Lead in the environment - origins, pathways and sinks

1. Lead is a natural constituent of the environment. 2. In many urban areas, the principal source of elevated lead in soils is the weathering of paint on houses. 3. Burning of lead in gasoline is the main source of lead in air in many areas. This lead is removed by sedimentation and in rainfall and snowfall. 4. Soil and sediments are the ultimate sinks for lead. 5. Man receives an average of about 300 mug of lead per day in his food, but the range is between 100 and 400 mug. 6. The natural concentration of lead in food resulting from the natural lead content of soil is a few tenths of a microgram per gram of wet plant material. 7. Present concentrations of lead in air do not measurably increase the lead content of the edible portion of most plants. 8. A several-fold increase in lead in soil does not measurably change the concentration of lead in plants. 9. Leafy portions of plants near busy highways contain higher concentrations of lead. 10. Rainwater does not appear to be a significant source of lead in crops.