Study Cites Threat From Exposure To Lower Levels of Lead
As school administrators tackle numerous instances of water, paint, and soil tainted by lead, a recent study shows that blood lead levels officially considered safe are now believed to hurt a person's intellectual development.
The home, however, remains the most likely place children will be exposed to harmful lead levels, researchers say.
The study, published in the April 17 edition of the The New England Journal of Medicine, says children with blood levels of lead below the federal "level of concern"of 10 micrograms per deciliter could face an IQ drop of up to 7.4 points. The average IQ is about 100.
"We don't have evidence of a safe level" of lead exposure, said Richard Canfield, one of the study's authors and a Cornell University researcher. "We certainly prefer children not to be exposed at all."
The current standard of 10 micrograms per deciliter was approved in 1991. But a work group at the federal Centers for Disease Control and Prevention, which sets the guideline, is reviewing evidence showing adverse effects below that level, said Susan McClure, a spokeswoman for the CDC's National Center for Environmental Health.
The CDC estimates that about 434,000 U.S. children ages 1 to 5 have blood lead levels higher than the acceptable level. Children under the age of 6 are most at risk because they are at a high point of growth and also tend to put their hands and other objects in their mouths, said Dr. Bruce Lanphear, one of the study's authors and a pediatrician at the Cincinnati Children's Hospital Medical Center.
Keeping Schools Safe
For the study, researchers measured blood lead concentrations in 172 children at ages 6 months and 12, 18, 24, 36, 48, and 60 months. The children took IQ tests at ages 3 and 5.
Children are more likely to be exposed to high levels of lead in the home rather than at school, Mr. Lanphear emphasized. About 24 million housing units in the country, around 4 million of which house young children, are contaminated with lead, the CDC estimates.
Though threats are minimal, Mr. Lanphear said, many schools around the country are struggling to reduce students' lead exposure, which can cause severe learning disabilities and behavioral problems. Seizures, comas, and even death can also result from high blood lead levels.
In schools, lead is often found in water used in drinking fountains and cafeteria cooking because of lead pipes, in soil surrounding playgrounds, and in dust from chipped lead paint, which was banned in 1978.
In the 1.1 million- student New York City school system, for example, water fountains have been shut off and warning signs posted near sinks where lead levels exceed national guidelines. The water system of all city schools was flushed daily in August to decrease the possibility of lead in the water. Of the roughly 34,000 water outlets tested in the city's schools, 370 had high levels of lead, said Kevin Ortiz, a district spokesman.
This February, all of the water fountains in the 95,000-student Baltimore school district were turned off after the school board received a report that many were tainted with lead. In response, the district made plans to put water coolers in all schools.
Meanwhile, officials at the 700-student Seawell Elementary School in Chapel Hill, N.C., conducted an impromptu cleaning after dust from exposed steel beams in the ceilings of a few preschool classrooms tested positive for lead. During tests required to attain national certification for their pre-kindergarten program, inspectors found lead levels in the dust that were not considered hazardous, said Tom Konsler, the environmental-health supervisor for the Orange County Health Department.
School officials there still used a trisodium phosphate solution to clean the beams and sprayed a polyurethane sealant to temporarily coat them, Mr. Konsler said. They plan to repaint the beams using special material this summer.
"The school wants to go the extra mile and see that this never arises into a problem," he said.
That kind of caution is crucial to prevent potentially hazardous lead exposure, Mr. Lanphear said. All administrators should get their schools' water tested for lead, and be aware of problems associated with lead-based paint.
"School buildings should be better maintained to begin with," he said.
Vol. 22, Issue 33, Page 13Published in Print: April 30, 2003, as Study Cites Threat From Exposure To Lower Levels of Lead