Household dust could rival food packaging as a potential major route for human exposure to C8 and related toxic chemicals, two federal government scientists conclude in a new study.
C8 and other perfluorinated compounds were found in 95 percent of the dust samples in homes in Ohio and North Carolina, according to the study by U.S. Environmental Protection Agency experts.
“This could indeed be a significant source of exposure,” said Andrew Lindstrom, an environmental scientist with the EPA’s National Exposure Research Laboratory in Research Triangle Park, N.C.
Lindstrom and Mark Strynar, an EPA physical scientist, tested dust taken from vacuum cleaner bags from 100 homes and 10 day-care centers for C8 and other perfluorinated compounds, or PFCs.
They found median concentrations of C8 of 142 parts per billion and median concentrations of the related chemical PFOS of 201 parts per billion.
“These results indicate that perfluorinated compounds are present in house dust at levels that may represent an important pathway for human exposure,” they reported this week in the peer-reviewed journal Environmental Science & Technology.
In West Virginia, C8 is a major issue because the water supplies for thousands of Parkersburg-area residents have been contaminated with the toxic chemical.
C8 is another name for ammonium perfluorooctanoate, or PFOA. DuPont Co. has used the chemical since the 1950s at its Washington Works plant south of Parkersburg. C8 is a processing agent used to make Teflon and other nonstick products, oil-resistant paper packaging and stain-resistant textiles.
Around the world, researchers are finding that people have C8 and other PFCs in their blood in low levels. Evidence is mounting about the chemical’s dangerous effects, but regulators have not set a federal standard for emissions or human exposure.
Scientists are still sorting out how humans are exposed, but previous studies have examined Teflon pans, food and food packaging as potential routes.
Studies in Canada and Japan have also found PFCs in household dust. One study in Canada found higher levels occurred in homes with more carpeting, perhaps because the chemicals were used for years to make carpets stain-resistant.
Lindstrom and Strynar did not evaluate the effects of carpet, because they did not have information on the extent of carpeting in the homes. Their dust samples came from vacuum bags collected in 2000 and 2001 for a separate EPA study of pesticide exposure.
In an interview, Lindstrom said testing household dust for PFCs was a natural step. Previous reports have found household dust to be a repository for pesticides, metals and other toxic materials.
The new study compared PFC levels found in dust to the average amount of dust the EPA believes people ingest daily – 50 milligrams for adults and 100 milligrams for children.
This calculation provided an estimate for children of 92 billionths of a gram per day of PFCs from household dust, and 46 billionths of a gram per day for adults, the study said.
That compares to a conservative estimate of 250 billionths of a gram per day of PFCs from food sources reported in a Canadian study, the new EPA report says.
“It looks like dust is in the same order of magnitude as these other routes of exposure, but a lot of that depends on how much dust people come into contact with and ingest,” Lindstrom said.
The study noted recent efforts by the EPA and industry to phase out the use of C8 and other related materials, but the study said “It is important to note that studies with pesticides have shown that materials that have been removed from the market may remain present in house dust for decades after their production is discontinued.
“Given the persistence of the PFCs, it is very likely that PFOS, PFOA and similar compounds will remain available in house dust for potential exposures for some time to come,” the study said.
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