Following pressure from environmental and consumer groups, the US imposed limits on PFAS substances, also known as “permanent chemicals”, a long-term threat that is now also of concern to Europe.
PFAS are found in the water we drink, food packaging, our cookware, the beds we sleep on, and even inside the human body.
Nowhere in the world is anyone safe from the ever-present chemicals that fall with rainwater.
PFAS, or perfluorinated alkylated compounds, are a group of thousands of industrial chemicals that do not break down in the human body and take decades to degrade in the environment.
For decades, they have been widely used in non-stick cookware, waterproof clothing, fireproofing, adhesives, and even product packaging.
Cancer, disruption of hormone levels, hypertension, developmental disorders in children and fertility problems are some of the possible side effects of these substances, although a causal relationship has not yet been proven.
The U.S. Environmental Protection Agency is imposing maximum limits for five PFASs for the first time, as well as mixtures containing a sixth such substance.
Meanwhile the European Commission is preparing to ban a number of PFASs in firefighting foams, a major source of pollution.
Some companies have already begun phasing out some of the more studied PFASs, PFOS and PFOA. They have been found to be harmful to the immune system and have been linked to problems with child development, fertility and metabolism.
How long do permanent chemicals last?
Since PFAS are very stable molecules and are not easily eliminated, they can accumulate in living organisms. And this means that even low levels of exposure can lead to consequences over time.
How stable permanent chemicals are depends on their chemical composition. And they are not all the same.
All PFAS substances have a backbone of carbon atoms. Those with fewer than six carbon atoms are called “short chain,” those with more are “long chain.”
Long-chain PFASs seem to stay in the human body longer, at least according to a small study (“Serum Half-Lives for Short- and Long-Chain Perfluoroalkyl Acids after Ceasing Exposure from Drinking Water Contaminated by Firefighting Foam“) of airport workers in northern Sweden.
Employees drank PFAS-contaminated water from firefighting foams used for accident management. Their blood was found to contain long-chain PFOS with a half-life of 2.93 years and PFOA with a half-life of 1.77 years – that’s the time it takes for the compound’s concentration to halve.
A shorter molecule called PFBS, in contrast, has a half-life of only 44 days, possibly because the kidneys eliminate short-chain molecules more easily.
Another study (“Half-lives of PFOS, PFHxS and PFOA after end of exposure to contaminated drinking water“), looking at people with longer exposure to PFAS in southern Sweden, estimated the half-life of another PFAS called PFHxS to be 5.3 years, compared to PFOS 3.4 years and PFOA 2.7 years.
For some PFOS with branched carbon skeletons the half-life in the human body reaches several decades.
In water, however, the perennial chemicals linger much longer, with some studies estimating that PFOA has a half-life of more than 90 years, while PFOS has a half-life of more than 40.
Where does pollution come from?
One of the most frequently reported sources of PFAS contamination is firefighting foams, especially those used to extinguish flammable liquids.
PFAS act as “surfactants”, i.e. they reduce the surface tension of water (the tendency of H2O molecules to stick together) so that the foam spreads more easily.
Except that the foam can wash off and end up in soils and groundwater.
In addition, the ubiquitous chemicals are widely used in waterproof coatings on clothing or food packaging, such as paper pizza boxes, to slow their permeation by lye.
For the same reason they are used in carpets and furniture upholstery. One study (“How Well Do Product Labels Indicate the Presence of PFAS in Consumer Items Used by Children and Adolescents?“) found such substances in 60% of children’s bedding and clothing.
PFASs are also widely used in plastics, such as plastic food containers, to prevent staining. And in this case, however, studies (“Directly Fluorinated Containers as a Source of Perfluoroalkyl Carboxylic Acids“) have shown leakage into food.
In 2022, the Environmental Working Group found another source of pollution: sewage sludge from biological treatment plants.
About 80 million acres of farmland in the US are estimated to be contaminated by sewage sludge used as fertilizer and soil conditioner.
In addition to long-chain PFASs that are difficult to eliminate from the human body, sewage sludge also contains microplastics, another modern scourge.
A recent study found PFAS even on toilet paper, which researchers say can increase concentrations in sewage sludge.
And once they reach the field, the ubiquitous chemicals will find a way to get to our food.
