This monograph re-evaluates the potential carcinogenic hazards to humans from exposure to inorganic and organic lead compounds. Human exposure comes from lead-contaminated air, dust, soil, water and food and through inhalation and ingestion. Recent human exposure has arisen predominantly from the widespread use of leaded gasoline. Occupations in which the highest potential exposure to lead exists include mining primary and secondary smelting, production of lead-acid batteries, pigment production, construction and demolition. In spite of the persistence of lead in the environment, exposures have decreased substantially in countries where lead control measures have been implemented over the past 10-30 years.