[Health risk assessment of traffic-related air pollution near busy roads]. / Exposition à la pollution atmosphérique de proximité liée au trafic : quelles méthodes pour quels risques sanitaires ?

BACKGROUND: Although ambient urban air pollution has well-established health effects, epidemiology faces many difficulties in estimating the risks due to exposure to traffic pollutants near busy roads. This review aims to summarize how exposure to traffic-related air pollution near busy roads is assessed in epidemiological studies and main findings regarding health effects. METHOD: After presenting the specificity of emissions due to traffic road, this review identifies the key methods and main results found in epidemiologic studies seeking to measure the influence of exposure to nearby traffic on health published over the past decade. RESULTS: The characterization and measurement of population exposure to traffic pollution faces many difficulties. Thus, epidemiological studies have used two broad categories of surrogates to assess exposure: direct measures of traffic itself such as distance of the residence to the nearest road and traffic volume and modeled concentrations of pollutant surrogates. Studies that implemented these methods showed that people living near heavy traffic road or exposed to near-road air pollution tend to report more health outcomes. DISCUSSION: Traffic-related air pollution near busy roads is the subject of increasing attention, and tends to be better characterized. However, its health impacts remain difficult to grasp, especially because of the vast diversity of approaches used in epidemiological studies. Greater consistency in the protocols would be desirable to provide better understanding of the health issue of traffic in urban areas and thus to better implement policies to protect those most at risk.

[Contribution of case-crossover design to the analysis of short-term health effects of air pollution: reanalysis of air pollution and health data]. / Apport de la méthode cas-croisé à l'analyse des effets sanitaires à court terme de la pollution atmosphérique: réanalyse de données du programme Erpurs.

BACKGROUND: During the last decades, numerous studies have shown significant links between short-term exposure to air pollution and health. Time series design have been widely used in order to study these associations. In recent years, the case-crossover design has been applied to the analysis of acute effects of environmental exposures, especially air pollution. The aims of this paper are to describe the case-crossover design and to compare this approach with time series design to assess the association between air pollution and health. METHODS: In the case-crossover approach, a case-control study is conducted whereby each person who had a health event (case period) is matched with himself/herself on a nearby time period where he/she did not have the event (control period). Review of the literature shows that the referent selection strategies can be associated to a bias in the estimation of the health effect of air pollution. In comparison with time series design, the case-crossover design is easier to conduct, and individual factors can be taken into account. Nevertheless, it is not possible to take into account the overdispersion in the health indicator with this approach. RESULTS AND CONCLUSION: In conclusion, we suggest to use time series analysis with population data and case-crossover design with individual data.

Short-term associations between fine and coarse particles and hospital admissions for cardiorespiratory diseases in six French cities.

OBJECTIVES: Little is known about the potential health effects of the coarse fraction of ambient particles. The aim of this study is to estimate the links between fine (PM(2.5)) and coarse particle (PM(2.5-10)) levels and cardiorespiratory hospitalisations in six French cities during 2000-2003. METHODS: Data on the daily numbers of hospitalisations for respiratory, cardiovascular, cardiac and ischaemic heart diseases were collected. Associations between exposure indicators and hospitalisations were estimated in each city using a Poisson regression model, controlling for confounding factors (seasons, days of the week, holidays, influenza epidemics, pollen counts, temperature) and temporal trends. City-specific findings were combined to obtain excess relative risks (ERRs) associated with a 10 mug/m(3) increase in PM(2.5) and PM(2.5-10 )levels. RESULTS: We found positive associations between indicators of particulate pollution and hospitalisations for respiratory infection, with an ERR of 4.4% (95% CI 0.9 to 8.0) for PM(2.5-10 )and 2.5% (95% CI 0.1 to 4.8) for PM(2.5). Concerning respiratory diseases, no association was observed with PM(2.5), whereas positive trends were found with PM(2.5-10), with a significant association for the 0-14-year-old age group (ERR 6.2%, 95% CI 0.4 to 12.3). Concerning cardiovascular diseases, positive associations were observed between PM(2.5) levels and each indicator, although some did not reach significance; trends with PM(2.5-10 )were weaker and non-significant except for ischaemic heart disease in the elderly (ERR 6.4%, 95% CI 1.6 to 11.4). CONCLUSIONS: In accordance with other studies, our results indicate that the coarse fraction may have a stronger effect than the fine fraction on some morbidity endpoints, especially respiratory diseases.