Social and Spatio-temporal Patterns of Arsenic Exposure and the Impacts on Respiratory Health in Rural Bangladesh
Bangladesh has a long history of exposure to high levels of inorganic arsenic in its drinking water as an unintended consequence of development programs that installed new wells. Arsenic occurs naturally in the sediments of this region, though with high spatial variability due to changes in geology. At the same time, human exposure to that arsenic varies due to social, economic, and political factors that influence both access to wells and mitigation projects, and the likelihood that a well taps a contaminated aquifer. Arsenic has no distinguishing color, odor, or taste so as many as 77 million people were exposed for decades until contamination was discovered in the 1990s. Since that time millions of dollars have been spent on testing water sources and encouraging household to adopt arsenic-safe sources.
This study takes an historical geographic approach to examine the patterns of arsenic exposure, how exposure has shifted since contamination was realized, and the subsequent impacts of exposure on respiratory health in the area of Matlab, Bangladesh. The analyses draw on new longitudinal survey data linked to 30 years of spatially-referenced health and demographic surveillance records and apply a combination of spatial statistical methods. The results show that since arsenic contamination was realized, exposure has declined dramatically overall. Yet within the overall trend for Matlab there are local areas that remain at increased risk for exposure, likely due to geologic variation. Furthermore a social gradient in exposure has recently emerged as wealthier households are far less likely to be exposed. The decline in exposure has not (yet) yielded health benefits. Higher lifetime exposures to arsenic are associated with reductions in objective pulmonary function (FEV1 and FVC) in both adults and in children.
These findings have important implications for understanding future health burdens in Bangladesh and planning arsenic mitigation projects. The results highlight the geographic areas and populations which are most vulnerable. While the decrease in arsenic exposure overall is positive, more mitigation work which addresses the root causes of vulnerability is needed as even low-levels of exposure have detrimental health consequences now and likely in the future.