Inorganic Lead in Man's Environment: Sources and Toxicological Significance

Major anthropogenic sources of lead in the general population are solder in canned foods and lead in air, originating from auto emissions and various industrial sources. In the US, approximately ten percent of total dietary lead originates from solder. The contribution of airborne lead to total daily lead absorption varies with air lead concentration in a non-linear fashion. Incremental rise in blood lead concentration decreases progressively with increasing air lead concentration and with the magnitude of blood lead concentrations derived from other sources. Hand-to-mouth transfer of lead from dust is a significant added source of lead in young children. Ingestions of flakes and chips of paint is probably still a significant problem when blood lead concentrations are grossly elevated. The major unresolved issue as to toxic effects in children concerns subtle neurobehavioral deficits. As yet, there is no clear knowledge as to the degree of exposure which causes these effects, nor as to the importance of age and duration of exposure as determinants of sensitivity. Occupational exposure, even at relatively moderate levels, causes a decrement in hemoglobin concentration, and reduction in the functional reserve of the kidneys. Recent studies conducted by two groups of investigators in the US indicate that a substantial number of workers in lead smelters have substantial loss of glomerular function as determined by renal clearance of inulin or iothalamate. This effect is probably due to reduc& ion in renal blood flow. It is most pronounced with long-term exposure.