Perfluorooctane sulfonate

Fluoro-organic chemicals such as perfluoro-octane sulfonate (C₈F₁₇SO₃H)(PFOS), have been used since the 1950s in soil- and stain-resistant coatings for fabrics, carpets, and leather (2.4 million lb [1 millionkg] in 2000), as well as in oil- and grease-resistant coatings for paper products (about 2.7 million lb [1.2 million kg]in 2000). Though PFOS is mostly applied to products in textile mills, leather tanneries, finishers, and carpet manufacturing facilities, the use of Scotchgard fabric protector also allows for the use of PFOS by the consumer. Additional uses of PFOS and related compounds in specialized industrial applications (1.5 millions lb [680,000 kg] in 2000) include fire-fighting foams, mining and oil well surfactants, acid mist suppressants for metal plating and electronic etching baths, alkaline cleaners, floor polishes, photographic film, denture cleaners, and shampoos, and ant insecti cide.

In May 2000, 3M Corporation announced that, by 2002, it would phase out a group of perfluorinated chemicals, including PFOS, used in Scotchgard and other products. 3M Corporation is the only manufacturer of PFOS in the United States. All of the fluorochemicals that are being phased out either use PFOS in their manufacture or breakdown to PFOS, which is persistent in the environment due to the high energy of the carbon-fluorine bond. 3M Corporation had conducted a major research effort to characterize the environmental presence, environmental and human effects, and environmental fate of PFOS; the results of those research efforts indicated that continued use of PFOS could potentially have severe long-term consequences to human health and the environment.

PFOS, unlike most other persistent organic compounds, does not accumulate in fats, but as a surfactant with both lipophilic and hydrophobic tendencies, binds to blood proteins and accumulates in the liver and gall bladder. In a study published in 2001, PFOS was shown to be present in each of 65 human blood samples from persons who had not been industrially exposed to PFOS. In another 2001 study, 247 tissue samples from marine mammals collected from Florida, California, and Alaskan coastal waters, as well as the northern Baltic Sea, the Arctic, and Sable Island in Canada were analyzed for PFOS. PFOS was found in the blood and livers of nearly all of the marine mammals. Although animals from sites nearer to developed and industrialized regions had higher levels of PFOS in their tissues, animals from even the most remote locations, including the Arctic Ocean, were found to have contain significant levels of PFOS. Near-shore animals had higher concentrations those that lived off shore. Further, fresh-water species had higher concentrations than ocean species. PFOS was also found in samples of 21 species of fish-eating birds, including eagles, ospreys, albatrosses, gulls, herons, loons, ibises, and gannets that had been collected from locations in the United States and the central Pacific Ocean. Birds in more urbanized areas had higher concentrations. Birds from the central Pacific also had measurable PFOS levels, indicating the presence of PFOS in remote marine locations. The lowest concentrations of PFOS were found in an insect-eating gull. Contamination levels observed in these studies were lower than those known to be toxic in wildlife ; however, additional studies are required to determine the long-term effects of low-level exposure to PFOS.

Toxicological studies have shown that PFOS can result in adverse developmental, reproductive, and systemic effects. In a study of two generations of rats and the effects of PFOS on reproduction, PFOS was found to cause postnatal death as well as have detrimental developmental effects. At the highest doses (3.2 mg/kg/day), the offspring in the first generation of rats died, while at one-half of the highest dose (1.6 mg/kg/day), almost one-third of the offspring in the first generation died. At a lower dose (0.4 mg/kg/day), PFOS resulted in lower pup weight compared to controls. Reversible delays in reflex and physical development were also observed in this study.(

In Rhesus monkey studies, no monkeys survived more than three weeks at 10 mg/kg/day or more than seven weeks at doses of 4.5 mg/kg/day. Cynomolgus monkeys also died at a dose of 0.75 mg.kg.day, after first becoming listless and exhibiting loss of appetite. Both species of monkeys showed liver enlargement and reduced cholesterol levels in the blood.

From the results of the toxicological studies and the survey of animals and human blood samples throughout the world, a representative of the U.S. Environmental Protection Agency (EPA) stated that PFOS exhibits "persistence, bioaccumulation , and toxicity to an extraordinary degree". Research is being conducted to develop safer substitutes for PFOS.

[Judith L. Sims ]

RESOURCES

PERIODICALS

Giesy, J. P., and K. Kannan.Global Distribution of Perfluorooctane Sulfonate in Wildlife. Environmental Science and Technology 35(2001): 1339–1342.

Kannan, Kurunthachalam, et al. "Accumulation of Perfluorooctane Sulfonate in Marine Mammals."Environmental Science and Technology 35 (2001): 1593–1598.

Kannan, Kurunthachalam, et al. "Perfluorooctane Sulfonate in Fish-eating Water Birds Including Bald Eagles and Albatrosses." Environmental Science and Technology 35 (2001): 3065–3070.

Renner, Rebecca. "Growing Concern Over Perfluorinated Chemicals." Environmental Science and Technology 35 (2001): 154A–160A.