{"hq_id":"hq-p-hom-000259","name":"Lawn Herbicide and Pet Exposure (2,4-D Residue on Grass, Pet Paw and Oral Contact, Bladder Cancer in Scottish Terriers)","category":{"primary":"home","secondary":"lawn_garden","tags":["2,4-D","herbicide","lawn","pet exposure","bladder cancer","Scottish Terrier","weed killer","grass","paw contact","oral"]},"product_tier":"HOM","overall_risk_level":"high","description":"2,4-dichlorophenoxyacetic acid (2,4-D) is the most widely used herbicide in the US — 46 million pounds applied annually, with residential lawn application comprising a major share. Pets, particularly dogs, have intense contact with treated lawns: walking, rolling, sniffing, and direct grass ingestion (70-80% of dogs eat grass regularly). A landmark 1991 JNCI study found that dogs exposed to 2,4-D-treated lawns had 2x increased risk of malignant lymphoma. A 2004 Purdue study in Scottish Terriers — the breed with highest bladder cancer (transitional cell carcinoma, TCC) incidence — found that exposure to herbicide-treated lawns increased TCC risk 3-7x. 2,4-D residue persists on grass for 24-72 hours after application and is detectable on pet paws and fur for 48+ hours post-exposure. A 2013 study found 2,4-D in the urine of 14 of 25 dogs (56%) from homes using lawn herbicides, with levels peaking 48 hours post-application. Dogs' paw pads lack the stratum corneum thickness of plantar human skin — increasing dermal absorption. Oral route is primary: dogs eat grass, lick paws, and groom herbicide-contaminated fur.","synthesis":{"derived_risk_level":"high","synthesis_confidence":0.673,"synthesis_method":"compound_composition","context_used":"human_child","context_source":"product_users_fallback","exposure_modifier":1,"vulnerability_escalated":true,"escalation_reason":"Child exposure group","compounds_resolved":1,"compounds_total":1,"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":"Scottish Terriers (18-20x baseline bladder cancer risk), all dogs with regular lawn access, cats with outdoor access, puppies (pica, grass eating, developing immune systems)","overall_risk":"high","primary_concerns":["2,4-D: 2x increased lymphoma risk in exposed dogs (Hayes et al. 1991)","Scottish Terriers: 3-7x increased bladder cancer risk with herbicide exposure","2,4-D detected in urine of 56% of dogs from herbicide-using homes","Residue persists on grass 24-72 hours — paw and oral contact route"],"exposure_routes":"Oral (grass ingestion, paw licking, fur grooming). Dermal (paw pad absorption, belly contact with treated grass)"},"exposure":{"routes":["dermal","oral"],"contact_types":["skin_direct","oral_direct"],"users":["pet","child"],"duration":"hours","frequency":"seasonal","scenarios":["Dog walking on 2,4-D-treated lawn within 24-72 hrs of application","Dog eating grass on treated lawn — direct oral herbicide ingestion","Paw licking after walking on treated grass — oral transfer of residue","Dog rolling on treated lawn — full-body dermal and fur contamination"],"notes":"2,4-D: most-used US herbicide (46M lbs/yr). IARC Group 2B (possibly carcinogenic to humans). Dog lymphoma: Hayes et al. 1991 (JNCI) — 2x risk with owner-reported 2,4-D use. Scottish Terrier TCC: Glickman et al. 2004 (JAVMA) — 3-7x increased risk with herbicide exposure, breed has 18-20x higher baseline TCC rate than other breeds. Biomonitoring: Knapp et al. 2013 — 2,4-D detected in urine of 56% of dogs from herbicide-using homes. 2,4-D residue on grass: 24-72 hour persistence depending on formulation, rainfall, and temperature. Paw absorption: dog paw pads are keratinized but thinner than human plantar skin — 2,4-D is a weak acid (pKa 2.6-2.8), enhancing skin penetration. Grass eating: 70-80% of dogs eat grass (Sueda et al. 2008) — this is the primary oral exposure pathway. Cats: lower lawn contact typically, but those with outdoor access have similar paw/grooming exposure. NPIC (National Pesticide Information Center): recommends keeping pets off treated lawns until dry (minimum 24 hrs, ideally 48-72 hrs)."