Exposure to low levels of lead, already linked to higher-than-average school failure rates in teen-agers, may cause learning deficiencies in children as young as 5 years old, according to a new study.
Doctors in Boston found that 2-year-olds exposed to lead at levels far lower than the government deems hazardous developed learning disabilities by the time they were 5.
The same study also discovered that in children exposed to lead as fetuses, learning comprehension returned by age 5 if they had no further exposure to lead after birth.
Children are most likely to be exposed by eating sweet-tasting paint chips containing lead.
David Bellinger of the Children's Hospital in Boston and colleagues studied 170 middle- and upper-class children in the Boston area for almost five years.
In the study, which appears in the February issue of the journal Pediatrics, the researchers measured the level of lead in the blood of the umbilical cords of the newborns.
Dr. Bellinger found that newborns whose lead levels were 10 micrograms or higher performed worse on learning and hand-eye coordination tests than children with lower lead levels.
By the time the children were 2 years old, the learning deficiencies were reversed, except in children from lower socioeconomic groups and in children continually exposed
to high levels of lead, said Herbert Needleman, an expert on lead exposure in children and one of the study's authors.
Two-year-olds whose lead levels remained at 10 micrograms or more had lower test scores at 5 years, said Dr. Needleman, a professor at the University of Pittsburgh.
Only one of the children studied by Dr. Bellinger had lead levels in the blood as high as 25 micrograms, the level at which the federal Centers for Disease Control advises doctors to treat children for lead exposure.
The CDC is scheduled to release a document by March advising doctors to treat children whose levels are between 10 to 15 micrograms, a CDC spokesman said.