"Work exposure to diesel fumes tied to lung cancer." That's the headline of a Reuters news story this week reporting on a new research analysis.

Hold on a minute. This is news?

I thought that was the whole reason we've been through a decade of turmoil as engine makers struggled to meet a new round of stricter federal emissions regulations every few years, trying to avoid trade-offs with engine reliability or fuel economy or weight. Isn't this why a new 2010-emissions-certified engine costs thousands of dollars more than its predecessors? Isn't this why we now have diesel engines where you can put a white handkerchief over the exhaust and have it stay white? Why in some areas of the country the air coming out the stack is actually cleaner than the air going into the engine?

The study, which analyzed the results from 11 previous studies in Europe and Canada, found that workers with the greatest lifetime exposure to diesel exhaust had a 31 percent higher risk of lung cancer than people without work exposure.

Overall, Reuters Health reported, "the magnitude of the lung-cancer risk associated with diesel exhaust was on par with the risks linked to habitual exposure to second-hand cigarette smoke and indoor radon."

Researchers considered certain workers -- including diesel-engine mechanics -- as having heavy exposure to diesel fumes. Other workers, such as truck drivers, were deemed to have relatively lower exposure.

The story is careful to note that the results don't prove that diesel exhaust caused the extra lung cancer cases among the people studied. But, it points out, diesel exhaust is already considered a probable human carcinogen by health authorities including the U.S. Environmental Protection Agency and the International Agency for Research on Cancer, a part of the World Health Organization.

I was glad to see Reuters did bring up the question of how relevant this research is with the advancements that have been made in cleaning up emissions:

"Another open question is how relevant the current findings are to workers with on-the-job exposure to diesel exhaust only in recent years. Some people in the 11 studies had work exposures dating as far back as the 1920s.

"It is difficult to say how exposures among today's workers would compare with those of workers in these studies ... Diesel engines have become 'cleaner' in the past 20 years, with innovations such as 'ultra-low' sulfur fuel."