Per- and polyfluoroalkyl substances, or PFAS, are a large group of manufactured chemicals used in industry and consumer products since the 1940s. They are often called “forever chemicals” because their defining feature is a chain of carbon-fluorine bonds, one of the strongest in organic chemistry. This bond makes them highly resistant to heat, water, and oil, but it also means they do not easily break down in the environment or in living organisms. This persistence leads to their accumulation over time.
Sources of PFAS Exposure
The primary way people are exposed to PFAS is through ingestion. Contaminated drinking water is a significant pathway, with the chemicals seeping into groundwater from industrial facilities, landfills, and sites that use firefighting foams, such as military bases and airports. These compounds move easily through many types of soil, allowing them to contaminate underground aquifers that supply public water systems and private wells.
Food represents another major exposure route. PFAS can be present in food packaging materials, like fast-food wrappers and microwave popcorn bags, and can migrate into the food itself. Beyond packaging, the chemicals accumulate in the tissues of animals. Fish from contaminated water bodies can contain high levels of these substances, which are then passed on to humans who consume them.
Beyond ingestion, exposure can occur through consumer products and the air we breathe. Many everyday items are treated with PFAS for their stain-resistant, water-resistant, or non-stick properties, including carpets, clothing, and some cosmetics. While research into airborne exposure is less extensive, inhalation of PFAS-laden dust in homes or particles released from manufacturing facilities is another potential pathway.
Human Health Consequences
Research has linked exposure to certain PFAS with a range of health issues. Studies suggest that PFAS can interfere with the endocrine system and thyroid function, potentially leading to thyroid disease and other metabolic disorders.
Developmental stages appear to be particularly sensitive to the effects of these chemicals. For children, exposure has been associated with developmental delays, including low birth weight, accelerated puberty, and variations in bone development. Because children consume more food, water, and air relative to their body weight, their exposure can be proportionally higher than that of adults. PFAS can also cross the placenta, leading to prenatal exposure.
The immune system can also be compromised. Research indicates that exposure to some PFAS may reduce the body’s ability to respond to vaccines, weakening its defense against infections. Furthermore, epidemiological studies have found associations between PFAS exposure and an increased risk for certain types of cancer, including kidney and testicular cancers. Elevated cholesterol levels and an increased risk of obesity have also been linked to these chemicals.
Environmental Contamination
The same chemical stability that makes PFAS useful in products also makes them persistent environmental pollutants. Once released, they can travel long distances through water and air, leading to widespread contamination of ecosystems far from the original source. They have been detected in soil, groundwater, rivers, and even remote ocean waters, demonstrating their pervasive nature.
This contamination has significant consequences for wildlife. As PFAS move through the environment, they are absorbed by plants and animals. Aquatic organisms, from small invertebrates to large fish, can accumulate these chemicals from the surrounding water and their food. This process introduces PFAS into the food web, impacting the health of a wide array of species.
The Challenge of Bioaccumulation
The environmental and health risks of PFAS are intensified by the processes of bioaccumulation and biomagnification. Bioaccumulation describes how these chemicals build up in a single organism over its lifetime. Because they are not easily metabolized or excreted, they are stored in the body’s tissues, reaching higher concentrations over time than are found in the surrounding environment.
This issue is compounded by biomagnification, which occurs as PFAS move up the food chain. When a predator consumes prey that has accumulated PFAS, it also ingests the chemicals stored in the prey’s tissues. This process repeats at each trophic level, causing the concentration of the substances to become progressively higher in animals at the top of the food chain, including birds of prey, marine mammals, and humans.
A factor driving this accumulation is the long biological half-life of many PFAS compounds. The biological half-life is the time it takes for the body to eliminate half of the total amount of a substance. For some of the most well-studied PFAS, such as PFOA and PFOS, this half-life can be several years in humans. This slow clearance rate means that even low levels of ongoing exposure can lead to a significant and persistent internal body burden.