<P> Exposure to lead can occur by contaminated air, water, dust, food, or consumer products . Children are at greater risk as they are more likely to put objects in their mouth such as those that contain lead paint and absorb a greater proportion of the lead that they eat . Exposure at work is a common cause of lead poisoning in adults with certain occupations at particular risk . Diagnosis is typically by measurement of the blood lead level . The Centers for Disease Control (US) has set the upper limit for blood lead for adults at 10 μg / dl (10 μg / 100 g) and for children at 5 μg / dl . Elevated lead may also be detected by changes in red blood cells or dense lines in the bones of children as seen on X-ray . </P> <P> Lead poisoning is preventable . This includes by individual efforts such as removing lead - containing items from the home, workplace efforts such as improved ventilation and monitoring, and nationwide policies such as laws that ban lead in products such as paint and gasoline, reduce allowable levels in water or soil, and provide for cleanup of contaminated soil . The major treatments are removal of the source of lead and the use of medications that bind lead so it can be eliminated from the body, known as chelation therapy . Chelation therapy in children is recommended when blood levels are greater than 40--45 μg / dl . Medications used include dimercaprol, edetate calcium disodium, and succimer . </P> <P> In 2013 lead is believed to have resulted in 853,000 deaths . It occurs most commonly in the developing world . Those who are poor are at greater risk . Lead is believed to result in 0.6% of the world's disease burden . People have been mining and using lead for thousands of years . Descriptions of lead poisoning date to at least 2000 BC, while efforts to limit lead's use date back to at least the 1500s . Concerns for low levels of exposure begin in the 1970s with there being no safe threshold for lead exposure . </P> <P> Classically, "lead poisoning" or "lead intoxication" has been defined as exposure to high levels of lead typically associated with severe health effects . Poisoning is a pattern of symptoms that occur with toxic effects from mid to high levels of exposure; toxicity is a wider spectrum of effects, including subclinical ones (those that do not cause symptoms). However, professionals often use "lead poisoning" and "lead toxicity" interchangeably, and official sources do not always restrict the use of "lead poisoning" to refer only to symptomatic effects of lead . </P>

When was it discovered that lead was poisonous