Should I be concerned about pollutants in fish?

To some degree. Here's why: Mercury from industrial pollution contaminates water systems when it rains. As fish feed on one another, mercury stores up in their bodies. The bigger the fish, the more mercury it contains, so it's wise to limit consumption of shark, swordfish, king mackerel, tilefish, and other larger types. The federal government advises pregnant women, nursing mothers, women of  childbearing age, and young children to avoid fish high in mercury and instead eat low-mercury varieties such as salmon and cod.
 
In addition, many lakes and rivers have high concentrations of other toxins (dioxins, PCBs, etc.) that can build up in fish flesh.  Consumer Reports recommends the following: "Your best strategy is to eat a variety of fish, freshwater and saltwater, that are known to have the fewest contaminants.  For a list, go to www.ConsumerReportsHealth.org/safefish.  You can also check local fish advisories at www.epa.gov/waterscience/fish/states.htm."
 
Source(s):
FDA "Mercury In Fish: Cause For Concern?"
 
Consumer Reports on Health, September 2009.