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close this bookFact sheet No 210: Arsenic in Drinking Water - February 1999 (WHO; 1999; 5 pages)

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.

• Arsenic is widely distributed throughout the earth's crust and is used commercially, primarily in alloying agents. It is introduced into water through the dissolution of minerals and ores, from industrial effluents, and from atmospheric deposition; concentrations in groundwater in some areas are elevated as a result of erosion from local rocks.

• Hyperpigmentation, depigmentation, keratosis, and peripheral vascular disorders are the most commonly reported symptoms of chronic arsenic exposure. Skin cancer and a number of internal cancers can also result. Cardiovascular and neurological diseases have also been found to be linked to arsenic ingestion and exposure.

• There is no consensus on the definition of arsenic poisoning.

• High concentrations of arsenic in a community's well do not necessarily correlate with high levels of arsenic symptoms within the community.

• Studies suggest that malnutrition and Hepatitis B will accentuate the effects of arsenic poisoning and that arsenic concentrations in wells in close proximity may vary widely.



• 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.

• Health effects from consuming arsenic-contaminated drinking-water are delayed. Skin lesions are generally first, and appear after a minimum exposure of approximately 5 years.

• Level of actual intake is often unknown so future health effects cannot be predicted.

• Knowledge of health effects of arsenic is incomplete and the situation is complicated by factors such as Hepatitis B, nutritional status and the actual form of arsenic.

• Most important remedial action is prevention of further exposure by providing safe drinking water.

• Measuring arsenic in water accurately is not simple at concentrations important for human health. Reliable field methods are yet to be fully evaluated.

• The technology for arsenic removal for piped supply is moderately costly and requires technical expertise. It is inapplicable in most rural areas and some urban areas of developing countries.

• No proven technologies for the removal of arsenic at water collection points such as wells.

• Simple technologies for household removal of arsenic from water are few and have to be adapted to and proven sustainable in each different setting.


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.

• 0.01 mg/L was established as a provisional guideline value for arsenic, with a view to reducing the concentration of carcinogenic contaminants in drinking water.

• An earlier edition of the Guidelines established 0.05 mg/L as the guideline value. Many countries have either kept this as the national standard or as an interim target before tackling populations exposed to lower but still significant concentrations in the 0.01-0.05 range.

• The guideline value for arsenic of 0.01 is provisional because of the lack of suitable testing methods. Based on health concerns alone it would be lower still.

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.



• 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.

• Doubts concerning the reliability of analytical results can cause confusion and concern; according to a WHO assessment carried out in Bangladesh, available kits can detect high levels of arsenic but negative results may occur at concentrations of concern for human health.

• New types of treatment technologies, including co-precipitation treatment, ion exchange, activated alumina filtration, and chemical packages for household treatment, are being tested.

• Some studies have reported preliminary successes in using packets of chemicals for household treatment. Some mixtures combine arsenic removal with disinfection. One example, developed by the WHO/PAHO Pan American Center of Sanitary Engineering and Environmental Sciences in Lima, Peru (CEPIS), has proven successful in Latin America.

• Acceptability and affordability by the potentially affected population are as important for sustainability as technical and economical aspects of interventions and require evaluation



• Simple, reliable, low cost field testing equipment.
• Increased availability and dissemination of all information.
• Robust technologies for arsenic removal at wells and in households.


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).


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.

• The number of people drinking arsenic-contaminated water has increased over the past 25 years due to well-drilling and population growth. The number of affected persons may therefore increase further; the most commonly manifested disease so far is skin lesions.

• The national standard for drinking water remains high at 0.05 mg/L.

• District and sub-district health officials and workers lack sufficient knowledge as to the symptoms of arsenic poisoning and what to do about it.

• The poor availability of reliable information hinders action at all levels and may lead to panic, exacerbated if misleading reports are made. Effective information channels have yet to be established to those affected and concerned. A recent meeting of the Global Applied Research Network (GARNET) deplored the lack of reliable information reaching the grassroots level - only 20% of the local nongovernmental organizations (NGOs) attending had any real knowledge about the extent and nature of the problem.

• Malnutrition and Hepatitis B, both of which are prevalent in Bangladesh, will accentuate the effects of arsenic poisoning.



• 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.

• There are about 0.9 million public and 1.6 million private wells. More than 95% of the Bangladesh population of 120 million drinks well water. Until the discovery of arsenic in groundwater in 1993, well water was regarded as safe for drinking. Piped water supplies are available only to a small portion of the total population.

• The amount of testing required and the need to provide feedback to those using well water, suggest use of field testing kits. Several kits exist, but are not readily available in Bangladesh.

• It is now generally agreed that the arsenic contamination of groundwater in Bangladesh is of geological origin. The arsenic derives from the geological strata underlying Bangladesh. There are two main theories as to how this contamination occurs:

Pyrite oxidation. In response to pumping, air or water with dissolved oxygen penetrates into the ground, leading to decomposition of the sulphide minerals and release of arsenic.

Oxyhydroxide reduction. Arsenic is naturally transported and adsorbed onto fine-grained iron or manganese oxyhydroxides which slowly break down

• It is increasingly accepted that the second theory is the most likely explanation.

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.

For further information, journalists can contact:
WHO Press Spokesperson and Coordinator, Spokesperson's
WHO HQ, Geneva, Switzerland / Tel +41 22 791 4458/2599 / Fax
+41 22 791 4858 / e-Mail:

© WHO/OMS, 2000

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