BMJ 2017;357:j3137 doi: 10.1136/bmj.j3137 (Published 2017 June 29)
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RESEARCH NEWS Air pollution link to premature death is supported by US study Jacqui Wise London
Long term exposure to airborne fine particulate matter (PM2.5) and ozone increases the risk of premature death even at levels below current air quality standards, a US study of 60 million people suggests.1 Researchers writing in the New England Journal of Medicine said that lowering PM2.5 by just 1 microgram per cubic metre (μg/m3) throughout the United States could save 12 000 lives every year. Similarly, if the level of ozone could be lowered by just one part per billion (ppb) nationwide, another 1900 lives a year could be saved. The study also found that black men and people with low incomes had much higher risks of premature death associated with exposure to air pollution than people in other subgroups. The researchers examined Medicare claims of 60 925 443 people aged over 65 from 2000 to 2012, representing 460 million person years of follow-up. They also estimated air pollution levels at each 1 km grid over the whole of the United States, using satellite measurements and a computer simulation.
increase was associated with an increase in the risk of death by 13.6% (13.1% to 14.1%), and at ozone levels below 50 ppb each 10 ppb increase was associated with a higher risk of death by 1.0% (0.9% to 1.1%). Moreover, the researchers found no evidence of a threshold value—namely, a concentration at which PM2.5 exposure does not affect mortality. The study leader, Francesca Dominici, professor of biostatistics at Harvard Chan School in Boston and codirector of the Harvard Data Science Initiative, said, “This is a study of unprecedented statistical power because of the massive size of the study population. These findings suggest that lowering the National Ambient Air Quality Standards for fine particulate matter will produce important public health benefits, especially among self identified racial minorities and people with low incomes.”
The current annual National Ambient Air Quality Standard, set by the Environmental Protection Agency, is 12 μg/m3 of PM2.5, and the current standard for daily ozone exposure is 70 ppb. Average PM2.5 concentrations ranged from 6.21 μg/m3 to 15.64 μg/m3, the highest concentrations being in California and in eastern and southeastern states. The warm season average ozone concentrations ranged from 36.27 ppb to 55.86 ppb, the highest concentrations being in the mountain states and California. The study found that each increase of 10 μg/m3 in annual exposure to fine particulate matter was associated with an increase in all cause mortality of 7.3% (95% confidence interval 7.1% to 7.5%). Each increase of 10 ppb in ozone was associated with an increase in all cause mortality of 1.1% (1.0% to 1.2%). When the analysis was restricted to lower levels of air pollution the researchers still found a considerable association between exposure and mortality. Below 12 μg/m3 of PM2.5 each 10 μg
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Di Q, Wang Y, Zanobetti A, et al. Air pollution and mortality in the entire Medicare population. N Engl J Med 2017. doi:10.1056/NEJMoa1702747.
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