Poisoning, lead: An environmental hazard capable of causing brain damage. In the US lead poisoning is formally defined as having at least 10 micrograms of lead per deciliter of blood. (The average level of lead, for people ages 1 to 70, is 2.3 micrograms.) The lead may come, for example, from lead-containing paint, leaded gasoline, etc. Lead was used in household paint until 1978 and was also found in leaded gasoline, some types of batteries, water pipes, and pottery glazes. Lead paint and pipes are still found in many older homes and lead is sometimes also found in water, food, household dust and soil. Lead can be a workplace hazard for people in certain occupations. Diagnosis is by blood test: Blood lead levels of 10 ug/dL or greater are dangerous to children, even if the person has no apparent symptoms.