Polycyclic aromatic hydrocarbons (PAH)

We work with the Washington State Department of Health, along with industry and environmental stakeholders, to identify and take action to phase out the use, release, and exposure to polycyclic aromatic hydrocarbons (PAH) chemicals in Washington. Working with partners, we have developed a chemical action plan to reduce or eliminate the use of these chemicals.

What are PAH chemicals?

Polycyclic aromatic hydrocarbons, or PAHs, are a group of more than 100 different chemicals and generally occur as complex mixtures. They can come from natural sources or from human activity.

Sources and exposure

PAHs are found in some natural substances like oil and coal. They are formed during the incomplete burning of organic matter such as coal, oil, gas, wood, garbage, or other organic substances.

The largest man-made sources of PAH release are wood stoves, creosote-treated wood, and vehicle emissions, including tire wear, improper motor oil disposal, and leaks. Sealants used on asphalt are also a source of PAHs.

Charring or barbecuing meat and other foods, and smoking cigarettes are the largest exposures of PAHs for most people. Air emissions are a minor source.

Toxicity and health effects

PAHs are toxic to people and other organisms. They are widespread in Washington’s environment. Studies have linked PAHs to cancer, reproductive problems, and weakened immune systems.

Taking action against PAHs

Current programs address the major sources of concern in Washington. Our chemical action plan didn't identify the need for any additional actions to address the major sources of PAHs beyond existing programs.
Ecology and the Washington State Department of Health have programs to reduce PAH releases from wood smoke, diesel, and creosote. Many businesses, state and federal agencies, local clean air agencies, counties, ports, cities, and nonprofit organizations also work to reduce emissions from combustion.

The chemical action plan did find that current programs can be enhanced to improve or speed up results. Recommendations focus on initial sources of PAHs, but it's also important to manage pathways like stormwater, where PAHs from multiple sources combine. Developing more effective strategies for controlling stormwater is an important tool in limiting the impact of PAHs in Washington.

Chemical action plan recommendations

Wood smoke

  • Develop education, outreach, and voluntary incentive programs to reduce wood smoke emissions.
  • Local clean air agencies may prohibit the use of uncertified wood stoves in specified areas that don’t meet federal air quality standards.


  • Develop education, outreach, and incentives to reduce fuel consumption, reduce automotive drips and leaks, and reduce vehicle idling.
  • Continue anti-idling education programs and write an anti-idling rule.
  • Continue Ecology's current strategy to reduce diesel pollution.
  • Support new federal actions on vehicle efficiency, cleaner burning fuel, and lowering diesel emissions.

Creosote-treated wood and other products

  • Continue removing creosote piling from derelict structures.
  • Map railroad tie locations near sensitive habitats.
  • Monitor uses and environmental fate of PAHs from other PAH-containing products, like asphalt shingles and roofing.

Human health

  • Continue anti-smoking programs and work to enhance them.
  • Develop outreach on food preparation methods that reduce exposure to PAHs.

History of actions to address PAH in Washington

2012 — Ecology finalizes chemical action plan for PAH.

2011 — Washington bans the sale and application of coal tar pavement sealants.