The State of Arsenic in Nepal - 2003 - Harvard University ...

1. Introduction
Providing safe drinking water is one of the most critical issues
for all Nepali government and non-government organizations
concerned with water supply and sanitation. High
concentrations of arsenic have been found in the wells that
supply drinking water in several districts of the Terai region
of Nepal by the Department of Water Supply and Sewerage
(DWSS) and by several non-government organizations.
Providing clean drinking water and developing groundwater
for agriculture are significant challenges for government and
non-government organizations. Therefore, it is important to
compile all available existing data on the current state of
arsenic in groundwater in Nepal. The state of arsenic
presented in this report is provided to assist in efficient
planning, policymaking, and project implementation of water
development and arsenic mitigation programs.
The National Arsenic Steering Committee (NASC) and United
States Geological Survey (USGS) agreed to cooperate to
develop an integrated national database of arsenic-tested
tube wells. The Nepali government agencies and NGOs that
participate in the NASC agreed to share all arsenic data that
have collected to construct a national database. The nongovernment
organization “Environment and Public Health
Organization” was selected to compile and edit the arsenic
database and to produce a report on “The State of Arsenic in
Nepal - 2003”. The project was funded by the USGS through
a US government Public Diplomacy Grant from the US
Embassy in Kathmandu.
The main objectives of this project are to 1) compile all available
analyses of water tested for arsenic in the Terai region, 2) edit the
data entries, 3) check location information for each entry, 4) add
GPS location information where feasible, 5) display arsenic data on
maps, 6) interpret and display some statistical parameters of the
arsenic data, and 7) produce a report on the state of arsenic in
Nepal - 2003 that includes a CD-ROM of an integrated national
database of arsenic tested tube wells. Statistical analyses are
presented in user-friendly forms such as tables, charts, graphs
and maps. The information are analyzed and presented in
different government levels, including national, district and
village development committee (VDC) or municipality.
1
2. Sources and occurrences of arsenic in the
environment
Arsenic contamination of natural waters has become an issue
of growing concern around the world during the past decade.
Although arsenic contamination has been found in China,
Taiwan, Chile, Argentina, Mexico, Hungary, Mongolia, Japan,
Canada, and USA, scientists were unprepared by the scale of
arsenic contamination found in Bangladesh and West Bengal,
India during the 1990’s (Mandal and others, 1996; Jain and
Ali, 2000). In fact, The World Health Organization (WHO)
declared in 2001 that groundwater contamination on the
Bengal delta is the potentially largest environmental
catastrophe in modern history, exceeding even that of the
Chernobyl catastrophe. Because much of southern Nepal lies
within the same Ganges drainage basin as West Bengal and
western Bangladesh, it is prudent and necessary to examine
whether or not arsenic is contaminating ground waters in the
Kingdom of Nepal.
Arsenic is an element, a metal that is found in rocks, soil,
natural waters, and organisms. Arsenic is a transitional
reactive element that forms chemical and organic complexes
together with other metals (most commonly with iron), carbon,
sulfur, and oxygen. Dominant natural arsenic bearing rocks
include realgar (AsS), orpiment (As 2
S 3
), lollingite (FeAs 2
),
and arsenopyrite (FeAsS), which is the most common arsenic
ore mineral (Internet/1 and Internet/2). These minerals form
primarily under high-temperature conditions in the earth’s
crust. Arsenic concentrations are generally low in igneous
rocks and higher in metamorphic and some sedimentary rocks.
Pelitic (slates and phyllites) and argillaceous (black shales,
coals) have among the highest average values of arsenic,
and are not uncommon rocks in the Himalaya Mountains.
Concentrations of arsenic in unconsolidated sediments are
similar to those found in rocks, with higher concentrations
generally found in muds and clays.
Soils, which are composed of the weathering products of
rocks, contain an average of 4-6 mg/kg of arsenic. Arsenate
[As(V)], the oxidized form of arsenic, is common in soils that
are situated above the water table, while arsenite [As(III)] is