Anthropogenic influence on groundwater metal toxicity and risk to human health assessment in Umaria coalfield of Madhya Pradesh, India

Metal toxicity in groundwater surrounding coal mines is a major concern because it may pose a significant risk to human health of the local populace. The present study investigated Al, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, Sr, and Zn concentrations in the groundwater of Umaria coalfields during the post-monsoon season and pre-monsoon season. The study was carried out to investigate the spatial and temporal variation of the metals in the groundwater along with statistical source identification of the metals and assessment of human health risks due to intake of the metals through the groundwater. The metals of concern were Al, Fe and Mn, which exceeded the Indian drinking water quality standards in 26%, 38% and 12% of samples in the post-monsoon season and 38%, 40% and 14% of samples in the pre-monsoon season. A marked decrease in metal concentrations in the post-monsoon season was also observed, which may be attributed to the dilution effect associated with the heavy rainfall during the monsoon season. Principal component analysis used to identify contamination sources of the metals indicated geogenic attributes, coal mining activities and vehicular load as the sources of the metals in the groundwater. The human health risk assessment suggested considerable risk to the local populace using the groundwater for drinking purposes. The probable health risk, as suggested by the Hazard Index, depicted a higher risk to the child population as opposed to the adults. The Hazard Index for the child population was greater than unity in 60% and 76% of the samples in the post- and pre-monsoon seasons, respectively, suggesting a significant risk of metal exposure from groundwater intake. The study also suggested that ingestion was the primary exposure pathway and risk due to dermal exposure was trivial. The carcinogenic risk due to As and Cr were within the acceptable limits except for one location each for As and Cr. The present study suggests a potential non-carcinogenic human health risk due to groundwater intake; hence, the study area needs routine groundwater quality monitoring.