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.