Acute lead poisoning affected millions of American children and caused thousands of deaths throughout much of the 20th century. Victims were predominantly black residents of dilapidated, inner-city housing.
When screened in outpatient clinics in Baltimore in the early 1950s, 90 percent of children age 6 months to 5 years had blood lead levels above 30 micrograms per deciliter, considered the upper limit of safety at the time. (A microgram is one-millionth of a gram; a deciliter is 100 milliliters). Average blood lead levels of inner-city children were five times greater than suburban children of similar age.
Lead attacks the nervous systems of children. It may be inhaled or ingested. Children afflicted with acute lead poisoning might have seizures, become semi-comatose or have loss of coordination. Exposure of pregnant women leads to fetal injury.
Before the 1950s, one-quarter of these children died. Thereafter, treatment became available that could reverse the most obvious symptoms, and mortality decreased dramatically. Pediatricians in multiple urban medical centers recognized, however, that long-term behavioral and intellectual deficiencies persisted.
The most prominent sources of lead were household paints and gasoline. In 1950, up to 70 percent of a gallon of paint consisted of lead pigments. Children ate the paint that peeled and flaked from walls in their dwellings. Dust in homes contained high concentrations of lead. Lead paints were used on children's toys, cribs and play pens.
Lead compounds were added to gasoline for decades to improve engine performance. A gallon of 1950s gasoline contained 4 grams of lead. Children who lived along busy urban roadways had a steady exposure to lead in automotive exhausts which polluted the air, roadways and yards.
Research and clinical pediatricians lobbied state and national officials to reduce lead content in paint and gasoline, citing extensive clinical studies of the acute and chronic harm to children. Even low levels of environmental lead could cause permanent injury. The Lead Industries Association, the trade group representing manufacturers of paints and fuels, fought back with intense lobbying and attacks on the credibility of the children's advocates. It challenged the studies' data and funded bogus research indicating that lead exposure had no lasting effects upon children. Intense battles ensued in academic conferences and legislative hearings.
National attention to the dangers of lead and other environmental toxins was promoted by the 1970 launch of the Environmental Protection Agency. Children's advocates initiated nationwide campaigns on the dangers of lead. A bill to limit lead content of paint passed Congress in 1970, and use of lead in paints was banned in 1978.
Because of the costs, few cities undertook removal of lead paint from old buildings. Studies in 2003 revealed that 10 percent or more of children residing in several major American cities had dangerous levels of blood lead.
The removal of lead compounds from gasoline seemed a dead issue legislatively, but the adoption of catalytic converters for automobiles in the 1970s -- a move to lessen air pollution -- quickly showed that lead compounds fouled the new devices, giving a strong impetus to decrease lead in fuel. Lead content was gradually reduced until EPA banned the sale of leaded gasoline in 1996. Blood lead levels for urban children steadily declined as lead disappeared from fuel.
In 1960, the "level of concern" for blood lead in children was 60 micrograms per deciliter. This was reduced to 30 micrograms per deciliter in 1978; to 10 micrograms per deciliter in 1991, and to 5 micrograms per deciliter in 2012. These reductions resulted from studies that confirmed that lifelong damage to children's brains occurred even at very low concentrations of lead in blood. How much inner-city violence or intellectual retardation stems from chronic effects of lead poisoning?
Currently, 95 percent of American children have blood levels below 5 micrograms per deciliter. The 5 percent at risk most likely live in poorly maintained, urban housing with decades-old lead paint on the walls. Do we write them off or do we finally undertake the removal of lead from slums?
"Lead Wars: The Politics of Science and the Fate of America's Children" by Gerald Markowitz and David Rosner (University of California Press, 2013) is an invaluable history of the fight to remove lead from the environments of children. It should inform the campaigns to remove other environmental threats to the health of all Americans.
Contact Clif Cleaveland at email@example.com.