I've frequently discussed in recent years the mounting evidence for the need to lower the National Ambient Air Quality Standard for PM2.5. There is also substantial evidence that PM exposure is an environmental justice issue. In this context, electrification of our transportation system is seen as having a substantial co-benefit in the reduction of vehicle-related PM emissions, particularly in EJ communities.
Two recent stories both confirmed the validity of these issues and made manifest the complexity of the problems we are trying to solve. First up - "PM2.5 polluters disproportionately and systemically affect people of color in the United States," published this week in Science Advances. The authors looked at exposures to PM2.5 from 14 different sources. The short version that, pretty much across the board, POC are disproportionally exposed to PM2.5. For Blacks, it was literally true across the board:
Blacks are exposed to higher-than-average concentrations from all sectors.
OK, so we need to reduce PM2.5 emissions, particularly in EJ communities. We also need to decarbonize our transportation system. The obvious solution is EVs - no carbon emissions and no PM2.5 emissions. Right?
Not so fast. It turns out that the biggest source of PM2.5 emissions from vehicles is apparently from tire wear, not vehicle exhaust.
And thus we arrive at the second recent story. As noted this week in ClimateWire (subscription required), EVs tend to be heavier that internal combustion vehicles, and to accelerate faster, both of which tend to increase particulate emissions.
I'm not suggesting that we shouldn't be transitioning to EVs as quickly as possible. I'm just providing a gentle reminder that these issues are really complex and that policy makers have to be vigilant about unintended consequences.
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