Health science summary: Long-chain perfluorocarboxylic acids (PFCAs), their salts and related compounds
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The Government of Canada has nominated long-chain PFCAs, their salts and related compounds (also known as precursors) for consideration under the Stockholm Convention on Persistent Organic Pollutants (POPs). The Stockholm Convention is a multilateral treaty aimed at eliminating or restricting the global production and use of POPs in an effort to protect human health and the environment. POPs are chemicals that:
- remain intact in the environment for long periods of time
- accumulate in living organisms
- are harmful to humans and/or to the environment
- have properties that cause them to travel long distances and become widely distributed throughout the environment
Although long-chain PFCAs, their salts and related compounds have previously undergone a Canadian ecological screening assessment, these substances have not been evaluated in Canada from a human health perspective. Consequently, in preparation for the nomination, the Government of Canada has examined the science as it relates to human health. Canada’s nomination of long-chain PFCAs, their salts and related compounds under the Stockholm Convention will be considered at the seventeenth meeting of the Persistent Organic Pollutants Review Committee (POPRC-17).
Long-chain PFCAs, their salts and related compounds are a sub-group of the per- and polyfluoroalkyl substances (PFAS) chemical family. PFAS are a broad group of over 4,700 human-made substances that contain linked carbon and fluorine atoms. Because of their unique properties, they have a wide range of uses including as surfactants, lubricants, and repellents (for dirt, water, and grease). PFAS can be found in products as diverse as firefighting foams, textiles (including, carpets, furniture, and clothing), cosmetics, and in food packaging materials. PFAS are not manufactured in Canada but enter through importation, within products or manufactured items. Due to the strength of the carbon-fluorine bond, most PFAS do not readily degrade, leading to their persistence in the environment.
In August 2012, the Government of Canada published an ecological screening assessment report on long-chain PFCAs, their salts and their precursors and then took action to address identified risks. The report concluded that long-chain PFCAs, their salts and their precursors are entering the environment at levels that are harmful to the environment. The manufacture, use, sale, offer for sale or import of long-chain PFCAs, their salts and precursors and products that contain them have been prohibited since 2016, under the Prohibition of Certain Toxic Substances Regulations, 2012 , with a limited number of exemptions. Visit the LC-PFCAs their salts and precursors web page for more information on the ecological assessment and the risk management actions.
At the time of the ecological assessment, long-chain PFCAs were not evaluated under the Canadian Environmental Protection Act, 1999 (CEPA 1999) with respect to impacts on human health. New scientific data has since become available and based on the current evidence, there are indications that exposure to long-chain PFCAs, their salts and related compounds may be associated with human health effects. Although risk management activities have been undertaken in Canada to control releases to the environment, human exposure to long-chain PFCAs is still of concern due to their potential for long-range transport, their persistence in the environment (which increases the chance for human exposure) and because they take a long time to be eliminated from the human body.
Identity and uses
Long-chain PFCAs and their salts are organic compounds with a fluorinated carbon chain structure and a molecular formula of CnF2n+1CO2H (where 8 ≤ n ≤ 20). They contain a total of between 9 and 21 carbon atoms (C9-C21). Long-chain PFCAs can be formed from the degradation or transformation of parent compounds and chemical products (known as related compounds or precursors) that contain long-chain PFCAs. The precursors of long-chain PFCAs have been commonly used in commercial products to provide oil-, grease-, water- and stain-repellent properties. However, apart from the ammonium salt of C9 PFCA (ammonium perfluorononanoate or APFN), long-chain PFCAs themselves are infrequently used intentionally in products. Rather, long-chain PFCAs are unintentionally produced during the manufacture and use of other PFAS. Long-chain PFCAs, their salts and related compounds have been found in numerous commercial products (for example, water-, soil-, and stain-resistant coatings for clothing, textiles and carpets, oil-resistant coatings for food contact paper, firefighting foams, paints, adhesives, waxes, polishes, cosmetics and lotions) and industrial uses (for example, surfactants, sealants).
