High Levels of Lead Toxicity Lead to Increased Health Risks. RedOrbit.May 9,  2008.Nearly 40 percent of Americans have toxic levels of lead in their bodies, and most don’t even know it. The symptoms of lead poisoning — headaches, insomnia, irritability, nausea, depression, and memory difficulties — are often attributed to other conditions, leaving Americans with increased health risks due to lead poisoning.[ See ]