Anyone who has followed the news about PFAS knows the basics. These “forever chemicals” are everywhere – in nonstick pans, fast-food wrappers, firefighting foam, and thousands of other products. They do not break down in the environment, and they accumulate in human blood. Studies have linked them to kidney cancer, testicular cancer, thyroid disease, ulcerative colitis, and high cholesterol. That sounds like an open-and-shut liability case for someone with those conditions who also has high PFAS levels in their blood. But it is not. The single biggest obstacle in any PFAS lawsuit is proving that the chemicals actually caused the specific injury. Many people have high PFAS levels and never get sick. Many people get kidney cancer without any significant PFAS exposure. So how does a plaintiff bridge that gap? The answer is not simple, and it is where most cases fail.
The legal system separates causation into two parts. First, general causation: can PFAS cause the disease at all? Second, specific causation: did PFAS cause this particular person’s disease? General causation is hard enough. The science on PFAS is still evolving. While there is strong evidence for some diseases, the U.S. Environmental Protection Agency and major health agencies do not formally classify PFAS as causing kidney cancer or testicular cancer at typical environmental levels. They say “suggestive” or “likely” – not definitive. Courts rely on expert testimony, and opposing experts will argue that the epidemiological studies are inconsistent or that the exposure levels in those studies were far higher than what the plaintiff experienced. Plaintiffs need to present peer-reviewed research that meets the legal standard of “more likely than not” – meaning there is a greater than 50 percent chance that PFAS caused the harm. For many conditions, that bar simply has not been met yet.
Specific causation is even harder. To prove it, you must show that the plaintiff’s exposure was high enough, long enough, and started early enough to trigger the disease. PFAS levels in blood tell you about current and past exposure. But they do not tell you the exact source. A plaintiff who lived near a chemical plant and also used nonstick pans may have gotten most of their exposure from the pans. The defendant will argue that the exposure from their product or facility was too low to matter. You need a dose-response relationship: higher exposure leads to higher risk. You need to compare the plaintiff’s blood serum concentration to levels seen in occupational studies where workers handled PFAS daily. Most residential exposures are far below those levels. The defense will hammer this point. They will also bring up other risk factors – smoking, genetics, obesity, heavy alcohol use – that offer alternative explanations for the disease. In a no-jury context, a judge will look for a credible expert who can rule out those alternatives with reasonable confidence.
Some plaintiffs avoid the causation trap by not claiming a physical injury at all. They file for “medical monitoring” – a legal remedy that requires companies to pay for ongoing testing and screening of people who were exposed, even if they are not currently sick. The rationale is that the exposure created a significant increased risk, and early detection could save lives. Medical monitoring cases still require proof of exposure above normal levels and evidence that a reliable screening test exists. But they do not require you to prove that cancer or any specific disease has already developed. This is often the smarter strategy for communities with contaminated drinking water. It shifts the burden to the defendant to pay for blood tests and follow-up care, without the impossible task of linking a particular illness to a particular discharge.
What does this mean for someone considering a PFAS claim? First, get your blood tested. Know your serum PFAS levels compared to the national average. Second, document everything you know about your exposure – the dates, the duration, the products you used, or the water you drank. Were you a firefighter who used aqueous film-forming foam? Did you eat fish from a contaminated river? Did you work at a plating facility? Third, gather medical records that establish a diagnosis date and a chain of treatment. Fourth, and most importantly, find an expert witness willing to testify on your specific causation. That expert will need to calculate your cumulative dose over time, model how your body absorbed the chemicals, and explain why your disease is more likely than not tied to that exposure. This is expensive and time-consuming. If your case involves a widely used consumer product, the defendant will have a fleet of high-priced scientists working to poke holes in that testimony. Do not go into this expecting a quick settlement.
The bottom line is that PFAS liability is real but legally immature. The science is moving fast, and courts are slowly recognizing that these chemicals are dangerous at lower levels than previously thought. But the burden of proof remains on the plaintiff. Until more studies pin down precise exposure thresholds and disease risks, every PFAS case will be a battle of dueling experts. The winners will be those who did their homework before filing. If you cannot show enough exposure to matter, and enough evidence to connect that exposure to your specific illness, your case will collapse under its own weight.
