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Just how bad is air pollution for you? A study of more than 60 million Medicare recipients has found that even pollution levels below those generally considered safe increase the risk for premature death. Using satellite, meteorological and other data, plus data gathered from 3,805 monitoring stations maintained by the Environmental Protection Agency, researchers were able to accurately estimate daily air pollution levels nationwide. The study is in The New England Journal of Medicine. (Bakalar, 6/28)

The nationwide study of more than 60 million senior citizens linked long-term exposure to two main smog pollutants — ozone and fine particulate matter — to an increased risk of premature death. The analysis found no sign of a “safe” level of pollution, below which the risk of dying early tapered off. (Barboza, 6/28)

"We are now providing bullet-proof evidence that we are breathing harmful air," says Francesca Dominici, a professor of biostatistics at the Harvard T.H. Chan School of Public Health, who led the study. "Our air is contaminated." (Stein, 6/28)