Per- and polyfluoroalkyl substances, better known as PFAS, are a family of more than 12,000 synthetic chemicals manufactured since the 1950s to make everyday products resist water, grease, stains, and heat. They show up in non-stick cookware, waterproof clothing, food packaging, cosmetics, and firefighting foam. What makes PFAS unusual, and what makes them a serious concern for marine biodiversity, is the carbon-fluorine bond at the core of their structure. It is one of the strongest bonds in organic chemistry, and it means PFAS do not break down through natural processes, such as sunlight, bacteria, or heat, that eventually degrade most pollutants. This is why they have earned the nickname “forever chemicals.” Once released into rivers, groundwater, or coastal waters, they persist for decades, and the ocean has become their final destination.

How PFAS Build Up in Marine Life

PFAS enter the ocean through wastewater discharge, industrial runoff, landfill leachate, and firefighting foam used at airports and military installations. A field study of New Hampshire’s Great Bay Estuary, an area contaminated by a former Air Force base, illustrates this pathway directly: researchers there have been measuring PFAS concentrations in sediment, water, and lower trophic-level organisms such as amphipods and forage fish to understand how the chemicals first enter the food web.

Unlike older persistent pollutants like PCBs and DDT, which dissolve into fatty tissue, PFAS are amphiphilic, meaning they bind instead to proteins such as serum albumin. This changes where they accumulate in an animal’s body. Research on the Barents Sea food web, published in the journal Environmental Pollution, found that PFAS accumulate more in protein-rich organs such as liver and blood than in fat, and that the degree of bioaccumulation tends to rise with chain length, since longer-chain PFAS compounds bind more tightly to proteins and are excreted more slowly.

Bioaccumulation describes what happens within a single organism, as it absorbs PFAS faster than its body can eliminate them. Biomagnification is what happens as those chemicals move up the food chain, becoming more concentrated in predators than in their prey. Evidence for this has been documented across a wide range of marine species and locations:

A 2025 study on PFAS in marine food webs from Liaodong Bay in China found trophic magnification factors greater than one for several compounds, including PFOS, meaning concentrations genuinely increased at each step up the food chain rather than simply reflecting exposure.

Long-term monitoring of striped dolphins in the northwest Mediterranean, using tracking data from 1990 to 2021, found that long-chain PFAS biomagnify in these apex predators, with a particular PFOS isomer accumulating preferentially. The same research pointed to links between PFAS exposure and neurotoxic effects during fetal development, along with reduced reproductive potential in cetaceans.

White sharks sampled in the northwest Atlantic have also been found to carry measurable PFAS burdens, consistent with their position at the top of the ocean food web, while a separate study comparing coastal sharks in the New York Bight to those in the Bahamas found PFAS concentrations were roughly 79 percent lower in the less populated Bahamian waters, a strong signal that human activity on land is the primary driver of ocean concentrations.

Even sub-Antarctic seabirds, sampled far from major population centers, have been found carrying twenty-two distinct PFAS compounds, underscoring how far these chemicals travel through ocean currents and atmospheric transport once released.

Documented biological effects on marine animals include immune system disruption, described in bottlenose dolphins as chronic immune activation, along with liver damage and reproductive impairment. Because much of this research is still emerging relative to the scale of the contamination, scientists studying wildlife exposure describe the field as one where the picture for marine species remains far less complete than it is for humans, even as the exposure itself is now considered widespread and effectively unavoidable in ocean environments. For readers who want to go deeper into the underlying science, a comprehensive literature review of PFAS bioaccumulation patterns across marine taxa, drawing on two decades of published research, is available through the National Library of Medicine.

The Human Connection: From Ocean to Dinner Plate

The same biological mechanism that concentrates PFAS in a shark’s liver or a dolphin’s bloodstream also concentrates it in the fish and shellfish that end up on a dinner plate. Because PFAS bind to protein rather than fat, they accumulate in muscle tissue, the exact part of a fish that is typically eaten as a fillet. This differs from legacy pollutants like PCBs, where trimming fat or skin can meaningfully reduce exposure. With PFAS, that strategy offers far less protection, and research on cooking methods for PFAS-contaminated seafood has found only modest reductions in concentration regardless of preparation technique.

