From ground to home: Evidence, extent and potential controls on groundwater sourced household drinking water contamination in Bihar, India

Groundwater, a major source of available freshwater ¹, is central to meeting the drinking water needs globally ², and in the eastern Indian state of Bihar ³. Groundwater in parts of Bihar however, has elevated levels of geogenic inorganic contaminants ⁴, with more recent studies also indicating microbial contamination ⁵ and presence of antimicrobial resistance (AMR) genes ⁶ in shallow and deeper depth groundwater. However, studies investigating contamination of groundwater-derived household drinking water at the point of consumption (PoC), as compared to the point of source (PoS), are limited in Bihar. Paired water samples (n = 39) were collected from groundwater wells at the PoS, and the corresponding household drinking water containers at the PoC; and tested for arsenic (As), Escherichia coli (E. coli) and extended spectrum beta-lactamase (ESBL) producing E. coli (ESBL-Ec) - as an exemplar of inorganic chemical contaminant, microbial contaminant, and AMR indicator organism, respectively. Results indicate samples exceeding the 10 µg/L WHO provisional guideline value for As to be same (at 5 %) between PoS and PoC. However, presence of E. coli increased from 46 % to 59 % (McNemar’s p = 0.27) while that of ESBL-Ec rose from 10 % to 46 % (McNemar’s p < 0.01) between PoS and PoC samples. 74 % of the households reported collection and storage of water prior to consumption, of which 72 % reported the storage vessels to be covered, and another 69 % reporting cleaning of the container’s multiple times a day. However, more than half of the sampled households owned livestock within premises, had kids under the age of five, and just 13 % reported any kind of treatment (including boiling) being done to the groundwater prior to drinking. No improvement in water quality was observed from PoS to PoC for E. coli. On the contrary, deterioration in water quality from PoS and PoC was indicated based on ESBL-Ec (Wilcoxon signed rank test; p < 0.05). As expected of inorganic contaminants, no significant shift (at the 0.05 level) in overall concentration was observed for As between PoS and PoC. The results call for sustainable management of groundwater sources, and improvements in delivery and treatment of contaminated groundwater prior to consumption so that potable drinking water is ensured at the end-user stage.

References: [1] Weblink: https://portals.iucn.org/library/sites/library/files/documents/2016-039.pdf; [2] DOI: 10.1016/C2018-0-03156-4; [3] Weblink: https://nhm.gov.in/uhc-day/Session%202/NFHS-5%20State%20Factsheet%20Compendium_Phase-I%20%281%29.pdf; [4] DOI: 10.3390/ijerph17072500; [5] Roshan et. al., AGU 2025; [6] 10.1016/j.envpol.2024.124205. This work was supported by MR/Y016327/1 (to LAR et. al.,) and Cookson Scholarship (to AR).