Even low lead levels harm kids' development -study
* Even low lead levels in blood can harm child development
* Lead could be cause of education and behaviour problems
LONDON, Sept 17 (Reuters) - Young children's intellectual and emotional development can be harmed by levels of lead in the blood even well below the threshold accepted as "safe", researchers said on Thursday.
Scientists at the University of Bristol looked at blood samples from around 500 children and found a clear link between blood lead levels in early childhood and academic performance and behaviour by the ages of 7 and 8.
The higher the level of lead in the blood at the age of 30 months, the poorer were reading, writing, and spelling grades achieved by those children in Standard Assessment Tests (SATS) -- a recognised exam standard for this age-group in Britain.
Bad behaviour and hyperactivity were also more common in children who had higher blood lead levels as toddlers.
"Lead is a toxin which been in the environment for the last 5,000 years and remains a global hazard for health," Alan Emond and colleagues wrote in a study in the Archives of Disease in Childhood journal.
"Exposure to lead may interact with other environmental factors associated with educational disadvantage to have a cumulative long-term impact."
The current safety threshold above which blood lead levels are considered worrying is 10 micrograms of lead per decilitre of blood -- a level recommended by the U.S. Centers for Disease Control and Prevention in 1991 -- but some are concerned this threshold is too high.
The World Health Organisation estimates that half of all children under five living in cities and towns across the world have blood lead levels above 10 micrograms per decilitre.
The researchers warned that lead poisoning was "a continuing hazard" and called for a new safety threshold to be set at 5 micrograms per decilitre. With lead levels up to that limit, "no obvious effect on intellectual capacity or behaviour was apparent", they said. But levels of between 5 and 10 micrograms were associated with significantly poorer scores for reading (49 percent lower) and writing (51 percent lower).
And children with lead levels higher than 10 micrograms per decilitre were almost three times as likely to display antisocial behaviour patterns and be hyperactive as those whose levels were between 0 and 2 micrograms.
The effects of lead exposure are greater when children are very young, because the toxin is readily absorbed into their bodies and their tissues are especially vulnerable to damage.
Lead levels plummeted in countries that required its removal from petrol (gasoline) but it can still be found in paint, water piping, toys and other sources. (Reporting by Kate Kelland; Editing by Maggie Fox)
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