Do the Health Benefits of Boiling Drinking Water Outweigh the Associated Impacts of Increased Household Air Pollution Exposure?

Abstract:

Globally, 1 billion people lack access to safe drinking water, contributing to 1.7 million deaths annually due to unsafe water, sanitation, and hygiene. Boiling unsafe drinking water is a common treatment method in low-income settings. However, 2.8 billion people globally cook and heat using solid fuels, resulting in 2.6 million deaths annually from illnesses related to poor air quality. Many of the countries with high solid fuel use also have limited access to safe drinking water. This study bridges the areas of water quality and indoor air pollution (IAP) by conducting a Monte Carlo simulation to quantify the health trade-offs from boiling drinking water with solid fuels, focusing on Malawi. Pre and post-boiling microbiological water quality of improved and unimproved sources were characterized by E. coli concentrations. 24-hour indoor fine particulate matter (PM_2.5) exposure and daily doses of E. coli were modeled for boiling water at different daily frequencies, quantities, and temperatures, using both clean and dirty fuels, to calculate the total change in disability adjusted life years (DALYs) and deaths from IAP and drinking water. Time dependent recontamination after boiling was also modeled. Continually boiling water right before consumption had the lowest recontamination but correspondingly increased the IAP due to high emissions during ignition. Preliminary results showed that boiling water daily using wood caused on average a 30% increase in 24-hour PM_2.5 concentrations causing an additional 326 DALYs and 9 deaths per 25000 people per year. For households with very high IAP, boiling water has a limited increased risk due to the log-linear nature of the relative risk curve. For different boiling scenarios and source water quality, average reductions of DALYs and deaths from diarrhea both ranged from 0 to 3300 per 25000 people per year. In some scenarios, post-treatment water quality was worse than the source water quality due to recontamination, resulting in increased PM_2.5 exposure with little to no benefit. This study emphasizes the need for education on proper boiling and water storage practices, cleaner methods of boiling water, alternative treatment methods, and investigation of trade-offs between health impacts/benefits and costs for different scenarios of water treatment.