Respirable crystalline silica exposure in agate-stone workers in Khambhat, India: a human health risk assessment using a probabilistic approach

Crystalline silica, a Group 1 carcinogen, is present in dust generated during cutting, polishing, chipping and drilling activities in cottage-scale agate units. This study quantified respirable crystalline silica (RCS) exposure amongst workers in such units in Gujarat, India, and assessed associated carcinogenic and non-carcinogenic health risks. Personal respirable dust samples of workers were collected across four distinct work areas and quantified for RCS. Associated health risks were evaluated using Monte Carlo–based probabilistic inhalation risk assessment model. The activity-specific arithmetic mean RCS concentrations ranged from 0.039 to 0.359 mg/m³, surpassing occupational exposure limits in all work areas. Average carcinogenic risk estimates exceeded the US Environmental Protection Agency (USEPA) screening benchmark in all work areas, with cutting exhibiting the highest observed mean modelled cancer risk ( n = 13), although differences in RCS concentrations between activities were largely not statistically significant. The non-carcinogenic hazard quotients in the cutting and polishing areas exceeded safety thresholds. Simulated implementation of engineering controls and respirator use reduced 95th percentile upper-bound health risks by 78% and 62.5%, respectively; however, mean cancer and non-cancer risks in these areas still exceeded reference values. Sensitivity analysis revealed that RCS concentration exerted significant influence and accounted for 61% of variance in carcinogenic risk and 82% in non-carcinogenic risk. Findings of this study highlight the urgent need for implementing effective exposure control measures amongst this informal workforce.