Lead solvency

Aside from the pathologies discussed in table 2.1, there is growing evidence that lead exposure is associated with an increased risk of cardiovascular disease. The correlation between lead exposure and cardiovascular disease holds true even for individuals who were exposed to lead as children but not as adults. One study shows that if the mean blood-lead level in the United States could be cut in half, the annual number of myocardial infarctions would fall by about twenty-four thousand, and the incidence of cardiovascular disease would fall by over one hundred thousand. According to the author of the study, this represents a large attributable risk compared to most environmental toxins. Moreover, the geographic distribution of cardiovascular disease, in both the United States and Europe, is correlated with the lead solvency of public water supplies, although the source of this correlation is subject to multiple interpretations. ... 

In the five years after this discovery, the Milford Water Company took several steps to reduce the lead solvency of its water supply. The company began to remove the lead service pipes and replace them with pipes made of safer materials. This, however, was a slow process because replacement was expensive. The company also abandoned the wells it had been using as the city s water sovuce, and began drawing water from the... 

Charles River. Water from the river was more polluted than that from the wells, and therefore had to be filtered. The company installed a slow-sand filtration system, which not only eliminated bacterial contaminants, it also reduced the lead solvency of the river water." The introduction of these measures in 1902 and 1903 reduced the average water-lead levels in area homes from 1.39 ppm (627 times the modern EPA standard) to 0.27 ppm (175 times the modern EPA standard). Although 0.27 ppm is a high lead level by modern standards, it was well below the 0.5-ppm threshold then considered safe by the Massachusetts Board of Health." ... 

There are two notable features of Milford s experience. First, by the standards of the day, Milford acted quickly. As soon as officials discovered the lead in their water was making people sick, they adopted measures that reduced the lead solvency of the water. As will be made clear in later chapters, Milford accomplished in ten to twenty years what it... 

Several examples illustrate the unpredictability of the lead solvency of any given water supply. First, during the 1880s, cities and towns in the north of England experienced a severe outbreak of water-related lead poisoning. The British Medical Journal estimated that as many as eight million people might have been affected by the epidemic. The specific... 

Observers warned that the inferences drawn from laboratory experiments are to be accepted with great caution, unless the experiments are conducted under conditions similar to what obtain in the actual distribution of water. Observations such as these were at the heart of the arguments made by Adams and Nichols regarding the necessity of real-world experience, and not simply laboratory experiments, in ascertaining the safety and lead solvency of any given water supply. ... 

As first suggested by the Edinburgh doctrine, water hardness and alkalinity are negatively correlated with lead solvency hard water usually dissolves less lead than does soft water. Unfortunately, many historical actors mistook correlation for identification and assumed that hard water never dissolved lead, rather than the more accurate principle that hard water usually did not dissolve lead. This mistaken assumption often prompted towns and homeowners to install lead pipes without properly investigating the lead-solvent properties of their water suppHes, and to develop a false sense of security regarding their vulnerability to water-related lead poisoning. 

A water s hardness is correlated with its alkalinity. Elard waters tend to be alkaline soft waters tend to be acidic. This can be seen in figure 6.2, which plots the relationship between hardness and alkalinityAlkalinity turns out to be a more reliable predictor of lead solvency than does water hardness, or at least it does for this sample. This can be seen in figures 6.3 and 6.4, which plot the relationship between water lead... 

One objection to the discussion thus far is that the various doctrines of protective power imply a multivariate model of lead solvency, while the visual depictions above indicate a bivariate relationship. To address this objection, a series of regressions are run using the Maine data. The methods and results are reported in appendix C. The results indicate... 

The legacy of the doctrine of protective power was mixed. On the one hand, it helped guide water treatment strategies aimed at reducing the lead solvency in some water supplies. On the other hand, it was applied asymmetrically by cities in their decisions to install lead service pipes. Cities with hard water blindly applied the doctrine to justify their decisions to use lead, ignoring the possibility that hard water sometimes had the capacity to dissolve lead as well. Cities with soft water appear to have... 

