Geographic, Demographic, and Economic Overview of Bangladesh. The People’s Republic of Bangladesh is a developing country overburdened with an enormous population, severe poverty, common illiteracy, and frequent natural disasters. It is located at one of the largest river deltas in the world: The Ganges, Brahmaputra, and Meghna rivers flow through Bangladesh to the Bay of Bengal. Very little of the country is more than 12 m (40 feet) above sea level, and in a normal monsoon season one-third of its cultivated land is flooded (1). Bangladesh has 127 million people (2) living on 144,000 km2 (1); this would be equivalent to one-half the population of the United States living in an area the size of Wisconsin. The infant mortality rate is 58 per 1,000 live births (2). There is one doctor per 5,200 people; by comparison, the United Kingdom has one doctor per 650 people (1). The adult literacy rate is 63% for men and 48% for women. The average annual income is equivalent to US$370 per capita (2). The life expectancy is 55 years (1).
Bangladesh is an agricultural country with the vast majority of its people involved in food production. Rice is grown during the rainy season and is used primarily for domestic consumption. In irrigated areas, a second rice crop is possible, followed by wheat and vegetables in the short, dry winter from November to February. Bangladesh is the world’s leading producer of jute, a strong natural fiber used in the carpet and sacking industries. The principal exports of Bangladesh from largest to smallest are garments, jute and its products, shellfish, tea, and leather (1).
Project Overview. Much of Bangladesh’s surface water is microbially unsafe to drink. Since independence in 1971, between 8 million and 12 million tubewells have been installed to supply microbially safe drinking water to the people of Bangladesh. Today, 97% of Bangladeshis drink well water (3,4). Unfortunately, vast areas of this 127 million-person country contain groundwater with arsenic (As) concentrations above the World Health Organization (WHO) drinking water guideline of 0.01 mg/L (5,6). Chronic As poisoning attributed to groundwater ingestion was first diagnosed in 1993. By 1999, a total of 2,953 cases of chronic As poisoning were identified in Bangladesh (7); however, most of this country remains unsurveyed, and the actual number of cases is expected to be in the tens or hundreds of thousands (8). These diagnoses include melanosis, leukomelanosis, keratosis, hyperkeratosis, nonpitting edema, gangrene, and skin cancer (9).
The 1997 U.S. Agency for International Development (USAID) field program produced the first national-scale map of As concentration in Bangladesh’s tubewell water (10,11). This map indicates that approximately 45% of Bangladesh’s area contains groundwater with As concentrations greater than the 0.05 mg/L Bangladesh national drinking water standard (10). The principal source of As in Bangladesh’s groundwater is geologically deposited sediments. In particular, the major sources might be the reductive dissolution of nonpyrite iron (Fe) or nonpyrite phosphate minerals and the anion exchange of sorbed arsenate or arsenite (10,11).
In addition, the 1997 USAID field program discovered that many of the 127 million people in Bangladesh may be drinking unsafe levels of toxic metals other than As (10,11). At least 27% of the samples contained an analytical interference to the 1,10-phenanthroline methods for measuring Fe(II) and total Fe. This interference was observed from suppressed matrix spike recovery (34%) during the measurement of Fe(II) and from improper color development during the measurement of total Fe. This interference could not be further characterized during the 1997 USAID field program; however, the literature suggested that it resulted from one or more toxic nonarsenic metals in these drinking water samples (12,13). In response to this discovery, we assessed the hypothesis that Bangladeshis are exposed to toxic metals other than As in their drinking water during our 1998-1999 field program. In this assessment, the concentrations of several analytes (Ag, Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cs, Cu, F-, Fe, H+, K, Mg, Mn, Mo, Ni, Pb, Rb, S, Sb, Si, Se, Sr, Tl, V, W, and Zn) in tubewell water were mapped on a national scale (Figure 1). These analytes were selected based on their toxicity and potential to be the analytical interference observed during the 1997 USAID field program. This exposure assessment of As and other toxic metals in Bangladesh’s drinking water is reported here for the first time.
Furthermore, the contention that Bangladeshis are exposed to toxic metals other than As was strengthened by the finding of severe melanosis, keratosis, skin cancer, and other symptoms of chronic As poisoning especially among children (14,15). This observation was the first indication that multimetal health effects might be involved. Therefore, we assessed the hypothesis that Bangladeshis are exposed to antimony (Sb), a metal that magnifies chronic As poisoning (16), during our 1998-1999 field program. Conversely, we also assessed the hypotheses that Bangladeshis are not exposed to selenium (Se) or zinc (Zn), metals that inhibit chronic As poisoning (17,18). This exposure assessment of metals that affect As toxicity is reported here for the first time.