One private well in West Deptford was found to have PFNA at a level 10 times higher than the 150 parts per trillion detected in Paulsboro, according to results obtained by The Inquirer through an open public records request.
Another well in West Deptford was found to contain 640 parts per trillion of PFNA.
Solvay Specialty Polymers, a West Deptford plastics company, announced late last month that the results of private well tests showed that only seven of the 50 wells examined thus far in the township and in East Greenwich had "quantifiable levels" of PFNA. But the company refused to publicly release the wells' levels.
"They were keeping from the public some startling results," said Tracy Carluccio, deputy director of the Delaware Riverkeeper Network. "This really makes it clear that we have a very serious pollution problem that's affecting individual homeowners."
The company, which had cited residents' privacy when declining to provide the levels, did not return requests for comment Tuesday. The DEP redacted addresses when supplying the figures.
Experts say the exact health effects of PFNA remain unclear due to a paucity of studies. A scientific panel that studied perfluorooctanoic acid (PFOA), a sibling chemical, found "probable links" to illnesses including kidney cancer and thyroid disease. PFNA is considered more toxic and biologically persistent than PFOA.
Perry Cohn, a retired state Department of Health researcher and former member of the state Drinking Water Quality Institute, said he was surprised to see the levels found in the private wells.
"We had not seen a level this high," Cohn said. "People who are drinking that water are going to have a lot of PFNA in their blood."
Given the uncertainties surrounding PFNA, those whose wells were found with the highest levels might consider consulting a physician with a background in environmental toxicology, Cohn said.
West Deptford Township Administrator Brandon Umba said he had been in contact with affected residents, and that they were receiving bottled water offered by Solvay.
"I've been in regular contact with those residents," he said, declining to comment more specifically on the conversations.
A DEP spokesman said Tuesday that remedies for the properties with private wells are being considered - such as extending public water lines or filtration systems to them.
"At this point, residents with affected wells should drink bottled water as longer-term solutions are worked out," Larry Hajna said in an e-mail. "We still need to learn a lot more about the dynamics of how the contamination occurred."
Five towns - Paulsboro, Greenwich, East Greenwich, Woodbury, and West Deptford - have stopped using wells with elevated levels of PFNA. The chemical and related perfluorinated compounds (PFCs) have gained the attention of environmental and health officials in recent months.
The DEP is considering an interim groundwater criterion for PFNA (a proposal calls for a 20 parts per trillion limit). Separately, the Drinking Water Quality Institute, the department's advisory panel, also is working on a health-based maximum contaminant level.
The federal Agency for Toxic Substances and Disease Registry, in partnership with the state Health Department, will also be investigating PFCs in the area, officials said.
PFCs have been used to make water-resistant materials. Solvay has said it stopped using PFNA in 2010.
The company, which is facing lawsuits by Paulsboro residents, has offered bottled water in the borough and to private well owners, but has said its gesture does not indicate culpability. It has also said there could be other sources for the PFNA, which the DEP has acknowledged as possible.