},"consumer_guidance":{"usage_warning":"Keep all pets off 2,4-D-treated lawns for minimum 48-72 hours after application (until residue has degraded and been watered in). Do not allow dogs to eat grass on any lawn treated with herbicides. After walks on unknown lawns: wipe paws with damp cloth to remove herbicide residue. Scottish Terrier owners: strongly consider herbicide-free lawn care due to breed-specific bladder cancer risk. If your dog is diagnosed with lymphoma or TCC: discontinue all lawn chemical exposure. Report suspected pesticide poisoning to NPIC (1-800-858-7378) and your veterinarian.","safer_alternatives":["Organic lawn care (no synthetic herbicides)","Corn gluten meal as pre-emergent weed control (pet-safe)","Manual weed removal and overseeding to outcompete weeds","Clover lawns or native ground cover (no herbicide needed)"]},"regulatory":{"applicable_regulations":[{"jurisdiction":"USA","regulation":"EPA FIFRA — 2,4-D Registration Review + Residential Use Restrictions","citation":"EPA FIFRA Sec. 3; EPA RED for 2,4-D (2005, revised ongoing); IARC Monograph 113 (2015)","requirements":"EPA: 2,4-D registered for residential lawn use with label-mandated re-entry intervals. Label language: 'Keep children and pets off treated areas until dry.' No specific pet cancer warning on labels despite epidemiological evidence. IARC: Group 2B (possibly carcinogenic to humans, 2015). Several Canadian provinces ban cosmetic 2,4-D use on lawns (Ontario, Quebec). EPA residential risk assessment: based on human exposure modeling — does not account for pet-specific exposure pathways (grass eating, paw licking).","compliance_status":null,"effective_date":null,"enforcing_agency":"EPA / State pesticide regulators","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":"Dispose unused 2,4-D products through local hazardous waste collection — do not pour into storm drains or waterways (toxic to aquatic organisms). Rinse empty concentrate containers per label (triple rinse) and dispose per local regulations. Do not burn.","hazardous_waste":true,"expected_lifespan":"2-4 years (concentrate, unopened)"},"formulation":{"form":"varies","key_ingredients":[],"certifications":[]},"materials":{"common":[],"concerning":[],"preferred":[]},"compound_composition":[{"hq_id":"hq-c-org-000130","compound_name":null,"role":"active_ingredient","typical_concentration":"0.5-4% in consumer lawn products, residue on grass 24-72 hrs"}],"identifiers":{"common_names":["lawn herbicide and pet exposure (2,4-d residue on grass, pet paw and oral contact, bladder cancer in scottish terriers)"],"aliases":[],"manufacturer":null,"brands":[]},"brand_examples":[{"brand":"SC Johnson","manufacturer":"SC Johnson","market_position":"mass_market","notable":"Household product conglomerate"},{"brand":"Clorox","manufacturer":"Clorox","market_position":"mass_market","notable":"Household cleaning market leader"},{"brand":"3M","manufacturer":"3M","market_position":"mass_market","notable":"Home safety and maintenance products"}],"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":"2026-03-25"},{"type":"regulation","title":"EPA FIFRA — 2,4-D Registration Review + Residential Use Restrictions (EPA FIFRA Sec. 3; EPA RED for 2,4-D (2005, revised ongoing); IARC Monograph 113 (2015))","jurisdiction":"USA","citation":"EPA FIFRA Sec. 3; EPA RED for 2,4-D (2005, revised ongoing); IARC Monograph 113 (2015)","id":"src_c8f693db"},{"id":"iarc_113_herbicides","type":"regulatory","title":"IARC Monographs Volume 113: Some Organophosphate Insecticides and Herbicides — 2,4-D Group 2B Classification, NHL Epidemiology, Glyphosate Group 2A, and Agricultural Worker Cohort Studies (2015)","year":2015,"inherited_from_compound":"hq-c-org-000130"},{"id":"epa_2_4_d_registration","type":"regulatory","title":"US EPA: 2,4-D Registration Review (2005/2012) — Group D Carcinogenicity Classification, Dietary Residue Tolerances, Lawn Re-Entry Exposure Assessment, and Aquatic Life Risk Assessment","year":2012,"inherited_from_compound":"hq-c-org-000130"}],"meta":{"schema_version":"4.0.0","last_updated":"2026-03-25","timestamp":"2026-05-14T01:32:24.238Z"}}