6PPD (N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine)
•Purpose: Antioxidant to prevent rubber cracking.
•Danger: When it reacts with ozone and air, it forms 6PPD-quinone, a toxic compound shown to kill salmon and other aquatic life at trace levels.
•Status: Under increasing regulatory scrutiny (e.g., Washington State has started restricting it).
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2. Polycyclic Aromatic Hydrocarbons (PAHs)
•Purpose: Byproducts from extender oils and carbon black.
•Danger: Known carcinogens, mutagens, and endocrine disruptors. Persist in the environment and can leach from tire wear particles.
•Status: Regulated in the EU; linked to air and soil contamination.
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3. Benzothiazoles (e.g., 2-mercaptobenzothiazole)
•Purpose: Vulcanization accelerators.
•Danger: Toxic to aquatic organisms, possibly carcinogenic, and bioaccumulative.
•Status: Found in tire leachate and considered a contaminant of emerging concern.
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Nothing definitive about harm to human welfare yet, as far as I know.
"When tires wear on pavement, 6PPD is released. It reacts with ozone to become a different chemical, 6PPD-q, which can be extremely toxic — so much so that it has been linked to repeated fish kills in Washington state.... Testing by a British company, Emissions Analytics, found that a car's tires emit 1 trillion ultrafine particles per kilometer driven — from 5 to 9 pounds of rubber per internal combustion car per year....
a team of researchers, led by scientists at Washington State University and the University of Washington, who were trying to determine why coho salmon returning to Seattle-area creeks to spawn were dying in large numbers.... in 2020 they announced they'd found the culprit: 6PPD....
Tests by Emissions Analytics have found that tires produce up to 2,000 times as much particle pollution by mass as tailpipes."
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2. Polycyclic Aromatic Hydrocarbons (PAHs) •Purpose: Byproducts from extender oils and carbon black. •Danger: Known carcinogens, mutagens, and endocrine disruptors. Persist in the environment and can leach from tire wear particles. •Status: Regulated in the EU; linked to air and soil contamination.
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3. Benzothiazoles (e.g., 2-mercaptobenzothiazole) •Purpose: Vulcanization accelerators. •Danger: Toxic to aquatic organisms, possibly carcinogenic, and bioaccumulative. •Status: Found in tire leachate and considered a contaminant of emerging concern.
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Nothing definitive about harm to human welfare yet, as far as I know.