Wednesday, May 9, 2012

Harvard Six Cities Study Update on Mortality from Exposure to Fine Particles

Chronic Exposure to Fine Particles and Mortality: An Extended Follow-Up of the Harvard Six Cities Study from 1974 to 2009 (31 page pdf, Johanna Lepeule, Francine Laden, Douglas Dockery, Joel Schwartz, Environ Health Perspect, Mar. 28, 2012)

 The research article of interest today is an update of the famous 1993 Six Cities Study (in the USA) that established links between long term exposure to fine PM and mortality. The newer research continued to showed a significant relationship between PM 2.5 and both lung and cardiovacular mortality, without any lower safe threshold and points to the public health benefits of further reductions in PM 2.5 levels.  
Key Quotes:

“Our goal was to test the robustness of the association between chronic exposure to PM2.5 and mortality observed in the original study (Dockery et al. 1993)…..by replicating the analyses using eleven additional years of follow-up with exposures well below the US annual standard (15μg/m3)”

 “Including more recent observations with PM2.5 exposures down to 8μg/m3, we continued to find a statistically significant association between chronic exposure to PM2.5 and all-cause and cardiovascular mortality”

“Our results indicated a statistically significant 14% increase in all-cause mortality for a 10μg/m3 annual increase in PM2.5” “the present extended follow-up estimated a statistically significant 37% increase in lung cancer mortality (for each 10μg/m3 increase in PM2.5)”

 “Given that there were 2,423,712 deaths in the US in 2007..and that the average PM2.5 level was 11.9μg/m3 (EPA), our estimated association between PM2.5 and all-cause mortality implies that a decrease by 1μg/m3 in population average PM2.5 would result in 33,932 fewer deaths per year”

 “the relationship between chronic exposure to PM2.5 and all cause, cardiovascular and lung cancer mortality was found to be linear without a threshold.. further public policy efforts that reduce fine particulate matter air pollution are likely to have continuing public health benefits
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