Lead is a heavy metal, and a toxin, that affects the central nervous system of organisms. The LD50 of lead, the amount needed to kill 50 percent of people who come in contact with it, is 4665 milligrams per kilogram of body weight in men, and 5610 for women.
Lead can be found in old paints, old gasoline, car batteries, and other automotive parts, old water pipes, imported canned goods, and pottery glazes. Lead is also mined in the U.S, Australia, Canada, China, Peru, and Kazakhstan.
Lead was added to paint to speed up drying, increase durability, maintain fresh appearance, and to resist moisture that causes increased corrosion.
Lead was added to gasoline to increase efficiency and performance of the engine.
To prevent possible lead poisoning you need to clean dusty surfaces, remove shoes before entering a house, wash hands and child toys, prevent children from playing in soil, eat a healthy diet, keep your home well maintained, and run cold water for consumption. Running hot water in old piping may lead to increased dissolved lead content in the water lines.
To prevent possible lead poisoning in animals you need to secure or fence areas with garbage, batteries, or old farm equipment. Test eggs, backyard poultry, and the environment for increased lead content, particularly in urban areas.
Leaded paint is still used in developing countries. It is used because it is a cheap and effective paint, other than the poisoning.
The use of leaded gasoline has been banned globally, but still has lasting effects. Exposure to leaded gasoline has decreased 50 percent of the U.S' population's IQ by 2.6 IQ points per person effected; 824 million points total.
To avoid excess lead exposure you should change out leaded paints with non lead-based paints, have proper PPE for miners in the lead mines, and automotive workers who work with leaded parts. Where PPE in broken down buildings because of possible lead dust. Replace leaded pipes with newer ones, and check for lead in canned goods.