LEAD: Why do we care about exposure to lead?

Why is a  baby’s exposure to lead is more significant than an adult’s exposure to lead?

  • First, children are more sensitive to the health effects of lead than adults.  
  • Second, children’s physiological uptake rates of lead are higher than adults (children absorb/retain 50% of the lead they ingrest, aduls absorb/retain 5% to 15%).  
  • Third, children engage in activities more likely to lead to lead exposure.

Lead poisoning poses the greatest threat to children under the age of six because their brains are still forming and they are more vulnerable than adults to lead.

The scary facts are that lead exposure may result in developmental disabilities and cognitive impairment, as measured by IQ tests (lowered IQ).  Other health effects include slowed growth, damage to the central nervous system, hypertension, impaired hearing acuity, impaired hemoglobin synthesis, and male reproductive impairment.  Lead exposure has been linked with aggression and attention problems, hyperactivity and impulsivity, which are the common behavioural problems of attention deficit hyperactivity disorder.

Unfortunately, lead poisoning may have no major symptoms.  In some cases, a toddler may have delayed speech.  A school age child may seem more aggressive, or may have trouble paying attention.  Symptoms may include headaches, appetite loss, impaired hearing, hyperactivity, irritability, and learning disabilities.  Acute lead poisoning is rare, but can cause vomiting, abdominal pain, diarrhea, weakness in the limbs, seizures, coma and death.  Unfortunately, a 4 year old boy died last year after ingesting a heart-shaped charm on Valentine’s Day that was a gift with a park of Reebok sneakers.

It takes a blood test to actually verify lead poisoning.  The current screening level set by the Centers for Disease Control and Prevention (“CDC”) for pediatric blood lead levels is 10 micrograms per deciliter of blood (10 ug/dL).  

But, there may be no safe lead blood level.  More than ten years ago, the National Academy of Sciences wrote that

“[t]here is growing evidence that even very small exposures to lead can produce subtle effects in humans [and] that future guidelines may drop below 10 µg/dL as the mechanisms of lead toxicity become better understood.” 

A recent study found that lead levels believed to be safe in children actually produce a severe impact on intellectual development.  According to a study reported in April 2003 in the New England Journal of Medicine and funded by the National Institute of Environmental Health Sciences, pediatric blood levels of lead below the current federal and international guidelines of 10 ug/dL produced a large drop in IQ, of up to 7.4 points.  The researchers also discovered that the amount of impairment was more pronounced at lower levels of blood lead levels.  That is, IQ scores of children who had blood lead levels of 10 ug/dL were 7.4 points lower than for children with blood lead levels of 1 ug/dL, but an increase in lead blood levels from 10 to 30 ug/dL was only associated with a small additional decline in IQ.

A report from the Work Group of the Advisory Committee on Childhood Lead Poisoning Prevention to the CDC concluded that the overall weight of available evidence supports the finding that blood lead levels below the supposed “safe” level have a negative impact on children’s cognitive development.  The Work Group found that the available research indicate that blood lead levels below 10 ug/dL impacts children’s health.  Recent research suggests that health effects can occur at blood lead levels as low as 2.5 ug/dL.  According to the CDC’s figures, almost 1 in 10 children have a blood lead level above 5 ug/dL.

The impact of lead on children’s development disproportionately affects minority children.  University of Wisconsin researchers found that while 9.3% of children in the overall population who are exposed to lead score below 80 IQ points, that number increases to 14.2% in African-American children.

It used to be thought that the impacts of lead disappeared or declined if the child’s exposure to lead was stopped or reduced.  Unfortunately, recent studies suggest that the effects are largely irreversible.  The recent research underscores the importance of preventing your baby’s exposure to lead.

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