This article was researched and written by a student at Mount Holyoke College participating in the Encyclopedia of Earth's (EoE) Student Science Communication Project. The project encourages students in undergraduate and graduate programs to write about timely scientific issues under close faculty guidance. All articles have been reviewed by internal EoE editors, and by independent experts on each topic.
Perfluorooctanoic acid (PFOA), also known as “C8”, is a synthetic chemical and one of the perfluoroalkyl acids used to make fluoropolymers during the manufacture of a wide variety of products. Its properties as a surfactant and its chemical stability make it an ideal candidate for many industrial applications (for example, use as non-stick coatings for cookware; moisture- and stain-resistant coatings for textiles; grease-resistant food wrapping; firefighting foams; and many other products). Since it has a wide variety of industrial uses and since manufacturers use it around the world, scientists have found PFOA globally in the environment. It is one of the most predominant perfluorinated compounds (PFCs) in the environment—although it tends to be more concentrated in more populated areas and industrial regions. Although scientists' understanding of the environmental fate of PFOA and related compounds, as yet, is evolving, scientists have identified PFOA in low parts per billion (ppb) concentrations in wildlife and in humans. To improve the quality of the data (for example, concentrations reported in humans, wildlife and water), scientists have conducted one worldwide inter-laboratory study (another was underway as of 2007) that revealed agreement amongst the majority of laboratories for measurements of PFOA in humans.
PFOA in the environment
Following the discovery that perfluoroalkyl substances are persistent in the environment, researchers began to focus on measuring PFOA in wildlife and in surface water. Studies documented the presence of this chemical in wildlife, but not in all locations, suggesting variable spatial distribution. In the Southern Hemisphere, researchers tested albatross livers and reported PFOA concentrations of <0.6-2.45 ng/g wet weight (parts per billion) in 30% of the albatross liver samples - though the authors note that PFOA was detected in 90% of albatross samples from the North Pacific. In another study, researchers also found measurable PFOA concentrations in cormorants (ppb) from the Mediterranean Sea, while reporting much lower concentrations in some other non-avian species (see Table 1).
One of the main routes into the aquatic environment is discharge of municipal wastewater. Also, PFOA can be detected in Atlantic and Pacific oceanic water and coastal seawater. Even in deep waters (4,000-4,400 meters) of the Central to Eastern Pacific Ocean, concentrations range from 45-56 parts per quadrillion (pg/L), confirming widespread distribution of PFOA.
Table 1. PFOA Concentrations in Livers(ng/g, Wet Wt) from the coast of the Mediterranean Sea
PFOA Concentration Range (ng/g Wet Wt)
29 - 450
North Thyrrenian Sea
Adapted from Kannan et al. 2002
Table 2. PFOA Concentrations in Oceanic Water and Offshore Coastal Seawater
1,800 - 192,000
Offshore of Japan
137 - 1,060
Coastal area of China
243 - 15,300
Western Pacific Ocean
Central to Eastern Pacific Ocean (Surface)
15 - 62
Central to Eastern Pacific Ocean (Deep water, 4,000-4,400 m)
45 - 56
North Atlantic Ocean
160 - 338
100 - 439
Adapted from Yamashita et al. 2005
One of the main sources introducing this chemical into the aquatic environment is discharge of municipal wastewater. Sources and pathways leading to human and mammalian exposure, however, are not clearly understood—although likely they include exposure through industrial releases and consumer products. Studies show that PFOA is readily absorbed following ingestion, poorly eliminated, and tends not to be metabolized. As such, PFOA enters the circulation and is primarily distributed and taken up by the kidneys and liver. Additionally, detection of PFOA in umbilical cord blood indicates that it crosses the placenta.
A number of studies on acute, short term, and longer-term toxicity of PFOA on various species suggest developmental toxicity, reproductive toxicity, immunotoxicity, and carcinogenicity in test animals. Many of these effects are thought to be related to interactions between PFOA and peroxisome proliferator activated receptor alpha (PPARa). Activation of the PPARa results in transcription of a range of genes including those involved in specific lipid metabolism and biosynthesis of sterol and bile acids. It is believed that PPARa activation may play a role in causing a number of different adverse outcomes including developmental, reproductive, immunotoxic and carcinogenic effects.
Additionally, exposure can cause irreversible changes in adult mice brains, resulting in such altered spontaneous behavior as reduced/lack of habituation and hyperactivity. It has been demonstrated in some fish (for example, Gobiocypris rarus, the "rare minnow") that PFOA can act as an endocrine disruptor, by inhibiting genes responsible for the formation of thyroid hormones as well as by inducing estrogen-responsive genes significantly.
Consistent with toxicological studies linking PFOA with lower birth rates in mice and rats, a recent epidemiological study found a relationship between lower birth weight in humans and concentration of PFOA in umbilical cord serum. The U.S. Environmental Protection Agency (EPA) has listed PFOA as a likely carcinogen, and the presence of this chemical in the environment and in humans raises concerns about the potential for other health effects.
In April 2003, the EPA completed preliminary risk assessments on PFOA, and later that year took the first steps towards developing an enforceable consent agreement for PFOA and related fluoropolymers. Subsequently in 2006, members of an EPA science advisory board found PFOA to be a likely carcinogen (by a 3/4 majority). In an effort to quickly reduce releases of PFOA into the environment, the EPA established the 2010/15 stewardship program in cooperation with eight major uses of the chemical. The program’s goals are to reduce PFOA use 95% by 2010 and completely eliminate its use by 2015. Progress reports submitted to the EPA suggest the that the program is on track, with some companies reporting a greater than 90% reduction in release of PFOA, and precursors and like chemicals. Although the United States is phasing PFOA out of use, its use in other parts of the world, especially developing nations, may continue.
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- Centers for Disease Control and Prevention—National Report on Human Exposure to Environmental Chemicals Factsheet: Spotlight on Polyfluorochemicals.
- The Encyclopedia of Earth article "Endocrine disruption" relates to this entry.