Lead appears as dust or fumes in the air of the work-place. Occupational exposure may occur in mines; but more commonly in lead smelters, where lead is produced from lead ore or scrap, and in occupations where lead or lead compounds are used, such as the production and repair of storage batteries and the polishing and welding of lead-coated or lead-painted materials. This may occur in shipyards, car factories, glass and ceramic factories, and printing and paint shops. Lead also exists in air due to pollution of exhaust gases of automobiles. Manifestations of lead poisoning (mainly in occupationally exposed adults) include gastrointestinal disturbances, anaemia, neuropathy and renal damage. Lead has a toxic effect on the human foetus through the mother's employment in lead-using industries.