6PPD-quinone (6PPD-Q), a transformation product of the tire rubber anti-degradant 6PPD, has been identified as the cause of Urban Runoff Mortality Syndrome (URMS) in coho salmon. It is highly toxic to coho and other aquatic species, even at low surface water concentrations. While monitoring efforts have expanded rapidly since 2020, characterizing when and where aquatic life are exposed to lethal environmental concentrations remains difficult because 6PPD-Q occurs in episodic, storm-driven pulses, degrades quickly, and has toxic thresholds near analytical detection limits. To address these limitations, we evaluated passive samplers as screening tools for 6PPD-Q in small streams across King County, Washington. Polar Organic Chemical Integrative Samplers (POCIS) and Diffusive Gradients in Thin Films (DGT) were deployed at multiple sites spanning a gradient of urbanization. Samplers provided time-weighted average concentrations, capturing cumulative mass loadings over multi-week deployments. Across basins with 5–53% impervious cover, estimated time-weighted average concentrations ranged from 0.4 to 67 ng/L 6PPD-Q. Results showed elevated loadings consistent with known URMS hotspots, and loadings generally increased with impervious surface cover. Our findings support the use of passive samplers as a sensitive, cost-effective tool for risk assessment, pollution identification, and long-term status and trend monitoring. By identifying hotspots, passive samplers can help prioritize locations for mitigation efforts and inform stormwater infrastructure investment planning.