As a toxicologist, I’ve 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 et al1 study 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 et al reported. If you use the US Environmental Protection Agency’s own model, the Integrated Exposure Uptake Biokinetic Model,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 μg/dL over the first 60 months of his/her age, and even at a concentration of 4 ppb (the default value) the range is 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 observation. 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 that 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 that may relate to soil temperature and thus the temperature of supply water. Recent reports support that lead in water can be an appreciable etiologic factor for elevated blood lead levels.4
I was previously accustomed to explaining that there 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 with the use of either a National Science Foundation–certified water filter or bottled water. Given the paradox of numbers of IQ points killed for low levels of lead, my observation may be generalizable.
CONFLICT OF INTEREST: None declared
- ↵Environmental Protection Agency. Integrated exposure uptake biokinetic model. Available at: https://www.epa.gov/superfund/lead-superfund-sites-software-and-users-ma. Accessed July 10, 2016
- Ngueta G,
- Prévost M,
- Deshommes E,
- Abdous B,
- Gauvin D,
- Levallois P
- Copyright © 2017 by the American Academy of Pediatrics