Releases of long-chain PFCAs, their salts and related compounds may occur during manufacture and processing operations. They can also occur during the use and disposal of industrial and consumer products containing these substances. Therefore, landfills and wastewater treatment facilities are potential sources of these substances in the environment. Due to the ongoing international use and the many applications of PFCA precursors, long-chain PFCAs, their salts and related compounds are found widely in the environment, including in remote areas such as the Arctic. Studies investigating the concentrations of these substances globally in the environment show that they can be present in surface and ground water in the lower pg/L to low ng/L range, in sediments and soils in the pg/g to low ng/g (dry weight) range and in outdoor air at pg/m3 levels. An indoor study found levels of PFCA precursors to be present at ng/g levels in house dust.
Canadian biomonitoring studies, which measure specific chemicals in the bodies of Canadians, have detected long-chain PFCAs in blood samples from people across Canada, including in pregnant women and Inuit and First Nations peoples. In the Canadian Health Measures Survey (CHMS) cycle 2 (2009–2011) and cycle 5 (2016–2017) mean plasma concentrations of C9 to C11 PFCAs in Canadians ranged from 0.12 to 0.82 µg/L in participants aged 12-79 years. Concentrations of C9 to C11 PFCAs in the serum of pregnant Inuit women (measured in 2016-2017) and C9 PFCAs in First Nation Anishinabe youth (measured in 2015) have been found to be higher than these CHMS values with mean concentrations ranging from 0.61 to 9.44 µg/L.
Human and animal toxicity data are not available for every long-chain PFCA, salt or related compound. However, considering that long-chain PFCAs have similar structures and that substances with similar structures behave similarly in the body, all of these substances may be associated with similar health effects.
Long-chain PFCAs are generally well absorbed in the body and can be distributed to many tissues (for example, brain, liver and kidney). These substances can also pass through the placenta into the fetus and they can be transferred through breast milk. According to available data on C9-C11 PFCAs, these substances are eliminated from the body very slowly, and so long-chain PFCAs may persist in the body for years.
Experimental studies in which laboratory animals (primarily rodents) were exposed to high doses of long-chain PFCAs over different time periods show that a variety of effects can occur. Effects have been observed mainly in the liver, thyroid, on the immune system and in reproduction/development. Examples of some of the effects observed include reduced liver function, changes to thyroid hormone levels, reduced immune response and decreased pup birth weight. Other effects reported to a lesser extent include kidney, cardiovascular and neurological effects, metabolic disruption, body and organ weight changes, and mortality.
Some studies in human populations have shown that exposure to certain long-chain PFCAs (that is C9 – C14 PFCAs) may be associated with various health related outcomes (for example effects on the liver, thyroid, kidney and immune system, as well as with cardiovascular, reproductive and developmental outcomes, obesity and metabolic disorders). Some of these findings are consistent with the results from laboratory studies in animals. The clinical significance of these findings, and new data, continues to be examined.
A growing number of jurisdictions, including the United States, Australia and the European Union are developing action plans to address the PFAS class of chemicals, including long-chain PFCAs. In 2009, the United States Environmental Agency (US EPA) published an Action Plan for addressing potential concerns with long-chain perfluorinated chemicals, including long-chain PFCAs. The US EPA is currently conducting health hazard assessments of the C9 and C10 PFCAs under its Integrated Risk Information System Program. In Australia, the government has published human health and environmental risk assessments of indirect precursors to long-chain PFCAs. The assessment found long-chain PFCAs to affect the liver, the immune system and reproduction/development endpoints in animal studies. In the European Union, assessments of the C9 and C10 PFCAs and their salts have resulted in them being classified for their carcinogenic potential and reproductive toxicity. C9 PFCA is also classified for its toxicity on the liver, thymus, and spleen.
For further information on the health effects of long-chain PFCAs, their salts and related compounds, please refer to the Stockholm Convention nomination document.
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