A ubiquitous substance that can cause liver cancer can be found in water, food wraps, shampoo, and non-stick pans. It is the toxin known as “forever chemicals”—per- and poly-fluoroalkyl substances (PFAS).
Not long ago, the U.S. Environmental Protection Agency (EPA) reduced the recommended standard limits for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS)—members of PFAS—in drinking water by more than a thousandfold. Its 2016 health advisories for PFOA and PFOS were both 70 parts per trillion (or 70 ppt), and the recently updated health advisories for PFOA and PFOS are 0.004 ppt and 0.02 ppt, respectively.
The PFAS are a group of man-made organofluorine chemical compounds that contain multiple fluorine atoms attached to an alkyl chain to form stable strong carbon-fluorine bonds. This structure has high thermal and chemical stability, making these substances incredibly hard to break down both in body and in the environment.
PFAS substances break down very slowly and accumulate continuously in the environment, humans, and animals. PFAS are among the most environmentally persistent substances among organic chemicals, and they are thus called “forever chemicals.”
PFAS were invented in the late 1930s and have been in widespread use since the 1940s due to their unique properties of hydrophobicity and oleophobicity. PFAS can enter the human body through food and drinks, breathing, and skin contact. They are found throughout the body, accumulating mainly in the kidneys, liver, and blood. As some of them are readily absorbed by the body and cannot always be filtered by the kidneys, they eventually accumulate in organs such as the liver.
People are worried about the impact of PFAS on the human body, and researchers have also conducted many animal experiments. However, it is not easy to study the toxicity and effects of such substances on the human body due to its long term nature.
Nevertheless, a breakthrough has been made in the studies: American scientists published an epoch-making study in the Journal of Hepatology in August 2022, which is the first practical proof that PFAS substances can cause hepatocellular carcinoma (HCC) in humans.
Scientists have identified 50 people with HCC from among 200,000 U.S. residents. They obtained the blood samples of these people before they were diagnosed with liver cancer. The results showed that several PFAS substances were prevalent in their blood. Ultimately, the researchers focused on PFOS.
They found that the top 10 percent of people with the highest levels of PFOS in their blood were associated with a 4.5 fold increased risk of HCC over those with low levels of PFOS in their blood.
The researchers further found that PFOS affected the normal function of the liver by altering the metabolism of four substances in the liver, including glucose, a bile acid, an amino acid, and a keto acid.
In addition, PFAS substances may cause cardiovascular diseases, thyroid problems, immune system problems, liver damage, and kidney and prostate cancers.
Common Sources of PFAS
The EPA has currently identified more than 8,000 types of PFAS compounds. Aside from the non-stick cookware coating that everyone knows, PFAS are everywhere around us:
- Drinking water
- Fish and livestock exposed to PFAS
- Food packaging (grease-resistant paper, food containers/wrappers)
- Personal care products (certain shampoos, dental floss, and cosmetics)
- Household products (waterproof and stain-resistant carpets, waterproof clothing, non-stick cookware, cleaning products, paints, varnishes, and sealants)
Scientists have tested 2,094 serum samples collected from the general U.S. population older than 12 years of age to assess exposure to a dozen types of PFAS. Four types of PFAS were detected in the blood of at least 98 percent of the people, among which PFOS (99.9 percent) and PFOA (99.7 percent) were the most common.
PFOA and PFOS are the two most widely used PFAS substances. In recent years, these two substances have been replaced by other PFAS substances in the United States: GenX as a replacement for PFOA, and perfluorobutane sulfonate (PFBS) as a replacement for PFOS. However, the EPA acknowledges that GenX can affect the liver, kidneys, immune system, and has developmental effects, and it is also linked to cancer; and that PFBS can affect the health of the thyroid, reproductive system, and kidneys and people’s development.
4 Ways to Avoid PFAS
Although PFAS substances are pervasive around us and in the environment, we can adjust certain lifestyles and habits to minimize our exposure to these substances.
- Replace non-stick cookware with stainless steel cookware
PFAS substances in non-stick cookware can be transferred to food during the cooking process. Scientists tested this with salted tomato paste and found that PFOS and PFAS substances in non-stick cookware are gradually transferred into food.
You can replace non-stick cookware with stainless steel cookware. If you are worried that the food might stick to the stainless steel cookware while cooking, you can pour a little oil, heat the cookware, let it cool naturally, and then put it aside. Then when you start cooking, add oil into the cookware, and this can prevent food from sticking to it.
If using non-stick cookware, pay attention to the following to reduce the amount of PFAS and other toxic substances in your food:
- Do not heat empty cookware. Cook on medium-low heat. Turn on the ventilation fan or open the windows when cooking on high heat.
- Avoid using utensils that can scratch the surface of the cookware.
- Do not use abrasive cleaning products.
- Replace the cookware if they become damaged or worn.
- Replace potentially health-threatening carpets in your home
Some oil- and stain-resistant carpets contain PFAS.
Modern people spend 90 percent of their time at home or in other indoor environments. A study published in Environmental Science and Technology Letters shows that the concentrations of volatile PFAS in indoor air, carpets, and dust are closely related to one another, indicating that carpets and dust are major sources of these substances in air.
Rainer Lohmann, the study’s co-author and a professor of oceanography at the University of Rhode Island, said that PFAS-treated carpets are an important exposure pathway and can be replaced with PFAS-free carpet.
- Cook your own food
A wide variety of food packaging can contain PFAS. The best solution is to buy raw food and cook at home.
Researchers have found that people who regularly ate at home had significantly lower levels of PFAS in their body. For every 100 kcal of food eaten at home, the concentrations of PFAS substances would be decreased by 0.5 percent. In contrast, people who ate a lot of fast food or frequently ate at restaurants tended to have higher PFAS serum levels.
This means that foods from fast food and other restaurants contain more PFAS, as foods in these places are more likely to have been in contact with PFAS-containing food packaging.
- Be careful when buying waterproofing and antifouling clothes
In outdoor clothes and protective workwear, water- and oil-resistant materials that contain PFAS substances are usually used. These garments gradually degrade and release these substances during their use and washing.