National Air Pollution Surveillance Network Research Articles

Spatiotemporal trends of PM2.5 and its major chemical components at urban sites in Canada

To evaluate the effectiveness of emission control regulations designed for reducing air pollution, chemically resolved PM2.5 data have been collected across Canada through the National Air Pollution Surveillance network in the past decade. 24-hr time integrated PM2.5 collected at seven urban and two rural sites during 2010-2016 were analyzed to characterize geographical and seasonal patterns and associated potential causes. Site-specific seven-year mean gravimetric PM2.5 mass concentrations ranged from 5.7 to 9.6 µg/m3. Seven-year mean concentrations of SO42−, NO3−, NH4+, organic carbon (OC), and elemental carbon (EC) were in the range of 0.68 to 1.6, 0.21 to 1.5, 0.27 to 0.71, 1.1 to 1.9, and 0.37 to 0.71 µg /m3, accounting for 10.8%-18.1%, 3.7%-16.7%, 4.7%-7.4%, 18.4%-21.0%, and 6.4%-10.6%, respectively, of gravimetric PM2.5 mass. PM2.5 and its five major chemical components showed higher concentrations in southeastern Canada and lower values in Atlantic Canada, with the seven-year mean ratios between the two regions being on the order of 1.7 for PM2.5 and 1.8-7.1 for its chemical components. When comparing the concentrations between urban and rural sites within the same region, those of SO42− and NH4+ were comparable, while those of NO3−, OC, and EC were around 20%, 40%-50%, and 70%-80%, respectively, higher at urban than rural sites, indicating the regional scale impacts of SO42− and NH4+ and effects of local sources on OC and EC. Monthly variations generally showed summertime peaks for SO42− and wintertime peaks for NO3−, but those of NH4+, OC, and EC exhibited different seasonality at different locations.

Comparison of remote sensing and fixed-site monitoring approaches for examining air pollution and health in a national study population

Satellite remote sensing (RS) has emerged as a cutting edge approach for estimating ground level ambient air pollution. Previous studies have reported a high correlation between ground level PM2.5 and NO2 estimated by RS and measurements collected at regulatory monitoring sites. The current study examined associations between air pollution and adverse respiratory and allergic health outcomes using multi-year averages of NO2 and PM2.5 from RS and from regulatory monitoring.RS estimates were derived using satellite measurements from OMI, MODIS, and MISR instruments. Regulatory monitoring data were obtained from Canada's National Air Pollution Surveillance Network. Self-reported prevalence of doctor-diagnosed asthma, current asthma, allergies, and chronic bronchitis were obtained from the Canadian Community Health Survey (a national sample of individuals 12 years of age and older). Multi-year ambient pollutant averages were assigned to each study participant based on their six digit postal code at the time of health survey, and were used as a marker for long-term exposure to air pollution.RS derived estimates of NO2 and PM2.5 were associated with 6–10% increases in respiratory and allergic health outcomes per interquartile range (3.97 μg m−3 for PM2.5 and 1.03 ppb for NO2) among adults (aged 20–64) in the national study population. Risk estimates for air pollution and respiratory/allergic health outcomes based on RS were similar to risk estimates based on regulatory monitoring for areas where regulatory monitoring data were available (within 40 km of a regulatory monitoring station). RS derived estimates of air pollution were also associated with adverse health outcomes among participants residing outside the catchment area of the regulatory monitoring network (p < 0.05).The consistency between risk estimates based on RS and regulatory monitoring as well as the associations between air pollution and health among participants living outside the catchment area for regulatory monitoring suggest that RS can provide useful estimates of long-term ambient air pollution in epidemiologic studies. This is particularly important in rural communities and other areas where monitoring and modeled air pollution data are limited or unavailable.

Comparison of Remote Sensing, Land-use Regression, and Fixed-site Monitoring Approaches for Estimating Exposure to Ambient Air Pollution Within a Canadian Population-based Study of Respiratory and Cardiovascular Health

