Mercury levels in women of childbearing age dropped by a third in the past decade, a survey by the U.S. Environmental Protection Agency has found.
Mercury is a neurotoxin. Research has shown that it can be harmful for a baby's growing brain and nervous system. Children who have been exposed in the womb to methylmercury -- a version of mercury that is even more toxic than the original -- have shown impacts on cognitive thinking, memory, attention, language, and fine motor and visual spatial skills.
High mercury levels have been associated with eating certain kinds of fish, or fish from waters that are known to have mercury contamination.
But, in general, fish in a person's diet are also highly beneficial. Fish contain high-quality protein, vitamins and minerals and omega-3 fatty acids. They're also low in saturated fat. So officials have struggled with getting across a complex message.