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Tuesday, July 1, 2014



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 
Nursing, Philadelphia.

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."

NIEHS supports research to understand the effects of the environment on human 
health and is part of NIH. For more information on environmental health 
topics, visit <>. Subscribe to one or more of the 
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events, and publications.

About the National Institutes of Health (NIH): NIH, the nation's medical 
research agency, includes 27 Institutes and Centers and is a component of 
the U.S. Department of Health and Human Services. NIH is the primary federal 
agency conducting and supporting basic, clinical, and translational medical 
research, and is investigating the causes, treatments, and cures for both 
common and rare diseases. For more information about NIH and its programs, 
visit <>.

NIH...Turning Discovery into Health -- Registered, U.S. Patent and Trademark 
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. 

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