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Ground water arsenic: Arsenic in drinking water
Arsenic may be found in water which has flowed through
Severe health effects have been observed in populations drinking
water over long periods in countries world-wide.
- Arsenic is
widely distributed throughout the earth's crust.
- Arsenic is
introduced into water through the dissolution of minerals and ores, and
concentrations in groundwater in some areas are elevated as a result of
erosion from local rocks.
effluents also contribute arsenic to water in some areas.
- Arsenic is
also used commercially e.g. in alloying agents and wood preservatives.
of fossil fuels is a source of arsenic in the environment through
disperse atmospheric deposition.
arsenic can occur in the environment in several forms but in natural
waters, and thus in drinking-water, it is mostly found as trivalent
arsenite (As(III)) or pentavalent arsenate (As (V)). Organic arsenic
species, abundant in seafood, are very much less harmful to health, and
are readily eliminated by the body.
poses the greatest threat to public health from arsenic. Exposure at
work and mining and industrial emissions may also be significant
arsenic poisoning, as occurs after long-term exposure through drinking-
water is very different to acute poisoning. Immediate symptoms on an
acute poisoning typically include vomiting, oesophageal and abdominal
pain, and bloody "rice water" diarrhoea. Chelation therapy may be
effective in acute poisoning but should not be used against long-term
- The symptoms
and signs that arsenic causes, appear to differ between individuals,
population groups and geographic areas. Thus, there is no universal
definition of the disease caused by arsenic. This complicates the
assessment of the burden on health of arsenic. Similarly, there is no
method to identify those cases of internal cancer that were caused by
arsenic from cancers induced by other factors.
Long-term exposure to arsenic
via drinking-water causes
cancer of the skin, lungs, urinary bladder, and kidney, as well as
changes such as pigmentation
- health of
arsenic. Similarly, there is no method to identify those cases of
internal cancer that were caused by arsenic from cancers induced by
exposure to arsenic via drinking-water causes cancer of the skin,
lungs, urinary bladder, and kidney, as well as other skin changes such
as pigmentation changes and thickening (hyperkeratosis).
risks of lung and bladder cancer and of arsenic-associated skin lesions
have been observed at drinking-water arsenic concentrations of less
than 0.05 mg/L.
of arsenic through the skin is minimal and thus hand-washing, bathing,
laundry, etc. with water containing arsenic do not pose human health
long-term exposure, the first changes are usually observed in the skin:
pigmentation changes, and then hyperkeratosis. Cancer is a late
phenomenon, and usually takes more than 10 years to develop.
relationship between arsenic exposure and other health effects is not
clear-cut. For example, some studies have reported hypertensive and
cardiovascular disease, diabetes and reproductive effects.
- Exposure to
arsenic via drinking-water has been shown to cause a severe disease of
blood vessels leading to gangrene in China
known as 'black foot disease'. This disease has not been observed in
other parts of the world, and it is possible that malnutrition
contributes to its development. However, studies in several countries
have demonstrated that arsenic causes other, less severe forms of
peripheral vascular disease.
- According to
some estimates, arsenic in drinking-water will cause 200,000 -- 270,000
deaths from cancer in Bangladesh
alone (NRC, 1998; Smith, et al, 2000).
measurement of arsenic in drinking-water at levels relevant to health
requires laboratory analysis, using sophisticated and expensive
techniques and facilities as well as trained staff not easily available
or affordable in many parts of the world.
quality control and external validation remain problematic.
- Field test
kits can detect high levels of arsenic but are typically unreliable at
lower concentrations of concern for human health. Reliability of field
methods is yet to be fully evaluated.
