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Prevention of Childhood Lead Toxicity
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- 16 October 2016
- 16 October 2016
- 25 July 2016
- 10 July 2016
- 16 October 2016Seasonal Variation in Lead Poisoning: An Enduring Mystery
Dr. Marcus:
Thank you for sharing your epiphany on the impact of low-levels of lead on children’s intellectual abilities and the contribution of lead from water, as well as your question about seasonal variation in blood lead concentrations.
It is difficult to appreciate how exceedingly small amounts of lead can impact brain function, especially for pediatricians who can recall when blood lead concentrations < 30 μg/dL (< 300 ppb) were considered “acceptable”. The Canfield study, along with dozens of other studies from around the world, have confirmed that blood lead concentrations < 5 μg/dL (< 50 ppb) can adversely impact brain development (1-3). This shouldn’t be surprising; the concentrations of toxic chemicals in children’s blood that are harmful, like lead, PBDEs and PCBs, are comparable with the therapeutic range of chemicals administered as drugs to alter behaviors, like methylphenidate (3). Moreover, on an evolutionary scale the levels found in contemporary children aren’t small; they are 10- to 100-times higher than our pre-industrial ancestors (4).
Seasonal variation in lead poisoning is one of the enduring mysteries of childhood lead poisoning. Cases of lead poisoning and children’s blood lead concentrations appear to increase during summer months for various reasons. As Dr. Marcus noted, warmer temperatures enhance water’s ability to leach lead from lead service lines and lead solder (5). The amount of lead in house dust also...
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None declared. - 16 October 2016Preventing Lead Poisoning and Litigation
Dr. Volk was bothered that the new AAP Policy described, “ever-greater dangers of lead poisoning … with no new data”, since the 2005 AAP Lead Policy Statement was published. I counted the number of new references in the 2016 policy statement that were published in 2005 or later (2004 was the latest citation in the 2005 policy statement). Thirty-five (48%) of the references in the 2005 AAP Lead Policy Statement were published after 2004; 14 (19%) were new studies about the impact of low-level lead toxicity on IQ scores, ADHD, antisocial behaviors and birth outcomes, or on sources of childhood lead exposures. Moreover, although we didn’t describe all the original studies, we cited the National Toxicology Program (1) which reviewed and reported on dozens of other new studies about the impact of blood lead concentrations < 10 micrograms per deciliter (<100 ppb) on IQ deficits, ADHD and antisocial behaviors.
Dr. Volk was also concerned that children who have behavior or mental problems exhibit pica and thus would likely have higher lead levels than their less affected peers. This may be true for extreme mouthing behaviors (i.e., pica) and behavior problems, but this observation is largely anecdotal. In contrast, we found that children who have lower IQ scores don’t exhibit more frequent mouthing behaviors than children with higher IQ scores; we also showed that adjusting for mouthing behaviors didn’t change the impact of low-level lead toxicity on IQ deficits (2)...
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None declared. - 25 July 2016RE: no new data - just new recommendations
Although the AAP has now signed off on the ever greater dangers of lead poisoning, it has done so with no new data. Checking the references one will find no new studies since the last policy statement in 2005 which correlate blood levels with mental disabilities. Even those studies are careful to conclude that an association is not the same as a cause. One might expect that children with behavior or mental problems have more pica and thus would likely have higher lead levels than their less affected peers. The one effect of this policy statement is that it provides cover to all those who claim that children in Detroit were damaged and the possibility of class action lawsuits.
Conflict of Interest:
None declared. - 10 July 2016RE: My Recent EpiphanyRe:Major Cause of Lead Exposure
As a toxicologist, I always considered the length of exposure as more important than the peak exposure, looking at the area under the curve as being more important than actual lead levels of children. The Canfield study(1)clearly illustrates this concept that even at low levels of lead exposure and blood lead levels, the effects can be pronounced.
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The recent revelations of lead contamination of water in Flint, Michigan, served as an epiphany for me. I examined the evidence that water lead may be an important factor, particularly at the lead levels that Canfield reported. If you use the United State’s Environmental Protection Agency’s own model, the Integrated Exposure Uptake Biokinetic Model (IEUBK)(2), a child drinking tap water, or having tap water used to mix his/her formula, with a lead concentration of 15 ppb will sustain blood lead levels in the range of 3 mcg/dl over the first 60 months of his/her age, and even at a concentration of 4 ppb (the default value), the range is very similar. That area under the curve might produce a deleterious effect on cognitive development.
As a clinician, I saw elevations in blood lead levels during the warmer, summer months. I was never able to find a reasonable explanation for this. It does appear that there was some relationship to temperature. Recent literature reveals a seasonal change in water lead levels, even after flushing, suggesting that there may be a change in lead water concentrations in the supply sys...Conflict of Interest:
None declared.
