Fish Facts

• Healthy Fish Guide

• Health Benefits of Fish

• Advice for Women & Children

• Fish Consumption Advisories in WA

• Puget Sound Advisories

• Mercury Advisories

• Frequently Asked Questions

• Grocery Store Pilot

• Public Resources

• Questions? Ask our Fish Team

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• Other Environmental Health Programs and Services

How Contaminants Get in Fish

Contaminant levels in fish slowly build up over time as they eat other fish containing contaminants. This process is called bioaccumulation.

Washington waters accumulate contaminant from natural and man-made sources.  Mercury is the most common contaminant found in Washington waters. It is a natural-occurring metal that recycles between land, water, and air and enters fish tissue.  Most of the mercury which enters Washington waters comes from household and industrial wastes released into the environment during incineration,  and burning of coal and other fossil fuels.  Once in water, mercury is converted to methylmercury.  Methylmercury quickly enters the food chain where it increases up the food chain as it is passed from smaller organisms to larger predatory fish. The methylmercury is then stored in the muscle of the fish.  There is no method of cooking or cleaning fish which will reduce mercury. 

Fish also absorb polychlorinated biphenyls (PCBs),  polybrominated diphenyl ethers (PBDEs), and chlorinated pesticides from water, sediments, and the food they eat.  These contaminants concentrate in the fat of fish.  Cleaning and cooking fish properly will lower the amount of PCBs, PBDEs, and chlorinated pesticides by 40-50 percent.