Plumbosolvency

Sherlock JC, Smart G, Forbes GI, et al. 1982. Assessment of lead intakes and dose-response for a population in Ayr exposed to a plumbosolvent water supply. Human Toxicol 1 115-122. 

Lead in Drinking Water. The naturally soft, slightly acidic, plumbosolvent water of the Loch Katrine water supply for the Glasgow area was recognized many years ago to release lead from the lead pipes and tanks in the domestic plumbing of the Victorian and subsequent (even post-World War II) eras. ... 

Although there are numerous different water types to be considered, for the purpose of validation of the protocol the actual lead concentration found in a test area is the most important factor. Three types of area can be distinguished, namely areas with low, medium and high plumbosolvency. A number of properties with comparable water quality (not necessarily the same supply area) is considered as one area. Per area about 30 properties were selected. 

Area Water composition plumbosolvency pH range Remarks... 

Setting priorities for the intermediate PV Five years after implementation of the DWD, a transitional period of 10 years starts when the PV for lead in drinking water is set at 25 ag/l. Water eompanies will take appropriate control measures to lower plumbosolvency. To set priorities, distribution areas will have to be tested. From the results of the field test we can calculate the following ... 

Concern over plumbosolvency in drinking water has grown in several parts of the UK where water sources are naturally acidic. Concern has been particularly concentrated in Glasgow in Scotland, and Manchester in the north west of England. 

The major source of high concentrations of lead in drinking water is the dissolution of lead from lead pipes or lead solders used in the distribution system, known as plumbosolvency (Section 3.3.5). In Britain, it is estimated that roughly 7 million households have lead somewhere between the water main and the tap. Many households may thus be exposed to elevated levels of lead in their drinking water (Section 3.3.5). Attention is currently focused on possible remedial actions. 

U.S. studies of plumbosolvency in the 1970s and 1980s clearly indicated that there was a high correlation between soft, acidic water and associated lead surface corrosivity and that the overall U.S. picture for contamination frequencies of water by Pb was a variable one. U.S. national household tap water lead surveys (Patterson and O Brien, 1979 U.S. EPA/Levin, 1986 McCabe et al., 1970 Craun and McCabe, 1975) showed (1) one-sixth (16%) of U.S. tap water lead levels were >20 pg/1 (2) 100% of residences with new plumbing with recently soldered connections in copper systems showed Pb s20 pg/1 and that (3) for the sampling year 1988, a total of 42 million U.S. residents had some exposure to water Pb >20pg/l, about 34 million from older housing exposures and 8 million from newly constructed residences (U.S. ATSDR, 1988). 

Whilst every reasonable attempt has been made to present the information in this Guide in a fair and balanced manner, the reader should none-the-less satisfy themselves of its relevance to their specihc circumstances. It must also be appreciated that some aspects of the topic of plumbosolvency control do not enjoy total consensus of opinion and that practices have varied around the world. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of any organization mentioned in this publication concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. 

Random stagnation sampling is not suitable for zonal compliance assessment because of dilution effects and stagnation sampling at selected properties, for the purpose of zonal compliance assessment, is sensitive to property selection. However, stagnation sampling can benchmark treatment changes at suitably selected houses and provide a direct measure of the reductions in plumbosolvency achieved. 

Virtually all drinking water is sufficiently plumbosolvent to cause exceedence of modern day standards for lead in drinking water, unless corrosion inhibitors are dosed and/or optimised pH adjustment is implemented. As an early estimate, about 25% of houses in Europe are possibly supplied by a lead pipe, and between 2 and 3% in North America. On the basis of two major European studies, two-thirds of the houses supplied by a lead pipe will likely fail the WHO Guideline Value of 10 pg/1 for lead in drinking water. 

Iron red-water discolouration will exacerbate lead dissolution from lead pipes and may need to be minimised if fully effective plumbosolvency control is to be achieved by corrective water treatment. 

Poly-phosphate dosing can also exacerbate lead dissolution from lead pipes, and is not a preferred treatment strategy for plumbosolvency. 

The Charter specifically draws attention to its support of water safety plans as described by the WHO in their 3rd Edition of Drinking Water Quality Guidelines and will provide a foundation for significant improvement in water supply, worldwide. It reinforces the view that effective plumbosolvency control... 

The WHO Guidelines (2004) devote an entire chapter to the topic of drinking water safety planning. It is recommended that a risk assessment and risk management approach should be implemented in the design and operation of water supply systems, additional to the verification of water safety by sampling. The risk assessment and risk management approach should extend from source to tap , that is, the entire water supply chain. This is considered further in Chapter 6 in the context of risk assessment in plumbosolvency control. 

In the context of plumbosolvency control, drinking water safety planning should focus on ... 

The corrosivity (plumbosolvency) of the water supplies to lead, as influenced by pH and alkalinity. 

The extent of exacerbation of plumbosolvency by natural organic matter. 

The two principal exceptions were (i) the UK, which implemented the standard on the basis of random sampling (see Chapter 3) and found that corrective actions were required in some areas, particularly in areas with low alkalinity water, and (ii) the Netherlands, where wide-spread reductions in plumbosolvency were initiated by pH elevation and centralised water softening. 

An ad-hoc Working Group has recently put forward recommendations to the European Commission for revision of the Directive in relation to sampling and monitoring (Hoekstra et al, 2008). In summary, the Working Group has recommended (as relates to plumbosolvency control) that ... 

Assuming that these recommendations are adopted by the Member States, there will be a clear requirement for problems with lead in drinking water to be quantified and for improvement measures to be taken to protect public health, where necessary. This will be a very significant step forward, bearing in mind the extent of current difficulties in the implementation of standards for lead in drinking water. The incorporation of risk management strategies is particularly important as it will require Member States and their water suppliers to proactively determine the extent of plumbosolvency in their areas and to take appropriate improvement action. 

Some water systems have compromised optimal plumbosolvency and lead release control because of difficulties in meeting other drinking water regulatory standards. 

In consequence, water suppliers will in future need to look more deeply into the causes and extent of plumbosolvency problems in their area. 

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