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Smell of Diesel in the Morning

July 21, 2011
What happens when you put sixteen men in a house after asking them not to have drank alcohol for the last 24 hours and no smoking or caffeine in the last 4 hours. No this isn’t the next reality TV show. One at a time and every two weeks subjects underwent two hours of testing with a stationary bike in a chamber that may or may not have been pumping diesel engine exhaust fumes into the room with them. 10% of the exhaust gas from a 2.2L diesel engine was diluted with air and fed into the room in such a way that there was a 300 μg/m^3 concentration which is supposedly similar to high traffic areas or especially congested and polluted cities. In another configuration they passed this concentration through a teflon filter and in another they had a concentration of carbon nanoparticles.

It’s no secret diesel technology is of great interest to me. Over at Engineer Blogs one of my earliest posts was on the Military’s Love Affair with Diesel. I also just talked a few days about how the Chevy Cruze might have a diesel version coming to America. So it’s interesting to see where we go forward as we worry about emissions and cardiovascular health. Also what kind of technology might move us forward in the direction we want.

When the research team filtered the exhaust gas they ended up with a much lower concentration. Their exhaust gas averaged 348 μg/m^3 and regular, filtered air was less than 1 but the filtered exhaust averaged 6.

So what’s the end result? Well a lot of things were, perhaps surprisingly, not affected by the fumes. No difference in resting heart rate or blood flow. Systolic blood pressure took a hit up, but diastolic did not. What their carbon-only concentration was useful for is that it could be it’s not the parts of diesel exhaust that we need be concerned about but something about the whole. Something that’s happening in combustion might be making these nanoparticles more harmful.

Their conclusion is this: diesel exhaust fumes in the concentration tested impaired vasomotor vascular function. Filtered exhaust and the carbon nanoparticles did not affect vascular function. What they showed is a filter than can reduce concentration effectively can make a big difference. But they admit at the end that these kinds of filters are pricey and not applicable to a lot of commercial applications where those filters would have to be tested separately. Being an engineer, I keep thinking about the engine sitting in another room idling for two hours. Still the implications for design work on reducing the environmental impact of diesel exhaust is there. And there’s the lesson that individual pollutants can’t always be used to draw conclusions from as it’s important to test the whole system and see what a difference that makes. The combustion was obviously a key factor in making this combination of elements dangerous, and possibly more dangerous than the sum of its parts.

Mills, N., Miller, M., Lucking, A., Beveridge, J., Flint, L., Boere, A., Fokkens, P., Boon, N., Sandstrom, T., Blomberg, A., Duffin, R., Donaldson, K., Hadoke, P., Cassee, F., & Newby, D. (2011). Combustion-derived nanoparticulate induces the adverse vascular effects of diesel exhaust inhalation European Heart Journal DOI: 10.1093/eurheartj/ehr195

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