🇺🇸▼
Per- and polyfluoroalkyl substances, known as PFAS, are man-made chemicals found in nearly every living thing on Earth. This includes Patagonian penguins and newborn human infants. It is very hard to find a sample of human blood, tissue, or breast milk that does not have detectable levels of at least one type of PFAS. These chemicals have become a common part of the global environment.
Researchers keep finding links between human exposure to PFAS and bad health results. These risks include a weaker immune system and a higher chance of getting kidney or testicular cancer. Pregnancy problems, such as high blood pressure during pregnancy (preeclampsia) and low birth weight, are also linked to these chemicals. Because of these dangers, the levels of some PFAS considered safe in U.S. drinking water are going down. However, political changes have made it harder to create new rules. In the past, the Trump administration tried to cancel proposed regulations for most PFAS, except for two chemicals: PFOA and PFOS. These two were among the most used until the early 2000s. The U.S. Environmental Protection Agency (EPA) has set maximum contaminant level goals for PFOA and PFOS at zero parts per trillion. This means the agency believes no amount of these chemicals is safe.
At the same time, thousands of other PFAS variants are not regulated. They have not been studied in depth, and there is little oversight. In many cases, there is no data about their presence in consumer products, water, or food. This lack of data makes it hard to know the full scope of the problem.
As an expert in chemical pollution, I have studied many synthetic and natural chemicals that harm humans and wildlife. My current research focuses on tracing PFAS from their initial sources. These sources include consumer products, contaminated food and water, and the air. I trace these chemicals to the "fingerprint" they leave in an organism’s blood and tissues.
By following the journey of how PFAS move into the bodies of living things, scientists like me are working to improve safety recommendations. We aim to create better usage guidelines for these chemicals. However, we must first understand how these complex chemical mixtures transform as they accumulate in the body.
PFAS are a large class of organic chemicals. Organic chemicals are molecules that contain carbon atoms. In PFAS, fluorine atoms are added to these carbon chains. This process, known as fluorination, allows PFAS to stick to surfaces in ways that are useful for many applications.
For example, PFAS are used in nonstick cookware, food packaging, cosmetics, textiles, and even toilet paper. They are also heavily used in making semiconductors and lithium-ion batteries. The strong chemical bonds between carbon and fluorine make these chemicals extremely stable. They do not break down easily. This durability is good for manufacturers. Materials made with PFAS can function for a long time without degrading.
However, this persistence becomes a problem when PFAS leak or evaporate out of products. They enter the surrounding environment and can remain in drinking water sources and sediment for decades or even centuries. If dissolved in water or released into the air, PFAS can travel long distances. They can end up in remote locations far from their point of origin. For instance, PFAS released from industrial regions can end up in the blood of white sharks in the Atlantic Ocean or in Arctic environments.
When PFAS are absorbed and accumulate in the body, they leave a unique pattern of chemical contamination. Researchers call this pattern a "PFAS fingerprint." Studying these fingerprints enables scientists to learn about sources of exposure. It helps them understand how exposure differs among people who live in different places, have different jobs, or use different products.
However, the composition of this fingerprint is different from the mixture of chemicals a person was initially exposed to. Some PFAS accumulate in blood to a greater extent than others. Without understanding how a PFAS mixture is distorted and changed in the body, it is difficult to know which sources were major contributors to a person’s lifelong exposure.
Firefighters and military service members provide a clear example. They use aqueous film-forming foams that contain hundreds of poorly studied PFAS. These foamy materials form a film over fire, starving it of oxygen. They are commonly used in emergencies, such as airplane crashes, train wrecks, vehicle fires, or any other fire involving fuels.
Many firefighters and first responders who have used these foams are now grappling with serious health problems, including cancer. Many have wondered whether PFAS contributed to their illness. A clearer understanding of the expected PFAS fingerprint after years of using these foams could help determine if they are a unique source of the chemicals accumulating in their blood.
Fingerprints at a crime scene often lead detectives to a perpetrator. When it comes to identifying sources of PFAS contaminating human bodies, researchers are not always so lucky. For one, PFAS are typically present at low concentrations in the environment. However, they can build up to higher levels in the body. For example, people drinking water containing PFOS typically have levels 50 to 100 times higher in their blood than were measured in the water. This occurs because the body’s rate of PFOS uptake exceeds its rate of excretion.
Not all PFAS increase in blood to the same degree. PFAS that are more likely to bind to biological components, such as proteins and fats, will more readily accumulate. As the mixture of chemicals in drinking water accumulates, these more bioaccumulative PFAS, such as PFOS, will make up a higher proportion of the fingerprint. This distortion complicates the job of scientists like me. We need to be able to predict how much each PFAS accumulates to estimate how these chemicals will change over time.
In addition to predicting accumulation, researchers must contend with human metabolism. Metabolism is the process by which the body biologically transforms chemicals, including some PFAS. Although the chemical structure of PFAS may change in the body, the resulting chemical is usually still a PFAS. It remains a highly fluorinated molecule.
After entering the body, many types of PFAS used in different products can be transformed over days to years. During this process, the highly fluorinated backbone of the molecule remains intact. Through these processes, many different PFAS eventually transform into just a few highly persistent PFAS. For example, many distinct PFAS containing a PFOS backbone can ultimately change into PFOS in the body.
Once these distinct PFAS have all become the same common chemical, it may be impossible to identify how a person was initially exposed. This loss of origin information is a significant challenge for toxicologists.
Despite the complexities of PFAS research, progress is being made. Researchers are working toward a better understanding of how these thousands of chemicals accumulate and transform in the body. Studying real products that contain complex PFAS mixtures can help researchers find biomarkers. These biomarkers can pinpoint a PFAS source in a person’s blood.
The most effective way to protect human health would be to cease the use of PFAS entirely. This should happen in all but the most essential products. Until then, consumers can take steps to avoid exposure. Resources from organizations like the Green Science Policy Institute and the Environmental Working Group can help. They provide lists of products to avoid.
There are also commercial laboratories that offer drinking water and blood testing for some common PFAS. However, it is important to remember that these tests do not capture the whole picture of your PFAS fingerprint. Scientists are still working to identify and capture many more PFAS that have been overlooked. Understanding these "forever chemicals" requires ongoing research and vigilance. By tracing their journey from product to body, we can better protect public health.