There is need for the assessment of long-term effects of outdoor air pollution. In fact, a considerable part of the large amount of U.S. research money that has been dedicated to investigate effects of ambient particulate pollution should be invested to address long-term effects. Studies that follow the health status of large numbers of subjects across long periods of time (i.e., cohort studies) should be considered the key research approach to address these questions. However, these studies are time consuming and expensive. We propose efficient strategies to address these questions in less time. Apart from long-term continuation of the few ongoing air pollution cohort studies in the United States, data from large cohorts that were established decades ago may be efficiently used to assess cardiorespiratory effects and to target research on detection of the most susceptible subgroups in the population, which may be related to genetic, molecular, behavioral, societal, and/or environmental factors. This approach will be efficient only if the available air pollution monitoring data will be used to spatially model long-term outdoor pollution concentrations across a given country for each year with available pollution data. Such concentration maps will allow researchers to impute outdoor air pollution levels at any residential location, independent of the location of monitors. Exposure imputation may be based on residential location(s) of participants in long-standing cardiorespiratory cohort studies, which can be matched to pollutant levels using geographic information systems. As shown in European impact assessment studies, such maps may be derived relatively quickly. Key words: exposure models, geographic information systems, GIS, long-term effects, outdoor air pollution, particulate matter. Environ Health Perspect 108:915-918 (2000). [Online 18 August 2000]
On both sides of the Atlantic, research advisory boards have emphasized the need for the investigation of long-term health effects of outdoor air pollution (1-3). Although air pollution-related health effects have received considerable attention and funding in the last two decades, efforts have focused primarily on short-term effects through controlled exposure studies and a variety of epidemiologic study designs (4-8).
A few longitudinal studies (9-11) and many cross-sectional studies have evaluated potential long-term health effects. However, additional epidemiologic studies are needed to evaluate potential long-term health effects of exposures to ambient air pollution. In particular, such studies should be able to provide reasonable estimates of past exposures that extend over many years, either for groups (populations) or individuals. These studies also are needed to better estimate the public health impact of air pollution and the benefit of air pollution control (12).
Apart from intervention studies (which usually are not suitable in environmental health), cohort studies (which follow the health history of the same people over long periods of time) remain the "gold standard" design used to assess the effects of air pollution on life expectancy or on the incidence, course, resistance, and remission of diseases. However, cohort studies have disadvantages that stem both from inherent features of the exposures of interest as well as from the health outcomes. We will discuss these issues and propose efficient strategies to overcome the main problems and to facilitate optimal use of the substantial research money dedicated to investigate the health effects of particulate pollution (as one of the key surrogates of overall outdoor air pollution).
A Challenging Research Setting
In contrast to occupational or behavioral risk factors, exposure to outdoor ambient air pollution is ubiquitous. Lifetime exposures to outdoor air pollution, which are relatively homogeneously distributed across large areas [e. …