Lead is an ubiquitous and persistent metal, found in virtually all media that people directly contact, including air, water, soil, dust, and food. During the last century, over one billion pounds of lead have been dispersed into the California environment. It has been widely used in industrial products, including paint and gasoline, resulting in contamination in many residential and occupational settings. Lead exposure in children occurs largely as a result of ingestion of lead-contaminated soil and house dust, and poses neurological risks. Lead exposure in adults currently occurs primarily in occupational environments, and poses cardiovascular, renal, neurological and reproductive risks.

Lead compounds are considered probable human carcinogens. Cancer risks due to ambient air exposures to lead were not estimated because of the substantial declines in outdoor lead concentrations that have occurred since use of lead in gasoline was phased out.

Adverse health effects of high dose lead exposures are well-documented with extensive toxicological and epidemiological data. Impact of moderate blood lead levels in children on neurological development and intelligence supported by numerous epidemiological studies. Recent studies indicate that there is no apparent threshold for lead's adverse neurological effects, although the severity of effects at low doses (< 10 µg/dl) remain the subject of debate. Moderate level of confidence in exposure estimation, because lead is only stressor for which there is extensive monitoring in the population. Extrapolating results from studied populations to the entire California population of children is complicated by bias in existing sampling programs towards high-risk groups.

V. POPULATIONS OF CONCERN

All individuals are susceptible to adverse effects of lead. Preschool-age children, fetuses, pregnant and lactating women are particularly sensitive to neurotoxic and developmental effects of low level lead exposure. Children with inadequate nutrition (particularly for calcium, iron and other minerals) are particularly sensitive due to increased lead absorption and retention.

Highest exposures in general population occur among children in low-income families, particularly if living in older housing stock near major transportation corridors. Children with pica (habit of eating dirt or dust) can experience very high exposures. Adults can be exposed to lead at very high levels occupationally, particularly in lead industries with poor exposure controls.

Medium impact in the general population, because toxicological significance of very low blood lead levels is uncertain. Considerable debate in the HHC about general rank for lead, with a minority maintaining that general impact was high. High impact on poor children in older housing stock or in lead-contaminated inner city areas. Several tens of thousands of children under 6 have blood lead levels that are likely to exceed 20 µg/dl. High impact occupationally, as several thousand adults are identified annually as lead poisoned due to workplace exposures.