State health officials are urging anglers not to eat fish they catch in two popular Twin Cities lakes, citing new evidence about a chemical contaminant found in fish that led the agency to cut the standard considered safe for consumption.
The Minnesota Department of Health on Thursday cautioned people against eating any fish caught from Lake Elmo in the east metro or any largemouth bass from Lake Harriet in Minneapolis, pointing the finger at perfluorooctane sulfonate, or PFOS.
"In some studies, higher levels of PFOS in a person's body have been associated with higher cholesterol, changes to liver function, changes in thyroid hormone levels and reduced immune response," the agency said. "Based on updated scientific evidence and risk assessment for PFOS, MDH last month changed the level at which it begins to advise to not eat the fish at all — from 800 ng/g (nanograms per gram) to 200 ng/g — adding greater health protection."
Lowering that threshold led to the warnings about Lake Elmo and Lake Harriet. The agency said several other Twin Cities waters — Bde Maka Ska (formerly Calhoun), Lake of the Isles, Johanna and Twin, as well as the Mississippi River between the Ford Dam and the lock and dam at Hastings — are getting additional guidance about the contamination.
Given the potential health effects of long-term exposure at elevated levels, the new guidance applies to everyone, not just higher risk populations, Assistant Health Commissioner Paul Allwood said in a statement.
"We recognize that some people may like to eat the fish they catch from these lakes, but this recommendation is prudent based on the available information," said Allwood. "It's important to note that our guidelines are based on long-term exposure, not the kind of short-term exposure you might have from a few meals."
In the past, these waters had levels of PFOS contamination that prompted a guidance limit of one meal per month for certain fish species.
State health and pollution control officials believe the most likely source of the elevated levels of PFOS in Lake Elmo is surface and groundwater contaminated by the former 3M disposal site in Oakdale. They said the recent 3M settlement will "allow further investigation and action as warranted to reduce the contamination."
PFOS levels in Lake Harriet have been declining since the source of the PFOS, the nearby Douglas Corporation plating facility, was addressed starting in 2010, the Health Department said, adding, "if PFOS levels in Lake Harriet continue to decline, the advice to avoid eating largemouth bass from the lake is likely to change as well."
The agency said it cited the six lakes and Mississippi River stretch because those were the bodies of water for which recent fish tissue data were available.