{"hq_id":"hq-p-spe-000154","name":"Tire Wear Particles and 6PPD-Quinone (Coho Salmon Lethal Toxicity, Urban Stormwater Runoff, Microplastic Source, 1.8M Tons/Year US)","category":{"primary":"specialty","secondary":"tire_wear_pollution","tags":["tire wear","6PPD","6PPD-quinone","coho salmon","stormwater runoff","microplastic","tire particle","rubber","antioxidant","urban runoff","aquatic toxicity","road wear","non-exhaust emissions"]},"product_tier":"SPE","overall_risk_level":"high","description":"Tire wear is the single largest source of microplastic pollution in many urban environments, with the United States generating approximately 1.8 million metric tons of tire wear particles annually (Kole et al., 2017 estimated tires contribute 28% of primary microplastic inputs to the global ocean). A landmark 2020 paper in Science (Tian et al.) identified 6PPD-quinone — a transformation product of the ubiquitous tire antioxidant 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) — as acutely lethal to coho salmon at concentrations as low as 0.8 ug/L. 6PPD is added to virtually all commercial tires at 0.5-2% by weight to prevent ozone-induced cracking, and it transforms to 6PPD-quinone upon contact with ozone and UV light during normal tire wear. Stormwater runoff from roads carries 6PPD-quinone directly into urban streams — monitoring in Puget Sound tributaries (Washington state) found concentrations of 0.1-19 ug/L during storm events, well above the lethal threshold for coho salmon. Pre-spawn mortality (PSM) in coho salmon returning to urban streams in the Pacific Northwest has been observed at rates of 40-90% during fall rain events, now attributed substantially to 6PPD-quinone toxicity. Beyond aquatic toxicity, tire wear particles contain zinc (1-2%), PAHs (including benzo[a]pyrene), benzothiazole, and heavy metals. The particles range from 10 um to 200 um, with ultrafine fractions (<100 nm) potentially entering airborne PM2.5. Washington state became the first jurisdiction to ban 6PPD in tires (SB 5931, signed 2024, effective 2030).","synthesis":{"derived_risk_level":"low","synthesis_confidence":0.665,"synthesis_method":"compound_composition","context_used":"human_infant","context_source":"available_priority","exposure_modifier":1,"vulnerability_escalated":false,"escalation_reason":null,"compounds_resolved":3,"compounds_total":3,"synthesis_date":"2026-05-09","synthesis_version":"1.2.0","methodology_note":"exposure_modifier and adjusted_magnitude are computed from ALETHEIA-calibrated heuristics (route × duration × frequency multipliers, clamped to [0.5, 1.4]). Multipliers are directionally informed by EPA Exposure Factors Handbook (2011) and CalEPA OEHHA but are not regulatory consensus. See /api/methodology for full disclosure."},"hazard_summary":{"sensitive_populations":"coho salmon (LC50 0.8 ug/L — most acutely sensitive species identified), urban stream aquatic ecosystems, Pacific Northwest indigenous communities dependent on salmon runs, roadside workers and cyclists (tire wear PM2.5 inhalation)","overall_risk":"high","primary_concerns":["6PPD-quinone lethal to coho salmon at 0.8 ug/L (Science 2020) — among most toxic environmental contaminants for vertebrates","US generates 1.8 million metric tons tire wear particles/year","Tires contribute 28% of primary ocean microplastics (Kole et al. 2017)","Pre-spawn coho mortality 40-90% in urban streams during rain events"],"exposure_routes":"Environmental (6PPD-quinone in stormwater runoff to aquatic ecosystems). Inhalation (tire wear PM2.5 fraction at roadside). Ingestion (tire wear contaminants in surface drinking water sources)"},"exposure":{"routes":["inhalation","ingestion","environmental"],"contact_types":["inhalation_ambient","environmental_runoff","ingestion_water"],"users":["general_population","aquatic_ecosystem"],"duration":"chronic","frequency":"continuous","scenarios":["Urban