What Are Forever Chemicals?

After the sixth former Philadelphia Phillies player died from brain cancer last year, the Philadelphia Inquirer decided to investigate if the artificial turf at Veterans Stadium, which was knocked down in 2004, contained harmful chemicals.

Dr. Kathleen Egan, Cancer Epidemiologist

Reporters collected turf samples and had them tested at two different laboratories. The tests found 16 different PFAS substances, which are a group of chemicals used to make coatings and products that resist heat, oil, stains, grease and water. Also known as forever chemicals, they do not break down in the environment and can move through soils and contaminate water sources.

There are known health risks of PFAS exposure, including increased cancer risk, but there is no evidence that playing on a ground that contains these toxic chemicals poses any danger.

Dr. Kathleen Egan, an epidemiologist at Moffitt Cancer Center, discusses forever chemicals and their possible link to cancer.

What are forever chemicals?

Forever chemicals refer to a large class of chemicals called PFAS, or per- and polyfluoroalkyl substances. These chemicals are used in industry to make coatings and products that repel water and oil and are resistant to heat. Because of these characteristics, the chemicals have been used in a variety of consumer products such as cookware, sofas, carpets, clothing, grease-resistant food packaging (like your pizza box and takeout food containers), paints and cleaning products.

The qualities that make PFAS so useful in industry also make them resistant to degradation. The persistence of these chemicals combined with their widespread use in many different industries has led to widespread contamination of PFAS in the environment. The chemicals can leak into the environment where they are made, used, disposed of or spilled. Runoff from industrial facilities, military bases, airports and firefighter training facilities have been shown to infiltrate surface water, soil, plants and groundwater.

The primary sources of human PFAS exposure are thought to include drinking water, indoor dust and air, and food (including contamination from food packing). PFAS are so ubiquitous that nearly all of us have been exposed. One study of the U.S. population found that more than 98% of people tested had measurable levels of one or more PFAS in their blood.

Epidemiological studies have identified possible links between exposure to specific PFAS and a variety of health effects, including altered immune and thyroid function, liver disease, lipid and insulin dysregulation, kidney disease, adverse reproductive and developmental outcomes, and potentially cancer. 

Is there a link between forever chemicals and cancer?

There is limited support for a link between PFAS and most cancers in humans. These chemicals have been shown to cause tumors in rodents though the animals were exposed to much higher levels of the chemicals than people are exposed to and the types of tumors observed in rodents were benign and are rare in humans.

PFAS exposure in humans could elevate cancer risk by different mechanisms. For example, PFAS has been linked to immune system dysfunction, and these chemicals may affect the endocrine system and the expression of genes linked to cancer.   

Evidence from human epidemiological studies is weak and inconsistent. Most occupational studies do not show a consistent pattern of elevation of the incidence of cancer at any specific site. A recent study based on a representative sample of the U.S. population 60 and older found no association between the chemicals tested and all-cancer mortality. PFAS could, however, potentially contribute to cancers at individual sites.

A review of studies published through September 2020 found some evidence of association for testicular and kidney cancer and liver cancer not related to viral exposures.

Given the uncertainties, the U.S. Environmental Protection Agency concluded that there is suggestive evidence of a carcinogenic potential of certain PFAS in humans, citing strongest evidence for testicular cancer. 

What are the challenges when it comes to studying forever chemicals and determining links to cancer and other diseases?

Much of the research on PFAS and health risks were based on occupational studies, and exposure estimates were inferred from job title or estimated/modeled serum levels. This exposure assessment is imprecise.

Most of what we know about PFAS and health effects is based on the older “legacy” chemicals that have been largely phased out in the U.S. A challenge in studying the newer “alternate” chemicals is that because they are eliminated from the body more quickly, a person exposed in the past may no longer have a positive test result.

Another problem is the sheer number of these chemicals that could potentially pose risk. In 2015, it was estimated that at least 3,000 types of PFAS have been on the global market. Testing a large number in any one study is impractical given the complex tests that are performed to identify them. 

Finally, much of the risk assessment has been done in populations with high exposure from specific occupations or industrial contamination of local environments. Studying risk associated with much lower background levels of PFAS is more difficult because levels in blood or urine are usually very low and there may be little contrast between people studied. Large and carefully designed studies are needed to rule out cancer risk from lower background levels of next-generation PFAS.

What should the public be aware of when it comes to forever chemicals?

Unfortunately, exposure to these chemicals may be unavoidable. However, based on what we know now, it seems that the small background levels to which most of us are exposed are likely not causing many cancers, although that is still being studied.

Legacy PFAS that tend to stay in the body longer than the newer PFAS have been phased out in most parts of world and biomonitoring studies show that human exposures to them have been dropping in the past two decades. However, the replacement chemicals are also polluting the environment and entering the drinking water and food supply just as the legacy chemicals.

The good news is that there is now much more awareness of PFAS pollution and human exposures and health risks, and governments are at least addressing the problem, though much work needs to be done. Early this year, the EPA proposed new limits to tackle drinking water contamination from PFAS.  Many states have also adopted restrictions and prohibitions in several product categories and some have even implemented bans on the sale of products containing intentionally added PFAS.