Box 2 – Domestic Well Contamination Discovered by Health Effects
In Bangladesh and India, arsenic in groundwater was first discovered in domestic wells in the 1980s after patients were diagnosed with arsenic-induced skin lesions (Figure Box 2-1). The source of the arsenic was eventually discovered by analyzing the well water used by the patients. A subsequent regional well survey involving 200 villages with suspected arsenic contamination was carried out to determine the extent of the arsenic problem. Approximately 62 percent of the 33,000 wells sampled had arsenic concentrations greater than 100 µg/L (Smith et al., 2000). Since this discovery, Bangladesh has introduced programs to reduce arsenic exposure from well water, which primarily involve drilling deeper wells that avoid the high arsenic levels found in the local shallow aquifers (Kundu et al., 2016).
In Nova Scotia, Canada, arsenic contamination in groundwater was first discovered in 1976 after a patient at a local hospital was found to have chronic arsenic intoxication. The source of the arsenic was found to be the patient’s domestic dug well. Historically, dug wells in Nova Scotia were sometimes constructed by lining the well walls with arsenopyrite-rich waste rock from gold mine sites. The arsenic concentration from the patient’s dug well was 5,000 µg/L (Grantham and Jones, 1977), which is 500 times higher than the current Canadian drinking water guideline (10 µg/L). This discovery led to an investigation of arsenic levels in groundwater in former gold mining districts throughout the province. The investigations found that arsenic was not restricted to gold mining districts but was a province-wide problem associated with naturally occurring arsenic, particularly in metamorphic and plutonic bedrock aquifers. It is estimated that about 20 percent of domestic wells in the province exceed the drinking water quality guideline for arsenic, and it is now routine to analyze for arsenic in domestic well water in Nova Scotia.
Figure Box 2–1 – Skin lesions caused by arsenic in well water (photograph by World Health Organization (photograph from Smith et al., 2000).
A similar situation occurred in Nova Scotia, Canada, in 1978. In this case, previously unknown groundwater contamination was discovered by chance when a research project at Dalhousie University was studying the levels of various metals in the general population. The study found high levels of uranium in the hair samples collected from one of the study participants. Further investigations traced the source of the uranium to the domestic drilled well where the person obtained their drinking water (Grantham, 1986). As result of this discovery, regional well water surveys were carried out in the 1980s which found that naturally occurring uranium in groundwater is a province-wide problem, especially in plutonic and sedimentary bedrock aquifers. It is estimated that more than 6 percent of domestic wells in the province exceed the drinking water quality guideline for uranium (20 µg/L). It is now routine to analyze for uranium in domestic well water in Nova Scotia.
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