Lead solvency of water

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. 

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. 

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. 

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. 

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

Any increase in temperature would seem likely to disrupt specific interactions, such as hydrogen bonding, between the water molecules and the segments of the polymer chains. This could lead to a decrease in the solvency of the dispersion medium for the stabilizing moieties. There is some indirect evidence for this in the case of poly(oxyethylene) (Volkov, 1973 1974 1976) but it is far from conclusive. 

The solvency of a liquid, or its ability to dissolve a certain solute, is often named its solvent power. This expression should, however, be used with care. There is, for instance, a tendency to rank solvents in order of increasing solvent power, but this is only possible for a specific solute. In former days this was usually a widely used binder for paints. For other solutes the order may well decrease rather than increase. The term solvent power, therefore, may lead to confusion and one should always bear in mind for what when it is said that a solvent has a good solvency. A typical example can be given for water and toluene. Water is an excellent solvent for sugar, but not for fat, whereas the reverse is true for toluene. 

The percentage of houses that have problems, I think it is very difficult to say, but, the local water authority has taken very vigorous action to reduce the problem by adding lime to the water supply, and this has probably reduced exposure to lead by 80% or more. Evidence has been published in the Lancet to show that blood leads have decreased dramatically in Glasgow, over the years, as the plumbo-solvency of the water has been reduced, I don t think there is much doubt about that, but even so probably at least 5% of the households in Glasgow still have water, tap water, which contains more than about 100 yg per litre of lead. 

Meanwhile, an increase in the salinity of the dispersed medium leads to a reduction in the attractive electrostatic interactions. In addition, salinity drastically affects the solvency of the thermally sensitive polymers, as mentioned earlier. An increase in the electrolyte concentration leads to an increase in the Flory-Huggins [42] interactions parameter between the polymer and water, resulting in reduced poly(A-alkylacrylamide) solvency. Consequently, the amount of nucleic acids adsorbed onto the cationic poly(NIPAM) microgel particles was reduced, as has been widely reported for the... 

Adams was not the only observer to suggest caution in trying to predict the solvency of particular water supplies. Even proponents of the doctrine of protective power published articles encouraging doctors to be sensitive to the possibility of water-related lead poisoning among individuals who drew their water from supplies pronounced safe by prominent chemists. For example, in 1860, James R. Nichols published an article in the Boston Medical and Surgical Journal arguing that water supplies in Massachusetts were usually safe because they contained... 

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... 

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 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. ... 

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