The Science of PFAS and Firefighting Foam

We felt it might be helpful to provide some additional information about PFAS and the science behind firefighting foam.

The term “PFAS” describes a very large class of synthetic chemicals that have been used in consumer products across several industries since 1949. They have been used in fabric stain protection and waterproofing, chemical/heat-resistant tape, non-stick cookware, waxes and adhesives, greaseproof food packaging and firefighting foams, as well as various industrial processes. For example, in the Marinette and Peshtigo region, there are many different companies and manufacturers that may have historically used PFAS in their products.

PFOA and PFOS are two of the more well-known versions of PFAS. Tyco has never manufactured either of these chemicals, and neither is manufactured in the U.S. anymore. As a result, blood levels of these two chemicals have steadily decreased in the general U.S. population over the last 10 years. Scientists have heavily studied PFOA and PFOS in animal and human populations that lived near or worked at facilities that produce PFOA and/or PFOS.

How Health Advisory Levels Are Determined

In 2016, the U.S. Environmental Protection Agency (EPA) established a lifetime health advisory level (HAL) for PFAS at 70 parts per trillion (ppt), indicating that a person could drink an unlimited number of glasses of water with 70 ppt or less of PFAS for the rest of their life and experience no detrimental health effects. In other words, regulatory values like this, or Wisconsin’s proposed groundwater standard of 20 ppt, are based on various restrictive assumptions and conservative margins of error below which these agencies believe the public will be safe.

When faced with this kind of scientific uncertainty, state and federal agencies are charged with developing conservative safety standards for drinking water. These regulatory limits do not represent scientific findings regarding human health risk. Instead, state and federal agencies derive these limits by choosing an animal study and then extrapolating from that study to arrive at a regulatory level based on various assumptions, margins of error and policy judgments.

The U.S. EPA developed its HAL of 70 ppt by starting with a single mouse study from 2006 that found reduced bone development and accelerated puberty in mice pups. Although scientists do not believe that either of these effects are directly relevant to humans, the EPA converted findings of this single study to a human dose by applying a safety and uncertainty factor of approximately 56,000 times to account for the conversion from mice to humans and in applying various “uncertainty factors.”

The EPA then derived the HAL by applying further conservative assumptions regarding how much water the average person drinks per day. Neither the EPA nor individual states have concluded that exposure above the regulatory limit causes any disease or adverse effect, and the same is true regarding the Wisconsin proposed groundwater standard.

What the Science Says

Regulatory agencies have not found a cause-and-effect relationship between PFAS and human disease, and the effects observed have not been consistent.

Although some studies have proposed possible associations between PFAS exposure and human disease, every regulatory agency that has studied the issue to date has emphasized that science has not established a cause-and-effect relationship between PFAS exposure and human health. For example, the Wisconsin Department of Health Services has said:

Scientists are still learning about the health effects that various PFAS can have on the body.”

According to the Agency for Toxic Substances and Disease Registry, the federal public health agency of the U.S. Department of Health and Human Services:

“Available human studies have identified some potential targets of toxicity; however, cause-and-effect relationships have not been established for any of the effects, and the effects have not been consistently found in all studies.”

Furthermore, regulatory agencies do not recommend any monitoring or blood testing based on exposure to PFAS. For example, the Wisconsin Department of Natural Resources has stated that:

“While you can do a blood test to determine the amount of PFAS in your body, there is not enough research currently to determine if your levels would cause specific health problems.”

PFAS and Firefighting Foam

Class B Aqueous Film-Forming Foams (AFFFs), which ensure the military can safely accomplish many of its critical firefighting missions, use what is known as a fluorosurfactant. Tyco’s AFFF firefighting foams have always used a fluorosurfactant. This chemical allows our firefighting foams to be effective against high-hazard fires by suppressing these fires in enough time to save lives and equipment and to prevent severe damage to the environment from uncontrolled chemical and oil and gas fires.

The fluorosurfactant in Tyco’s firefighting foam is not PFOA or PFOS, but advances in testing technology have shown that this specialized fluorosurfactant could contain trace amounts of PFOA or break down to create PFOA. The fluorosurfactants used in Tyco’s foam do not contain PFOS and cannot break down to create PFOS. You can view our white paper on firefighting foams here.

The U.S. Department of Defense and the Federal Aviation Administration have concluded that fluorosurfactant-based firefighting foams are critical to ensuring the military and aviation industries can operate safely and deal with the extreme hazards presented by liquid hydrocarbon fires. For example, on 9/11, two firefighting trucks from Ronald Reagan National Airport were able to extinguish the Pentagon fire within seven minutes of arriving on the scene using fluorosurfactant-based firefighting foam. They saved the building and countless lives. Still today, there is no agent other than fluorosurfactant-based firefighting foam that could effectively control a fire like that.


Federal and state drinking water testing indicates that PFAS in drinking water is an important, but manageable, problem. For example, in 2015, the EPA released data from the testing of nearly 5,000 public water supplies serving more than 250 million American citizens that showed just 1.3% of these individuals used drinking water sources that potentially contained PFOS or PFOA above 70 ppt.

In 2019, Michigan released testing data of every public water supply in the state that showed only 0.2% of water sources exceeded the EPA’s HAL, and only 2.6% exceeded Michigan’s proposed standards of eight ppt for PFOA and 16 ppt for PFOS.

Where PFAS have been detected in drinking water, there are reliable methods to mitigate the issue. For example, a municipality can retire a contaminated source and move to an alternate source of water, as with the proposed solution of providing municipal water to Peshtigo residents. There are also effective remediation technologies, like the granular activated carbon (GAC) systems that can be used to filter drinking water like those Tyco installed at Ditches A and B to remediate surface water flows.