The draft advice issued Tuesday by the Food and Drug Administration and the Environmental Protection Agency is unlikely to clear up confusion over exactly what seafood pregnant women and young children should eat and what they should avoid. Consumer groups have sued the agency, saying its warnings haven't been clear about what fish could pose a risk.
Those groups asked for labels on packages or at fish counters to help shoppers remember which products are OK during pregnancy or for youngsters.
The FDA says the update to its 2004 advice is an attempt to get pregnant women to eat more fish, since many types of low-mercury seafood are good sources of omega-3 fatty acids important for brain development.
But fish also can absorb mercury, a neurotoxin, from streams and oceans - and a small number of varieties harbor higher levels.
The advice echoes the 2010 Dietary Guidelines, which say that pregnant women should consume at least 8 ounces and up to 12 ounces - or two to three servings - of a variety of seafood per week. But it said they should not eat tilefish, shark, swordfish and king mackerel because of the mercury content and it advised limiting white albacore tuna to six ounces a week.
For most people, accumulating mercury from eating seafood isn't a health risk. But for a decade, the FDA has warned that pregnant women, those who may become pregnant, and young children avoid certain types of high-mercury fish because of concern that too much could harm a developing brain.
The seafood industry has said the government shouldn't look at mercury by itself, but at the overall benefits of seafood.