The state is acting to protect Washington County residents affected by a new lower level for the risk of the chemical TCE.
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.