EPA changes PAH Risk Status: Science or Politics? What does it mean for Region 10?

In 2017 the EPA published updated toxicity values for one type of prevalent petroleum contaminant, benzo[a]pyrene (BaP), in its IRIS database (Integrated Risk Information System). BaP is among a set of chemicals known as polycyclic aromatic hydrocarbons (PAHs). PAHs are widespread pollutants caused by the incomplete combustion of petroleum products. Benzo[a]pyrene has been recognized as the most toxic of the set. EPA uses BaP’s toxicity values as the basis for assessing risk for six other carcinogenic PAHs. In other words, a change in value for BaP affects all six related PAHs. Essentially, the change means they have all been downgraded. IRIS toxicity values determine the amount of cleanup needed at sites, so the change affects numerous sites in Region 10 and throughout the US.

EPA’s update implies that 7 times greater amounts of BaP exposure are safe, alarming scientists

The change updates BaP’s status from suspected carcinogen to known carcinogen and upholds its status as a mutagen. Oddly though, it implies safe levels of exposure are approximately seven times greater than the amount established 30 years ago. According to NWTCC Summit speaker, Dr. Bruce Lanphear[1], it is extremely rare for EPA to downgrade a chemical’s toxicity level. In fact, when asked, he didn’t recall it ever happening before.

IRIS regulatory updates are intended to be a result of research undertaken by EPA’s internal and external scientists. EPA representatives maintain that the BaP toxicity update has been peer-reviewed and accepted by the scientific community. However, the decision was based on two rodent studies that are over 20 years old. Dr. Thomas Brubacher of the University of Washington’s Superfund Research Center[2], told Grist in an interview, “The whole weight of evidence is very weak. If you look at the past 20 years since [the studies] were published, there’s nothing that would give you confidence that these new numbers are accurate, that they’re good for public health and safety.” He added that “If I were on that committee, my recommendation would be that EPA should go get more data.” (Grist interview with Joseph Winters)[3]

Railroad Bridge over the Willamette River with St. Johns Bridge in background

Independent scientists have discovered BaP is MORE toxic, not less

Furthermore, research at Oregon State University’s Superfund Research Center has found that mixtures of different PAHs and by-products created by their breakdown can actually be more toxic than any single chemical in the set. It appears independent scientists have discovered it is MORE toxic than originally thought rather than less.

The inconsistency is unsettling. One has to wonder why EPA is not consulting with university research scientists whose work is intended to help agencies in decision making.

How will the PAH update apply to sites in Region 10? It is expected to affect projects under federal oversight such as CERCLA[4] and RCRA [5] especially if their status is pre-Record of Decision (ROD). In the case of post-ROD superfund sites such as Portland’s Willamette River, and Washington’s, Duwamish River, community advocates are rightfully alarmed that the change would lead to more carcinogenic toxins being left behind and more harm to humans.

Other sites may not be affected at all if they have low PAH levels or if their state has already defined BaP risk levels since that would supersede that of EPA. States that have not defined the pollutant’s risk levels, may phase in the federal update when they update their standards though in many cases they can implement the new values before formal adoption. In states where cleanup standards for BaP are based on background levels, the updated toxicity values may not affect cleanup goals.

Besides the worrisome political overtones of the change, the other issues Region 10 communities should be aware of:

  • The regulatory values for six other carcinogenic PAHs will also be increased by seven times. This could have a major impact on clean up levels at all sites.
  • The study only includes cancer risk levels for ingestion. It does not include risk values for skin contact. This is a significant omission for sites such as Portland that have recreational beaches.
  • It is unclear if the regulatory change included appropriate study of effects on people in development stages: infants, children, and adolescents who are particularly vulnerable to affects of mutagens.
  • There has not been enough study of its affect on the elderly and others with compromised immune systems.
  • PAHs rarely occur alone. The update does not adequately address mixture toxicity levels, nor that of breakdown byproducts that OSU research shows can be even more toxic than any single PAH.

Stay tuned to NWTCC updates for more on this subject. To learn more about the latest research on PAH toxicity by Oregon State University’s Superfund Research Program, see the NWTCC lunchtime webinar entitled “Polycyclic Aromatic Hydrocarbons (PAHs), Detection, Evaluation and Remediation.” It can be accessed from the homepage at NWToxicCommunities.org.

  1. Dr. Bruce Lanphear MD, Simon Fraser University, BC, Dept. of Health Sciences, Fetal and Childhood exposure to toxins
  2. Dr. Thomas Brubacher, PhD, University of Washington Superfund Research Program, Director of Community Engagement and Research Translation Cores, Professor, Department of Environmental and Occupational Health Sciences
  3. Winters, Joseph, “EPA might water down its cleanup standards for Seattle’s only river.” Grist, 9/2/2021, https://grist.org/science/epa-proposal-environmental-justice-lower-duwamish-superfund-seattle.
  4. Comprehensive Environmental Response, Compensation, and Liability Act
  5. Resource Conservation and Recovery Act