Biomonitoring data from the Minnesota Department of Health also confirms that years of cleanup efforts are showing positive results.
An analysis of PFC levels in residents of Cottage Grove, Lake Elmo and Oakdale confirms the cause-effect link between how much unfiltered water those people drank and the amount of the pervasive chemical compounds were found in their system.
“It really is the water,” said Ginny Yingling, a hydrogeologist in the Environmental Health Division of the Minnesota Department of Health (MDH) who is part of the agency’s team that has been investigating PFCs — perfluorochemicals. Results of the analysis were discussed at a recent public meeting in Oakdale.
“This confirms that drinking water was a major source of exposure,” said Jean Johnson, director of the agency’s biomonitoring program. “It also conforms that efforts to reduce PFC levels are working.”
Thanks to dozens of volunteers in the three communities, MDH officials knew through biomonitoring (sampling of blood and tissues) that PFC levels among residents had fallen significantly from 2008 to 2010.
The numbers had been well above the U.S. average. But they had declined following a mammoth cleanup of groundwater by 3M Co. at sites where PFCs had been legally dumped over decades. The company stopped making the chemical compounds, used in an array of products, in 2002, but they continue to be used by other manufacturers. PFCs are so widely used — in microwave popcorn bags and other food packaging, water-resistant materials, carpet stain preventives, to name a few — that the three most common types are found in more than 98 percent of the U.S. population.
What the local numbers didn’t show was the more detailed connection between the data and the nearly 200 study participants. To drill deeper, the MDH investigators got more personal in their quest for answers. The follow-up used detailed survey questions to clarify if efforts to remove the PFCs from water co-related with reduced exposure, Johnson said, and whether other habits like diet and use of particular consumer goods had an effect.
Biomonitoring measured levels of seven different types of PFCs, she said. The three most common — with alphabet-soup chemical names of PFOA, PFOS and PFHxS — were found in all participants.
The analysis found three main findings:
• The longer a resident drank unfiltered water, the higher the PFC levels. “For all three types of PFCs, the number of years is an important predictor of PFC levels,” she said. And that was consistent regardless of other variables like age or gender.
• Participants who donated blood more frequently — three or more times a year — had lower PFC levels. “We can’t say with certainty why that would be,” Johnson said. It could be the chemical nature of the way that PFCs bind to proteins in the blood. PFC levels were still low, she added, and people shouldn’t be inhibited from donating or receiving blood.
• Diet and the use of certain consumer products was generally not a factor in higher PFC levels. The survey asked many questions about foods like red meat, microwave popcorn, fast foods and garden produce, but there was no clear link found to PFCs in the blood, Johnson said. One exception: People who had a carpet installed within a year of being tested showed elevated PFC levels. But that was a small sample, she added, and might merit a closer look.
Yingling said the MDH continues to closely monitor water supplies in Washington County. Two city wells in Oakdale are measured monthly for PFCs, others there are measured annually or twice a year. Cottage Grove wells get scrutinized quarterly. In St. Paul Park, Woodbury and Newport, they are now checked annually.
In almost all cases, she said, levels of the various types of PFCs are either not detectable, or well below the levels considered a health risk.
And just what those health risks might be is still a mystery, Johnson said. Some research suggests “probable links” to a variety of disease risks, but studies are contradictory and, for now, inconclusive. “As scientists, it’s hard for us to draw conclusions from this,” she said. “… We’re still waiting for the scientific consensus on all this.”
In the meantime, it’s important to keep collecting the data and asking the questions, she said, to gain a more complete understanding of what PFCs are doing in the environment.
The one-time funding for the PFC biomonitoring program had been due to expire in June. However, it will continue for another two years after $626,000 to keep the program running was restored this session by the Legislature.
The money will enable the work to continue and build on the research, she said, and track whether PFCs continue to diminish.