How Low is Low Enough for Blood Lead Levels?

by Gopalan on Nov 5 2007 12:13 PM

How low is low enough for blood lead levels. That is a question now haunting experts in the West.

For a new report in US finds that children with blood lead levels lower than the current standard may still suffer lower IQs or other problems.

The news comes amid a number of recent alerts warning of lead in painted toys from China.

At 10 micrograms of lead per deciliter of blood, corrective action is called for says Health Canada. The agency has never set a limit on lead blood levels since no one has ever been able to determine what is a "safe" amount.

Lead blood levels in the range of 10 to 15 micrograms per decilitre in infants and children have been associated with adverse neuron-behavioural and cognitive changes, it says. But now, a new warning in a report from the U.S. Centers for Disease Control and Prevention (CDC) says kids with lead blood levels lower than 10 micrograms may still suffer neurological problems.

"Research conducted since 1991 has strengthened the evidence that children's physical and mental development can be affected" at blood levels below 10 micrograms/dL,says the report, which is published in the latest issue of the journal Pediatrics.

The new CDC report was prompted by recent research that showed differences in the intellectual development of children with "measurable" levels of lead poisoning as compared to other kids.

Children with lead blood levels below 10 often exhibit no obvious symptoms. Even kids with blood levels at 20 micrograms/dL can be symptom-free but the lead can still slow children's neurological development. At levels above 40 micrograms per decilitre, there is a decrease in the body's capacity to produce red blood cells.

This is the first time the CDC's Advisory Committee on Childhood Lead Poisoning Prevention has focused on the risks to children with lower levels of lead in their blood, said Dr. Helen Binns of Northwestern University, the lead author of the report.

She says the panel isn't proposing a new standard, but is emphasizing that all levels are important.

There is no treatment that has been proven effective at removing lead from the blood of children. Health Canada says absorbed lead is usually stored in the bones where it remains for long periods.

"The half-life (time for the body to excrete half the accumulated lead) is about 25 years," the agency says. "Therefore, high lead concentrations can stay in the body for many years after exposure to lead has stopped."

Rather than focus on treatment, the report advises doctors with young patients with elevated lead blood levels to describe the risks of lead exposure to the child's parents and advise them on nutrition changes and safeguards to prevent further exposure.

Since low-level lead poisoning is often unrecognized, Health Canada says it is difficult to determine the number of Canadians affected by exposure to low levels of lead. But the agency says there are very few documented cases in Canada of lead blood levels that required intervention.

In areas where there are unusual sources of lead exposure, such as areas that have had soil contamination from a smelter, higher lead blood levels have been found.

"If you live in one of these communities, you can contact your local medical officer of health for more information," the agency says.