Molybdenum accumulation in wastewater-ırrigated rice and human exposure risks

This study evaluated Molybdenum (Mo) accumulation and potential health risks associated with four rice varieties (Super Kernel, Kainat, Basmati, and Irri 6) irrigated with tube well water (T1) and mixed wastewater (T2). Rice and irrigation water samples were analyzed for Mo concentrations by flame atomic absorption spectrophotometry (AAS). Mo concentrations varied by variety and irrigation water source, increasing from 0.014 mg/kg under T1 to 0.0274 mg/kg under T2, while Kainat accumulated the lowest levels under both treatments. Molybdenum concentrations in rice grains remained low, ranging from 0.00073 to 0.012 mg/kg. Enrichment and transfer indices were consistently low, reflecting weak Mo enrichment and mobility within the soil-plant system. Serum Mo concentrations varied among age groups, ranging from 0.00162 to 0.01433 mg/L, with relatively higher values observed under mixed-water irrigation. The health risk assessment showed that the Target Hazard Quotient (THQ) for all age groups was below 1, with a maximum THQ of 0.00572, indicating no appreciable non-carcinogenic health risk associated with rice consumption. Although mixed-water irrigation resulted in higher Mo concentrations and THQ values, these differences represent increased estimated exposure rather than confirmed adverse health effects, supporting routine monitoring rather than implying chronic exposure risk.