SNS - Scientists tested nine fish species from four northern Illinois rivers for contamination with per- or polyfluoroalkyl substances, synthetic chemicals found in numerous industrial and commercial products and known to be harmful to human health. They found fish contaminated with PFAS in every one of their 15 test sites. Elevated levels of PFOS, one type of PFAS compound, were found in nearly all fish tested.
Study found that there were high levels of PFASs contamination levels in channel catfish found in Illinois waterways.
G.C./Pixabay
The qualities that make PFAS desirable for industrial uses — their durability and stability under stresses such as high heat or exposure to water, for example — also make these chemicals particularly problematic in the environment and hazardous to human and animal health, said Joseph Irudayaraj, a professor of bioengineering at the University of Illinois Urbana-Champaign who led the new study.
The findings are reported in the journal Science of the Total Environment.
Short-chain PFASs (per- and polyfluoroalkyl substances) are widely used as alternatives to long-chain PFASs. Long-chain PFASs become gradually regulated under REACH (EC No. 1907/2006) and other international regulations, due to having persistent, bioaccumulative and toxic properties and/or being toxic for reproduction. The increasingly used short-chain PFASs are assumed to have a lower bioaccumulation potential.
“PFAS contain multiple carbon-fluorine bonds, one of the strongest bonds in organic chemistry,” Irudayaraj said, who is also a professor in the Beckman Institute for Advanced Science and Technology and an affiliate of the Carl R. Woese Institute for Genomic Biology and the Carle Illinois College of Medicine at the U. of I. “Because of this, they are also very hard to break down. They persist for a long time because they are very, very stable.”
Considering such permanent exposure, it is very difficult to estimate long-term adverse effects in organisms. Enriched in edible parts of plants, the accumulation in food chains is unknown.
There are nearly 15,000 PFAS chemicals, according to the U.S. Environmental Protection Agency. These are classified either as short-chain PFAS, which have less than six carbon-fluorine bonds, and long-chain PFAS, with six or more of these bonds, Irudayaraj said.
Long-chain PFAS were widely used before awareness grew about the hazards of these chemicals. More recently, many industries switched to using short-chain PFAS.
“It was thought that the short-chain PFAS were less toxic, and that they could more easily degrade,” he said. “But surprisingly, that was not the case.”
Now, both types of PFAS are found in groundwater, soil and human tissues.
Short-chain PFASs have a high mobility in soil and water, and final degradation products are extremely persistent. This results in a fast distribution to water resources, and consequently, also to a contamination of drinking water resources. Once emitted, short-chain PFASs remain in the environment. A lack of appropriate water treatment technologies results in everlasting background concentrations in the environment, and thus, organisms are permanently and poorly reversibly exposed. Considering such permanent exposure, it is very difficult to estimate long-term adverse effects in organisms. Enriched in edible parts of plants, the accumulation in food chains is unknown.
“About 99% of people living in the U.S. have PFAS in their system,” Irudayaraj said.
Studies on animals have shown that short-chain PFAS (per- and polyfluoroalkyl substances) are almost completely absorbed when ingested or inhaled but not much through the skin. Both short- and long-chain PFAS don't break down easily in the body due to their strong chemical bonds. Even if these chemicals start off in different forms, they eventually turn into acids through several steps, which can be more toxic than the original chemicals. One such toxic substance, perfluorohexyl ethanoic acid (FHEA), has been found in various tissues from deceased people, according to research published by The Danish Environmental Protection Agency in 2015.
The time it takes for these acids to leave the blood varies depending on the specific chemical, the species, and even the sex of the animal. In general, sulfonates (a type of PFAS) take longer to be eliminated than carboxylates (another type), and
longer chains take longer to leave the body than shorter ones. In animals, the time is often shorter for females due to differences in how their bodies process these chemicals. The time these substances stay in the blood can range from a few hours to days in rodents, a bit longer in monkeys, and much longer in humans, sometimes lasting years. However, shorter-chain PFAS tend to leave the body faster, except for PFHxS (a six-carbon chain PFAS), which has a longer half-life in humans than some other PFAS like PFOA and PFOS.
Despite a voluntary phasing out of some PFAS in industry in the U.S. and efforts to reduce PFAS pollution, these chemicals are still found in drinking water, household products, food packaging and agricultural products, he said.
Fish from the Rock River had the highest concentrations of PFAS in their tissues.
The manufacturers of chemical products using PFAS argue that the newer short-chain PFAS is safer than the widely known long-chain contaminants. Despite this assertion, the Auburn study's significant findings challenge these statements. The research indicates that short-chain chemicals are frequently present in drinking water systems and could potentially endanger human and environmental well-being. Additionally, current removal methods are relatively less efficient when it comes to eliminating short-chain PFAS in comparison to long-chain PFAS.
The Auburn study analyzed over 200 individual studies on PFAS finding that the short-chain contaminants may be just as harmful as the long-chain versions, if not more. The short-chain PFAS have been
linked to hormonal and reproductive system harm.
The researchers in the U of I study focused on fish in northern Illinois rivers because they are close to urban and industrial areas. Industrial emissions and urban rainwater runoff may further contaminate local waterways with PFAS. Sport fishing is also popular across the state, including in areas inside and near Chicago. More than 666,000 fishing licenses were issued across the state of Illinois in 2020.
The researchers narrowed their research down to the fish in the Pecatonica River, Rock River, Sugar River and Yellow Creek from 2021-22. The team collected dozens of samples from nine species of fish, including bluegill, channel catfish, common carp, northern pike, smallmouth bass and walleye. The fish represented different levels of the food chain, from those that feed only on plants, like bluegill, to those eating other fish, such as channel catfish and northern pike.
Back in the lab, the scientists analyzed fish tissues for 17 PFAS chemicals. They found PFAS-contaminated fish in every river they tested and in every one of their 15 sampling sites. Fish from the Rock River had the highest concentrations of PFAS in their tissues. Contamination levels were highest in channel catfish, at the top of the food chain, and lowest in the plant eaters.
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