Last month, scientists from around the world issued a report about air pollution, classifying it as a carcinogen. After looking at scores of studies relating air particles to disease outcomes, WHO researchers found that the evidence for a cancer link was overwhelming. Their conclusions were underscored by a case report of an 8-year-old in China — the most heavily polluted country in the world — who developed lung cancer.

A second report from Lancet — a leading British medical journal — linked air pollution to increased rates of low birth weight infants. Their data indicated that more than 20 percent of cases of fetal growth retardation could be prevented by improving air quality in European cities.

Over the last decades, most Americans have come to realize that we control our health, to a great degree, by the choices we make regarding diet, exercise and habits. We don’t have a lot of control over our genetic predispositions for diseases, though knowledge about how our genes interact with the environment is expanding rapidly.

As individuals, we also have little control over what we breathe. Clean air is a public policy issue — with health concerns balanced against cost. Strengthening the federal Clean Air Act is our best protection against dangerous air pollution; states can’t do it alone. Citizens need to know that the health risks of air pollution are real, and support measures that reduce its impact. “You are what you eat” is an old adage — new data add that you also “are what you breathe.”

Sydney R. Sewall, MDMaine Physicians for Social Responsibility Hallowell