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Department of Ecology
Committees, Boards, and Workgroups

Research and Proposed Alternatives to 6PPD

This page is run by the Washington State Department of Ecology and provides information about identifying a safer alternative to 6PPD. For more general information about 6PPD, please visit our website.

Urban Runoff Mortality Syndrome and 6PPD

Urban runoff mortality syndrome (URMS), also known as Coho pre-spawn mortality, is a condition where Coho salmon die prior to spawning. It's directly related to urbanization density, specifically proximity to roadways—roadway runoff contains a mixture of chemicals that pollutes streams during rain events and is shown to cause URMS. 

While the source was narrowed to roadway runoff, UW and WSU scientists only recently identified the specific chemical responsible for URMS: 6PPD-quinone, a transformation product of 6PPD, which is used as an anti-degradant in almost every automobile tire on the road. 6PPD-quinone is toxic to Coho salmon at very low concentrations (less than 1 part per billion). Concentrations of 6PPD-quinone in urban streams in cities such as Seattle, San Francisco, and Los Angeles frequently exceed this level, particularly during storm events.

Hazard Assessment and Alternatives Assessment

In 2021, the Washington State Legislature passed an operating budget proviso allocating $195,000 to Ecology to assess “potential hazards of 6PPD and other chemical classes and breakdown products used as antioxidants and/or antiozonants in tires. A technical memo outlining the results of this study is included in the "documents" section below.

Following the hazard assessment, the Washington State Legislature tasked the Department of Ecology with performing an Alternatives Assessment on 6PPD in motor vehicle tires to identify compounds with the potential to replace 6PPD in these products. We have published 6PPD Alternatives Assessment Hazard Criteria, which we will use to conduct an alternatives assessment around 6PPD. 

These hazard criteria are similar to the Safer Products for Washington criteria for safer, with three additions: 1) Alternatives must have data on acute aquatic toxicity to coho salmon and rainbow trout, as well as data on two other trophic levels; 2) alternatives must have data on the toxicity of transformation products after exposure to ozone; and 3) we will place a limit on the acute toxicity LC50 values allowed in the minimum criteria (>0.1 mg/L). We originally published the 6PPD Hazard Criteria in June 2023. The 6PPD Hazard Criteria linked above was revised in response to public input received from June 14, 2023, to July 14, 2023. You can view our responsiveness summary here.

We are currently funding studies to make progress on the alternatives assessment and evaluate the toxicity of 6PPD, 6PPD-q, and potential alterantives on several aquatic species. 

Contact information

6PPD team
Department of Ecology | Hazardous Waste & Toxics Reduction Program
6PPD@ecy.wa.gov

ADA Accessibility

The Department of Ecology is committed to providing people with disabilities access to information and services by meeting or exceeding the requirements of the Americans with Disabilities Act (ADA), Section 504 and 508 of the Rehabilitation Act, and Washington State Policy #188.

To request an ADA accommodation, contact Ecology by phone at 360-407-6700 or hwtrpubs@ecy.wa.gov. For Washington Relay Service or TTY call 711 or 877-833-6341. Visit Ecology’s website for more information.

Documents

 File NameFile SizeDescriptionCategoryDate Added
6PPD Alternatives Technical Memo.pdf 634.4 KB 6PPD Alternatives Technical Memo
6PPD Alternatives Technical Memo
None 11/29/21 03:37 PM
GreenScreenExecutiveSummaryFor6PPD.pdf 6.1 MB GreenScreen® Executive Summary for 6PPD
GreenScreen® Executive Summary for 6PPD
None 12/02/21 03:26 PM
GreenScreenExecutiveSummaryFor6QDI.pdf 6.1 MB GreenScreen® Executive Summary for 6QDI
GreenScreen® Executive Summary for 6QDI
None 12/02/21 03:34 PM
GreenScreenExecutiveSummaryFor77PPD.pdf 1.7 MB GreenScreen® Executive Summary for 77PPD
GreenScreen® Executive Summary for 77PPD
None 12/02/21 03:34 PM
GreenScreenExecutiveSummaryForCCPD.pdf 2.3 MB GreenScreen® Executive Summary for CCPD
GreenScreen® Executive Summary for CCPD
None 12/02/21 03:35 PM
GreenScreenExecutiveSummaryForEthoxyquin.pdf 2.9 MB GreenScreen® Executive Summary for Ethoxyquin
GreenScreen® Executive Summary for Ethoxyquin
None 12/02/21 03:35 PM
GreenScreenExecutiveSummaryForGS-108.pdf 15.6 MB GreenScreen® Executive Summary for Dilauryl Thiodi...
GreenScreen® Executive Summary for Dilauryl Thiodipropionate
None 12/02/21 03:36 PM
GreenScreenExecutiveSummaryForGS-1203.pdf 786.8 KB GreenScreen® Executive Summary for GS-1203
GreenScreen® Executive Summary for GS-1203
None 12/02/21 03:37 PM
GreenScreenExecutiveSummaryForIPPD.pdf 8.6 MB GreenScreen® Executive Summary for IPPD
GreenScreen® Executive Summary for IPPD
None 12/02/21 03:38 PM
GreenScreenExecutiveSummaryForNBC.pdf 1.7 MB GreenScreen® Executive Summary for Nickel Dibutyld...
GreenScreen® Executive Summary for Nickel Dibutyldithiocarbamate
None 12/02/21 03:38 PM
GreenScreenExecutiveSummaryForTMDHQ.pdf 1.8 MB GreenScreen® Executive Summary for TMDHQ
GreenScreen® Executive Summary for TMDHQ
None 12/02/21 03:38 PM

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