stormwater runoff: 6PPD-quinone 0.1-19 ug/L in Pacific Northwest streams during rain events","Roadside air: tire wear particle PM2.5 fraction inhaled by pedestrians and cyclists at intersections","Drinking water: tire wear contaminants in surface water sources downstream of urban areas","Coho salmon pre-spawn mortality: 40-90% in urban streams attributed to 6PPD-quinone"],"notes":"Science (2020, Tian et al.): identified 6PPD-quinone as the causative agent for coho salmon acute mortality. LC50 for coho salmon: 0.8 ug/L — among the most toxic environmental contaminants ever measured for a vertebrate species. 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine): added to virtually all commercial tire rubber at 0.5-2% by weight as an antioxidant (prevents ozone cracking). Transforms to 6PPD-quinone via ozone and UV oxidation on road surface. Kole et al. (2017, Int J Environ Res Public Health): estimated 28% of ocean primary microplastics from tire wear. US generates ~1.8 million metric tons tire wear particles/year. Puget Sound monitoring: 6PPD-quinone 0.1-19 ug/L in urban stream stormwater. Coho salmon PSM (pre-spawn mortality): documented 40-90% in urban streams since 1990s — now substantially attributed to 6PPD-quinone. Chum and chinook salmon less sensitive. Washington state SB 5931 (signed 2024): first jurisdiction to ban 6PPD in tires — compliance deadline 2030. Alternatives under investigation: 6PPD-free antioxidant packages (e.g., functionalized carbon black, hindered amine light stabilizers). Green infrastructure (bioretention, bioswales) removes 60-90% of tire wear particles from stormwater. Tire industry position (USTMA): exploring safer alternatives while maintaining tire safety performance."},"consumer_guidance":{"usage_warning":"Individual consumer action is limited for this systemic issue, but awareness of tire wear as a major pollution source is important. Drive smoothly (avoid hard acceleration and braking) to reduce tire wear particle generation. Maintain proper tire inflation (underinflation increases wear rate by 15-25%). Support green infrastructure (bioretention, rain gardens) in your community — these systems remove 60-90% of tire wear particles from stormwater. When replacing tires, consider manufacturers investing in 6PPD-free alternatives. Support policies mandating stormwater treatment for urban roads.","safer_alternatives":["Green infrastructure: bioretention systems and bioswales for stormwater treatment","6PPD-free tire formulations (under development — no commercial availability as of 2024)","Proper tire inflation and alignment (reduces wear rate by 15-25%)","Stormwater filtration and treatment at road drainage outfalls"]},"regulatory":{"applicable_regulations":[{"jurisdiction":"USA","regulation":"Washington State SB 5931 (6PPD Ban) + EPA Stormwater Regulations","citation":"Washington SB 5931 (2024); Clean Water Act Sec. 402 (NPDES stormwater permits); EPA TSCA","requirements":"Washington SB 5931 (signed 2024): first jurisdiction globally to ban 6PPD in tires — manufacturers must use alternatives by 2030. EPA: tire wear particles contribute to stormwater pollution regulated under Clean Water Act NPDES permits, but no specific tire wear or 6PPD-quinone effluent limits. TSCA: 6PPD is a registered chemical — EPA has not initiated risk evaluation under TSCA Sec. 6. California: considering similar 6PPD restriction legislation. EU: ECHA is evaluating 6PPD under REACH — no restriction proposal as of 2024. UNEP: tire wear particles included in global plastics treaty negotiations.","compliance_status":null,"effective_date":"2030-01-01","enforcing_agency":"Washington State Department of Ecology / EPA / ECHA (EU)","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: recycle through tire retailer take-back programs (mandatory in most US states). Tire-derived fuel (TDF) and