By Adeline Lopez
Researchers funded by the NIH Fogarty International Center (FIC) recently identified climate change and land use as two key factors compromising groundwater quality in Bangladesh. Their findings highlight the need for new technologies and policies to adapt to and mitigate these forces to protect human health.
The research team, led by principal investigator and former NIEHS grantee Michael Emch, Ph.D., from the University of North Carolina at Chapel Hill (UNC), Jianyong Wu, Ph.D., also from UNC, and collaborators at the International Centre for Diarrhoeal Disease Research in Bangladesh, found that weather extremes and land use practices associated with urbanization promote fecal contamination in shallow groundwater tubewells. The synergistic effects between climate and urbanization make this particularly relevant for areas like Bangladesh that are both susceptible to climate change and experiencing increased urbanization.
According to the World Health Organization, 1.8 billion people around the globe use drinking water sources that are contaminated with feces, leading to over 500,000 deaths from diarrheal disease annually – predominantly in low- and middle-income countries. In Bangladesh, where high population density, frequent flooding, and poor sanitation threaten surface water supply, diarrheal diseases are the largest cause of death among children under the age of 5, and account for 20% of all infant deaths.
To address this health problem, Bangladesh has spent the last 30 years shifting the source of drinking water from contaminated surface water to groundwater, which was assumed to be protected from fecal contamination. However, as evidenced by this study, groundwater quality is threatened by global environmental change.
Bangladesh is recognized as being particularly vulnerable to climate change, and extreme wet weather events in particular. “Frequent heavy rainfall and floods are expected to have a devastating impact on water quality and human health. Rainfall can exacerbate fecal contamination in water bodies and transport microbes from contaminated areas to uncontaminated areas. Heavy rain can also flush pathogens from latrines or other sources into water bodies and increase the transportation and infiltration of these contaminants into groundwater,” said Wu.
In addition to impacts on groundwater quality from climate, the population of Bangladesh is also increasing rapidly, putting greater strain on the existing resources and infrastructure. In response to this, land use decisions associated with conversion of rural areas into developed areas (i.e., urban, industrial, and agricultural land use) have increased. Wu noted that urbanization may have significant negative impacts on water quality, “A larger percentage of developed land around a tubewell suggests a larger population density and a larger number of latrines around the tubewell. In rural Bangladesh, latrine-polluted ponds are significant sources of contamination for shallow groundwater tubewells.”
Wu and his colleagues are the first to evaluate the impact of fecal contamination in groundwater, and also the first to investigate the combined effect of land use and extreme weather resulting from climate change on bacteria loads in shallow groundwater tubewells in Bangladesh. The study,published in Environmental Science and Technology, showed that the presence of Escherichia coli (E. coli) was significantly correlated with both the number of heavy rain days and with the number of hot days recorded prior to sample collection. E. coli presence was also positively associated with the percentage of developed land area. Interestingly, his team found a synergistic effect on E. coli when extreme weather and developed land use were combined.
“Our findings suggest that climate change and urbanization in Bangladesh might enhance the likelihood of fecal contamination of shallow tubewells, thus increasing the risk of diarrheal diseases. It is expected that climate change and land use change will have adverse effects on drinking water quality in many other countries in Southeast Asia, Africa, and South America, where diarrheal disease is also a severe public health issue,” said Wu.
Their findings have important implications for identifying reliable safe drinking water resources and reducing the risk of microbial contamination in regions like Bangladesh that are both vulnerable to climate change and experiencing rapid urbanization. Moving forward the team will expand their work to investigate further how climate change and land use are directly linked to disease outcomes like diarrheal diseases in Bangladesh. They will also explore if using deep groundwater rather than shallow groundwater tubewells is a suitable adaptation measure to provide millions with safe, clean drinking water.
Wu J, Yunus M, Islam MS, Emch M. 2016. Influence of climate extremes and land use on fecal contamination of shallow tubewells in Bangladesh. Environ Sci Technol 50(5):2669-76. doi: 10.1021/acs.est.5b05193.