{"hq_id":"hq-p-wer-000068","name":"Tire Wear Particles and 6PPD-Quinone (Coho Salmon Mass Mortality Agent, Microplastic Pollution, Stormwater Toxicity)","category":{"primary":"wearables_equipment","secondary":"tire_wear","tags":["tire wear particles","6PPD-quinone","TWP","microplastics","coho salmon","stormwater","rubber","antioxidant","aquatic toxicity","urban runoff"]},"product_tier":"WER","overall_risk_level":"high","description":"Tire wear particles (TWP) are the largest source of microplastic pollution in aquatic environments, with an estimated 6 million tonnes generated globally per year (Kole et al., 2017). In 2020, researchers at the University of Washington identified 6PPD-quinone — a transformation product of the tire rubber antioxidant 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) reacting with ground-level ozone — as the causative agent of recurring coho salmon mass mortality events in Pacific Northwest urban streams. 6PPD-quinone is acutely lethal to coho salmon at concentrations as low as 0.8 ug/L (LC50 0.095 ug/L for juvenile coho), making it one of the most toxic identified urban stormwater contaminants. Tire rubber contains 0.4-2% 6PPD by weight; upon wear, 6PPD oxidizes to 6PPD-quinone on road surfaces and is transported to waterways via stormwater runoff. Beyond 6PPD-quinone, tire wear particles contain zinc (1-2% by weight from zinc oxide vulcanization activator), PAHs, benzothiazoles, and microplastic rubber fragments that persist in aquatic sediments. Washington State became the first jurisdiction globally to ban 6PPD in tires (HB 1085, signed 2024, effective 2030).","synthesis":{"derived_risk_level":"moderate_to_high","synthesis_confidence":0.88,"synthesis_method":"compound_composition","context_used":"human_child","context_source":"product_users","exposure_modifier":1,"vulnerability_escalated":true,"escalation_reason":"Child exposure group","compounds_resolved":2,"compounds_total":2,"synthesis_date":"2026-03-27","synthesis_version":"1.0.0"},"hazard_summary":{"sensitive_populations":"coho salmon (species-specific acute lethality at 0.095 ug/L), other salmonids (steelhead, chinook — moderate sensitivity), aquatic invertebrates, communities dependent on salmon fisheries","overall_risk":"high","primary_concerns":["6PPD-quinone is acutely lethal to coho salmon at sub-microgram-per-liter concentrations","Tire wear particles are the largest single source of aquatic microplastic pollution globally","6PPD is present in virtually all tires worldwide — no approved alternative is currently in production-scale use","Urban stormwater transports tire toxicants directly to salmon-bearing streams without treatment"],"exposure_routes":"Aquatic (stormwater transport of 6PPD-quinone and tire particles to waterways). Inhalation (resuspended tire wear PM on roads). Ingestion (contaminated sediment contact; bioaccumulation through aquatic food web)."},"exposure":{"routes":["inhalation","ingestion"],"contact_types":["inhalation_ambient","ingestion_indirect"],"users":["adult","child","aquatic_organisms"],"duration":"chronic","frequency":"continuous","scenarios":["Coho salmon in urban streams receiving stormwater — acute lethal exposure to 6PPD-quinone at sub-ug/L concentrations","Cyclist or runner on busy road — inhalation of resuspended tire wear PM2.5/PM10","Urban stormwater carrying tire particles and 6PPD-quinone into rivers, estuaries, and Puget Sound","Child playing near road drainage — dermal and ingestion contact with tire-particle-contaminated sediment"],"notes":"6PPD (CAS 793-24-8): N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine; universal tire antioxidant preventing ozone cracking. 