Mercury naturally occurs in the environment, but it is also found as a result of pollution that enters our oceans & lakes. The mercury gets absorbed by fish, building up inside of the fish. As we eat contaminated fish the mercury can build up in our bloodstreams, acting as a neurotoxin and causing damage to the brain and nervous system. In pregnancy, infancy and young children, mercury contamination is especially hazardous due to rapid growth and nutrient absorption.
Cooking fish does not remove mercury. The fish used in sushi that contains the highest levels of mercury include: swordfish, mackerel, yellowtail, tuna and sea bass. Mercury accumulates in these predatory fish as they consumed contaminated smaller fish.
Women of child‐bearing age should avoid all high‐mercury fish. Others should limit intake of those fish to once per week.