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Electric cars and particulate pollution May 15, 2016

Posted by Maury Markowitz in Uncategorized.

You think it’s bad now? It is.

The latest bit of news-mongering in the electric car world hit the press a few days ago, a new report noting that emissions from EVs are no better, and perhaps worse, than from normal cars. And because of that, they will cause just as much pollution and related health problems.

Well, at least that’s the way 3rd party news outlets reported it. If this is starting to sound familiar, that’s because it is. The original paper’s conclusions are quite a bit at odds with the conclusions being suggested by the news blogs.

The actual paper

The paper, Non-exhaust PM emissions from electric vehicles, is behind an Elsevier paywall (burn in hell Elsevier) but you can find out the key elements if you do a little poking.

Basically the paper notes that when you compare cars that come in both conventional ICE and EV versions, the EV is, on average, 24% heavier. Although there’s not a tremendous amount of data on PM, there’s enough, especially from Simons 2003, to suggest that heavier weights will cause more tire and road wear, two major sources of PM. It would also normally increase brake wear as well, but the authors reduce this contribution because of regenerative braking.

When all is said and done, they predict that PM of 10 microns and larger will be 65.7 mg/vkm for an EV, compared with 66.0 mg/vkm for a traditional ICE. For the smaller 2.5 micron PM, it’s 22.4 mg/vkm vs. 23.2 mg/vkm. So basically, a very slight advantage to the EV.

Now it is worth noting that for both of these numbers, the majority of the PM, about 75%,  is caused by “resuspension”, existing PM on the road surface being blown into the air. But since that PM is caused largely by the sources mentioned earlier, it seems further detail on this source would be needed. It would seem at first glance that the entire PM pollution content could be greatly reduced simply by periodically washing the roads.

And that’s about it. As the paper itself puts it, “EVs are not likely to have a large impact on PM emissions from traffic”.

And then how it’s reported

So let’s see how the blogs have reported this:

Ok, not bad, pretty much right so far. But then the first text you come across is this caption on the lead image:

Screen Shot 2016-05-15 at 5.20.32 PM

What? That’s the exact opposite if that the paper says… it’s the exact opposite of what their own article says. Ugh. But here’s where it really goes off the rails. They quote the EPA:

Numerous scientific studies have linked particle pollution exposure to a variety of problems, including: premature death in people with heart or lung disease; nonfatal heart attacks; irregular heartbeat; aggravated asthma; decreased lung function; and increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.

You see the problem here, right? They’re basically lumping all emissions together. The whole point of reducing combustion related PM is that is is more dangerous than non-combustion PM. I don’t think I want to breath particulate rubber, but I guarantee you that airborne lead, sulfides and carbon monoxide are way worse for you.

No, they don’t say that at all. In fact, the article clearly notes, diesel is less dirty than gasoline. But what do you expect from the Mail, a site who’s every page is filled with boob shots?

Yahoo, oh Yahoo… It states:

However, because they’re 24 percent heavier on average, the study found that EVs shed more particulate matter from tires and brakes, and also kick up more particulate matter from road surfaces.

I love this one, because it’s very clear that they didn’t read the actual article. Had they, they too would have noticed that the emissions from the brakes was reduced to zero, directly the opposite of this statement. You might have got that impression only if you read other articles about the paper, a fine example of this.

And that, surprisingly, is about that. Compared to previous articles covering EV emissions, this one seems to have garnered less press coverage than normal.



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