Many countries have expressed concerns about elements being present in the food we eat. Fish are known to have high levels of arsenic. Fishermen are warned not to eat fish in certain areas because it may contain high levels of mercury. While mercury has been the one most discussed, studies are being conducted to see if lead fish problems exist. Some scientists say that lead does not enter the organism's muscle. Because lead poisoning is known to have many effects on a child's nervous system, parents and health officials are concerned. Problems arising from lead poisoning include: Problems paying attention, Learning disabilities, Stunted growth, Behavior problems. Often these problems are attributed to other causes and it is not known until years after the first signs were exhibited that lead was the actual cause. Adults exposed to toxic amounts of lead experience similar problems. However studies have shown that adults can ingest lead more easily so the lead will have fewer severe effects.