PFOA. However, not all 615 have the potential to break down to form PFOA. A majority of waste water treatment plants (WWTPs) that have been tested output more PFOA than is input, and this increased output has been attributed to the biodegradation of fluorotelomer alcohols. A current PFOA precursor concern are fluorotelomer-based polymers; fluorotelomer alcohols attached to hydrocarbon backbones via ester linkages may detach and be free to biodegrade to PFOA. Sources to people Food, drinking water, outdoor air, indoor air, dust, and food packagings are all implicated as sources of PFOA to people. However, it is unclear which exposure routes dominate because of data gaps. When water is a source, blood levels are approximately 100 times higher than drinking water levels. People who lived in the PFOA-contaminated area around DuPont's Washington Works facility were found to have higher levels of PFOA in their blood from drinking water. The highest PFOA levels in drinking water were found in the Little Hocking water system, with an average concentration of 3.55 parts per billion during 2002–2005. Individuals who drank more tap water, ate locally grown fruits and vegetables, or ate local meat, were all associated with having higher PFOA levels. Residents who used water carbon filter systems had lower PFOA levels. Food contact surfaces PFOA is also formed as an unintended byproduct in the production of fluorotelomers and is present in finished goods treated with fluorotelomers, including those intended for food contact. Fluorotelomers are applied to food contact papers because they are lipophobic: they prevent oil from soaking into the paper from fatty foods. Also, fluorotelomers can be metabolized into PFOA. In a U.S. Food and Drug Administration (USFDA) study, lipophobic fluorotelomer-based paper coatings (which can be applied to food contact paper in the concentration range of 0.4%) were found to contain 88,000–160,000 parts per billion PFOA before application, while the oil from microwave popcorn bags contained 6–290 parts per billion PFOA after heating. Toxicologists estimate that microwave popcorn could account for about 20% of the PFOA levels measured in an individual consuming 10 bags a year if 1% of the fluorotelomers are metabolized to PFOA. In 2008 as news stories began to raise concerns about PFOA in microwaved popcorn, Dan Turner, DuPont's global public relations chief, said, "I serve microwave popcorn to my three-year-old." Five years later, journalist Peter Laufer wrote to Turner to ask if his child was still eating