New research from the National Cancer Institute documents elevated cancer risk in miners exposed to diesel exhaust underground. Their study of 12,000 miners and their diesel particulate matter (DPM) exposure revealed correlations with lung cancer down to the lowest levels of exposure. Yes, cancer risk was significant even at levels that overlap what is present in sooty urban air from buses, trucks, construction machinery and trains. The message to miners is to demand better underground working conditions if you want to live to see your kids graduate college. The message for the rest of us who frequent urban landscapes is the less diesel exposure the better. And this noxious exhaust is not just an eventual cancer risk but there is a mountain of research showing that its also an immediate stress on the lungs, heart and nervous system. The greatest acute risks are borne by babies and the elderly as they have less ability to fend off diesel's inflammatory effects in the deep lung.
While diesel particles are ubiquitous, there are "micro-environments" that are particularly high. Urban commuters are on the diesel front lines as bus, highway and rail travel often involves being surrounded by big diesel engines. The Clean Air Task Force did a fascinating study in 2007 in which they measured DPM in cars and on buses and trains in Boston and NYC. DPM levels shot up when following behind a truck that had no particle capture which unfortunately is still typical. Regarding bus travel, even though the exhaust is outside the bus, it finds its way into the interior causing four fold higher diesel exposures than in typical urban air. I can remember getting bus sick at the back of the school bus as a kid -- now I know that it wasn't just because it was the bumpiest part of the ride, but closest to where the exhaust comes out.
Walking, jogging or bike riding downtown make their contribution if along busy roadways with truck and bus traffic. Cities are converting their fleet of buses over to greener cleaner burning natural gas buses and more trucks are being required to wear particle diapers (filters). So urban air is slowing improving. In the meantime, a few tips to duck that diesel plume:
1) When driving or cycling keep your distance from buses and trucks. In the car keep windows rolled up and vent on recirculate while in diesel traffic. Try to find less busy commuting routes especially if on a bike. Just budget the extra travel time if necessary to get away from the bus and truck routes.
2) Pay attention to air pollution alerts from USEPA (AirNow.gov). Avoid heavy exercise on the bad air days -- even if you are a healthy all weather walker/jogger/cyclist, you should keep in mind that the toll on your lungs adds up.
3) Recognize that idling buses pollute the street as well as the bus interior. Ask the driver not to idle (some cities and states have anti-idling laws, especially for school buses parked near schools).
4) Look for playgrounds and schools for your kids that are away from busy roads and diesel fallout. The classic environmental justice image is the inner city school with a highway on one side and a factory or landfill on the other.
You may be wondering about diesel cars. Current emissions standards have forced the newer models to carry particle traps which are pretty effective if the driver pays attention to the lights and messages and gets the filter serviced when called for. This is not to say that you should drive your personal car rather than take mass transit into work. Mass transit overall is a huge benefit to urban air quality -- we just have to make it better by converting our cigar-smoking sooty diesel vehicles to the cleaner technology that is already available. We as a society are kicking the cigarette habit -- it's time to kick diesel as well.
Stay tuned to this blog as next time I will talk about my adventures in a major rail station taking diesel measurements and trying to not gag on the horrid air quality.