Prevention and control
The most important remedial action is prevention of
further exposure by
providing safe drinking- water. The cost and difficulty of reducing
drinking-water increases as the targeted concentration lowers. It
the arsenic concentration in the source water, the chemical matrix of
including interfering solutes, availability of alternative sources of
arsenic water, mitigation technologies, amount of water to be treated,
Control of arsenic is more complex where drinking-water
is obtained from
many individual sources (such as hand-pumps and wells) as is common in
areas. Low arsenic water is only needed for drinking and cooking.
water can be used safely for laundry and bathing. Discrimination
high-arsenic and low-arsenic sources by painting the hand-pumps (e.g.
green) can be an effective and low cost means to rapidly reduce
arsenic when accompanied by effective health education.
Alternative low-arsenic sources such as rain water and
treated surface water
may be available and appropriate in some circumstances. Where low
is not available, it is necessary to remove arsenic from drinking-water:
technology for arsenic removal for piped water supply is moderately
costly and requires technical expertise. It is inapplicable in some
urban areas of developing countries and in most rural areas world-wide.
- New types of
treatment technologies, including co-precipitation, ion exchange and
activated alumina filtration are being field-tested.
- There are no
proven technologies for the removal of arsenic at water collection
points such as wells, hand-pumps and springs.
technologies for household removal of arsenic from water are few and
have to be adapted to, and proven sustainable in each different setting.
- 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,
(CEPIS), has proven successful in Latin America.
WHO's activities on arsenic
WHO's norms for drinking-water quality go back to 1958.
Standards for Drinking-Water established 0.20 mg/L as an allowable
concentration for arsenic in that year. In 1963 the standard was
and reduced to 0.05 mg/L. In 1984, this was maintained as WHO's
Value"; and many countries have kept this as the national standard or
an interim target. According to the last edition of the WHO Guidelines
Drinking-Water Quality (1993):
arsenic is a documented human carcinogen.
- 0.01 mg/L
was established as a provisional guideline value for arsenic.
- Based on
health criteria, the guideline value for arsenic in drinking-water
would be less than 0.01mg/L.
- Because the
guideline value is restricted by measurement limitations, and 0.01 mg/L
is the realistic limit to measurement, this is termed a provisional
The WHO Guidelines for Drinking-water Quality
is intended for use as
a basis for the development of national standards in the context of
national environmental, social, economic, and cultural conditions.
The summary of an updated International Programme on
Environmental Health Criteria Document on Arsenic published by WHO is
It addresses all aspects of risks to human health and the environment.
text will be published in late 2001.
A UN report on arsenic in drinking-water has been
prepared in cooperation
with other UN agencies under the auspices of an inter-agency
(the Administrative Committee on Coordination's Sub-committee on Water
Resources. It provides a synthesis of available information on
toxicological, medical, epidemiological, nutritional and public health
develops a basic strategy to cope with the problem and advises on
technologies and on water quality management. The draft of the report
available at http://www.who.int/water_sanitation_health/dwq/arsenic3/en/
Information on arsenic in drinking-water on a
country-by-country basis is
being collected and will be added to the UN report and made available
As part of WHO's activities on the global burden of
disease, an estimate of
the disease burden associated with arsenic in drinking-water is in
A report entitled "Towards an assessment of the socioeconomic impact of
arsenic poisoning in Bangladesh"
was released in 2000.
A United Nations Foundation grant for 2.5 million
approved in July 2000,
will enable UNICEF and WHO to support a project to provide clean
alternatives to 1.1 million people in three of the worst affected
The project utilizes an integrated approach involving communication,
building for arsenic mitigation of all stakeholders at subdistrict
below, tube-well testing, patient management, and provision of
water supply options.
support to the management of the problem in developing countries with
substantial, severely affected populations.
reliable, low-cost equipment for field measurement.
availability and dissemination of relevant information.
affordable technologies for arsenic removal at wells and in households.
The delayed health effects of exposure to arsenic, the
lack of common
definitions and of local awareness as well as poor reporting in
are major problems in determining the extent of the
Reliable data on exposure and health effects are rarely
available, but it is
clear that there are many countries in the world where arsenic in
drinking-water has been detected at concentration greater than the
Value, 0.01 mg/L or the prevailing national standard. These include Argentina,
the United States of America.
