Three times greater risk to health than believed
a university of Southern California led study has found air pollution poses almost three times greater danger to health than previously thought. The study by a team of American and Canadian researchers was based on almost two decades of data on chronic health effects of particulate matter less than 2.5 microns or pm2.5, on residents of Los Angeles metropolitan area.
Researchers also noted specificity in cause of death with pm2.5 more strongly with ischemic heart disease (ailments caused by a decreased blood supply due to narrowing of the coronary arteries) than with cardiopulmonary or all-cause mortality. They measured the relative risk of mortality -- measure of the contribution of a particular risk factor (of pm2.5) -- associated with a 10 microgramme per cubic metre increase of pm2.5. The findings appeared in the November issue of the journal Epidemiology (Vol 16, No 6).
Earlier studies took 1 or 2 pollution measures from several cities and compared health effects amongst cities. But for this study, pollution exposures of pm2.5 were interpolated from 23 state and local district monitoring stations within Los Angeles to more accurately reflect air pollution exposure where residents live and work. The study involved 22,905 participants (American Cancer Society subjects) over a period from 1982 to 2000.
The researchers found the health effects increased to nearly 17 per cent from about 6 per cent increase in mortality found in earlier studies. In case of cancer deaths, there was an increased risk from lung cancer. According to researchers, since lungs would be most directly affected by air pollution, this finding gives corroborative evidence that the association did not occur by chance. Few elevated risks were noted with ozone. Researchers also recorded more than two-fold increased risk of death from diabetes although number of diabetes-related deaths was smaller than that for heart disease, making findings less reliable.
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