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    Pediatrics
    June 2016
    From the American Academy of Pediatrics
    Policy Statement

    Prevention of Childhood Lead Toxicity

    COUNCIL ON ENVIRONMENTAL HEALTH
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    • Seasonal Variation in Lead Poisoning: An Enduring Mystery
      Bruce P. Lanphear
      16 October 2016
    • Preventing Lead Poisoning and Litigation
      Bruce P. Lanphear
      16 October 2016
    • RE: no new data - just new recommendations
      James Volk
      25 July 2016
    • RE: My Recent EpiphanyRe:Major Cause of Lead Exposure
      Steven M Marcus
      10 July 2016
    • 16 October 2016
      Seasonal Variation in Lead Poisoning: An Enduring Mystery
      • Bruce P. Lanphear, Professor Simon Fraser University

      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...

      Show More

      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 increases during summer months (6). Windows are frequently opened; dust trapped in the window troughs is blown indoors or accessible to children’s curious hands. Soil that was contaminated by lead from past use of leaded gasoline or lead-based paints can also be “tracked-in” from outdoors or become re-suspended and settle in house dust, which is then readily accessible to children (7). Children also spend more time outdoors in the summer (6); a sizable fraction of children (~30%) are reported to put soil or dirt in their mouths, especially during the second year of life, when blood lead levels tend to peak (8). The original description of overt lead poisoning among children in 1904 included paint from porch railings as an important source of lead intake (9). Many toddlers in Rochester reportedly played on weathered porches that were covered with leaded paint during summer months; exterior paints typically contained higher concentrations of lead than interior paints. Finally, calcium absorption is increased by greater sun exposure (vitamin D activation) during summer months and, by its mimicry of calcium, lead absorption may also increase.

      1. Canfield RL, Henderson CR, Cory-Slechta DA, Cox C, Jusko TA, Lanphear BP. Intellectual impairment in children with blood lead concentrations below 10 micrograms per deciliter. N Engl J Med 2003;348:1517-1526.

      2. National Toxicology Program. Monograph on health effects of low-level lead. 2012 Jun;(1):xiii, xv-148.

      3. Lanphear BP. The impact of toxins on the developing brain. Annual Review in Public Health 201536:211-230.

      4. Flegal AR, Smith DR. 1992. Lead levels in preindustrial humans. NEJM 326:1293-1294.

      5. Ngueta G, Prevost M, Deshommes E, et al. Exposure of young children to household water lead in Montreal area: The potential influence of winter-to-summer changes in water lead levels on children’s blood lead concentration. Env Intl 2014;73:57-63.

      6. Yiin LM, Rhoads GG, Lioy PJ. Seasonal influences on childhood lead exposure. Environ Health Perspect 2000;108:177-182.

      7. Laidlaw MAS, Filippelli GM, Sadler RC, Gonzales CR, Ball AS, Mielke HW. Children’s blood lead seasonality in Flint, Michigan (USA) and soil-sourced lead hazard risks. International J Environ Res Public Health 2016;13:358.

      8. Lanphear BP, Hornung R, Ho M, Howard CR, Eberly S, Knauf K. Environmental lead exposure during early childhood. Journal of Pediatrics 2002;140:40-47.

      9. Rosner D, Markowitz G, Lanphear BP. J. Lockhart Gibson and the discovery of the impact of lead pigments on children’s health: A review of a century of knowledge. Pub Health Rep 2005;120:296-300.

      Show Less
      Conflict of Interest:
      None declared.
      • Back to top
    • 16 October 2016
      Preventing Lead Poisoning and Litigation
      • Bruce P. Lanphear, Professor Simon Fraser University

      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)...

      Show More

      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).

      Dr. Volk was worried that the AAP Policy Statement provides “cover to all those who claim that children in Detroit were damaged and the possibility of class action lawsuits” and that “these studies can only conclude that an association is not the same as a cause”. This is not a new criticism of the literature on lead poisoning (2). Still, short of randomly assigning children to be dosed with lead there is little else that can be done to prove lead exposure is causally associated with IQ deficits, ADHD or other adverse health effects (2). Moreover, an independent scientific panel concluded, based on both human and toxicologic studies (that did rely on experimental study designs), that there is sufficient evidence to conclude that blood lead concentrations < 5 micrograms per deciliter (<50 ppb) are risk factors for IQ deficits, diminished academic abilities, ADHD, antisocial behaviors and birth outcomes (1).

      It is unfortunate that past critiques of lead toxicity, like Dr. Volk’s, have delayed efforts to prevent lead poisoning. If we had heeded past calls for more action to protect children from lead poisoning, there would be little need for litigation or class action lawsuits today.

      1. National Toxicology Program. Monograph on health effects of low-level lead. 2012 Jun;(1):xiii, xv-148.

      2. Lanphear BP, Hornung RW, Khoury J, Dietrich KN, Cory-Slechta DA, Canfield RL. The conundrum of unmeasured confounding: Comment on “Can some of the detrimental neurodevelopmental effects attributed to lead be due to pesticides? by Brian Gulson.” Sci Total Environ 2008;396:196-200.

      Show Less
      Conflict of Interest:
      None declared.
      • Back to top
    • 25 July 2016
      RE: no new data - just new recommendations
      • James Volk, pediatrician - retired Hendersonville Pediatrics

      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.
      • Back to top
    • 10 July 2016
      RE: My Recent EpiphanyRe:Major Cause of Lead Exposure
      • Steven M Marcus, Physician Professor Emeritus, Pediatrics, Emergency Medicine, Prev Med and community Health, NJ Medical School, Rutgers University

      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.
      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...

      Show More

      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.
      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 system which may relate to outdoor temperature.(3) Changes in the planting zones as published by the US Department of Agriculture reveal that there may be demonstrable climate change which may relate to soil temperature and thus temperature of supply water. Lead in water can be an appreciable etiological factor for elevated blood lead levels is supported by recent reports.(4)
      I was previously accustomed to explaining that here are more laws to protect the municipal water supply, urging parents not to spend the money for bottled water. I now believe that this may not be the case as to potential lead exposure and caution families with lead exposed children. I now caution them to avoid using tap water, substituting either using an National Science Foundation certified water filter, or bottled water. Given the paradox of numbers of IQ points sacrificed for low levels of lead, my observation may be generalizable.

      (1)Canfield RL, Henderson CR, Cory-Slechta DA et al. Intellectual Impairment in Children with Blood Lead Concentrations Below 10 ug per Deciliter. N Engl J Med 2003;348(16)1517-1526
      (2) Available at https://www.epa.gov/superfund/lead-superfund-sites-software-and-users-ma... accessed July 10, 2016
      (3) Ngueta G, Prevost M, Deshommes E, et al. Exposure of young children to household water lead in Montreal area (Canada): The potential influence of winter-to-summer changes in water lead levels on children’s blood lead concentration. Env Intl 2014; 73 (December) 57-63
      (4) Etchevers A, Le Tertre A, Lucas JP, et al. Environmental determinants of different blood lead levels in children: A quantile analysis from a nationwide survey. Env Int 2015 74 (January) 152-159

      Show Less
      Conflict of Interest:
      None declared.
      • Back to top
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    Prevention of Childhood Lead Toxicity
    COUNCIL ON ENVIRONMENTAL HEALTH
    Pediatrics Jun 2016, e20161493; DOI: 10.1542/peds.2016-1493

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    Prevention of Childhood Lead Toxicity
    COUNCIL ON ENVIRONMENTAL HEALTH
    Pediatrics Jun 2016, e20161493; DOI: 10.1542/peds.2016-1493
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