Fish can pose considerable health risks when contaminated with metals (e.g., mercury and lead), industrial chemicals (e.g., PCBs) and pesticides (e.g., DDT and dieldrin), which build up in your body over time.
Children are especially sensitive since their nervous systems are still developing.
Developing fetuses are exposed to stored toxins through the placenta—which means that mothers may be putting their children at risk if they eat contaminated fish even before becoming pregnant.
Check out this consumption advisory chart to see how many seafood meals you can safely eat per month.
Excerpted from Environmental Defense's Oceans Alive project