Project

Background. The Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA) is a unique nearly 20-year old cohort study, investigating the health effects of air pollution. It was incepted in 1991 (SAP1) with baseline health examination in 8 areas of 9600 participants, with a first follow up in 2002-03 (SAP2) and a second one in 2010-11 (SAP3). In past, SAPALDIA has strongly contributed in understanding the association between respiratory and cardiovascular health effects with regulated air pollutants, PM10 and NO2. Partly, it was possible due to the state of the art air pollution exposure models that were developed for these pollutants. As the second follow up (SAP3) has expanded on the measured health outcomes, it is in a state where improved exposure assessment is pivotal to further advance our understanding on health effects of air pollution on Swiss population. In fact, SAPALDIA is also participating in a European Study of Cohorts for Air Pollution Effects (ESCAPE), a collaboration of 34 European cohort studies for quantification of effects of long-term exposure to outdoor air pollution on human health.

Why this study needed? Recent findings in SAPLADIA and elsewhere in North American and European studies suggest even stronger associations for traffic related air pollutants. These studies have indicated that concentrations of traffic exhaust pollutants (e.g. ultrafine particles, NO2 and soot) vary greatly within 200m of major roads, a centrally located monitoring site can not capture the high exposures of SAP3 subjects living near busy roads. SAP2 has advanced air pollution exposure science by conducting innovative exposure modeling across 8 geographically diverse areas in Switzerland using dispersion modeling and NO2 land use regression modeling. However, exposure to specific traffic related pollutants such as ultrafine particles and PM chemical components was not assessed. Furthermore, exposures were only assessed at outdoor home addresses without taking into account outdoor exposure at workplaces or indoor exposure at homes.

What this study will do? This study will capitalize on air pollution exposure information gathered in earlier studies and existing SAPALDIA-ESCAPE collaboration and expand exposure science research to focus on characterizing spatial variability of size-segregated outdoor and indoor PM viz. ultrafine particles measured as particle number concentration (PNC), PM2.5, PM10, together with NO2 and PM2.5 chemical constituents including soot, trace metals and inorganic ions. The overarching aim of the proposed study is to provide the estimates of individual long-term outdoor traffic-related air pollution exposures of the study participants to complement the health data currently assessed. To that effect, outdoor and indoor exposure models will be built for the key pollutants in different SAPALDIA areas. The study, for very first time in any epidemiological study, will investigate the spatial variation of outdoor PNC within and across areas as well as its short- and long-term relationship with indoor PNC exposure.

How the study will be conducted? The study will be conducted in all SAPALDIA areas for NO2 and four (of the eight) areas for PM over a period of 2 years. 2-week NO2 measurements will be made at 40 outdoor locations in each study area over three different seasons. In four key areas, 20 out of the 40 locations will be monitored for indoor and outdoor PNC, PM2.5, PM10, and indoor NO2. PM2.5 filters will be analyzed for their chemical composition such as heavy metals and inorganic ions and soot. Individual time-activity patterns i.e. where the participants spent their time during monitoring will be collected and additionally home indoor activities and ventilation characteristics will be gathered.

Air pollution exposure models will be built for outdoor air pollutants using statistical methods utilizing geographic information system obtained parameters (such as distance from nearest main road, traffic volume, population density etc,) land-use, meteorological and dispersion model estimates predictor variables. Indoor exposure models will be built using statistical methods utilizing outdoor pollutant concentrations and collected information on home ventilation and indoor sources. Models will be built for biweekly as well as annual average exposures for all key pollutants of interest including ultrafine particles.

What will be the implications? The validated models will then be applied to the SAP3 cohort study to derive participants’ individual exposure to traffic-related air pollution. The study will advance exposure science by gaining understanding of the relationship between indoor, outdoor and personal ultrafine particle exposures in the general population. The subsequent modeling results will provide long-term ultrafine particle exposure estimates for the first time in the air pollution cohort studies for health assessment. In addition, PM2.5 and PM10 measurements will add to the existing knowledge of outdoor spatial distribution of long-term air pollution exposures. Thus by providing traffic-related novel key air pollution exposure data for each SAP3 participant, the study will make a fundamental contribution to SAPALDIA to investigate key exposure-health effect research questions. From a policy perspective, the study will also contribute to the discussion about whether and how to regulate particles of different size fractions in Switzerland and EU at large.