Fact sheet No 210: Arsenic in Drinking Water - February 1999
Arsenic is a natural part of the earth's crust in some parts of the globe and may be found in water which has flowed through arsenic-rich rocks. Drinking arsenic-rich water over a long period is unsafe, and in some countries around the world the health effects are well known. In Bangladesh, West Bengal (India) and some other areas, most drinking water used to be collected from rivers and ponds with little or no arsenic, but with contaminated water transmitting diseases such as diarrhoea, dysentery, typhoid, cholera and hepatitis. Programmes to provide "safe" drinking water have helped to control these diseases, but in some areas they have had the unexpected side-effect of exposing the population to a new health problem - arsenic.
• Human arsenic intake is more associated with food, e.g. seafood, than with drinking water. However, arsenic in fish, for example, is overwhelmingly low toxicity organic arsenic. Drinking water, represents by far the greatest hazard, since arsenic in groundwater is predominantly inorganic and of higher toxicity.
OUTSTANDING QUESTIONS AND KEY ISSUES
• The human health significance of other sources of arsenic, such as those via the food chain, needs to be further explored, as do the relationships between diet/nutrition and the long-term effects of arsenic, and the dose-response and dose-effect relationships in drinking water.
WHO GUIDELINES FOR DRINKING-WATER QUALITY
The WHO Guidelines for Drinking-water Quality are intended for use as a basis for the development of national standards in the context of local or national environmental, social, economic, and cultural conditions The last edition of the Guidelines (1993) stated:
• Inorganic arsenic is a documented human carcinogen.
A technical monograph on the control of health hazards from arsenic in drinking water is to be prepared in cooperation with other agencies. It will address the poor synthesis of available information, develop a basic strategy to cope with the problem and deal with chemical, toxicological, medical, epidemiological, nutritional and public health issues, as well as removal technology and water quality management. An update of WHO's International Programme on Chemical Safety Environmental Health Criteria Monograph on Arsenic, addressing all aspects of risks to human health and the environment, is also under preparation.
TESTING FOR ARSENIC
• Measuring arsenic in drinking water traditionally required laboratory analysis, often using sophisticated and expensive atomic adsorption spectrophotometers (AAS) requiring special facilities and trained staff (considered expensive in developing countries). Even where AAS is available, quality control and external validation may remain a problem.
• Simple, reliable, low cost field testing equipment.
Delayed effects from arsenic poisoning, the lack of common definitions and poor reporting and local awareness in affected areas are major problems in determining the extent of the arsenic-in-drinking-water problem and developing adequate solutions. However, WHO (the World Health Organization) has compiled reports of cases of arsenic in drinking water in countries such as Argentina, Bangladesh, China, Chile, Ghana, Hungary, India, Mexico, Thailand and the United States of America, and more detail on situations in these countries can be obtained from WHO headquarters in Geneva. WHO is working to develop responses which can be applied not only in Bangladesh but in all countries where preventing arsenic from contaminating the normal sources of drinking may be a problem (see section on WHO activities below).
SITUATION IN BANGLADESH
Arsenic in drinking water in Bangladesh is attracting much attention. Important reasons for this include it being an unfamiliar problem (to the population, including concerned professionals); the number of people who may be exposed; and fear for dramatic future health effects as a result of water already consumed.
• According to data from about 25,000 tests carried out on wells by field test kits, 20% have high levels of arsenic (above 0.05mg/l). Thirty seven of the 64 districts have 5% or more wells with this level. In these studies, wells were not randomly selected and the proportion does not reflect the real proportion of wells contaminated.
• In recent years, one of the most effective public health measures in the country has been an extensive well programme, which, together with other water, sanitation and hygiene measures, has resulted in a significant decrease in the incidence of diarrhoeal diseases.
What is being done
Within Bangladesh a number of governmental technical and advisory committees have been formed and a co-ordinating mechanism established among the interested external support agencies. One of the positive outcomes of this collaboration (including work with local institutes) has been the testing of new types of treatment technologies.
The Governmental Arsenic Co-ordinating Committee headed by the Minister of Health & Family Welfare (MHFW) and several technical committees have been established. The Government is receiving considerable international support to address this problem, e.g. in August 1998 the World Bank approved a $32.4 million credit to Bangladesh to help tackle the water contamination crisis. So far, many initiatives have focused on water quality testing and control with a view to supplying arsenic-free drinking water, thereby reducing the risk of further complications and further arsenic-related disease.
Based on the current situation and the limited knowledge available, only a few reliable options are available to provide safe drinking water in Bangladesh. These include: shallow hand pumps for zones where arsenic is undetected; arsenic-free water from deeper aquifers (>100 or 200 m); rain water harvesting; pond-sand-filtration; bucket-type household treatment; and piped water supply from safe or treated sources.
Measures taken by WHO
The WHO Environmental Health Team in Bangladesh has supported the Government of Bangladesh since the early stages of recognition of the problem (1994), mostly by providing technical expertise.
In 1997, WHO acknowledged that arsenic in drinking water was a "Major Public Health Issue" which should be dealt with on an "Emergency Basis" and launched an expanded programme of activity in 1998. Joint studies with local institutes have been carried out to test household arsenic removal techniques and the quality of alternative drinking water sources. The programme is being further expanded in 1999. The initiative was launched in the context of inter-agency concern, and partners include other UN agencies such as UNESCO, IAEA, UNICEF, UNIDO, FAO and the World Bank.
It is doubtful that the existing problem in Bangladesh could be solved without further development of feasible and sustainable technical measures adapted to the Bangladesh situation.
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© WHO/OMS, 2000
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