Modeling of gaseous pollutant emissions following a battery failure event: occupational exposure estimation for a mining scenario

The present study describes the implementation of a probabilistic Near-Field/Far-Field model based on the “Two-Box Model with a constant emission rate”, applied for the characterization of a selected scenario. The aim was to describe the chemical agents (i.e., HF, HCl, H2SO4 , Al, Ni) potentially emitted after a severe failure (i.e., thermal runaway event) of a Sodium/Metal Chloride battery during service in a simulated mining scenario. Risk management procedures are expected to be already implemented in the considered scenario; nevertheless, the use of a probabilistic approach for risk assessment indicated the presence of a certain level of risk in those scenarios (which could be however reduced by further implementing risk management procedures). More in detail, considering hazard quotients (HQ) calculated based on the far-field 95th percentile of estimated concentrations, the predicted exposure risk can be considered well-controlled in all the selected scenario, since all the HQ values calculated for the considered pollutants are stably below 0.1 of the respective OELV (both 8-h-TWA and 15-min -TWA OELVs), as well as the resulting Hazard Index (HI) for cumulative exposure. On the contrary, when considering near-field estimated exposures, HQ values for Ni and HCl are above 0.1 (estimated exposure above 1/10 of the OELV) and 1 (estimated exposure above the OELV), respectively, thus indicating that the predicted exposure risk cannot be considered well-controlled in all considered scenarios for both Ni and HCl. Estimated near-field concentrations of HF, H2 SO4 and Al resulted in HQ below 0.1, thus the predicted exposure risk can be considered well-controlled in all the considered scenario for these pollutants.