6PPD + O3 → 6PPD-quinone (identified by Tian et al., Science, 2021). Coho salmon species-specific sensitivity: LC50 0.095 ug/L (juvenile); other salmonids (steelhead, chinook) show lower but measurable sensitivity. TWP composition: ~50% styrene-butadiene rubber, ~25% natural rubber, ~15% fillers (carbon black, silica), ~5% zinc oxide, ~2% processing chemicals. Estimated tire wear emission: 0.2-5.5 kg per tire over lifetime. Bioretention and biofiltration with activated carbon remove >90% of 6PPD-quinone from stormwater."},"consumer_guidance":{"usage_warning":"Support stormwater treatment infrastructure (bioswales, rain gardens with activated carbon) to reduce 6PPD-quinone reaching waterways. Drive at moderate speeds — tire wear increases exponentially with speed. Maintain correct tire pressure to minimize uneven wear. Choose tires with lower treadwear rates when possible. Advocate for municipal stormwater filtration near salmon-bearing streams.","safer_alternatives":["Green stormwater infrastructure with activated carbon filtration (removes >90% of 6PPD-quinone)","Low-rolling-resistance tires (reduced wear rate, lower emissions per kilometer)","Alternative tire antioxidants to 6PPD (research stage — IPPD, DTPD being evaluated)","Permeable pavement that filters stormwater before reaching storm drains"]},"regulatory":{"applicable_regulations":[{"jurisdiction":"USA","regulation":"Washington State HB 1085 — Ban on 6PPD in Motor Vehicle Tires","citation":"Washington HB 1085 (2024); RCW 70A.560; California AB 2622 (study bill, 2024)","requirements":"Washington State became the first jurisdiction globally to pass legislation restricting 6PPD in tires (signed 2024, effective 2030 or when safer alternative is identified by Department of Ecology). California AB 2622 requires DTSC to study alternatives. EU REACH is evaluating 6PPD under substance evaluation. No current EPA restriction on 6PPD or 6PPD-quinone.","compliance_status":null,"effective_date":"2030-01-01","enforcing_agency":"Washington State Department of Ecology","penalties":null,"source_ref":null}],"certifications":[],"labeling":{"required_disclosures":[],"prop65_warning":{"required":null,"chemicals":[],"endpoint":null,"notes":null},"ghs_labeling":{"required":null,"signal_word":null,"pictograms":[],"hazard_statements":[],"notes":null},"hidden_ingredients":{"trade_secret_protected":null,"categories_hidden":[],"estimated_count":null,"known_concerns":null,"notes":null},"notes":null},"recalls":[],"regulatory_gap":null,"notes":null},"lifecycle":{"recyclable":true,"disposal_guidance":"Used tires should be recycled through tire retailers or municipal waste programs. Tire crumb rubber for playgrounds and artificial turf may leach 6PPD-quinone and zinc — consider alternatives. Tire pyrolysis and cement kiln co-processing are preferred end-of-life pathways.","hazardous_waste":false,"expected_lifespan":"40,000-80,000 miles per tire; continuous wear particle emission throughout life"},"formulation":{"form":"varies","key_ingredients":[],"certifications":[]},"materials":{"common":[],"concerning":[],"preferred":[]},"compound_composition":[{"hq_id":"hq-c-org-002083","compound_name":null,"role":"transformation_product","typical_concentration":"6PPD-quinone from 6PPD antioxidant (0.4-2% of tire rubber); coho salmon LC50 0.095 ug/L; formed by ozone oxidation of tire wear particles"},{"hq_id":"hq-c-mix-000003","compound_name":null,"role":"physical_contaminant","typical_concentration":"tire wear particles — largest single source of microplastics in aquatic environments; 6 million tonnes/year globally"}],"identifiers":{"common_names":["tire wear particles and 6ppd-quinone (coho salmon mass mortality agent, microplastic pollution, stormwater toxicity)"],"aliases":[],"manufacturer":null,"brands":[]},"brand_examples":[],"sources":[{"type":"expert_curation","name":"ALETHEIA Safety Database","date":"2026-03-26"}],"meta":{"schema_version":"4.0.0","last_updated":"2026-03-26","timestamp":"2026-05-02T18:17:57.471Z"}}