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

tube wells contain 0-10 ppb of arsenic. Moderate vulnerability
to arsenic: VDCs where 1-25% of tested tube wells exceed
the WHO Guideline for arsenic. Moderately high
vulnerability to arsenic: VDCs where 26-50% of tested tube
wells exceed the WHO Guideline. High vulnerability to
arsenic: VDCs where over 50% of arsenic-tested tube wells
exceed the WHO Guideline.
Among the 1,050 arsenic-tested VDCs, only 20 VDCs had
more than 100 tube wells that were tested for arsenic by
2003. Moreover, there were only five VDCs, in Nawalparasi
district, that contained more than 200 arsenic-tested tube
wells. Although 60% of VDCs have low vulnerability, nearly
74% of those VDCs have a high uncertainty for that assigned
vulnerability level, because of a very low number of wells
that were tested in those VDCs. In order to account for
VDCs with low levels of arsenic testing, a level of uncertainty
was characterized to help describe the confidence that
accompanies the level of vulnerability assigned to each VDC.
The uncertainty is based on the proportion of household in
a VDC that is using a tested tube well.
Among the 20 Terai districts only one district, Rautahat, is
characterized with high vulnerability to arsenic. The
uncertainty level is also low for this district. This indicates
that more than 50% of arsenic tested tube wells were above
the WHO Guideline, and that the percentage of households
using arsenic tested tube wells is 26-50%. Two districts,
Nawalparasi and Kailali, have been classified as having
moderately high vulnerability to arsenic; however, their
uncertainty levels are different. Nawalparasi has medium
uncertainty, and Kailali has high uncertainty. Therefore,
although both districts have moderately high vulnerability
to arsenic, Nawalparasi district has more arsenic-exposed
households than Kailali.
The majority of districts in the Terai have been classified as
moderate vulnerability to arsenic. However, the level of
uncertainty is different in these districts. Among 16 districts
classified with moderate vulnerability to arsenic, 9 districts
have high uncertainty, 4 districts have medium uncertainty
and 3 districts have low uncertainty. There is only one
ix
district, Chitwan, with low vulnerability to arsenic. However,
this classification has high uncertainty, because only 1% of
total households of the district were using arsenic-tested
tube wells.
In terms of population exposed to potential arsenic-related
health risks, the 2003 arsenic database indicates that 69,126
people (5.4%) were drinking water above the Nepal Interim
standard at the time of testing; 44% of those people live in
Nawalparasi district, 21% in Rautahat, and the rest, or 34%,
are distributed among the other districts. The population in
the Terai estimated to be drinking water that exceeds the
WHO Guideline is 272,626 (21.3%). These statistics will likely
change in the future, because arsenic testing has not yet
taken place in 345 VDCs - 25% of the total VDCs - in the
Terai.
Recommendations to improve the national arsenic database
The sources of arsenic in the ground water are believed to
be of geologic origin. However, the processes that
concentrate arsenic to environmentally dangerous levels in
the shallow aquifers are poorly understood. It is not yet
clear whether or not contamination is entirely natural or is
accelerated by human activities. Because the mechanisms
of arsenic contamination are not yet defined, it is important
to continue arsenic testing of wells in the Terai and, because
arsenic levels may increase over time, wells with arsenic
levels that exceed the WHO Guideline should be monitored
at some regular interval. Areas of anomalously high arsenic
concentrations found in the database should be tested
further to define the areal extent of the “arsenic hotspot”,
and mitigation efforts should be introduced to these areas
of concern. Health organizations should initially focus on
these arsenic hotspots to identify individuals in need of
medical attention.
Standard procedures need to be created for continued field
kit testing, laboratory analyses, and data maintenance. Most
important is the inclusion of GPS well location data with
arsenic tests. As more new field test kits become available,
they should be tested and verified with laboratory results.