Chronic dietary exposure and arsenic availability in tea agro-ecosystems: Insights from free ion activity model and sobol sensitivity analysis

This study aimed to evaluate the potential health hazards allied with arsenic (As) pollution in tea-growing ecosystems, including groundwater, soil, and two types of tea leaves (mature leaves and leaves with a bud), in Assam, India. Samples were collected from two major tea-growing sites: Site 1 (Jorhat) and Site 2 (Sivasagar). Mean As concentrations in groundwater, soil, two leaf and a bud, and mature tea leaf at sites 1 and 2 were 0.087 and 0.072 mg/L, 0.19 and 0.12 mg/kg, 0.63 and 0.51 mg/kg, and 0.77 and 0.66 mg/kg, respectively. Soil physicochemical investigation indicated acidic conditions (pH 4.7-5.2) and varied organic carbon levels affected As solubility and absorption. Geochemical indices (Single Pollution Index: SPI, Enrichment Factor: EF, and Geo-accumulation Index: Igeo) revealed moderate to high contamination at Site 1. The Free Ion Activity Model (FIAM) and Self-Organizing Map (SOM) analysis validated that soil organic C (OC) and pH were key determinants of As translocation from soil to tea leaves. Spatial mapping (Geographic Information System: GIS) further elucidated site-specific As accumulation patterns. Human health risk evaluation found ingestion as predominant exposure route, with children demonstrating greater vulnerability. Despite hazard index (HI < 1) and cancer risk (CR < 10^-4) levels being below critical thresholds, extended exposure may result in chronic health consequences. Sobol sensitivity analysis (SSA) highlighted that exposure-related factors play a critical role in arsenic-associated carcinogenic risk, emphasizing the importance of reducing human exposure through improved environmental management and monitoring strategies. Results emphasize that despite moderate As contamination, sustained monitoring and soil-water management interventions are essential to minimize exposure and ensure safe tea production in Assam's tea-growing regions.