In the US, switching to EVs would save lives and be worth billions

Common arguments about how electric vehicles cause more emissions than traditional vehicles when the electric grid is coal-powered are actually wrong. Still, it’s certainly true that a cleaner grid is needed to fully realize the benefits for climate change. Beyond the climate, part of the appeal of EVs is also the improved air quality, of course, and here the grid can be even more important. In the wrong situation, switching to an EV just moves the air pollution from the street to the power plant.

Building models

A team led by Northwestern’s Daniel Peters decided to have a particularly detailed look at this issue, examining several scenarios of grid generation and EV adoption in the US. The results show that even with today’s grid, switching to EVs produces significant benefits.

The researchers used simulated hourly air pollution data from vehicles around the country, along with emissions data for power plants. This went into a model of weather over the course of a year (2014, as it happens), which also simulated important chemical reactions and natural emissions of compounds that interact with pollutants. The resulting air quality simulations were applied to an EPA population health model to show the expected impact on human health.

Simulations were run for replacing 25 percent, 50 percent, and 75 percent of light-duty vehicles with EVs in each of three electric grid scenarios. There’s a baseline scenario, where electricity comes from the current mix of power plants. On one side of that, there was a scenario where the portion of electricity coming from emissions-free generators (wind, solar, hydroelectric, and nuclear). And for a worst-case scenario, the third scenario supplies all the electricity for EVs entirely with fossil fuel combustion plants.

The researchers were, of course, also interested in the climate benefits, as transportation accounts for about a bit under a third of CO₂ emissions in the US (light-duty vehicles account for 60 percent of that). Every scenario reduced CO₂ emissions, with the drops ranging from 217 million to 796 million tons per year. That’s because even EVs charged by coal plants produce less CO₂ than internal combustion vehicles. Obviously, a higher share of EVs and a cleaner grid means even greater savings.

Air Quality Over Pollution Quantity

One of the two categories of air pollution examined was fine particulate matter—termed PM_2.5 because the particles are 2.5 microns across or smaller. For pollutants like this, the grid makes an even bigger difference, as the sulfur emissions of coal-burning power plants, in particular, are potent sources.

For the extreme case where EV charging came only from fossil fuel combustion plants, a few states in the Northeast still see less PM_2.5 pollution. But it worsens things in much of the South and Midwest. Combining just Texas, Florida, North Carolina, and Minnesota in scenarios where 75 percent of vehicles are EVs, there are 130 more premature deaths per year because of PM_2.5 as power plant pollution increases. But on a cleaner grid than today’s, they would see 330 fewer deaths per year, instead. Even on today’s grid, every state but Florida would see an improvement.

For the US as a whole, every single scenario produces a net reduction in premature deaths from PM_2.5 pollution, despite the states mentioned above. If just 25 percent of vehicles swap to EVs and the grid is dirtier, the simulations estimate about 360 fewer premature deaths in the US each year. For a 75 percent conversion and a cleaner grid, that grows to over 2,900. And the researchers say this is based on a conservative estimate of PM_2.5’s health impact, with other estimates doubling those numbers.

Ozone, no hole

They also looked at ground-level ozone, which is produced by reactions between nitrogen oxides and volatile organic compounds. Ozone has an immediate effect that can trigger respiratory conditions, as those with asthma know well. The simulated benefit of EVs are a bit more consistent here, since even fossil-fuel-burning power plants don’t produce and distribute as much ground-level ozone as internal combustion vehicles.

There are fewer premature deaths in the US regardless of scenario, ranging from 100 fewer to 370 fewer per year. (Again, for the more conservative health impact estimate.) The improvement is largest in the Southeast this time. There are only a few states that, in one scenario or another, could see small increases in mortality. In an odd exception, for example, the simulations show that with 75 percent EVs and a cleaner grid, New York would see no change and New Jersey could see three more deaths per year. In the major urban centers, lowering the amounts of nitrogen oxides emitted happens to make the ozone reaction more efficient, so the remaining pollutants end up making a similar amount of ozone as before.

But overall, switching internal combustion engine vehicles for EVs while cleaning up the electric grid generates big benefits for human health and greenhouse gas emissions. (Notably, only premature deaths are estimated here, but they wouldn’t be the only health benefits.) Putting dollar values on all this requires quantifying some unquantifiable things, but the researchers use some standard numbers.

For greenhouse gas emissions, the researchers use an estimate of the “social cost of carbon”—the financial impact of emitting CO₂. They also apply the economic “value of statistical life” used by the EPA for evaluating regulations. For 25 percent EVs and the current electric grid, this all totals to a value of about $16.8 billion each year in damages avoided. For 75 percent EVs and a cleaner grid, that shoots up to $70 billion per year.

So while some areas would need to address their grid to fully realize the local air quality improvements, electrifying transportation can clearly yield meaningful benefits.

GeoHealth, 2020. DOI: 10.1029/2020GH000275 (About DOIs).

https://arstechnica.com/?p=1700226