For this reason, methylmercury poses some special concerns for the developing fetus and for young children. At higher levels, walking is affected, followed by blurred vision and decreased peripheral vision. Severely-affected patients have speech and hearing problems. If methylmercury exposure continues, a person can become paralyzed and die. In the early 1970s, more than 400 people in Iraq died from eating bread made from methylmercury-treated wheat that was intended for planting.
Fetuses are especially susceptible to methylmercury.
At high levels of exposure methylmercury interferes with the way nerve cells move into position as the brain develops. As a result, the brain does not develop normally. In both the Japan and Iraq disasters, some mothers who showed few obvious symptoms of mercury poisoning gave birth to children with severe mental and physical retardation. While fish seem to accumulate methylmercury throughout their lives, humans can eliminate methylmercury from their bodies over a period of months. When the amount of methylmercury taken into the body exceeds the amount that can be eliminated, methylmercury builds up in the body.