PFAS stands for per- and polyfluoroalkyl substances. The name covers a family of more than 12,000 synthetic chemicals, all sharing one defining feature: a chain of carbon atoms bonded to fluorine. That bond is one of the strongest in organic chemistry. It does not break down in water. It does not break down in soil. It does not break down in your body. That is why scientists call them forever chemicals.

Manufacturers have used PFAS since the 1940s because their properties are useful. They repel water and oil. They withstand extreme heat. They reduce friction. Those same properties make them a serious public health problem once they escape into the environment, which they do constantly.

Not all PFAS are the same. PFOA and PFOS are the two most studied and most regulated. When regulators moved against them, manufacturers replaced them with shorter-chain alternatives. A compound gets regulated. A replacement enters the market with less data and less scrutiny. Years pass before research catches up.

Every PFAS molecule shares a basic structure: a carbon backbone with fluorine atoms attached. Fluorine is the most electronegative element on the periodic table. When it bonds with carbon, it creates a connection with a bond dissociation energy around 544 kJ/mol. A carbon-hydrogen bond sits around 413 kJ/mol. That difference is why PFAS resist breakdown so effectively.

PFAS bind to proteins in blood and organs, particularly the liver and kidneys. Unlike fat-soluble contaminants, they do not accumulate in fatty tissue. They accumulate in protein-rich tissues. The primary elimination pathway is excretion, a slow process. PFOS has an estimated half-life in the human body of approximately five years.

Your body burden of PFAS reflects cumulative lifetime exposure. Reducing ongoing exposure matters more than any post-exposure action. The focus should be on source control: filtered water, reduced contact with PFAS-containing products, and awareness of high-exposure environments.

The strongest evidence links PFAS exposure to several serious conditions. The data comes from occupational studies of workers at manufacturing plants, community studies near contamination sites, and animal studies. Dose, duration, and life stage all matter. Exposures during pregnancy and early childhood carry higher risk.

Pregnant women, infants, and young children face the highest risk because PFAS transfer through the placenta and breast milk. People living near military bases, airports, or industrial PFAS sites carry higher body burdens. Firefighters represent one of the most heavily exposed occupational groups in the U.S.

Federal regulation of PFAS in drinking water arrived slowly. For decades, the EPA monitored PFAS without setting enforceable limits. That changed in April 2024 with the first national drinking water standards.

The federal MCLs apply only to public water systems serving 25 or more people. Approximately 43 million Americans rely on private wells, which are not subject to federal testing or treatment requirements. If you use a private well, testing is your responsibility.