Health survey links PFC levels to unfiltered tap water consumption
A state health survey has linked the consumption of unfiltered drinking water to higher PFC concentrations in surveyed residents of Cottage Grove and two other east-metro communities.
The results, released recently by the Minnesota Department of Health, generally show that the longer that residents had consumed unfiltered drinking water, the higher the level of PFCs, or perfluorochemicals, in their blood.
"The number of years that people drank (unfiltered water) is an important predictor," said Jean Johnson, director of the Health Department's Environmental Public Health Tracking and Biomonitoring Program.
Health officials acknowledge the roughly 160 survey participants represent a small sample size. Nevertheless, the survey provided the first data to identify how people might have been exposed to PFCs in communities where the chemicals had polluted groundwater.
3M manufactured and used PFCs in a variety of products for decades, and the chemicals were in waste disposed at multiple locations in the east metro, including at the company's Cottage Grove plant near the Mississippi River, a dump site near the Woodbury-Cottage Grove border and a Washington County landfill.
Since detection of the leaked pollutants nearly a decade ago, 3M has undergone an extensive cleanup at all of the sites. Cottage Grove and Lake Elmo residents on private wells affected by PFC contamination received filtration equipment and, in some cases, bottled water. The Oakdale municipal water system was upgraded.
State officials in 2008 and 2010 measured PFC in blood samples of east-metro residents as part of an ongoing biomonitoring project. Those tests looked closely at the levels of three PFCs -- PFOS, PFOA and PFHxS -- and found that the residents tested had higher PFC levels than the national average, but that the PFC presence generally had declined between the two testing periods and after the remediation work had begun.
The survey, done in 2010 and 2011 as part of the biomonitoring project, looked at the possible sources of PFC exposure.The survey included 80 residents of Cottage Grove and Lake Elmo, who use private wells, and another 86 people tapped into Oakdale's municipal water.
The key finding was that the presence of the three most abundant PFCs was higher the longer someone had consumed unfiltered drinking water. The average PFC blood level was highest in those who had been drinking the water 21 years or longer. The levels steadily declined in those who had been drinking the contaminated water for between 11 and 20 years, and further still in those who had been consuming the unfiltered water for up to 10 years.
"Drinking water in the county was a major source of exposure," Johnson said.
Other possible exposure sources were asked about in the survey.
Health officials concluded there generally was no correlation between higher-than-average PFC levels and a person's diet or their consumption of home-grown fruits and vegetables. One form of PFC, PFBA, was found in 98 percent of tested produce samples, but the levels were very low, officials said.
Gardening and eating home-raised produce are healthy activities, said Jim Kelly of the Health Department's Environmental Health Division.
"Nothing we have found suggests they should alter those activities," Kelly said of east-metro residents.
The survey also found that frequent blood donors had lower levels of PFCs in their blood. That would make sense, Johnson said, because PFCs circulate in the blood system so if someone is donating blood frequently the PFCs could be leaving their body.
No conclusive health effects
State officials said they still do not know much about the health effects of PFCs. They are monitoring ongoing studies, but those have not conclusively pointed to adverse health effects.
"We just don't see that in the studies right now," Johnson said.
Following a PFC contamination in Ohio and West Virginia, three scientists determining a monetary settlement found a probable link between exposure of one type of PFC and a small number of health outcomes, but Minnesota officials said that is different than concluding there is a direct effect from exposure.
"We're sort of still waiting for the scientific consensus on this," Johnson said.
PFC research is still relatively new.
"These literally burst onto the scene in the late 90s or early 2000s," said Ginny Yingling, a Department of Health hydrogeologist monitoring PFC groundwater pollution in the east metro area.
The east-metro PFC contamination is estimated to cover some 100 square miles, making it one of the biggest contaminated groundwater areas in the country, Yingling said.
The Health Department plans to continue testing east metro groundwater for PFC contamination, but the future of the biomonitoring work is less certain. Health officials were waiting to learn whether the biomonitoring project received more state funding in the closing days of the legislative session.
If funding is available, Johnson said the department yet this year could begin conducting a third round of blood sample testing of the east metro residents participating in the biomonitoring project.