to young children and fetuses . According to the American Academy of Pediatrics , during the first several years of life , a child 's brain is still developing and absorbing nutrients . Prenatal and infant mercury exposure can cause poor mental development , cerebral palsy , deafness and blindness . Even in low doses , mercury may affect a child 's development , delaying walking and talking , shortening attention span and causing learning disabilities . Having mercury levels that are too high is n't someone else 's problem . In a recent study from the Centers for Disease Control and Prevention , one out of 17 women of childbearing age in the United States has mercury in her blood above the level that could pose a risk to a developing fetus -LRB- 5.8 micrograms per liter -RRB- . So the federal government advises pregnant women and those thinking of becoming pregnant to avoid certain fish , such as shark , swordfish and fresh tuna , usually found in fish markets and sushi . Canned tuna seems to be less of a threat , but the U.S. Department of Agriculture says consumption should be limited . Why avoid these
-LRB- CNN -RRB- -- Every week , Jackie Kaminer of Roswell , Georgia , buys fish for dinner at the local market . Although she knows it 's full of nutrients -- including good-for-your-heart omega-3 fatty acids -- she 's careful of the types of fish she brings home . Jackie Kaminer contemplates fish choices ; she buys only `` safe '' fish , like salmon , haddock and tilapia . Her concern ? Mercury and the dangers it poses to her children . So , she sticks to certain varieties : salmon , cod , tilapia and haddock are `` safe fish , '' but she stays away from swordfish , sea bass and tuna . As a mother of three , Kaminer should be concerned . Released into the atmosphere by industrial pollution , mercury contaminates water systems -LRB- and soil -RRB- when it rains . As fish feed on one another , the mercury stores up in their bodies . The toxic metal affects the nervous system . And although studies have shown large amounts of mercury can also affect fertility and blood pressure , and possibly cause memory loss in adults , it 's particularly dangerous