Groundwater contamination by arsenic was first discovered in the west of Bangladesh in late 1993 following reports of extensive contamination of water supplies in the adjoining areas of India. A World Bank Fact Finding Mission visited Bangladesh in April 1997 to assess the situation and to initiate a mitigation programme. Part of their recommendations included a broad-ranging Rapid Investigation Programme to collate the available data, fill in critical gaps in knowledge and undertake surveys of the affected area. This eventually led to the project entitled ‘Groundwater Studies for Arsenic Contamination in Bangladesh’ which was approved by the Government of Bangladesh in late December 1997. The UK Department for International Development (DFID) agreed to finance the project.
Arsenic in drinking water
Arsenic
is both toxic and carcinogenic. Inorganic forms of arsenic dissolved
in drinking water are the most significant forms of natural exposure.
Organic forms of arsenic that may be present in food are much less
toxic to humans. Clinical manifestations of arsenic poisoning begin
with various forms of skin disease, and proceed via damage to internal
organs ultimately to cancer and death.
The symptoms of chronic arsenic poisoning may take between five and fifteen years to reveal themselves. The principal treatment is to provide the patient with arsenic-free drinking water. The Bangladesh Standard for arsenic in drinking water is 0.05 mg/l. This standard was based on World Health Organisation (WHO) advice at the time when the regulations were drafted. In 1993 WHO lowered their guideline value for arsenic to 0.01 mg/l. This value has not been adopted in either Bangladesh or India.
Outline of the project
The Department of Public Health Engineering (DPHE), which is responsible for water supply throughout the country other than in the cities of Dhaka and Chittagong, is the executing agency for the project. The Bangladesh Water Development Board (BWDB) and the Geological Survey of Bangladesh (GSB) also provided counterparts for the study. On behalf of the Government of Bangladesh, DFID appointed the British Geological Survey (BGS) as lead consultants for the study. BGS appointed Mott MacDonald Ltd (MML) to carry out much of the Phase 1 work. A team of national experts was recruited to assist with the work.
The project began in mid January 1998 and was structured to have a six month Phase 1 and an eighteen month Phase 2 with about half the funding allocated to Phase 1. The principal aims of Phase 1 were to: (i) collate and review existing data for arsenic in Bangladesh groundwaters; (ii) carry out a regional survey of arsenic in groundwaters in what was believed to be the worst-affected parts of Bangladesh (approximately the southern and eastern two-thirds of Bangladesh); and (iii) to carry out a more detailed study of three small areas (thanas) to assess the possible source, mobility and fate of arsenic in the aquifers. Phase 1 was due to be completed in July 1998 but was delayed due to the need to reanalyse all of the 2000 regional survey samples in the UK. The arsenic analyses were completed in October 1998, and the draft final report was submitted for review in November. This delay did not prevent the start of Phase 2 work, and a number of Bangladesh sediments have now been analysed for arsenic and other elements.
A typical rural scene in Nawabganj district, western Bangladesh.
The small building on the left is situated over a shallow tube well
which is pumped with a motorized centrifugal pump. This is used for
irrigating the rice crop during the dry season (January to April).
