This Friday (December 13, 2019) the Department of Environmental Health Sciences at the Yale School of Public Health will host a symposium on chemicals known as per- and polyfluoroalkyl substances (PFAS). The day-long event organized by Professor Vasilis Vasiliou will be held in Winslow Auditorium and feature a range of experts from Yale and beyond who will discuss the latest research on PFAS and possible health implications associated with the manmade compounds. Citing scientific research, U.S. Congresswoman Rosa DeLauro (D-CT) recently called for banning the chemicals in food packaging.
Zeyan Liew, Ph.D., an assistant professor at the Yale School of Public Health and one of the featured speakers at Friday’s event, has been studying the compounds for years and shares his insights here.
When were PFAS first introduced?
ZL: PFAS have been manufactured and used in a variety of commercial products and industrial processes since the 1940s around the globe, including in the United States. It was not until the 1990s, however, when scientists discovered that these chemicals were widespread and bioaccumulated in the environment. Early research focused on the two most commonly used PFAS (PFOS and PFOA) but more recent attention has been given to newer types of PFAS.
PFAS are now used in a wide variety of products. What are some of the most common ways people can come into contact with these compounds?
ZL: PFAS are ubiquitously detected in the general population and people can be exposed in a variety of ways. Primary exposure sources are believed to be contaminated food products (e.g. through bioaccumulation, such as absorption of PFAS in foods from soil and water, and contamination through food packaging materials), household products including non-stick cookware, and drinking water supplies. Some groups might be exposed to higher levels in occupational settings through air contamination at manufacturing and application sites (such as firefighters and military personnel).
Is there conclusive evidence at this point that PFAS harm health?
ZL: Some human studies, but not all, that evaluated the health effects of exposure to the commonly detected PFAS have shown that these compounds may:
- Affect growth, learning, and behavior of infants and older children
- Lower a woman’s chance of getting pregnant
- Interfere with the body’s natural hormones
- Increase cholesterol levels
- Affect the immune system
- Increase the risk of developing cancer
Scientists are still learning about the health effects of exposures to PFAS and attention is needed on other newer types of PFAS, those introduced in production facilities and manufacturing industries.
What are some of the ways that PFAS might harm health?
ZL: Studies have shown toxicity in reproductive and developmental functions, as well as in the liver and kidney. Immunological effects, and potential carcinogenicity have been reported for the most common types of PFAS in laboratory settings. PFAS can activate some nuclear receptors (PPAR-α and γ) and impact lipid and glucose homeostasis, cell proliferation, and inflammation. Cumulative evidence from animal studies also revealed PFAS’s ability to suppress the primary antibody response in mice, i.e. the IgM antibody production to T-cell-specific antigens. Human epidemiological studies have consistently shown that exposure to commonly used PFAS have been associated with an increase in cholesterol levels and a disruption in normal thyroid hormone function. The potential toxicological impacts for the newer types of PFAS and other fluorinated compounds are unknown.
What about prenatal exposure to PFAS? What affect might these chemicals have on developing babies?
ZL: The developing fetus might be more sensitive to PFAS exposures compared with adults. We know that even low levels of external chemical exposure during this critical time of development can lead to unfavorable and possibly permanent or irreversible consequences in the offspring. In pregnant women, a considerable amount of PFAS can pass through the placenta and transfer to the babies. We have recently published a comprehensive review of more than 60 epidemiological studies regarding the potential health effects associated with developmental exposures to PFAS. We concluded that these studies have consistently suggested a possible adverse effect of exposure to PFAS on impaired fetal and postnatal growth, and an immunosuppressive effect in children indicated by a decreased response to vaccines. To date, findings on neurodevelopmental endpoints are inconclusive and need further evaluation. Newer reports on the influence of prenatal PFAS on the pubertal development of the offspring were not included in our review.
It is imperative to find out more about these chemicals and how they may influence human health.
Zeyan Liew
Are these compounds currently regulated in any way in the United States? How about in Europe?
ZL: The regulation of PFAS has focused almost exclusively on two synthetic chemicals: Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS). The Stockholm Convention on Persistent Organic Pollutants (POPs), a global treaty aiming to protect the environment and human health from the effects of POPs, has listed PFOS and PFOA for regulation under the Convention.
In the United States, the EPA has collected data on six PFAS as suspected contaminants in drinking water supplies but there are no health-based standards and no maximum contamination levels (MCL) set for these PFAS under the Third Unregulated Contaminant Monitoring Rule (UCMR3).
Under the Toxic Substances Control Act, 330 non-Confidential Business Information (CBI) PFAS chemicals have been reported to the EPA and are listed in the public interim report. In addition, there are 148 CBI PFAS substances that have been reported. Since 2006, the EPA claims to have reviewed 294 new PFAS chemicals and regulated 191 through a combination of orders and Significant New Use Rules.
In Europe, meanwhile, the production, and use of PFOS is regulated by EU laws. Restrictions related to PFOA manufacture and introduction to markets will come into effect on July 4, 2020, following scientific evaluations by the European Chemicals Agency (ECHA). Denmark is the first country that has announced plans to ban all organic fluorinated compounds in paper and paperboard materials in contact with foods.
Where is the scientific research in terms of understanding these compounds?
ZL: There’s a long road ahead. We still need to develop tools to study atmospheric fate and transport of PFAS in the environment, perform evaluation of technologies for treatment of contaminated sites and wastewater management, continue the biomonitoring programs of exposure to PFAS in the population, conduct toxicological and epidemiological assessments of potential health impacts of PFAS, and develop policy regulations on the usage of PFAS and other fluorinated chemicals.
What drew you to study these compounds?
ZL: I have been studying the potential health effects of exposures to PFAS, specifically in the context of maternal and child health, for more than 8 years since the beginning of my doctoral training.
My interest in PFAS began with my graduate studies when I read the news about a manufacturer of plastic materials in Parkersburg, West Virginia, that had polluted drinking water sources in the community for decades. I thought this was an environmental injustice and a major public health issue that needed to be tackled immediately. I later discovered that these chemicals were widespread, meaning everyone could be affected. While we know very little about the potential health consequences of PFAS exposure, it is imperative to find out more about these chemicals and how they may influence human health.
At the time, I also discovered reading the literature that the developmental period might be the most sensitive to these pollutants’ effects. With my mentors and collaborators, we set out to study health consequences stemming from prenatal exposure to PFAS using the large national birth cohort in Denmark. The birth cohort study has collected prenatal bio-samples for 100,000 pregnancies and measured a wide range of maternal and child developmental outcomes prospectively, providing us a unique and timely opportunity to use the data resource for this investigation. We have generated many influential findings and reports in this area of research.
In 2017, I received a 5-year NIH/NIEHS (2017-2021) career development award to support the further investigation of prenatal PFAS exposure on maternal and child health, specifically to explore a set of novel neurodevelopmental measures and mental health outcomes in children and young adolescents up to 18 years of age.