Effects of Lead May Be Reversible, Study Says
The early adverse effects of lead exposure on a child's growth and physical development may be reversible, the results of a new study suggest.
The study found that children whose growth had been slowed by prenatal or postnatal exposure to high levels of lead could overcome those effects if exposed to lower levels during their second year of life.
In fact, the study found, such children whose lead levels were low during their second and third years of life had higher-than-average growth rates.
"We are at a loss to explain why this occurs and are not aware of any similar situation in which previously depressed growth is followed by attainment of stature that clearly exceeds the expected norms," the study's authors wrote.
The study is the second on this subject to be conducted by a research team from the University of Cincinnati College of Medicine and the Children's Hospital Medical Center in Cincinnati. The earlier study found that children who were exposed to lead before and shortly after birth had slower growth rates as infants.
The latest article, appearing in the November issue of Pediatrics, which is published by the American Academy of Pediatrics, focuses on these same infants as they approached their 33rd month. The authors assessed 235 children every three months for lead exposure and stature and found that prenatal lead exposure did not predict a child's height at 33 months.
However, children who continued to be exposed to high levels of lead--more than 25 micrograms per deciliter of blood during years 2 and 3 did not reach the same stature at 33 months as children with lower lead exposures, the study found.
Children who had readings between 20 micrograms and 25 micrograms per deciliter between the ages of 18 months and 33 months were in a "borderline" area and consistent readings above 25 micrograms "could certainly be considered as having a significant and measurable negative effect on height," the study said.
Researchers have found that children who are exposed to lead--typically from lead-based paint--may also have impaired nervous-system functioning, delayed cognitive development, and lower I.Q. scores.
In response to findings that even low levels of lead may be hazardous, the U.S. Centers for Disease Control last month urged that all children be tested for the presence of lead in their blood by their first birthday.
It also lowered the level at which children should be considered at risk of becoming lead-poisoned from 25 micrograms per deciliter of blood to 10 micrograms. (See Education Week, Oct. 16, 1991.)