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Considering Alternate Pathways of Drinking-water Contamination: Evidence of Risk Substitution from Arsenic Mitigation Programs in Rural Bangladesh

Varun Goel
Corresponding author:
Department of Geography, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA

Griffin J. Bell
Gillings School of Global Public Health, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA

Sumati Sridhar
Department of Statistics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA

Md. Sirajul Islam
International Centre for Diarrhoeal Disease Research (icddr,b), Dhaka 1212, Bangladesh; sislam@icddrb.org (M.S.I.); myunus@icddrb.org (M.Y.); taslim@icddrb.org (M.T.A.); fazal@icddrb.org (M.A.K.); nalam@icddrb.org (M.N.A.); gfaruque@icddrb.org (A.F.); tooha.btech@gmail.com (M.M.K.); shahab.babu@gmail.com (S.B.)

Md. Yunus
International Centre for Diarrhoeal Disease Research (icddr,b), Dhaka 1212, Bangladesh

Md. Taslim Ali
International Centre for Diarrhoeal Disease Research (icddr,b), Dhaka 1212, Bangladesh

Md. Alfazal Khan
International Centre for Diarrhoeal Disease Research (icddr,b), Dhaka 1212, Bangladesh

Md. Nurul Alam
International Centre for Diarrhoeal Disease Research (icddr,b), Dhaka 1212, Bangladesh

ASG Faruque
International Centre for Diarrhoeal Disease Research (icddr,b), Dhaka 1212, Bangladesh

Md. Masnoon Kabir
International Centre for Diarrhoeal Disease Research (icddr,b), Dhaka 1212, Bangladesh

Shahabuddin Babu
International Centre for Diarrhoeal Disease Research (icddr,b), Dhaka 1212, Bangladesh

Katerina Brandt
Department of Geography, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA

Victoria Shelus
Gillings School of Global Public Health, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA

Mark D. Sobsey
Gillings School of Global Public Health, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA

Michael Emch
Gillings School of Global Public Health, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA

Abstract/ Executive Summary:

Deep tubewells are a key component of arsenic mitigation programs in rural Bangladesh. Compared to widely prevalent shallow tubewells, deep tubewells reduce ground-water arsenic exposure and provide better microbial water quality at source. However, the benefits of clean drinking-water at these more distant sources may be abated by higher levels of microbial contamination at point-of-use. One such potential pathway is the use of contaminated surface water for washing drinking-water storage containers. The aim of this study is to compare the prevalence of surface water use for washing drinking-water storage containers among deep and shallow tubewell users in a cohort of 499 rural residents in Matlab, Bangladesh. We employ a multi-level logistic regression model to measure the effect of tubewell type and ownership status on the odds of washing storage containers with surface water. Results show that deep tubewell users who do not own their drinking-water tubewell, have 6.53 times the odds [95% CI: 3.56, 12.00] of using surface water for cleaning storage containers compared to shallow tubewell users, who own their drinking-water source. Even deep tubewell users who own a private well within walking distance have 2.53 [95% CI: 1.36, 4.71] times the odds of using surface water compared to their shallow tubewell counterparts. These results highlight the need for interventions to limit risk substitution, particularly the increased use of contaminated surface water when access to drinking water is reduced. Increasing ownership of and proximity to deep tubewells, although crucial, is insufficient to achieve equity in safe drinking-water access across rural Bangladesh.

Keywords: Drinking water quality, Bangladesh, Household water storage, Arsenic mitigation, Risk substitution

Location: In Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Water Arsenic, Drinking water

Objectives:

The primary objectives are to (1) compare the prevalence of surface water use for washing drinking-water storage containers among deep tubewell users compared to shallow tubewell users and (2) determine the effect of tubewell type and tubewell ownership of drinking water source on using surface water for washing drinking-water storage containers.

Methodology:

