Angle Studied How Lead Is Consumed
In this study, which features data from 1990-1997 but did not become published until 2005, Dr. Carol Angle, Dr. William Manton, and Dr. Kaye Stanek Krogstrand used lead isotope ratios in handwipes, food, dust, soil, and aerosol samples from Omaha households built prior to 1950s with newborns to determine if lead ingested by humans after the gains in primary prevention made in the 20th century was still anthropogenic or not (Manton et al., 2005, p. 8995). Lead isotope ratios can be determined through mass spectroscopy of samples and are a molecular signature as to where lead originated (Ibid). If lead ratios in the food handwipes, or dust samples match aerosols or mined ores then they are presumed anthropogenic, whereas if they match published soil sample data the lead is presumed to be agricultural or natural (Ibid).
Angle, Manton, and Krogstrand found that the handwipe and dust lead samples were lacking a ratio of lead ore from Utah, indicating that Omaha has its own combination of lead distribution compared to the rest of the United States (2005, p. 8997). The aerosols were what was expected of average US anthropogenic lead ratios (Ibid). They did find high levels of the isotope ratio Pb 206/Pb 207 in food samples, which they explained through lead due to calcium additives, Omaha’s unique lead dust signature, and lead from tin coatings or perhaps imported foods not included in testing by the FDA (Manton et al., 2005, p. 8998-8999). Ultimately the researchers were unable to link agricultural sources to the diets of Omaha households because the anthropogenic lead dust readings were still too strong to give unambiguous results (Manton et al., 2005, p. 8999). They did not rule out the possibility of this if a research team were to investigate individual foods instead of total diet, however (Manton et al., 2005, p. 9000).
This study indicates a hopeful look at lead thresholds at the end of the 20th century where the researchers were looking for non-anthropogenic sources of lead because they hypothesized that primary prevention had worked enough to make those detectable (Manton et al, 2005, p. 8995). However, while the mean level of blood lead from 1976 to 1996 (the end of which is when Manton et al.’s samples were taken) did lower over 90%, so one can understand where Manton et. al were coming from, millions of American children in the year 2000 were still in the range of 2.5 μg/dL-10 or more μg/dL (Landrigan, 2000, p. 531). For context, levels as low as 2.5 μg/dL being found harmful for the neurons (Ibid).
These extremely low levels of lead toxicity caused debate as to how prevention should be managed. Some such as researcher Bruce Lanphear, whose own research indicated that no level of lead is safe (Landrigan, 2000, p. 531) stuck close to the precautionary principle and insisted that any amount of lead was too much and more aggressive preventative, pre-exposure steps should be taken in defiance of the lead industry. Lanphear wrote, “Most federal agencies involved in the prevention of lead poisoning acknowledge that primary prevention is preferable, yet our efforts continue to be focused on screening children” and then went on to say that, “…policy decisions about lead poisoning have ultimately favored the lead industry or economic concerns over children’s health” (Lanphear, 1998, p. 1618). This is representative of Lanphear’s view that primary prevention is key to ethically lowering lead levels entirely (Lanphear, 1998, p. 1617).
On the other hand, some scientists defended industry, as Claire Ernhart, a groundbreaking lead research scientist, embodied. Ernhart, who began to receive industry grants for her work just as she reversed her position on the dangers of lead (Markowitz and Rozner, 2013, p. 97), reportedly said in a contentious meeting between industry-influenced scientists and other uninfluenced scientists “a little lead poisoning in poor children didn’t matter because their life was of little value anyway” (Markowitz and Rosner, 1013, p. 98). Angle, who was present at that meeting, told Ernhart later that day, “You should wash your mouth out with soap” (Markowitz and Rozner, 2013, p. 99). This anecdote illustrates that while the precautionary principle and scientific data driving the lowering of lead levels considered safe was occurring, it did not occur in a vacuum without pushback from industry and its friends.
Landrigan, P. J. (2000). Pediatric lead poisoning: is there a threshold? Public Health Reports, 115(6), 530.
Lanphear, B. P. (1998). The Paradox of Lead Poisoning Prevention. Science, 281(5383), 1617-1618. https://doi.org/10.1126/science.281.5383.1617
Manton, W. I., Angle, C. R., & Stanek Krogstrand, K. L. (2005). Origin of Lead in the United States Diet. Environmental Science & Technology, 39(22), 8995-9000. https://doi.org/10.1021/es051145e
Markowitz, G. E., & Rosner, D. (2013). Milbank Memorial Fund(Eds.), Lead wars the politics of science and the fate of America's children. Berkeley: University of California Press; New York : Milbank Memorial Fund.