LEAD IN KIDS' BLOOD LINKED WITH BEHAVIORAL AND EMOTIONAL PROBLEMS
Emotional and behavioral problems show up even with low exposure to lead,
and as blood lead levels increase in children, so do the problems, according
to research funded by the National Institute of Environmental Health Sciences
(NIEHS), part of the National Institutes of Health. The results were published
online June 30 in the journal JAMA Pediatrics.
"This research focused on lower blood lead levels than most other studies
and adds more evidence that there is no safe lead level," explained NIEHS
Health Scientist Administrator Kimberly Gray, Ph.D. "It is important to
continue to study lead exposure in children around the world, and to fully
understand short-term and long-term behavioral changes across developmental
milestones. It is well-documented that lead exposure lowers the IQ of
Blood lead concentrations measured in more than 1,300 preschool children in
China were associated with increased risk of behavioral and emotional
problems, such as being anxious, depressed, or aggressive. The average blood
lead level in the children was 6.4 micrograms per deciliter.
While many studies to date have examined health effects at or above 10
micrograms per deciliter, this study focused on lower levels. The CDC now
uses a reference level of 5 micrograms per deciliter, to identify children
with blood lead levels that are much higher than normal, and recommends
educating parents on reducing sources of lead in their environment and
continued monitoring of blood lead levels.
"Young children are particularly vulnerable to the toxic effects of lead,
because lead can affect children's developing nerves and brains," said senior
author Jianghong Liu, Ph.D., from the University of Pennsylvania School of
Lead is a naturally occurring toxic metal, but sources of lead exposure are
often due to human activities, including burning fossil fuels, mining, and
manufacturing. In the United States, lead exposure usually comes from
lead-containing products, such as paint, caulking, and pipe solder, in older
homes. In China, lead exposure is more often related to air pollution.
"The sources of lead exposure may explain why concentrations of lead are
different," explained Liu. "In China, we found that blood lead concentrations
increased with age in preschool children. In the United States, however,
blood lead concentrations increase with age in children up to 2-3 years old
and then decline."
For the study, the researchers analyzed one blood sample taken from each
child between the ages of 3-5. Behavioral problems were assessed at age 6
using standardized questionnaires. The questionnaires were filled out by the
children's teachers and parents, which the authors noted is both a strength
and limitation. "The study used scores from two sources, but the ratings
do not provide a clinical diagnostic measure of behavioral problems," said
U.S. studies have reported that lead exposure causes what psychologists call
externalizing behavior problems, such as aggressiveness and bullying, which
may lead to truancy and even jail time as children get older. In this study,
children with higher blood lead levels had internalizing problems, such as
anxiety and depression, as well as some externalizing problems. Though not
addressed in this study, Liu said these differences could be explained by
cultural, genetic, or environmental variations, or research gaps.
The authors emphasized, "Continuing monitoring of blood lead concentrations,
as well as clinical assessments of mental behavior during regular pediatric
visits, may be warranted."
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REFERENCE: Liu J, Liu X, Wang W, McCauley L, Pinto-Martin J, Wang Y, Li L,
Yan C, Rogan WJ. 2014. Blood lead levels and children's behavioral and
emotional problems: a cohort study. JAMA Pediatr; doi:10.1001/jamapediatrics.2014.332.