Study Design: We conducted a cohort study of rural households using shallow tubewells or deep tubewells as their primary drinking-water source. Using a stratified random sampling design, we assigned households to two groups, deep tubewell users and shallow tubewell users. For each household, we measure the microbial quality of the drinking-water using samples collected from the drinking-water source and the POU container to compare microbial water quality among the two groups, both during the rainy season and the dry season. We supplement microbial quality with surveys to assess diarrhea prevalence among children under-five years of age and measure the distance between the tubewell and the household using global positioning system (GPS) units. In this paper, we consider a cross-section of the study and utilize the baseline survey during the rainy season to measure the prevalence of surface water use to wash storage containers among deep tubewell users and shallow tubewell users. Setting: The study area is in Matlab, Bangladesh, a rural area in southeastern Bangladesh, located 50 km southeast of Dhaka, which comprises 142 villages and approximately 56,000 households. Based on the last large-scale arsenic testing campaign in 2002–03, Matlab was characterized by high concentrations of arsenic in shallow aquifers. Out of the 12,500 tubewells tested for arsenic across the study area, the majority being shallow tubewells with depths between 0–140 feet, 64% of tubewells contained arsenic in concentrations above the Bangladeshi permissible limit of 50 µg/L [28,29]. The main arsenic mitigation strategy for households in the study area has been to switch to neighboring low arsenic shallow tubewells, followed by switching to deep tubewells, wherever available. According to the 2014 Matlab Household Socio-economic Census, 84% of households reported procuring drinking-water from a shallow tubewell, compared to 15% of households that reported using a deep tubewell [30]. Although there has been no major arsenic testing campaign since, 32% of households reported using a shallow tubewell that was either untested or marked as unsafe during the 2002–03 campaign. Eligibility Criteria: We initially selected households who identified either a shallow or a deep tubewell as their primary drinking-water source in the 2014 Matlab Socio-economic Census and contained at least one child born on or after 31 July 2016. Follow-up interviews for those households were conducted during the baseline survey and those not satisfying the eligibility criteria were excluded. In case of absence, migration, or exclusion, we interviewed a neighboring household in the same bari. Baris are clusters of households that are arranged spatially based on patrilineal linkages. Generally, members in the same bari drink from a common tubewell. Baris that do not own a tubewell usually collect drinking-water from wells owned by a neighboring bari or a community well such as those at a mosque or school. Variables and Measurement: The outcome for the analysis is a binary variable that identifies whether a household self-reports using surface water to clean their main drinking-water storage container. Households reporting mixing of water sources such as surface water and shallow tubewell water were also quantified as users of surface water. The type of tubewell used was the exposure variable. Although it is possible that households may intermittently use different tubewell sources for drinking, most households reported primarily using one tubewell for their drinking purposes throughout. Subsequently, the tubewell type was based on the primary well from which households usually fetch their water. In the statistical analysis, we considered the ownership status of the primary drinking-water tubewell as a potential effect modifier. Ownership status indicated whether the household owned the tubewell they reported using for consumption in their bari (referred to as inside bari) or not (referred to as outside bari). Statistical Methods: The analysis for the study was conducted in R 3.6.1 using the lme4 package version 1.1-21. We measured the odds ratios of the probability of surface water use for washing storage containers based on tubewell type before and after adjusting for covariates. A multi-level logistic model was fit to the data from households with no missing data (n = 488), with the odds of surface water use, as previously defined, as the outcome of interest. Model covariates included tubewell type, tubewell ownership, household SES, mother’s education, and the interaction between tubewell type and tubewell ownership. A random intercept for each village was included to account for correlation among households from the same village. We also ran a point biserial correlation test between ownership and distance, to formally test for multi-collinearity due to distance and ownership.

Source of Information: International Journal of Environmental Research and Public Health, Published: 26 July 2020

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Our findings suggest that the potential for cross-contamination due to the cleaning of drinking-water storage containers with surface water among deep tubewell users in rural Bangladesh is substantial and needs to be considered while evaluating the health impacts of deep tubewells as part of arsenic mitigation programs. In terms of interventions to ensure safe drinking water consumption from deep tubewells, external public pathways of contamination from external sources such as surface water should be addressed in addition to domestic pathways of safe water storage and handling. We argue, however, that while separate interventions targeting these two separate pathways (domestic and public) are important, addressing distal factors such as barriers to access (distance and ownership) has the potential to simultaneously address both pathways and reduce both longer storage times and surface water use in cleaning storage containers. There is an important need to consider ownership of tubewells, in addition to distance in future studies to fully address barriers to access and its impact on health. Studies from Bangladesh and beyond, have highlighted different methods to promote safe household drinking water storage. They include the need to target the neighborhood hygiene and sanitation environment, promote education and behavioral interventions, or target separate interventions for direct and indirect pathways to reduce microbial contamination and diarrheal disease risk [57]. In addition to these interventions, policy makers and researchers should consider the complex role and potential for substantive trickle-down effects of providing increased and equitable access to deep tubewells and ensure safe drinking water quality for all. Additionally, there is a need for the development and implementation of comprehensive, but user friendly WSPs and accessible supporting tools as practical guidance for safe water management in such communities and households.

Knowledge Management: Journal