Countries where adverse health effects have been documented include Bangladesh,
(West Bengal), and the United
States of America.
- Seven of 16
districts of West Bengal have been reported to have ground water
arsenic concentrations above 0.05 mg/L; the total population in these
seven districts is over 34 million (Mandal, et al, 1996) and it has
been estimated that the population actually using arsenic-rich water is
more than 1 million (above 0.05 mg/L) and is 1.3 million (above 0.01
mg/L) (Chowdhury, et al, 1997).
- According to
a British Geological Survey study in 1998 on shallow tube-wells in 61
of the 64 districts in Bangladesh,
46% of the samples were above 0.010 mg/L and 27% were above 0.050 mg/L.
When combined with the estimated 1999 population, it was estimated that
the number of people exposed to arsenic concentrations above 0.05 mg/l
is 28-35 million and the number of those exposed to more than 0.01 mg/l
is 46-57 million (BGS, 2000).
Protection Agency of The United
States of America has
estimated that some 13 million of the population of USA,
mostly in the western states, are exposed to arsenic in drinking- water
at 0.01 mg/L, although concentrations appear to be typically much lower
than those encountered in areas such as Bangladesh
and West Bengal. (USEPA, 2001)
Arsenic in Bangladesh
West Bengal (India)
and some other areas, most drinking-water used to be collected from
wells and ponds with little or no arsenic, but with contaminated water
transmitting diseases such as diarrhoea, dysentery, typhoid, cholera
hepatitis. Programmes to provide "safe" drinking-water over the past
30 years have helped to control these diseases, but in some areas they
the unexpected side-effect of exposing the population to another health
Arsenic in drinking-water in Bangladesh
is attracting much attention for a number of reasons. It is a new,
problem to the population, including concerned professionals. There are
millions of people who may be affected by drinking arsenic-rich water.
but not least, fear for future adverse health effects as a result of
- In recent
years, extensive well drilling programme has contributed to a
significant decrease in the incidence of diarrhoeal diseases.
- It has been
suggested that there are between 8-12 million shallow tube-wells in Bangladesh.
Up to 90% of the Bangladesh
population of 130 million prefer to drink well water. Piped water
supplies are available only to a little more than 10% of the total
population living in the large agglomerations and some district towns.
- Until the
discovery of arsenic in groundwater in 1993, well water was regarded as
safe for drinking.
- It is now
generally agreed that the arsenic contamination of groundwater in Bangladesh
is of geological origin. The arsenic derives from the geological strata
- The most
commonly manifested disease so far is skin lesions. Over the next
decade, skin and internal cancers are likely to become the principal
human health concern arising from arsenic.
- According to
one estimate, at least 100,000 cases of skin lesions caused by arsenic
have occurred and there may be many more (Smith, et al, 2000).
- The number
of people drinking arsenic-rich water in Bangladesh
has increased dramatically since the 1970s due to well-drilling and
- The impact
of arsenic extends from immediate health effect to extensive social and
economic hardship that effects especially the poor. Costs of health
care, inability of affected persons to engage in productive activities
and potential social exclusion are important factors.
- The national
standard for drinking-water in Bangladesh
is 0.05 mg/L, same as in India.
- District and
sub-district health officials and workers lack sufficient knowledge as
to the identification and prevention of arsenic poisoning.
- 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.
- 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. These committees include the Governmental
Arsenic Co-ordinating Committee headed by the Minister of Health
& Family Welfare (MHFW) and several technical committees. One
of the positive outcomes of this collaboration (including work with
local institutes) has been the testing of new types of treatment
- 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 arsenic-related disease. The amount of testing required
and the need to provide effective feedback to those using well water,
suggest use of field testing kits.
- Only a few
proven sustainable options are available to provide safe drinking-water
These include: obtaining low-arsenic groundwater through accessing safe
shallow groundwater or deeper aquifers (greater than 200 m); rain water
harvesting; pond-sand-filtration; household chemical treatment; and
piped water supply from safe or treated sources.
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