Michigan health officials are advising residents not to eat deer or fish taken from an area in Northern Michigan’s Iosco County.

A “Do Not Eat” advisory is in effect for deer, fish and other wildlife taken within 3 miles of Clark’s Marsh in Oscoda Township.

The advisory is due to evidence that deer and aquatic wildlife in the area are more likely to have chemicals — per- and polyfluorinated substances (PFAS), including perfluorooctane sulfonic acid (PFOS) — in their livers and muscle tissue.

Exposure to PFOS can cause harm to thyroid and liver function, changes in immune response, increases in LDL and total cholesterol levels, and pregnancy-induced hypertension and preeclampsia.

Clark’s Marsh has had various “Do Not Eat” advisories in effect since 2012. In 2021, officials shrank the five-mile advisory to three miles.

Related: Don’t eat fish from these 4 West Michigan waters

A map of the advisory area is available on the state website. For more information about PFAS, visit Michigan.gov/PFASResponse.

This spring, Michigan lowered the screening value it uses to calculate the risk of eating fish meat contaminated with PFOS. The move increased the number of water bodies with a “Do Not Eat” advisory for at least one species of fish from 33 to 98.

As of June, there were 782 fish advisories caused by PFOS across multiple species and water bodies in Michigan. The advisories are in the new 2025 Eat Safe Fish guidebook, which is separated by region.

For more information on the Eat Safe Fish Program, visit Michigan.gov/EatSafeFish or call the MDHHS environmental health hotline at 800-648-6942.

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