Whidbey Island Naval Air Station plans to sample privately- owned wells adjacent to Navy property to detect whether a chemical has migrated past the current treatment system.

According to a news release the base issued Tuesday, representatives from the base and Island County Health Department will discuss the situation in a media briefing today.

The chemical, 1,4-dioxane, was used as a stabilizer in degreasing solvents used to clean aircraft parts. In high levels, the chemical can cause cancer.

“At this point we don’t know the extent of the contaminant,” Keith Higman, Island County’s environmental health director, said Tuesday morning.

For the past 10 years, the Navy has been treating contaminated groundwater beneath an old landfill on Navy property known as Landfill 6. This former landfill is south of Ault Field Road and west of Highway 20.

Higman said Island County will work with the Navy to develop a testing program to discover where the dioxane has spread.

Higman stressed that the Enviromental Protection Agency’s recommended concentration level of 4 milligrams per liter is far above the level of dioxane in groundwater found at the Navy’s property line. That level is 7.95 parts per billion (ppb). The maximum level found in groundwater is 14 ppb at the landfill site.

Recent sampling has detected groundwater concentrations ranging from a high of 14 parts per billion to about 7 ppb at the Navy property line. While a federal Maximum Contaminate Level for consumption of 1,4-dioxane in drinking water has not been developed, Washington state has established a groundwater cleanup level of 7.95 ppb.

Higman said most residents in the area use city water but there are private wells in the area.

Higman referred to a data sheet issued by the Agency of Toxic Substances and Disease Registry that lists dioxane as a compound that is “reasonably anticipated” to cause cancer in humans.

In the early 1990s, solvents trichloroethylene (TCE) and 1,1,1-trichloroethane (TCA) were identified as contaminants and a treatment system was installed to remove them from the groundwater and return the treated water to the aquifer.

Ten years ago, when the base began monitoring the site, low levels of 1,4-dioxane could not be detected. New methods now make it possible to detect this chemical, according to the Navy’s news release. Tests of monitoring wells at Landfill 6 indicate the presence of 1,4-dioxane.

Web sites, including Clu-in.org, Envirotools.org and checnet.org, classify 1,4-dioxane as a “possible” or “probable” factor in human cancer. These sites list “chronic, long term exposure” as the most likely to cause cancer. Workers inhaling the chemical at industrial sites face the greatest human danger. Laboratory animals have developed certain kidney, liver and gall bladder cancers after exposure.

One Web site calculates a person would have to drink two liters of water with a level greater than 3 ppb for more than 70 years to generate one additional cancer case out of a population of 1 million people.