Lead in the Inner Cities by Howard Mielke
1. Introduction / 2. Sources of Lead / 3. Health Consequences / 4. Re-evaluations / 5. Children at Risk / 6. Prevention
5. Children at Risk [800 words]
Lead is a neurotoxin that can be especially harmful to the developing brains and nervous systems of young people. High doses can be fatal. Chronic exposures to as little as 10 micrograms of lead per deciliter of blood can permanently impair the brain’s functioning, thus limiting a child’s intellectual and social development. It can also result in behavioral problems, which are disruptive to other children in the classroom.
The survey conducted in the 1970s showed that nine of eleven children in the United States had lead concentrations of 10 mg/dL or higher in their blood. By that time, lead-based paint production had been curtailed. Since that time, lead has been removed by mandate from gasoline and eliminated from food processing, so that a survey conducted late in the 1980s indicated that only one out of eleven children was exposed to dangerously high levels of lead. Surveys show, however, that the children affected now are disproportionately African-Americans living in the inner cities of major U.S. cities.
The Environmental Protection Agency (EPA) has estimated that more than 12 million children living within U.S. urban environments are exposed to risk from 10 million metric tons of lead residues resulting from the use of leaded gasoline and lead-based paint. A child can safely tolerate an intake of only 6 micrograms of lead per day. The mass of lead in America’s urban environments that is potentially available to children is about 19 orders of magnitude (1019) greater than safe levels. Clearly, there is an unacceptable amount of lead potentially available to children. In the laboratory we have attempted to measure how much lead is actually available to the child.
Children frequently put their hands in their mouths, and this is the most common route of exposure to lead. To get an idea of how much lead children routinely ingest, Latonia Viverette, then on staff at Xavier, and I measured the amount of lead on children’s hands in New Orleans.
We visited several day-care centers in various parts of the city. Children’s hands were wiped after they had played indoors only and then a second time after they had played outside. Our general conclusion was that children have several times more lead on their hands after playing outdoors than they do after playing indoors. The amount of lead varies directly with amount of lead measured in the outdoor soil. For private day-care centers located in ordinary homes with soil in the yards, the amount of lead picked up by children varied directly with the amount of lead in the yard soil. The amount of lead in the soil also related to the part of the city in which the day-care center was located. In the inner city, the children picked up the most lead, whereas in day-care facilities in the outer city, children were least exposed. We also observed that soil was absent from public Head Start day-care centers. The soil in outside play areas was completely covered with rubberized matting or other playground covering and did not contain bare soil. Even in the inner city, children at public day-care centers did not pick up appreciable amounts of lead on their hands.
In collaboration with Dianne Dugas and her staff at the Department of Environmental Epidemiology and Toxicology in the Louisiana Office of Public Health, we then looked at the age of homes and soil lead to determine how they related to children’s blood-lead levels. Correlating the age of housing with blood-lead levels yields mixed results. In 96 percent of the areas where we found low levels of lead in children’s blood, a majority of the houses were newer, having been built after 1940, when the use of lead-based paint had been reduced. By contrast, in areas where children had high levels of lead in their blood, 51 percent of the houses in these areas were built after 1940, and 49 percent were built before. Newer housing is a good predictor of low blood-lead levels, whereas old housing is a poor predictor for the group of greatest interest, children with high blood-lead levels.
The strongest correlation linked soil-lead concentrations and blood-lead concentrations, as we had expected. The association between soil lead and blood lead was 12 orders of magnitude (1012) stronger than the association between the age of housing and blood lead levels. Soil-lead concentrations are more predictive of childhood lead exposure than is the age of housing. In New Orleans, housing tracts with low levels of lead in the soil are very strongly associated with low blood-lead concentrations, whereas areas high in soil lead are likewise associated with high blood-lead concentrations.
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