As a quick-and-dirty way to make this tag, I'll quote Wikipedia:

Lead poisoning is a type of metal poisoning caused by lead in the body. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, infertility, and tingling in the hands and feet. It causes almost 10% of intellectual disability of otherwise unknown cause and can result in behavioral problems. Some of the effects are permanent.

Lead poisoning is preventable. This includes individual efforts such as removing lead-containing items from the home, workplace efforts such as improved ventilation and monitoring, state and national policies that ban lead in products such as paint, gasoline, ammunition, wheel weights, and fishing weights, reduce allowable levels in water or soil, and provide for cleanup of contaminated soil.

In 2013, lead is believed to have resulted in 853,000 deaths worldwide. It occurs most commonly in the developing world.