The U.S. EPA identifies eating fish, along with drinking contaminated water, as one of the primary routes of PFAS exposure. This matters most for communities near coastal industrial sites, former military bases, and wastewater outfalls. Still, because ocean currents distribute PFAS globally, exposure is not limited to those regions. In humans, PFAS exposure has been associated with a range of health effects, including reduced antibody response after vaccination, elevated blood pressure during pregnancy, developmental effects in children, hormone disruption, and increased risk of certain cancers, with EPA identifying PFOA as a likely contributor to kidney and testicular cancer risk and PFOS to liver cancer risk. Pregnant women, nursing infants, and young children face proportionally higher exposure, since they consume more water and food relative to body weight and can be exposed prenatally or through breast milk.

Where PFAS Removal Stands, and Why Municipal Water Is Behind

Because the carbon-fluorine bond resists natural breakdown, removing PFAS from water is not a matter of destroying the chemical the way conventional treatment neutralizes many contaminants. Instead, it requires physically capturing PFAS molecules and removing them from the water entirely, typically through adsorption, ion exchange, or reverse osmosis membranes.

Municipal water systems were largely built decades before PFAS was identified as a contaminant of concern, and most were never designed with PFAS capture in mind. An analysis highlighted by The New Lede found that only about 8 percent of U.S. water systems currently operate filtration capable of removing PFAS. In comparison, 98 percent of systems with confirmed PFAS detections have no treatment specifically targeting the chemicals. The required retrofit is substantial. The EPA itself has estimated that somewhere between 4,100 and 6,700 water systems nationwide will need to install new treatment equipment to meet federal PFAS limits, at an estimated compliance cost of roughly 1.5 billion dollars annually, and available federal infrastructure funding is widely considered insufficient to cover both installation and the long-term cost of replacing PFAS-saturated filter media. Wastewater treatment plants face a parallel problem: they receive PFAS in industrial and residential influent but were never engineered to remove it, so the chemicals largely pass through treatment unchanged and re-enter rivers, biosolids, and farmland.

Regulatory timelines add further uncertainty. The EPA finalized the first enforceable federal drinking water limits for PFAS in April 2024, setting maximum contaminant levels of 4 parts per trillion for PFOA and PFOS. In May 2026, the agency proposed rescinding limits for four additional PFAS compounds and extending the compliance deadline for PFOA and PFOS from 2029 to 2031 for qualifying utilities. This shift is still moving through public comment and likely litigation. Whatever the outcome, the practical reality for most communities is the same: municipal infrastructure upgrades take years, and in the meantime, tap water in a large share of the country continues to carry measurable PFAS.

This gap is why point-of-use filtration at the household tap has become such an important stopgap. Among the available technologies, high-quality carbon block filtration stands out as one of the more accessible and genuinely effective options. A carbon block filter compresses finely ground activated carbon into a dense, solid cartridge rather than leaving it as loose granules. Water is forced through a fine, uniform network of pores instead of being able to channel around less-resistant paths, which increases contact time between the water and the carbon surface, the single biggest factor in how much PFAS a carbon filter can actually adsorb. Independent third-party testing on high-performance sub-micron carbon block filters has demonstrated a 99 percent reduction in total PFAS. This figure reflects how much filter design and carbon quality matter, since ordinary granular carbon systems perform far less consistently. That performance is backed up by independent academic research as well: a 2024 study published in Frontiers in Environmental Chemistry tested several point-of-use pitcher filters on real Canadian tap water and found that filters using dense, carbon block-style filtration media removed up to 99 percent of total PFAS, while looser granular designs removed as little as 20 to 48 percent under the same conditions.

For coastal communities and anyone concerned about the marine food web feeding back into their own kitchen, the practical takeaway is twofold. First, pressure for stronger, better-funded municipal PFAS treatment remains necessary, since no household filter can address contamination at the scale of an estuary or a fishery. Second, while that infrastructure catches up, a properly sized, third-party tested carbon block filter is one of the most evidence-backed ways to reduce PFAS exposure at the tap today. Protecting marine biodiversity from forever chemicals and protecting human health from the same chemicals are, in the end, the same fight, waged at both ends of the water cycle.