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Comment by helsinkiandrew | Hacker News Reader

> researchers grew human lung cells in a lab and exposed them to dust from car brakes and from diesel tailpipes, finding that brake dust caused greater injury to the cells.

I couldn’t tell if the study found that car brakes are more harmful than exhausts, or that car brake chemicals are more harmful than exhaust fumes - but that may not be significant because they are produced in less quantities.

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> I couldn’t tell if the study found that car brakes are more harmful than exhausts, or that car brake chemicals are more harmful than exhaust fumes

None of these.

The actual linked study found that the presence of specific metal particulates (copper, zinc and iron), which are found in modern brake dust, correlates with increase risk of asthma and allergy in kids.

I'm personally wondering if the article linked the wrong article? Because the article describes the study as "researchers grew human lung cells in a lab and exposed them to dust from car brakes and from diesel tailpipes", but the linked study is a cohort study of correlation, that doesn't involve any experimental manipulation.

I suspect it's even more complicated; if the particulate matter is different in size, the relative amount delivered to a human lung might depend on the distance.

So if you want to model somebody being 10 meters away from the street, you might need to use different ratios than for somebody being 100m away.

One other point is that brake dust is probably larger in size than particulate pollution from exhausts, and thus the nasal and breathing passage leading up to the lungs would do a better job at filtering them over more fine-sized particulate matter.

ooph. wouldn't the dust particles go through a whole lot of other bodily defense mechanisms before they reach actual lung cells?

Not if you're breathing through your mouth. Inhaled asthma medication has about the same consistency as brake dust.

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