Lead in blood tied to behavioral problems in preschool children

Date: Jul-02-2014Although it is well documented that lead exposure lowers children's IQ, we know little

about its effect on their behavioral and emotional health. Now, a new study shows that

emotional and behavioral problems are apparent even at relatively low levels of lead exposure in

preschool children, and they go up in line with rising blood lead levels.

Writing in the journal JAMA Pediatrics, Dr. Jianghong Liu of the School of Nursing at

the University of Pennsylvania, Philadelphia, and colleagues report how they analyzed links

between blood lead levels in over 1,300 Chinese preschoolers and behavioral and emotional

problems, such as showing signs of being anxious, depressed, or aggressive.

Dr. Liu says, "young children are particularly vulnerable to the toxic effects of lead, because

lead can affect children's developing nerves and brains."

Lead occurs naturally in the environment, but often human exposure is due to mining, burning

fossil fuels, and manufacturing. In the US, the common sources of lead exposure are

paint, caulking and pipe solder, mostly from older homes. In China, lead gets into people mostly

from polluted air.

The researchers found that in China, blood lead concentrations increased with age in preschool

children. This is in contrast to the US, where it goes up until around age 2 or 3, and then it goes

down again. The researchers suggest the different sources of lead exposure in the two countries

may explain these differences.

Studies of American children have linked lead exposure to externalizing behavioral problems - where the problem behavior is directed at others, in aggressiveness and bullying.

The study focuses on lower blood levels than most other studies, explains Dr. Kimberly Gray,

Health Scientist Administrator at the National Institute of Environmental Health Sciences (NIEHS),

which funded the study. The NIEHS is one of the National Institutes of Health.

Dr. Gray says the study "adds more evidence that there is no safe lead level," and that 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."

The average blood lead level in the children in the study was 6.4 mcg per deciliter -

well below the 10 mcg per deciliter and over that most studies have examined.

The Centers for Disease Control and Prevention now uses a reference level of 5

mcg per deciliter - concentrations above this level in children are considered higher

than normal and enough to warrant public health action. The federal agency estimates there are

approximately half a million American children aged 1-5 with blood lead levels above this.

American and Chinese children seem to show different lead-associated problems

In this study, the researchers analyzed blood lead levels in samples taken when the

preschoolers were aged between 3 and 5. Later on, when the children were aged 6, their teachers

and parents filled in questionnaires to assess their emotional and behavioral problems.

In this study, the children with higher blood lead levels showed a higher tendency to internalizing behavioral problems, such as anxiety and depression.

The authors acknowledge, however, that using data provided by parents and teachers does not constitute a

clinical diagnosis.

Studies of American children have linked lead exposure to externalizing behavioral problems - where

the problem behavior is directed at others, in aggressiveness and bullying.

In this study, the children with higher blood lead levels showed a higher tendency to

internalizing behavioral problems, such as anxiety and depression, in addition to some of the

expected externalizing problems.

Although the study did not explore this, Dr. Liu wonders if differences in culture, genes,

environment, or even research gaps, might offer an explanation for this apparent difference in American

and Chinese children.

The researchers also found patterns of emotional and behavioral problems depended on age and

sex. They conclude that "continuing monitoring of blood lead concentrations, as well as clinical

assessments of mental behavior during regular pediatric visits, may be warranted."

In 2011, Medical News Today reported how a study published in the  Journal of

Occupational and Environment Hygiene found higher levels of lead in children living near battery

plants in developing countries. The investigators found that children who lived near lead

battery manufacturing and recycling operations in developing countries had roughly 13 times more

lead in their blood than American children.

Written by Catharine Paddock PhD

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Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.