Particulate matter, science and EU policy

Several new research findings regarding the health effects of airborne particulate matter (PM) (usually studied by the size of the particles, e.g. PM10, particles with a 50% cut-off aerodynamic diameter of 10 μm, and PM2.5, particles with a 50% cut-off aerodynamic diameter of 2.5 μm) have been presented at two important scientific meetings held in September 2006: the Conference of the European Respiratory Society (ERS), in Munich, and the joint Conference of the International Society for Environmental Epidemiology (ISEE) and the International Society for Exposure Analysis (ISEA) in Paris. This is not surprising, since: 1) the health effects of air pollution are among the largest environmental problems worldwide 1; 2) several scientific questions are still open; and 3) common research efforts from the epidemiological, toxicological and clinical worlds are under way. A brief review of the evidence follows. The initial suggestion that mortality increases due to long-term, low-level exposure to PM was provided by the Harvard Six Cities study 2. These findings were confirmed in the long-term follow-up (1982–1998) of the American Cancer Society (ACS) II cohort, consisting of ∼500,000 adults from metropolitan areas throughout the USA 3, 4. In the latter study, each 10 μg·m−3 elevation in PM2.5 was associated with approximately a 6, 9 and 14% increased risk of all-cause, cardiopulmonary and lung cancer mortality, respectively. A recent report from Los Angeles 5, which included a large proportion of the ACS II cohort from that area, has indicated that a more refined method for assessing exposure produces a higher risk estimate of mortality increase (17% increase; 95% confidence interval 5–30%) for an increase of 10 μg·m−3 in PM2.5. Well-conducted cohort studies in Europe, which have estimated air pollution exposure at individual residences, confirm the findings from the USA …