Why PBT is a toxic chemical supervillain

Meet some of the most infamous chemicals in the world: Persistent, Bioaccumulative and Toxic chemicals- abbreviated as “PBTs.” The industrial chemicals PCBs, one of the first PBTs identified, were banned 4 decades ago yet to this day contaminate waterways, schools, and harm our health. Recent research from the Children’s Center at University of California, Berkeley links PCBs with increased risk of the childhood cancer leukemia. Another PBT, the “Silent Spring” pesticide DDT built up in wildlife like bald eagles, decimating their populations. DDT was banned 40 years ago, but evidence of exposure is still found in 100% of Californians tested!

These examples illustrate why the properties P, B & T in combination are so bad. Persistent means they don’t break down in the environment, so they don’t go away, often even after decades. Bioaccumulative means the chemical builds up in the bodies of animals and humans; even if you eat, breathe in or drink just a small amount, over time these many small exposures accumulate to higher levels because the chemicals get into our bodies and stay there. And toxic means harmful to the health of wildlife and people, such as by causing cancer. Put these properties together, and you open a chemical Pandora’s Box—once released, these chemicals will continue to pose global health threats for many generations.

That’s why the reformed federal Toxic Substances Control Act (TSCA) set PBT chemicals apart from all others, and mandated that the U.S. Environmental Protection Agency (EPA) take expedited action to curtail them. EPA identified the first five PBTs in 2016 and is moving forward with next steps now, as shown in the diagram below.

UCSF PRHE, academics, scientists and clinicians submitted comments highlighting that current science supports the criteria used to identify these chemicals, and that the rest of the world concurs—the criteria are consistent with those used in the Stockholm Convention, an international treaty agreed to by 180 countries and the EU that aims to limit PBTs.

But the chemical industry is making several last-ditch efforts to reverse EPA’s course on these chemicals– first by delaying the comment deadline after the Agency had already given stakeholders a year to comment. Then, attempting to move these chemicals off the list by proposing to change the definition of a PBT with flimsy, inadequate scientific justification: a non-peer reviewed report from a 2008 workshop sponsored primarily by the chemical industry. Despite not having a basis in the science, this effort could be a real threat in this administration where, according to an investigation by the NY Times, chemical industry insiders placed at EPA are rewriting policies to favor their former employers.

This is consequential for public health because this administration will pass, but its actions (or inaction) on PBTs will live on for generations, much like the chemicals themselves. For example, DecaBDE, one of the PBT chemicals under current EPA evaluation, is a type of PBDE (polybrominated diphenyl ether) flame retardant. Our systematic review on PBDEs found that prenatal exposures can damage children’s intelligence, resulting in significant loss of IQ points. The production of other PBDEs (not DecaBDE) ceased in the U.S. in 2005, but our recent paper demonstrates that because of their persistence and bioaccumulation, banning production is not enough. First, PBDE exposures are still ubiquitous in the population we studied, pregnant California women. Second, though the amount of PBDEs in the women initially declined after the ban, now levels appear to be holding steady, and may even be increasing for some specific PBDEs because they remain in the environment and our bodies for a long time.

Therefore, our comments to EPA emphasized the need to take swift and comprehensive actions that will address all sources of DecaBDE exposures: Manufacturing, import, processing and ongoing uses; AND DecaBDE within already existing products, their recycling and disposal.

Meanwhile, U.S. states and the rest of the world have already moved to address the threats of DecaBDE- Washington state banned it in many products, including televisions, and DecaBDE was globally banned by the Stockholm Convention in 2017. But as a recent report finding the banned DecaBDE in televisions in Washington shows, EPA action is still needed to truly tame this PBT supervillain.

The TSCA law unequivocally directs EPA to put rules in place to eliminate people’s health risks from  dangerous PBT chemicals, especially vulnerable populations like children. EPA should follow the science and move forward with comprehensive rules to protect public health, so we don’t repeat the disasters of the past.

About the Author

Veena Singla, PhD is a Senior Scientist in the Healthy People & Thriving Communities program at Natural Resources Defense Council. Prior to that, she was the Associate Director of Science & Policy at PRHE.