Recent studies have been examining a variety of potential ways that humans are exposed to C8 and similar toxic chemicals used in non-stick and stain-resistant products.

(See previous coverage here, here, here and here).

But now, the U.S. Environmental Protection Agency has quietly posted on its Web site a study — dated March 2009 — which tries to sort out and rank potential sources of exposure in non-occupational, indoor environments (our homes).

For this study, EPA scientists analyzed the amount of perfluorocarboxylic acids (PFCAs) in 116 samples of various consumer articles known to have been made with C8 and related chemicals. These items, purchased at retail outlets between March 2007 and March 2008, included pre-treated carpeting, carpet-care liquids, treated clothing, food wrappers, upholstery, cookware, sealants and tapes — even dental floss. They also tried to estimate how much of these items would be found in average American homes.

What did they find? In short:

In typical American homes with carpeted floors, pre-treated carpet and commercial carpet-care liquids are likely the most significant PFCA sources among the 13 article categories studied.

For homes without carpeting, floor waxes and stone/tile/wood sealants that contain fluorotelomers products are important sources of PFCAs.

The EPA scientists also reported:

Other potentially important indoor sources include treated home textile, upholstery and apparel, and household carpet/fabric care liquids and foams.

They also said:

The data presented in this report may help explain why PFCAs are frequently detected in house dust. While the mechanisms by which PFCAs are transferred from sources to dust are not well characterized, existing data strongly suggest that [Articles of Commerce] may contribute to indoor human exposures to PFCAs either directly (derman contact and hand-to-mouth activities) or indirectly (inhalation of dust).

The EPA study even included a chart that compared the various products tested

[Click here to see chart]

DuPont has argued that consumer products made from C8 and related chemicals are safe. Company officials point to their scientists’ study (Subscription required) projecting the half-life — the amount of time it takes for half of the chemical to break down — at between 1,200 and 1,700 years. But earlier this year, EPA scientist John Washington and some colleagues used a different laboratory method to try to estimate the half-life and came up with an estimate of 10 to 17 years.

Of course, EPA in 2006 announced plans for the industry to voluntarily reduce emissions and product content of these chemicals on a global basis by 95 percent no later than 2010. But as this new EPA study cautions, “significant numbers of articles with high PFOA content are still on the market” and in one instance, the PFOA content “even increased significantly.”

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