One might think that the chemistry of water and lead would have been uncomplicated as it seemed to involve only a simple compound, H2O, and a common element, Pb. During the nineteenth century, many scientists were seduced by the apparent simplicity of this chemistry, and acted on the assumption that it was easy to predict the lead solvency of any particular water supply. This was a dubious assumption that led many large cities astray. As shown previously, the chemical characteristics of water supplies were complex and random. While there were certain characteristics, particularly water hardness, that were correlated with lead solvency, these factors were imperfect predictors of a water s potential to dissolve lead from the interior of water pipes. Paradoxically, cities with the most corrosive water supplies used lead pipes more frequently than cities with non-corrosive supplies because lead pipes better withstood corrosion. 

One of the families injured in Milton s outbreak of lead poisoning was that of James and Louisa E. Welsh. The Welshes sued the Milton Water Company, a private enterprise, for selling them lead-contaminated water. Mrs. Welsh was directly injured by the water, while Mr. Welsh sued for the expenses of her illness and the loss of her society. At trial, the jiny ruled that the water company had been negligent because it failed to test its water for lead solvency, and had thereby unknowingly distributed water that inevitably became contaminated with lead. The Welshes were awarded 4,500 for their pain and suffering. Their victory was short-lived, however. ... 

Of course, those who favored municipal ownership hired their own experts and chemists to challenge the work of Professor Penny. Building a model that was designed to mimic the ultimate Loch Katrine aqueduct, these chemists examined the lead solvency of the water after it passed through the model aqueduct and distribution pipes. This approach was taken because many observers believed that the lead solvency of water was altered by contact with other metals and stones. The upshot of the... 

See chapter 6 for a discussion of how water treatment processes can affect the lead solvency of water supplies. 

See, for example, the many experiments conducted by Garrett (1891). See also Bunker (1921), who explored the lead solvency of a single water source over time and showed that it could vary greatly. 

White (1889), p. 459. Writing in 1922, Thresh explained why it was so difficult to identify the source of lead solvency in moorland water. Specifying two acids—quinic acid and humic acid—he wrote that these acids are worthy of especial mention, as without their aid the action of most moorland waters on lead could not be imitated in artificially prepared waters. If scientists in the nineteenth century had not happened to strike on these acids in their laboratory experiments, they would have floundered in their experiments. See Thresh (1922), p. 466. 

See, generally, Gregory (1993) for a straightforward and relatively accessible analysis of the factors determining lead solvency, including water hardness, alkalinity, and pH. 

Thresh (1905), pp. 1033-1034. Thresh specified water from the Bageshot Sands as a hard water supply that was also lead solvent. On the complex chemistry and geology that gave rise to lead solvency in waters from the Bageshot, see Irving (1883,1885). 

Two caveats are in order, though. Eirst, hindsight is always 20/20. Second, the fact that alkalinity is a near-perfect predictor of lead solvency in this sample does not imply that samples taken from other regions with different geophysical characteristics might not generate different patterns. 

See Foss-Mollan (2001), pp. 161-174. Foss-Mollan provides an accessible chemical rationale for the trade-off between lead solvency and viral eradication. See also Edwards and Dubi (2004), who analyze the role that chlorination and chlorination by-products play in relation to water-related lead exposure. 

See, for example, the following articles in the Washington Post Agencies Brushed Off Lead Warnings, February 29, 2004, p. A.Ol Blood and Water, March 4, 2004, p. C.Ol and D.C. Lead Issue Was Debated for Months, March 16, 2004, p. A.Ol. See also Accusations in Capital on Lead Levels in Water, New York Times, March 6, 2004, p. A.7. For a concise overview of the events in Washington, D.C., that explains the linkage between lead solvency and new water treatment processes, see Stephen (2004). 

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