[pjsg]

The numbers don't seem to add up. If an average set of tires lasts (roughly) 50,000km to 100,000km, and the average tire weights around 10kg, and you have 4 tires, then the (totally unrealistic) maximum loss per km is 4 * 10 * 1000 / 75,000 gms/km. This is 0.5g/km (and it assumed that there was no tire left). While these numbers are rough, I don't see any way to get to 5.8gm/km as quoted in the article. The brake pads aren't going to contribute all the rest (they aren't that heavy to start with).

What about the road surface? Maybe you can erode 1cm of surface over 10 years with 2,000 vehicles per hour (average down to 20,000 per day. Volume eroded (per km) in cc is 400 (width) * 1 * 100,000 (length) = 4e7 cc. Density is around 2.5 gm/cc. Mass eroded is 1e8 gms. Cars is 20,000 * 10 * 365 = 73e6. Amount eroded by each car is around 1.3gm/km.

Maybe someone could check my assumptions (and my math), but I still don't believe the numbers in the linked article.

[mokus]

To look at it the other direction, 5.8 g/km times 75,000 km means they have to somehow produce 435 kg of pollution per set of tires.

Without some more explanation (are they building some kind of model to extrapolate to the entire supply chain?) that seems more than a little implausible. It seems most likely from the context that they are measuring shedding of brand new tires and trying to pass that off as a representative value.

I guess the idea is that it’s a contributor to the acute dose in the car’s immediate vicinity, but without that context it seems like another misleading detail.

[magicalhippo]

As quoted by another poster:

> Using a popular family hatchback running on brand new, correctly inflated tyres, we found that the car emitted 5.8 grams per kilometer of particles.

Could it be that tire wear drops off? Initially it's shedding a lot, I dunno, due to surface layer being porous or something, and then the wear drops off to the normal rate?