Radon is behind tobacco the No. 2 environmental factor in causing lung cancer. It’s estimated that radon in homes results in 15,000 to 22,000 deaths a year in the U.S.

A disturbing new study from Johns Hopkins University found that radon concentrations in Pennsylvania homes near fracking areas have radon concentrations 39 percent higher than those in non-fracking areas. Great. With all the other negative effects of fracking, ruining people’s wells and water supplies, etc., it also releases a cancer-causing element.

The study, published in Environmental Health Perspectives, took more than 2 million radon readings between 1987 and 2013 in 860,000 buildings. Wow, seriously extensive.

The study did not find a direct link between the fracking and radon releases, but it’s a pretty easy conclusion that that link exists — 39 percent increase in radon is eyebrow-raising.

We’ve turned a big corner in lung cancer in the U.S. The lung cancer death rate among men have been dropping steadily for 30 years and the death rate for women started to drop (albeit more slowly) about 15 years ago — mostly because far fewer people are smoking obviously. We don’t need more fracking to put a dent in that trend.