Assessment of human health risk and fluoride contamination in the arid coastal aquifer, Saudi Arabia

A systematic study was performed to explore human health risks for the local populace due to fluoride contamination in the arid coastal aquifer, Saudi Arabia using fluoride contamination zone mapping, contamination index (Cd), chronic daily intake (CDI), and hazard quotient (HQ) calculations. The groundwater (n = 52) in the study region is neutral to alkaline, brackish to saline and very hard in nature. Groundwater in 27% of wells surpassed the drinking water fluoride level (F > 1.5 mg/l) recommended by the WHO and has Cd > 0, which is unpalatable for drinking. Groundwater chemistry in the study area is predominantly influenced by evaporation processes and high fluoride groundwater belongs to the NaCl type. During evaporation, precipitation of carbonate minerals triggered the dissolution of fluoride minerals; consequently, groundwater is enriched with fluoride and salinity. Adverse health effects, calculated using CDIoral and HQoral, suggested that 23% and 33% of samples show a non-carcinogenic threat to adults and children, respectively. The fluoride contamination zone mapping and the spatial distribution of Cd values and HQoral substantiated that groundwater in the downstream region is degraded due to higher fluoride content, which can cause a health threat to human beings. In the study area, evaporation along with mineral weathering resulted in fluoride enrichment in the groundwater. Thus, proper treatment is required to remove the fluoride and salinity from the groundwater before use. The outcome of this study can help local municipalities and water management authorities for planning.