Pollution from tire wear is worse than exhaust emissions? • Hacker News Board

Re: Pollution from tire wear is worse than exhaust emissions?

#21

Post by benkuhn » Sun, Mar 08, 2020, 2:16 PM UTC

the8472 wrote: post #11

Headline > Pollution From Tyre Wear [is] 1,000 Times Worse Than Exhaust Emissions Article > But tyre wear pollution is unregulated and can be 1,000 times worse

It's true that they weakened the wording in that section of the body, but the description of the actual research does make it sound like the factor of 1,000 was a typical case, not the worst case:

> 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. > > Compared with regulated exhaust emission limits of 4.5 milligrams per kilometer, the completely unregulated tyre wear emission is higher by a factor of over 1,000.

Of course, this assumes that the tyre particles captured by their methodology are (on average) equally bad as exhaust particles, and maybe brand-new tyres wear especially quickly or something. It does seem hard to square the factor of 1000 from this study with the estimate that non-exhaust emissions account for a mere 60% (rather than 99.9%) of PM2.5 emissions.

Would be curious to hear from anyone who understands emissions testing better.

Re: Pollution from tire wear is worse than exhaust emissions?

#22

Post by cowsandmilk » Sun, Mar 08, 2020, 2:17 PM UTC

the8472 wrote: post #11

Headline > Pollution From Tyre Wear [is] 1,000 Times Worse Than Exhaust Emissions Article > But tyre wear pollution is unregulated and can be 1,000 times worse

This isn’t an article, it is a press release.

Re: Pollution from tire wear is worse than exhaust emissions?

#23

Post by the8472 » Sun, Mar 08, 2020, 2:18 PM UTC

ajross wrote: post #20

the8472 wrote: post #11

Headline > Pollution From Tyre Wear [is] 1,000 Times Worse Than Exhaust Emissions Article > But tyre wear pollution is unregulated and can be 1,000 times worse

Also headline: "pollution", and article "harmful particle matter from tyres". The study was of particulate emissions only, where when we generally think of "car pollution" we're talking about carbon or unburned hydrocarbons or toxins, not smoke. And the comparison was to "what comes out of a car's exhaust", when the overwhelming contributor to the particulate composition of smog is reactions in the atmosphere and not…

"Smoke" is underselling it a bit. Tyre wear creates PM2.5, which is toxic. I don't consider that outright misleading in comparison to misstating an upper bound as a tight bound.

Re: Pollution from tire wear is worse than exhaust emissions?

#24

Post by pjsg » Sun, Mar 08, 2020, 2:18 PM UTC

0ldblu3 wrote: post #9

So to visualize this I'm thinking of a rectangle 2.5 feet long, 8 inches wide, and a half-inch thick times 4. That is what comes off my tires every 5 years so that I have to replace them. Every set of tires sold is to replace that.

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.

Re: Pollution from tire wear is worse than exhaust emissions?

#25

Post by scythe » Sun, Mar 08, 2020, 2:19 PM UTC

> 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.

>Compared with regulated exhaust emission limits of 4.5 milligrams per kilometer, the completely unregulated tyre wear emission is higher by a factor of over 1,000.

This is approximately as reasonable as declaring that a crossbow is more dangerous than a gun because it fires a heavier projectile. How large are the particles? What's their expected lifetime in the atmosphere? What proportion are smaller than 10 micron? 2.5 micron?

Re: Pollution from tire wear is worse than exhaust emissions?

#26

Post by lazyjones » Sun, Mar 08, 2020, 2:25 PM UTC

This is, as it stands in the headline, classic "fake news" that is being spread by people who want to exaggerate the problems with cars.

Re: Pollution from tire wear is worse than exhaust emissions?

#27

Post by vinw » Sun, Mar 08, 2020, 2:28 PM UTC

benkuhn wrote: post #21

the8472 wrote: post #11

Headline > Pollution From Tyre Wear [is] 1,000 Times Worse Than Exhaust Emissions Article > But tyre wear pollution is unregulated and can be 1,000 times worse

It's true that they weakened the wording in that section of the body, but the description of the actual research does make it sound like the factor of 1,000 was a typical case, not the worst case: > 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. > > Compared with regulated exhaust emission limits of 4.5 milligrams pe…

5.8 grams per kilometer would mean in only 10,000 KM your tyres lose 58 Kg. Seems way off.

Re: Pollution from tire wear is worse than exhaust emissions?

#28

Post by ajross » Sun, Mar 08, 2020, 2:29 PM UTC

the8472 wrote: post #23

ajross wrote: post #20

Earlier quoted context omitted.

Also headline: "pollution", and article "harmful particle matter from tyres". The study was of particulate emissions only, where when we generally think of "car pollution" we're talking about carbon or unburned hydrocarbons or toxins, not smoke. And the comparison was to "what comes out of a car's exhaust", when the overwhelming contributor to the particulate composition of smog is reactions in the atmosphere and not…

"Smoke" is underselling it a bit. Tyre wear creates PM2.5, which is toxic. I don't consider that outright misleading in comparison to misstating an upper bound as a tight bound.

As described in the article, the number they used for the "1000x" comparison wasn't PM2.5 due to car exhaust. It was PM2.5 IN car exhaust, which is quite literally the thing we call "smoke". The vast majority of smog particles due to automobile traffic appear in the atmosphere as reaction products, they aren't in the exhaust.

Re: Pollution from tire wear is worse than exhaust emissions?

#29

Post by kieranmaine » Sun, Mar 08, 2020, 2:32 PM UTC

For those people wondering about what percentage of PM2.5 and PM10 are caused by non-exhaust emissions.

"NEEs are currently believed to constitute the majority of primary particulate matter from road transport, 60 percent of PM2.5 and 73 percent of PM10 – and in its 2019 report ‘Non-Exhaust Emissions from Road Traffic’ by the UK Government’s Air Quality Expert Group (AQEG), it recommended that NEE are immediately recognised as a source of ambient concentrations of airborne particulate matter, even for vehicles with zero exhaust emissions of particles – such as EVs."

Re: Pollution from tire wear is worse than exhaust emissions?

#30

Post by thinkcontext » Sun, Mar 08, 2020, 2:32 PM UTC

> 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.

So this is based on n=1, very suspicious.

If tires really were this big a source of PM emissions then how would levels in US cities gone down through vehicle pollution control measures. Something is not adding up here.