> Compare relative volumes of materials. Brake dust is always going to be a much smaller source of particulate matter in the air than tire dust.
It's not a fair comparison, because you don't wear through the entire tire material as extensively as a brake pad. Fortunately we don't have to back of the napkin this one, there's lots of research showing brakes are near peers or exceed tires in contribution to PM 2.5.
As to your second point that brake material might be less harmful -- there is some initial research on how composition mediates impact.
Aluminum, sulfate, nickel, arsenic, and silicon seem to have the strongest relations. Aluminum is a frequent abrasive in brake pads, they aren't merely contributing some form of benign 2.5.
I can't do a comparison, you might be right it's "less bad" than tires, which contain other heavy metals. But I do not think the research is powerful enough to precisely settle that question beyond the overwhelming academic consensus that both are bad and we should definitely try to reduce both.
It's not a fair comparison, because you don't wear through the entire tire material as extensively as a brake pad. Fortunately we don't have to back of the napkin this one, there's lots of research showing brakes are near peers or exceed tires in contribution to PM 2.5.
As to your second point that brake material might be less harmful -- there is some initial research on how composition mediates impact.
Aluminum, sulfate, nickel, arsenic, and silicon seem to have the strongest relations. Aluminum is a frequent abrasive in brake pads, they aren't merely contributing some form of benign 2.5.
I can't do a comparison, you might be right it's "less bad" than tires, which contain other heavy metals. But I do not think the research is powerful enough to precisely settle that question beyond the overwhelming academic consensus that both are bad and we should definitely try to reduce both.
https://www.greencarcongress.com/2019/07/20190714-nee.html
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3755878/
https://dot.ca.gov/-/media/dot-media/programs/research-innov...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315878/#Sec6ti...
https://www.ncbi.nlm.nih.gov/pubmed/15337346