Diesel cars might get great gas mileage when compared to their gasoline counterparts, but now the World Health Organization has warned that diesel fumes are now known to prove lung cancer. In fact, the W.H.O. says, diesel fumes are more carcinogenic than secondhand cigarette smoke. So dangerous, it has decided to elevate diesel to the status of “known carcinogen,” reports the New York Times.

However, the health risk is most pronounced in countries with poor air quality standards, where diesel trucks, generators and machinery commonly produce black clouds of sooty exhaust fumes. By contrast, in the U.S. and Europe, tough emissions standards require diesel cars and trucks produce as little emissions and exhaust particulates as possible.

Even with higher-pressure direct injection and ultra-low sulfur fuel, so-called ‘clean-diesel’ engines may suffer at the hand of the W.H.O’s new classification of diesel fumes. According to Dr. Silverman, chief of environmental epidemiology at the National Cancer Institute, the WH.O ruling was one she was “totally in support” of, adding that the U.S. government may soon declare diesel exhaust fumes a known carcinogen. But the medical director of the American Cancer Society, Dr. otis W. Brawley, doesn’t think diesel cars are the main concern.

“I don’t think it’s bad to have a diesel car,” he told The New York Times. “I don’t think it’s good to breathe its exhaust. I’m not concerned about people who walk past a diesel vehicle, I’m a little concerned about people like toll collectors, and I’m very concerned about people like miners, who work where exhaust is concentrated.”

With gasoline exhaust still classified as a possible carcinogen by many health organizations, the W.H.O’s announcement regarding diesel fumes is likely to further incentivize the auto industry to develop greener-burning engines and better exhaust filtration systems to make cars as clean as possible.

For now however, it is unlikely to dramatically influence consumer choice at the dealer, where diesel cars represent a tiny fraction of the total number of new cars sold in the U.S. each year. There is one final thought we’d like to add: if you’re in the market for a diesel car, remember that cars made within the past few years are far cleaner — and greener — than older diesel engines.

________________________

This story originally appeared at Green Car Reports.