New research from the University of Pennsylvania School of Nursing, published in the current issue of JAMA Pediatrics, indicates that low lead levels, even at concentrations lower than the previously defined Center for Disease Control's (CDC) level of concern, are associated with increased child emotional and behavior problems. Until now, most studies have focused on the effect of lead on children's IQ and their externalizing behavior.
Lead is understood to lower children's IQ at commonly encountered exposures and to increase aggressiveness and bullying. This study shows that even low lead levels in children are also associated with internalizing behavior problems and can help scientists better understand early health-risk factors and short- and long-term behavioral changes across children's developmental milestones.
Researchers, led byJianghong Liu, PhD, RN, FAAN, associate professor at the University of Pennsylvania School of Nursing, found that blood lead concentrations, even at a mean concentration of 6.4 micrograms per deciliter (µg/dL), were associated with increased risk of behavioral problems in preschool children in China.
"We believe that continued monitoring of blood lead concentrations is necessary and that nurses should recommend screening for behavioral problems for children with lead exposure whose blood lead concentration is above 5 μg/dL," says Liu. According to the CDC, there are approximately half a million U.S. children ages 1-5 with blood lead levels above 5 µg/dL.
In the study, blood lead concentrations were tested once for each of 1,341 children in China at ages 3, 4 and 5 years. The mean blood lead concentration was 6.4 µg/dL. Children's behavioral problems were assessed in their last month of preschool at age 6. Results showed that a 1 µg/dL increase in blood lead concentration resulted in increased emotional reactivity, anxiety/depression and pervasive developmental problems such as speech problems and avoidance of eye contact. Results also showed that while boys had higher blood lead concentrations than girls, the association with behavioral problems was stronger in girls than found in boys.
Lead undermines a range of body processes and can damage many organs and tissues, including the nervous system, reproductive system, intestines, bones, kidneys, and heart. Children absorb lead at a faster rate than adults do and it is particularly damaging because it interferes with the development of the nervous system and can be the cause of lifelong learning and behavior disorders.
The research was funded by the National Institutes of Health's National Institute of Environmental Health Sciences and the University of Pennsylvania Center for Excellence in Environmental Toxicology.