Arsenic threat widens

The threat of arsenic poisoning from the use of groundwater (see October and December 2002 issues of EPN) is wider that the well-publicised delta of the Ganges-Brahmaputra rivers in Bangladesh (Pearce, F. 2003.  Arsenic’s fatal legacy grows.  New Scientist, 9 August 2003, p. 4-5).  Although springs from rocks that contain arsenic-bearing sulphides, particularly mine drainages, were once the main hazard, increasing use of water from tube wells into alluvium have greatly increased the incidence of arsenic-induced ailments.  This is sadly ironic, because massive investment in well boring since the 1960s aimed at reducing the endemic gastro-intestinal infections and parasites from polluted surface water in many third-world countries.  Arsenic is a cumulative poison, building up to dangerous levels over several years.  So ill-health, including fatal liver cancer, does not immediately appear in populations that are at risk.  Areas in which metals are mined are obvious places where caution is needed in groundwater development, particularly where the ores are sulphides – arsenopyrite is a common waste mineral in gold mining.  However, mines produce relatively small zones of risk.  The alluvium derived from large mountain ranges, in which sulphides occur commonly in sediments and igneous rocks, pose the widest hazards.  That is the case in Bangladesh.  However, reports are emerging of similar problems in the Ganges flood plain in Bihar, India and Nepal, the Mekong Delta in Vietnam, lowland China and the Argentine Pampas, each affecting more than half a million people, together with lesser cases in 11 other countries, including the USA.  Over a billion people world-wide have no access to clean drinking water, and a favoured solution is to develop local groundwater.  The arsenic tragedy is not going to stop that necessary improvement in people’s lives, but rigorous testing for chemical contaminants is now a must.  Also, there are means of cheaply removing arsenic from contaminated water – it is almost totally adsorbed by the iron hydroxides that form rust when conditions are oxidising.  In fact, if wells are driven into zones of oxygen-rich groundwater, dissolved arsenic is rarely apparent – part of the problem in Bangladesh is extraction from levels where groundwater has reducing chemistry.

Senile dementia and copper

The chemical constituents of drinking water vary a lot, according to where you live, and some like arsenic are widely feared.  Having a well drilled into pure silica sand fed with rainwater is not the answer.  Humans get a sizeable proportion of essential elements from the water that they drink, and pure water would result in deficiencies of many elements.  Upper limits for many potentially harmful elements are set legally in some countries, and the World Health Organisation offers useful advice (see http://www.who.int/water_sanitation_health/GDWQ/Summary_tables/Tab2a.htm).  However, little is known about the geochemistry of human health, when it lies within advised limits.  Recent biomedical research reveals a possible link between copper in drinking water and Alzheimer’s Disease (Sparks, D.L. & Schreurs, B.G. 2003.  Trace amounts of copper in water induce {beta}-amyloid plaques and learning deficits in a rabbit model of Alzheimer’s disease. Proceedings of the National Academy of Sciences, 14 August 2003 – online publication).  Two experiments investigating the effects of high-cholesterol intake on rabbits both suggested that beta-amyloid plaques, implicated in human senile dementia, build up with cholesterol intake.  Nothing too surprising in that.  However, the results differed significantly between the two laboratories, one in the USA, the other in New Zealand.  Trying to work out why two labs should get such different results, Larry Sparks of the Sun Health Institute in Arizona discovered that the New Zealand rabbits drank tap water, whereas his were given distilled water.  The US rabbits had significantly less plaque build-up than those studied in New Zealand, so perhaps water chemistry had an input.  Sparks and his colleague varied the copper content of their rabbits’ water, and found that even with one-tenth the maximum safe concentration advised by the WHO, plaque built up 50% faster in the hapless animals.  However, it is early days in this research.  Cells possibly contain numerous mechanisms that fight off accumulation of potentially harmful elements, and perhaps the plaques implicated in Alzheimer’s play such a role.  One line of investigation is to check records of the incidence of Alzheimer’s against local water chemistry, but both kinds of record, even in well-heeled countries like the USA and Britain, are rudimentary to say the least.  If there is a risk, it is likely to be highest among people who use local well water in metal mining areas, or where bedrock includes sediments that contain high copper concentrations, sulphidic shales being a widespread example.

Source: Marx, J. 2003.  Possible role for environmental copper in Alzheimer’s Disease.  Science, v. 301, p. 905

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