Residents of Baytown and West Lakeland townships, and a few in Bayport, have been living for years with wells tainted by trichloroethylene (TCE), but now the level at which the cancer-linked contaminant is considered dangerous has been lowered.

With the new TCE standard, the Minnesota Department of Health is taking action to protect more residents who are now considered at-risk, including a requirement that more filters be installed on private wells that supply drinking water.

Dozens of wells at homes in the rolling hills, rural subdivisions and hobby farms in the three communities near the St. Croix River are fitted with granular-activated carbon filters to strain out the chemical — and the filters are 100 percent effective, the Health Department said.

The new standard means that about 115 more residents will be notified that they need filters, said Kevin Mustonen, project leader with the Minnesota Pollution Control Agency's Superfund Remediation Division.

The contamination area, comprising about 7 square miles, has been a state and federal Superfund site for about 20 years.

The Pollution Control Agency has been monitoring about 600 wells in the area, and about 430 have detectable levels of TCE, he said.

"This issue is not new to Baytown," said Kent Grandlienard, chairman of the township board. "Our focus in the last 10 years has been about educating both our current residents and future people who are building here because previously, people were not really informed that there was an issue."

The township passed an ordinance requiring that all new wells be tested, and when a property is sold, information about the wells is required to be disclosed in the deed when it's transferred to a new owner.

"Our ordinance is actually working quite well," Grandlienard added. "But again, this is people's drinking water, so there may be some concern, especially by people who may not be aware of the issue."

The Health Department is now recommending that people don't drink water containing more than 0.4 micrograms per liter of TCE for extended periods of time, said Kate Sande, toxicologist with the department.

The former standard was 5 micrograms per liter. (Micrograms per liter are the equivalent of parts per billion. One part per billion is about one drop in an Olympic-sized swimming pool.)

The Health Department continually evaluates its risk assessments for chemicals that have found their way into the environment, Sande said.

The change is partly based on updated studies showing that TCE can disrupt immune systems and lead to some types of cancers at lower doses than previously thought.

Sande said the new studies also were able to better gauge the effects of TCE based on more variables such as age and body weight, which means that fetuses, infants and young children could be more sensitive to TCE than previously thought.

The change in the standard should not be cause for alarm, she added, "because we do have protections built into our guidance values."

The 0.4 level represents a conservative standard by which every person exposed to TCE would never see an adverse health effect.

Even at five times that level (2 micrograms per liter), the risk is negligible. Risks vary, she added, based on factors such as age, weight and length of exposure.

People at risk do need to take precautions, Sande said. Besides the filters, which have been found to be effective regardless of the TCE level, areas where water is used, such as showers and laundry rooms, should be well-ventilated because TCE moves easily from water to air.

Aside from affecting immune systems and potentially causing heart defects in fetuses, TCE has been linked to kidney cancer, liver cancer and non-Hodgkins lymphoma.

Cause and effect?

The Health Department is evaluating whether there is an increased incidence of these cancers in the contaminated area, said John Soler, epidemiologist with the Health Department's Minnesota Cancer Surveillance System, which tracks every case of the disease.

"I suspect that we're not going to find anything," Soler said. "It probably looks like every other place."

Connecting the cause-effect dots of a disease such as cancer is difficult, he said, because of so many unknown variables. Smoking, in particular, is the major X-factor because it is linked to so many types of cancers, including one-third of kidney cancers.

"The real problem is there's a lot of cancer out there, and there's a lot of things that cause it," Soler said.

Used in machine shops

TCE was once commonly used as a solvent in machine shops to remove grease, said the Pollution Control Agency's Mustonen. The TCE in Baytown and West Lakeland townships was found in 1987 when residential wells were sampled.

After years of investigation, the source of the pollution was traced to Neilsen Products Co., a metal shop in operation from about 1940 to 1968 that made specialized tools and equipment for the tire retreading industry. The site is in Lake Elmo where Hagberg's Country Market now stands.

From there, the plume of underground contamination affecting four aquifers flows east toward the St. Croix.

"That was just the state of practice at that time for disposing of chemicals and solvents, to just pour them down the drain or dump them out the back door when you were through with them," Mustonen said. "That's what everybody did — there just wasn't an understanding of what happened to those chemicals after they were dumped or where they would wind up."

Although the groundwater flows into the St. Croix, TCE has not shown up in the river at levels that cause concern, Mustonen said. The chemical is pretty well diluted by that point.

The Pollution Control Agency is pumping out and treating water at the Neilsen site to reduce TCE levels further, he said.

Because it was originally thought that the Lake Elmo Airport was the source of TCE, the state, by way of the Metropolitan Airports Commission, bore the cost of installing and maintaining the private well filtering systems on property platted before 2002. After that date, property owners have been responsible.

A filter system costs about $2,000 to install, Mustonen added, and it costs about $1,000 to change the filters every three to six years.