PFAS Health Effects: What "Forever Chemicals" Do to Your Body

If you've already read our plain-English guide to what PFAS are, you're probably asking the harder follow-up question: what are the health effects of PFAS, specifically? The direct answer is that long-term PFAS exposure is linked by the EPA and the Agency for Toxic Substances and Disease Registry (ATSDR) to increased risk of certain cancers, liver damage, immune suppression, thyroid disruption, and developmental harm in children — with the level of concern rising alongside how much PFAS a person is exposed to and for how long. None of that means today's glass of tap water causes disease tomorrow. It means the science has moved from "maybe" to "documented association," and that's worth understanding calmly, with the actual sources in hand.

What PFAS Are, Briefly

PFAS — per- and polyfluoroalkyl substances — are a large family of human-made chemicals prized for decades because they resist water, oil, heat, and grease. That same stability is why they've earned the nickname "forever chemicals": the carbon-fluorine bonds at their core barely break down in the environment or the human body, so they persist in blood and organ tissue for years after exposure — bioaccumulation over years, not a single exposure.^[2] For the fuller picture on where PFAS come from and how filtration reduces them, see our companion guide to PFAS in drinking water. This article stays focused on one question: what does PFAS actually do to your body once it's there?

The Documented Health Effects of PFAS in Drinking Water

This is the section to read closely. Everything below is attributed directly to the EPA and the ATSDR — the two federal bodies that review the human and animal studies on PFAS exposure. We're not editorializing on the science; we're reporting what they've published.^[1]

Can PFAS cause cancer?

The EPA has determined that PFOA is likely to be carcinogenic to humans based on the weight of evidence, and the EPA and ATSDR both associate PFOA and PFOS — the two most-studied PFAS compounds — with increased risk of kidney and testicular cancer.^[3] As with most environmental cancer risk factors, this is a population-level association tied to elevated, long-term exposure, not a certainty for any individual.

Liver damage and higher cholesterol

The ATSDR reports that PFAS exposure is linked to changes in liver enzymes — a marker of liver stress — and to increased cholesterol, one of the more consistently observed effects across human PFAS studies.^[1]

Immune-system suppression, including in children

Among the effects that concern public-health researchers most, the ATSDR reports that PFAS exposure is associated with a reduced antibody response to vaccines. In practice, that means a child's immune system may generate fewer protective antibodies after routine immunization — a measurable, documented way PFAS can suppress immune function.^[1]

Thyroid disruption

The EPA and ATSDR both note associations between PFAS exposure and thyroid hormone disruption. The thyroid regulates metabolism, energy, and (during pregnancy) fetal brain development, which is part of why thyroid effects are tracked closely in PFAS research on pregnant women and infants.^[1]

Developmental effects and lower birth weight

For infants and young children, the ATSDR reports links between prenatal PFAS exposure and lower birth weight, along with developmental delays. Because children have smaller body mass and still-developing organ systems, agencies generally treat childhood and prenatal exposure as a higher-priority concern.^[1]

Pregnancy-related risks

The ATSDR also reports an association between PFAS exposure and increased risk of high blood pressure and pre-eclampsia during pregnancy — a serious condition that raises risk for both mother and baby. This is one of several reasons the agencies flag pregnant women, alongside infants and young children, as populations warranting extra caution around PFAS exposure.^[1]

How PFAS Get Into Drinking Water

PFAS exposure pathways to drinking water are almost always environmental rather than something happening inside your home's plumbing. Manufacturing sites, aqueous film-forming firefighting foam used at airports and military bases, landfill leachate, and biosolids spread on farmland can all release PFAS into soil and groundwater. From there, it migrates into the wells, rivers, and reservoirs that public utilities and private wells draw from.^[4] In April 2024 the EPA finalized the first national drinking water limits for PFAS, setting a maximum contaminant level of 4 parts per trillion for PFOA and PFOS individually — a threshold low enough to signal how seriously the agency now treats chronic, low-level exposure.^[4]

Who's Most at Risk, and How Exposure Adds Up

PFAS exposure isn't evenly distributed, and it isn't a one-time event — it accumulates. A few groups face materially higher exposure or higher sensitivity to it:

• People near known contamination sources — industrial plants, airports, and military installations where firefighting foam was used historically.
• Private well owners in areas without utility-level testing or treatment, especially near agricultural land treated with PFAS-containing biosolids.
• Pregnant women, infants, and young children — smaller body mass and active developmental windows mean the same exposure level carries more weight, per ATSDR guidance.
• Long-term residents on an affected public water system — because PFAS barely breaks down in the body, years of even low-level daily exposure through tap water can add up to a meaningfully higher body burden than a single high dose.
• Certain occupational groups — firefighters and industrial workers with direct product or foam contact.

