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Concentrations of Lead in Blood
Lead is a major environmental health hazard for young children. Research shows that blood lead levels of 10 micrograms per deciliter of blood (µg/dL) in young children can result in lowered intelligence, reading and learning disabilities, impaired hearing, reduced attention span, hyperactivity, and antisocial behavior.37 However, there currently is no demonstrated safe concentration of lead in blood, and adverse health effects can occur at lower concentrations.
Today, high blood lead levels are due mostly to deteriorated lead paint in older homes and contaminated dust and soil.37 Soil that is contaminated with lead is an important source of lead exposure because children play outside and very small children frequently put their hands in their mouths. Research shows that pulverized leaded paint and past emissions of lead in gasoline that subsequently were deposited in the soil contribute to lead-contaminated soil and house dust.38
Children also may be exposed to lead through drinking water contaminated by pipes and fixtures containing lead. In the past, ambient concentrations of lead from leaded gasoline were a major contributor to childhood blood lead levels.
- Average blood lead levels in children 5 years old and under dropped from 16.5 micrograms per deciliter (µg/dL) between 1976 and 1980 to 3.6 µg/dL between 1992 and 1994, a decline of 78 percent.
- The decline in average blood lead levels is due largely to the phasing out of lead in gasoline between 1973 and 1995.12 Some decline also was due to legislation banning lead from paint and plumbing supplies.
- In 1976-1980 the average child, regardless of family income, had an elevated blood lead level (i.e. concentrations greater than 10 µg/dL). However, children living in families with incomes below the poverty line had higher average blood lead concentrations than those living in families with incomes at or above the poverty line. This disparity continued through the 1990s.
- Although the concentration of lead in blood is an important indicator for risk, it reflects only current exposures. Lead also accumulates in bone. Recent research suggests that concentrations of lead in bone may be more related to adverse health outcomes in children than concentrations in blood are.39 This suggests that concentrations in bone may better reflect the net burden of exposure. However, methods for measuring lead in bone are more time-consuming and expensive than those for measuring lead in blood.
- Concentrations of lead in air remain greater than the National Ambient Air Quality Standards in some areas in the United States. The main sources of ambient concentrations of lead are metals processors such as smelters and battery manufacturers.
Blood Lead by Race and Income
Many children still have elevated blood lead levels (levels above 10 µg/dL). Race and poverty affect the likelihood that a child has an elevated blood lead level. Blood lead levels are highest for younger children, because their exposure per pound of body weight is greater due to their smaller body weight.
The youngest age group for which data are available, ages 1-5, are presented here. Measures of blood lead by race and income can help identify the groups that are at greatest risk.
- In 1992-1994, approximately 1.5 million children (2.3 percent) 17 and younger had elevated blood lead levels (concentrations greater than 10 µg/dL). Four percent of children between the ages of 1 and 5 (890,000) had elevated blood lead levels.
- Children who lived in families with incomes below the poverty line had a greater risk of elevated blood lead levels than those who lived in families with incomes at or above the poverty line.
- For all income levels, non-Hispanic Black children had a greater risk of elevated blood lead levels than white children. However, the disparity is greater for Black children who live in families with incomes below the poverty line.
- Approximately 73,000 children had blood lead levels greater than 20 µg/dL between 1992 and 1994. This is twice the level considered to be elevated.
- Currently, there is no demonstrated safe concentration of lead in blood. Recent research on a national sample of children measured effects down to the lowest detectable concentrations of lead in blood, and the results suggest that health effects can occur at blood lead levels as low as 2.5 µg/dL.40 Approximately 11 million children between the ages of 1 and 5, about 54 percent of that age group, had blood lead levels of 2.5 µg/dL or greater between 1992 and 1994.