The Michigan Department of Health and Human Services says the guides help to ensure that people who eat fish are minimizing exposure to chemicals that can build up in fish.

Chemicals in fish are a worldwide problem, but officials say it’s important to note that fish from some areas in Michigan and the Great Lakes region are more contaminated than others.

MDHHS tests the portions of fish that people eat, typically the filets. The results from the state laboratory are used to determine what is safe for people to consume over the long-term. The guides aren’t laws or regulations, so following them isn’t required but is recommended.