That's why agencies focus on reducing ongoing exposure rather than treating PFAS like a one-time hazard. Cutting daily intake at the tap — the pathway most households can actually control — is the practical lever available.

What Reducing PFAS Looks Like

As a technology class, two approaches are the documented routes to PFAS reduction in drinking water: activated or catalytic carbon filtration, and reverse osmosis (RO). Both can be certified for the job — NSF/ANSI 53 covers carbon-based systems with a PFAS reduction claim, and NSF/ANSI 58 covers reverse osmosis systems with the same.^[5] The right question for any product isn't "does it filter water" — it's "was this specific system tested for these specific PFAS compounds."

The tradeoffs differ by technology. RO forces water through an extremely fine membrane and is effective against a wide range of contaminants, but most RO systems waste roughly 3 to 5 gallons of water for every gallon they produce, and they strip beneficial minerals along with everything else — which is why some RO setups add a remineralization stage afterward. Carbon-based systems designed and tested for PFAS avoid that wastewater tradeoff entirely. Neither boiling, standard pitcher filters, nor water softeners reduce PFAS — boiling can actually concentrate it as water evaporates.

What an Independent Lab Measured on the Sentry H2O Under-Sink System

Here's where we move from general health-agency findings to something you can check for yourself. Sentry H2O — the product brand behind the catalytic-carbon systems Mountain Pure Water carries — publishes independent laboratory testing, run through Tap Score by SimpleLab, on its under-sink Wellness System. The lab tested raw tap water against the same water after filtration, across the full range of PFAS compounds it could quantify.

The results: reductions ran from 97.44% to 99.93% across the forever chemicals the lab could measure before and after, and most individual PFAS compounds dropped to non-detect. Specifically:

• Non-detect after filtration: PFOS, PFOA, PFDA, PFNA, and PFTeDA
• PFBS: 99.93% reduction
• PFHpA: 99.29% reduction
• PFHxA: 97.44% reduction

These numbers describe the complete under-sink system tested as a whole, not a single component in isolation — that's the standard we hold ourselves to when we make a PFAS claim. Sentry H2O systems are tested to NSF standards; because certification documentation is still being finalized, we don't call them NSF certified. And to be clear about what this evidence does and doesn't say: it documents PFAS reduction in your water. It is not a claim about disease risk, and no filtration system prevents, treats, or cures cancer or any other condition discussed above — it removes the contaminant those conditions are statistically linked to. See every lab result on our Science page for the full before-and-after data.

Frequently Asked Questions

What are the health effects of PFAS exposure?

The EPA and ATSDR report that long-term PFAS exposure is linked to increased risk of certain cancers including kidney and testicular cancer, liver damage and elevated cholesterol, reduced immune response, thyroid disruption, developmental effects in children, and increased risk of high blood pressure during pregnancy. Risk generally rises with how much PFAS a person is exposed to and for how long.

How does PFAS affect the human body?

PFAS chemicals build up in the body over time because they resist breakdown and clear very slowly, with some compounds carrying a half-life of years. The ATSDR reports this accumulation is associated with effects across the liver, thyroid, immune system, and reproductive system.

Can PFAS cause cancer or other serious health conditions?

The EPA has determined that PFOA is likely to be carcinogenic to humans, and both PFOA and PFOS are linked by the EPA and ATSDR to increased risk of kidney and testicular cancer. These are population-level associations tied to long-term, elevated exposure, not a certainty for any one individual.

How does PFAS exposure affect children's health and development?

The ATSDR reports that PFAS exposure during pregnancy and childhood is linked to lower birth weight, delayed development, and a reduced antibody response to vaccines — meaning a child's immune system may respond less effectively to routine immunizations.

Does PFAS increase cholesterol levels?

Yes. The EPA and ATSDR both note that PFAS exposure, particularly to PFOA and PFOS, is associated with increased cholesterol levels — one of the more consistently observed effects across human studies.

How does PFAS suppress immune function?

Research reviewed by the ATSDR has found that PFAS exposure is linked to a weaker antibody response, meaning the immune system produces fewer protective antibodies after vaccination — an effect studied most closely in children.

Can PFAS damage the liver or kidneys?

The EPA and ATSDR report that PFAS exposure is associated with liver damage — including changes in liver enzymes — and with increased risk of kidney cancer.

What should I do if I've been exposed to PFAS in my water?

Start by testing your water through a certified laboratory to find out which compounds and levels are present, then talk with your physician or local health department about your specific exposure history. From there, a filtration system with system-level PFAS reduction testing — such as the Sentry H2O Wellness System — is the documented way to reduce PFAS at the tap going forward.

Educational guidance only — not medical advice. For health concerns related to PFAS exposure, consult your physician or local health department. This article documents general findings published by the EPA and ATSDR; it does not describe outcomes for any individual, and no water filtration system prevents, treats, or cures cancer or any other disease.