methods: The present analysis includes 7,019 subjects who underwent detailed baseline examinations in 1991 and a follow-up interview in 2002. Each subject was assigned model-based estimates of average PM10 during the 12 months preceding each health assessment and the difference was used as the exposure variable of interest (DeltaPM10). Analyses were stratified by symptom status at baseline and associations between DeltaPM10 and change in symptom status during follow-up were adjusted for important baseline characteristics, smoking status at follow-up, and season. We then estimated adjusted odds ratios for symptoms at follow-up and numbers of symptomatic cases prevented due to the observed reductions in PM10. Measurements and main results: Residential exposure to PM10 was lower in 2002 than in 1991 (mean decline 6.2 microg/m3; SD = 3.9 microg/m3). Estimated benefits (per 10,000 persons) attributable to the observed changes in PM10-levels were: 259 (95% confidence interval [CI]: 102-416) fewer subjects with regular cough, 179 (95% CI, 30-328) fewer subjects with chronic cough or phlegm and 137 (95% CI, 9-266) fewer subjects with wheezing and breathlessness. Conclusions: Reductions in particle levels in Switzerland over the 11-year follow-up period had a beneficial effect on respiratory symptoms among adults.
Annoyance due to air pollution in Europe
Background Annoyance due to air pollution is a subjective score of air quality, which has been incorporated into the National Environmental monitoring of some countries. The objectives of this study are to describe the variations in annoyance due to air pollution in Europe and its individual and environmental determinants. Methods This study took place in the context of the European Community Respiratory Health Survey II (ECRHS II) that was conducted during 1999–2001. It included 25 centres in 12 countries and 7867 randomly selected adults from the general population. Annoyance due to air pollution was self-reported on an 11-point scale. Annual mean mass concentration of fine particles (PM2.5) and its sulphur (S) content were measured in 21 centres as a surrogate of urban air pollution. Results Forty-three per cent of participants reported moderate annoyance (1–5 on the scale) and 14% high annoyance (≥6) with large differences across centres (2–40% of high annoyance). Participants in the Northern European countries reported less annoyance. Female gender, nocturnal dyspnoea, phlegm and rhinitis, self-reported car and heavy vehicle traffic in front of the home, high education, non-smoking and exposure to environmental tobacco smoke were associated with higher annoyance levels. At the centre level, adjusted means of annoyance scores were moderately associated with sulphur urban levels (slope 1.43 μg m−3, standard error 0.40, r = 0.61). Conclusions Annoyance due to air pollution is frequent in Europe. Individuals’ annoyance may be a useful measure of perceived ambient quality and could be considered a complementary tool for health surveillance.
Follow-up of the Swiss Cohort Study on Air Pollution and Lung Diseases in Adults (SAPALDIA 2) 1991–2003: methods and characterization of participants
Objectives: The Swiss Cohort Study on Air Pollution and Lung Diseases in Adults (SAPALDIA) was designed to investigate the health effects from long-term exposure to air pollution. Methods: The health assessment at recruitment (1991) and at the first reassessment (2001-3) consisted of an interview about respiratory health, occupational and other exposures, spirometry, a methacholine bronchial challenge test, end-expiratory carbon monoxide (CO) measurement and measurement for atopy. A bio bank for DNA and blood markers was established. Heart rate variability was measured using a 24-hour ECG (Holter) in a random sample of participants aged 50 years and older. Concentrations of nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3) and particulates in ambient air have been monitored in all study areas since 1991. Residential histories collected over the 11 year follow-up period coupled with GIS modelling will provide individual long-term air pollutant exposure estimates. Results: Of 9651 participants examined in 1991, 8715 could be traced for the cohort study and 283 died. Basic information about health status was obtained for 8047 individuals (86% of alive persons), 6 528 individuals (70%) agreed to the health examination and 5 973 subjects (62%) completed the entire protocol. Non-participants in the reassessment were on average younger than participants and more likely to have been smokers and to have reported respiratory symptoms in the first assessment. Average weight had increased by 5.5 kg in 11 years and 28% of smokers in 1991 had quit by the time of the reassessment.
Characterization of source-specific air pollution exposure for a large population-based Swiss cohort (SAPALDIA)
Background: Although the dispersion model approach has been used in some epidemiologic studies to examine health effects of traffic-specific air pollution, no study has evaluated the model predictions vigorously. Methods: We evaluated total and traffic-specific particulate matter < 10 and < 2.5 microm in aero-dynamic diameter (PM(10), PM(2.5)), nitrogren dioxide, and nitrogen oxide concentrations predicted by Gaussian dispersion models against fixed-site measurements at different locations, including traffic-impacted, urban-background, and alpine settings between and across cities. The model predictions were then used to estimate individual subjects' historical and cumulative exposures with a temporal trend model. Results: Modeled PM(10) and NO(2) predicted at least 55% and 72% of the variability of the measured PM(10) and NO(2), respectively. Traffic-specific pollution estimates correlated with the NO(x) measurements (R(2) >or=0.77) for background sites but not for traffic sites. Regional background PM(10) accounted for most PM(10) mass in all cities. Whereas traffic PM(10) accounted for < 20% of the total PM(10), it varied significantly within cities. The modeling error for PM(10) was similar within and between cities. Traffic NO(x) accounted for the majority of NO(x) mass in urban areas, whereas background NO(x) accounted for the majority of NO(x) in rural areas. The within-city NO(2) modeling error was larger than that between cities. Conclusions: The dispersion model predicted well the total PM(10), NO(x), and NO(2) and traffic-specific pollution at background sites. However, the model underpredicted traffic NO(x) and NO(2) at traffic sites and needs refinement to reflect local conditions. The dispersion model predictions for PM(10) are suitable for examining individual exposures and health effects within and between cities.
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.
PM2.5 assessment in 21 European study centers of ECRHS II: method and first winter results
The follow-up of a cohort of adults from 29 European centers of the former European Community Respiratory Health Survey (ECRHS) I (1989–1992) will examine the long-term effects of exposure to ambient air pollution on the incidence, course, and prognosis of respiratory diseases, in particular asthma and decline in lung function. The purpose of this article is to describe the methodology and the European-wide quality control program for the collection of particles with 50% cut-off size of 2.5 µm aerodynamic diameter (PM2.5 ) in the ECRHS II and to present the PM2.5 results from the winter period 2000–2001. Because PM2.5 is not routinely monitored in Europe, we measured PM2.5 mass concentrations in 21 participating centers to estimate background exposure in these cities. A standardized protocol was developed using identical equipment in each center (U.S. Environmental Protection Agency Well Impactor Ninety-Six [WINS] and PQ167 from BGI, Inc.). Filters were weighed in a single central laboratory. Sampling was conducted for 7 days per month for a year. Winter mean PM2.5 mass concentrations (November 2000–February 2001) varied substantially, with Iceland reporting the lowest value (5 µg/m3) and northern Italy the highest (69 µg/m3). A standardized procedure appropriate for PM2.5 exposure assessmnt in a multicenter study was developed. We expect ECRHS II to have sufficient variation in exposure to assess long-term effects of air pollution in this cohort. Any bias caused by variation in the characteristics of the chosen monitoring location (e.g., proximity to traffic sources) will be addressed in later analyses. Given the homogenous spatial distribution of PM2.5 , however, concentrations measured near traffic are not expected to differ substantially from those measured at urban background sites.