4 June 2009
The Health Effects Institute (HEI) published an extended analysis of the American Cancer Society (ACS) study linking particulate air pollution and mortality. The new analysis confirms the health risks associated with particulate pollution, and shows that mortality rates from heart disease among people exposed to PM2.5 may be much higher than previously thought.
The original ACS study, started in 1982, played a central role in the setting of National Ambient Air Quality Standards for fine particulate matter (PM2.5) pollution in the United States, as well as assessments of benefits from PM reduction worldwide. Because of the importance of the original ACS study in formulating regulations and the controversy generated by the limitations of that study, the US EPA, the Congress, and industry requested that the HEI conduct the Particle Epidemiology Reanalysis Project with the objective of independently assessing the original data and findings.
The new study increased the follow-up period to 18 years (1982 to 2000) and extend the range of analyses. The cohort for the study consisted of approximately 360,000 participants for 1980 and about 500,000 participants for 2000, residing in 116 American cities in areas with adequate PM2.5 monitoring data. The causes of death that were analyzed included all causes, cardiopulmonary disease (CPD), ischemic heart disease (IHD, reduction of blood supply to the heart, potentially leading to heart attack), lung cancer, and all remaining causes.
For the Nationwide Analysis, the associations between average PM2.5 concentrations and mortality from all causes (except the category of “all other causes”) were statistically significant. The hazard ratio (HR) for death was elevated by 3% to 15%, depending on the cause of death, for each increase of 10 µg/m3 in PM2.5. These estimates were in general higher than those found in previous analyses. The strongest estimate was for IHD: HR = 1.24, compared to about 1.12 in previous estimates.
In the Intra-Urban Analysis, differences existed between the New York and the Los Angeles metropolitan areas. The LA results showed much larger HRs than the NYC results, except for mortality due to IHD. The risks were also more evenly distributed in NYC, while some LA areas, including neighborhoods near the Ports of Los Angeles and Long Beach, had elevated health risks.
The analysis—published as HEI Report #140—was conducted by a team of researchers from the University of Ottawa, led by Dr. Daniel Krewski.