crumb rubber are recycling pathways, though crumb rubber in playgrounds and turf fields raises separate 6PPD and PAH exposure concerns. Do not illegally dump tires — tire piles are fire and mosquito breeding hazards. Tire wear particles during use: no collection method exists — this is a continuous non-point source emission.","hazardous_waste":false,"expected_lifespan":"40,000-80,000 miles (tire tread life); tire wear particles are emitted continuously during use"},"formulation":{"form":"varies","key_ingredients":[],"certifications":[]},"materials":{"common":[],"concerning":[],"preferred":[]},"compound_composition":[{"hq_id":"hq-c-org-000628","compound_name":null,"role":"tire_antioxidant","typical_concentration":"0.5-2% by weight in tire rubber; transforms to 6PPD-quinone (LC50 coho salmon 0.8 ug/L)"},{"hq_id":"hq-c-org-000029","compound_name":null,"role":"tire_wear_contaminant","typical_concentration":"trace PAH levels in tire wear particles — benzo[a]pyrene detected in road runoff"},{"hq_id":"hq-c-org-000096","compound_name":null,"role":"tire_wear_contaminant","typical_concentration":"PAH component in tire rubber and road surface — volatile fraction"}],"identifiers":{"common_names":["tire wear particles and 6ppd-quinone (coho salmon lethal toxicity, urban stormwater runoff, microplastic source, 1.8m tons/year us)"],"aliases":[],"manufacturer":null,"brands":[]},"brand_examples":[{"brand":"Viqua","manufacturer":"Trojan Technologies","market_position":"professional","notable":"Professional UV water treatment"},{"brand":"SteriPEN","manufacturer":"Katadyn","market_position":"mass_market","notable":"Portable UV water purifier"},{"brand":"HALO","manufacturer":"RGF Environmental","market_position":"premium","notable":"Whole-house UV water system"}],"brand_examples_disclaimer":"Representative branded products of this category. Concerning ingredients listed in materials.concerning[] apply to the category, not necessarily to every named brand. Specific formulations vary by SKU and may have changed since this record was written; consult the brand's current ingredient label before drawing brand-level conclusions.","sources":[{"type":"expert_curation","name":"ALETHEIA Safety Database","date":"2026-03-26"},{"type":"regulation","title":"Washington State SB 5931 (6PPD Ban) + EPA Stormwater Regulations (Washington SB 5931 (2024); Clean Water Act Sec. 402 (NPDES stormwater permits); EPA TSCA)","jurisdiction":"USA","year":2030,"citation":"Washington SB 5931 (2024); Clean Water Act Sec. 402 (NPDES stormwater permits); EPA TSCA","id":"src_e98212da"},{"id":"src_001","type":"journal","title":"Tire Antioxidants (6PPD and Related Compounds) in Environmental and Toxicological Context","year":2021,"inherited_from_compound":"hq-c-org-000628"},{"id":"src_002","type":"government","title":"US EPA — 6PPD-quinone Precursor and Tire Wear Pollution Assessment","year":2022,"inherited_from_compound":"hq-c-org-000628"},{"id":"iarc_100f_bap","type":"regulatory","title":"IARC Monographs Volume 100F: Benzo[a]pyrene — Chemical Agents and Related Occupations","year":2012,"inherited_from_compound":"hq-c-org-000029"},{"id":"epa_bap_iris","type":"regulatory","title":"US EPA IRIS: Benzo[a]pyrene — Toxicological Review (Final)","year":2017,"inherited_from_compound":"hq-c-org-000029"},{"id":"iarc_82_naphthalene","type":"regulatory","title":"IARC Monographs Volume 82: Some Traditional Herbal Medicines, Some Mycotoxins, Naphthalene and Styrene — Naphthalene Group 2B Evaluation","year":2002,"inherited_from_compound":"hq-c-org-000096"},{"id":"epa_iris_naphthalene","type":"regulatory","title":"US EPA: Naphthalene — IRIS Toxicological Review, Carcinogenicity Assessment and Reference Concentrations (Group C)","year":1998,"inherited_from_compound":"hq-c-org-000096"}],"meta":{"schema_version":"4.0.0","last_updated":"2026-03-26","timestamp":"2026-05-14T01:24:08.390Z"}}