The life expectancy in Bangladesh during the mid-1960s was only 46 years. Many premature deaths resulted from drinking surface water that was contaminated with bacteria causing diarrhea, cholera, typhoid, and other life-threatening diseases (Nyrop et al. 1975). Aid agencies, the Bangladesh government, and private individuals began installing 8,000,000 to 12,000,000 tubewells to prevent these deaths by providing access to microbially safe groundwater for drinking (WHO 2003). By 1995 Bangladesh had 120,000,000 people (Monan 1995), approximately 97% of Bangladeshis drank tubewell water (WHO 2000), and for a variety of reasons the life expectancy had increased to 55 years (Monan 1995).
Regrettably, this new source of drinking water was not tested for toxic metals. In 1993 Dhaka Community Hospital first diagnosed chronic As poisoning caused by drinking Bangladesh’s groundwater (BGS 1999a). In 1997 our team produced the first national-scale map of As concentration in Bangladesh’s groundwater. This map showed that 45% of Bangladesh’s area had groundwater with As concentrations greater than the 50-µg/L national standard (Frisbie et al. 1999; USAID 1997). In 2003 a risk assessment estimated that 28,000,000 Bangladeshis were drinking water with As concentrations greater than this national standard (Yu et al. 2003). As a result of this exposure, skin cancer, melanosis, leukomelanosis, keratosis, hyperkeratosis, and nonpitting edema from chronic As poisoning are common in Bangladesh (BGS 1999b; Frisbie et al. 2002). In addition, the rates of bladder cancer, liver cancer, and lung cancer are expected to increase in Bangladesh based on an analysis of death certificates for As exposures in Taiwan (Morales et al. 2000).
Fortunately, our 1997 study also suggested that testing and sharing tubewells could rapidly and inexpensively provide drinking water with As concentrations less than the 50-µg/L national standard to 85% of Bangladesh’s population. That is, 85% of Bangladesh’s neighborhoods have at least 1 tubewell that does not require treatment for As removal prior to drinking. Therefore, the vast majority of Bangladeshis with unsafe water could potentially get safe drinking water from their neighbors (Frisbie et al. 1999; USAID 1997). As a result of this discovery, groundwater testing has become a major component of an overall strategy for providing safe drinking water to the people of Bangladesh. To date, over 1,000,000 of Bangladesh’s approximately 10,000,000 tubewells have been tested for As with easy to use, relatively inexpensive, and semi-quantitative field kits (UNICEF 2004). Tubewells are considered safe and marked with green paint if the As concentration is less than or equal to the 50-µg/L national standard. Conversely, tubewells are considered unsafe and marked with red paint if the As concentration is greater than 50 µg/L. Those with safe water are asked to share with their less fortunate neighbors. In addition to this initial survey, periodic testing of tubewells has been recommended to ensure that the population has continued access to safe drinking water. This periodic testing is prudent because the As concentration in some of Bangladesh’s tubewells has changed dramatically over time (Frisbie et al. 1999; USAID 1997).
This urgent need to periodically test approximately 10,000,000 tubewells and the limited resources of Bangladesh has led to the use of these semi-quantitative field kits for measuring As. However, these field kits are not precise because the user must estimate the concentration of As from a color chart, similar to that used for measuring pH with pH paper. There are 2 commonly used field kits in Bangladesh. The first kit is not sensitive and must be modified to detect As at the 50-µg/L national standard. The second kit is inaccurate and must be modified to avoid underestimating the true concentration of As. After modification, this second kit overestimates the true concentration of As (Geen et al. 2005). As a result of these deficiencies, there is an urgent need to supplement and ultimately replace these field kits with a quantitative, accurate, precise, sensitive, inexpensive, and environmentally safe laboratory method for measuring As in Bangladesh’s drinking water. The development and evaluation of such a laboratory method is reported here for the first time.
This new method uses relatively inexpensive reagents and equipment that are easily obtained in Bangladesh and can be used to measure a wide variety of analytes. By design, it uses the same equipment as the AgSCSN(CH2CH3)2 method for measuring As (APHA et al. 1989); this latter method is commonly used in Bangladesh. Therefore, it can be readily implemented in Bangladesh. It does not use expensive equipment because such resources are rare in Bangladesh; for example, in 1997 there was only 1 atomic absorption spectrometer in the entire country that was used for the routine analysis of As (USAID 1997). It does not use highly specialized equipment, such as devoted As analyzers, because of their relatively high cost and limited utility (USAID 1997).
It is very important to realize that the 10-µg/L WHO drinking water guideline for As is based on a 6x10-4 excess lifetime skin cancer risk for human males, which is 60 times higher than the 1x10-5 factor that is typically used to protect public health (WHO 1996). WHO states that the drinking water guideline for As should be 0.17 µg/L based on the risk of death from skin cancer. However, the detection limit for most laboratories is 10 µg/L, which is why the less protective guideline was adopted. "Guideline values are not set at concentrations lower than the detection limit achievable under routine laboratory operating conditions (WHO 1993; WHO 1998)."
Similarly, Bangladesh has limited access to atomic absorption spectrometers or other sophisticated instruments for measuring As and uses a much higher 50-µg/L drinking water standard, largely due to the poor accuracy of the AgSCSN(CH2CH3)2 method (USAID 1997). However, a 50-µg/L drinking water standard not only fails to protect against death from skin cancer, it also fails to protect against death from bladder, liver, and lung cancers. Drinking water with 50 µg/L of As may cause 1 extra death from skin cancer per 500 people and 1 extra death from bladder, liver, or lung cancer per 300 people (Morales et al. 2000). Therefore, over 150,000 Bangladeshis are expected to die from skin, bladder, liver, or lung cancer caused by drinking water with more than 50 µg/L of As. Over 120,000 of these lives could be saved if Bangladesh complied with the more protective 10-µg/L WHO drinking water guideline for As by sharing safe water within affected neighborhoods. This study suggests that Bangladesh could adopt this more protective 10-µg/L WHO drinking water guideline for As if it used the arsenomolybdate method.