Exposure to Lead Found To Cause Long-Term Disabilities
Young adults who were exposed to low levels of lead during childhood may exhibit long-term, perhaps even permanent, developmental and learning disabilities, a new study has concluded.
A follow-up study of young adults first examined in the early 1970's found a correlation between the amount of lead exposure a person experienced as a child and his likelihood of graduating from high school or having a learning disability.
Although previous studies have shown that children who were exposed to lead have lower iq's and perform more poorly in school than children who were not exposed, the authors say this is the first study to show that these effects persist through young adulthood.
"This study tells us for the first time that the effects of low-level lead exposure on children are permanent and that they have a profound effect into adulthood," said the study's chief investigator, Dr. Herbert Needleman, professor of psychiatry and associate professor of pediatrics at the University of Pittsburgh.
The federal Agency for Toxic Substances and Disease Registry estimates that between 3 and 4 million children, or 16 percent of all children nationwide, have lead blood levels that could be harmful.
Children typically are exposed to lead from lead-based paints, gasoline, and drinking water. Young children and fetuses have been shown to be especially susceptible to even minute amounts of lead. Over the past 10 years, the federal government has continued to lower the limit of lead in blood it believes to be harmful.
The U.S. Centers for Disease Con8trol recommends that all children between the ages of 1 and 5 years have a blood test for lead.
An 'Enduring Effect'
In the study, the researchers re-examined 132 of 270 young adults who had been exposed to lead as children in Chelsea and Sommerville, Mass., and had been studied by the team since the early 1970's.
In the initial study, the group determined the child's exposure to lead by measuring the lead content of shed baby teeth.
They found that children who had higher levels of lead in their teeth--at least 20 parts per million--were more likely to score poorly on a battery of intelligence and behavioral tests when they attended elementary school than were children exposed to lower amounts.
The current study, published in the Jan. 11 issue of the The New England Journal of Medicine, found that 11 years later, young adults who had been exposed to greater amounts of lead--but who had exhibited no signs of lead poisoning--still lagged behind their less-exposed peers.
The young adults who were exposed to higher amounts of lead as children were seven times less likely to be high-school graduates, and six times more likely to read at least two years below grade level, than the less-exposed people their age.
They were also more likely to be absent from school, have longer reaction times, and poorer eye-hand coordination.
The researchers also found that young adults who had been diagnosed as having lead poisoning as children were even less likely to be graduates or to read at their grade level than other members of the study group.
The study concluded that "exposure to lead, even in children who remain asymptomatic, may have an important and enduring effect on the success in life of such children."
And because lead exposure is so widespread, it said, "the implications of these findings for attempts to prevent school failure is intriguing."
"I think it's an easy inference that a considerable proportion of school failures are lead-related," Dr. Needleman said in an interview. "It's the easiest source of preventable school failure."