O-31A5-5 Background/Aims: Remote sensing (RS) has emerged as a cutting edge approach for estimating ground-level concentrations of ambient air pollution. While the validity of RS has been demonstrated through comparisons to values obtained from fixed-site monitoring, no previous epidemiological studies have investigated the implications of using RS to characterize health risks. We examined respiratory and cardiovascular health outcomes associated with longer -term exposure measures of air pollution in a national population-based survey (N = 125,574), using estimates of annual average based on RS, land-use regression (LUR) models, and measured concentrations at the nearest fixed site monitor station. Methods: RS estimates of NO2 and PM2.5 were derived using satellite measurements from OMI, MODIS, and MISR. Multi-city LUR estimates were based on spatial models incorporating land-use characteristics such as traffic and industrial sources. Measured concentrations at the nearest regulatory continuous monitoring site were obtained from the National Air Pollution Surveillance Network. Self-reported health outcomes including diagnosis, age of onset, symptoms, and medication use for: asthma, bronchitis, COPD, heart disease, hypertension, congestive heart failure, angina, heart attack, and diabetes were collected through the Canadian Community Health Survey, a representative sample of Canadians 12 years of age and older. Results: RS estimates of PM2.5 and NO2 were highly correlated with ground-based measurements in North America (R = 0.9 and 0.8, respectively). Long-term exposures to ambient NO2 and PM2.5 were significantly associated with respiratory and cardiovascular health outcomes (OR = 1.1–1.4, P < 0.05) adjusting for age, sex, socioeconomic status, smoking status, and second-hand smoke. Effect estimates for RS were similar to those obtained using LUR and nearest fixed site monitor. Conclusion: These results suggest that RS can provide useful estimates of individual long-term exposure to ambient air pollution in epidemiologic studies, particularly in remote and rural areas for which monitoring and modeled air quality data are unavailable.

CAREX Canada—Development of a National Environmental Carcinogen Exposure Surveillance Tool

O-31B6-4 Background/Aims: Our goal is to produce indicators for the surveillance of Canadians' exposures to environmental carcinogens that reflect spatial variability. Methods: We developed a spreadsheet-based tool to estimate life-stage weighted average daily intake. Factors considered include frequency of detection, bodyweight, intake rates, and time spent indoor and outdoor for 5 life-stages (infant, small child, child, teen, and adult). Using benzene as an example, we populated the tool with data from the National Air Pollution Surveillance network, Canadian Food Inspection Agency reports, US Food and Drug Administration Total Diet Study reports, the 2006 Statistics Canada Food Statistics report, California Office of Environmental Health Hazard Assessment cancer potency values, and peer-reviewed literature. For outdoor air, we linked the results with a spatial model of benzene concentrations and block point population data from Statistics Canada. Results: Estimated lifetime average daily intake levels (and associated cancer risk) are: outdoor air, 3.4 μg/d (1:161,000); indoor air, 32 μg/d of benzene (1:20,250); drinking water, 1.5 μg/day (1:388,500); and food, less than 2.25 × 10–6 μg/day (>1:114 billion). After including the spatial variation in population locations and outdoor benzene concentrations, we assigned estimated excess lifetime risk for each of 487,000 block point locations (50th percentile = 1:263,000, 5th percentile = 1:399,000; 95th percentile = 1:75,250). Overall, we estimate that in 2006, the lifetime excess risk of cancer was 1:100,000 or more for 11.1 million Canadians, 35 percent of the total population. Conclusion: The tool provides a flexible but comprehensive method for producing comparable screening level indicators of exposure and excess cancer risk for numerous known and suspected carcinogens. Incorporating spatial variation, when appropriate, provides a new level of detail that aids in targeting prevention efforts.

The association between low level exposures to ambient air pollution and term low birth weight: a retrospective cohort study

BackgroundStudies in areas with relatively high levels of air pollution have found some positive associations between exposures to ambient levels of air pollution and several birth outcomes including low birth weight (LBW). The purpose of this study was to examine the association between LBW among term infants and ambient air pollution, by trimester of exposure, in a region of lower level exposures.MethodsThe relationship between LBW and ambient levels of particulate matter up to 10 um in diameter (PM10), sulfur dioxide (SO2) and ground-level ozone (O3) was evaluated using the Nova Scotia Atlee Perinatal Database and ambient air monitoring data from the Environment Canada National Air Pollution Surveillance Network and the Nova Scotia Department of Environment. The cohort consisted of live singleton births (≥37 weeks of gestation) between January1,1988 and December31,2000. Maternal exposures to air pollution were assigned to women living within 25 km of a monitoring station at the time of birth. Air pollution was evaluated as a continuous and categorical variable (using quartile exposures) for each trimester and relative risks were estimated from logistic regression, adjusted for confounding variables.ResultsThere were 74,284 women with a term, singleton birth during the study period and with exposure data. In the analyses unadjusted for year of birth, first trimester exposures in the highest quartile for SO2 and PM10suggested an increased risk of delivering a LBW infant (relative risk = 1.36, 95% confidence interval = 1.04 to 1.78 for SO2 exposure and relative risk = 1.33, 95% confidence interval = 1.02 to 1.74 for PM10). After adjustment for birth year, the relative risks were attenuated somewhat and not statistically significant. A dose-response relationship for SO2 was noted with increasing levels of exposure. No statistically significant effects were noted for ozone.ConclusionOur results suggest that exposure during the first trimester to relatively low levels of some air pollutants may be associated with a reduction in birth weight in term-born infants. These findings have implications for the development of effective risk management strategies to minimize the public health impacts for pregnant women.