Washington: School age children are at greater risk from lead exposure than toddlers, according to a Cincinnati Children's Hospital study.

'Although we typically worry about protecting toddlers, our study shows that parents and paediatricians should be just as, if not more concerned about lead exposure in school-aged children,' said Richard Hornung, of Cincinnati Children's Hospital and a co-author of the study.

The most common sources of lead exposure are lead-based paint in older homes, contaminated soil, household dust, drinking water, lead crystal and lead-glazed pottery.

While extreme exposure to lead can cause neurological disorders like muscular disorientation, convulsions and coma, lower lead levels have been linked with measurable deficits in children's intelligence and behaviour problems.

These include hyperactivity, or ADHD, lowered performance on intelligence tests, and deficits in fine motor function, hand-eye coordination and reaction time.

Chronic lead exposure in adults can cause increased blood pressure, decreased fertility, cataracts, nerve disorders, muscle and joint pain as well as problems with memory or concentration, reports Sciencedaily.

The researchers found that blood lead concentrations (BPb) at age of six, compared to toddlers, are more strongly associated with IQ and reduced volume of grey matter in the brain, operative in planning, complex thinking and moderating behaviour.

Overall, the children's average BPb levels peaked at 13.9 micrograms of lead in decilitre (one tenth of a litre) of blood at age two, then declined to an average of 7.3 micrograms per decilitre by age six.

For children, however, with the same average blood lead levels through age six, those who received more of their exposure at age six had substantially greater decrements in intellectual ability than those more heavily exposed at age two.

'Lead toxicity is difficult to recognise in a clinical setting, but it can have devastating effects,' said Bruce Lanphear, director of the Cincinnati Children's Environmental Health Centre and a co-author.

These findings were presented on Sunday at the annual meeting of the Paediatric Academic Societies in Honolulu. IANS