DOVER, Del. (AP) — Residents living near an Air National Guard base in northern Delaware have average blood levels of certain toxic manmade chemicals that are significantly higher than the national average, according to a report by federal researchers.

The Agency for Toxic Substances and Disease Registry tested 214 people from 134 households for exposure to fluorinated chemical compounds that are collectively known as PFAS. The study included analyzing blood and urine samples, as well as testing tap water and dust samples from a small subset of homes.

Average blood levels of five specific PFAS compounds in study participants were higher than national averages, according to a report released earlier this month. Those chemicals include PFOA and PFOS, which have been found in public and private water supply wells in all three counties in Delaware.

PFOA and PFOS are only two of hundreds of synthetic chemicals known as per- and polyfluoroalkyl substances, or PFAS. They have been associated with health effects including high cholesterol levels, thyroid disease, certain cancers and pregnancy-related problems. They often are referred to as “forever chemicals” because they do not easily degrade and can remain in the body for years, even decades.

Federal officials scheduled an online information session for area residents Thursday evening to discuss the report.

“It’s concerning that people’s blood levels are higher than the national average. That points to knowing that we have a serious problem,” said state Rep. Debra Heffernan, a Wilmington Democrat who planned to attend the information session.

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Heffernan is chief sponsor of legislation enacted last year directing Delaware environmental officials to conduct a statewide survey of PFAS in drinking water and to work with public health officials to set maximum allowable contaminant levels for PFOA and PFOS in public drinking water supplies.

The chemicals have been used for decades in a wide variety of manufacturing and industrial operations and consumer products, including outdoor and protective clothing, food packaging, carpet and nonstick cookware. PFOS has been an ingredient in firefighting foams commonly used at airports and military installations, such as the New Castle County Airport and adjacent National Guard base.

An Environmental Protection Agency spokesperson confirmed last year that 10 of 14 public supply wells in a 7-square-mile (18-square-kilometer) area surrounding the airport have been found with PFAS levels above the EPA’s lifetime health advisory levels.

The contamination involved all four New Castle city public wells and six Artesian Water Co. wells. PFAS levels in the city wells ranged from 630 parts per trillion to 4,500 ppt, well above the EPA health advisory level of 70 ppt. Contamination in the Artesian wells ranged from 71 ppt to 1,340 ppt.

Officials have noted however, that the water has been treated for years with carbon filters before it goes to customers, and that levels in treated water are within acceptable limits.

The ATSDR study, which began in 2019, found that the age-adjusted average PFHxS blood level was 9.8 times higher than the national average. Average blood levels for PFOS and PFOA were 2.9 and 2.4 times higher than the national average, respectively.

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“Elevated blood levels of PFHxS, PFOS, and PFOA may be associated with past drinking water contamination,” the report states.

Residents served by the city of New Castle’s Municipal Services Commission had significantly higher blood levels than those who lived in the Artesian Water service area.

The study also found that adults who reported cleaning their homes three or more times per week had significantly lower levels of the chemicals in their blood than those who reported cleaning their homes a few times per month or less.

Meanwhile, Heffernan is waiting for more information about the state survey of PFAS in drinking water supplies.

Officials with the Department of Natural Resources and Environmental Control failed to submit the survey results to the General Assembly and the governor by the Jan. 1 deadline. More than three weeks later, DNREC issued a three-page report indicating that 140 drinking water systems had been sampled, and that two had PFAS levels at or above the EPA health advisory limit. But DNREC has yet to provide any specific data, including PFAS levels for each water system. It also has failed to respond within the required time period to a public records request from The Associated Press regarding the survey.

Heffernan said she was disappointed with the lack of information provided by DNREC but believes more data will be forthcoming.

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“I was a bit frustrated that they’re not as far along as we had hoped they would be,” she said.

Nevertheless, Heffernan said she has been told that officials expect to provide draft maximum contaminant levels for PFOA and PFOS in drinking water by the end of this month.

“I better see them. I’m pushing to make sure that we do,” she said. “We need to get this done.”