Risk Assessment and Protective Effect of Respirators on Airborne Paraquat Exposure during Simulated Spraying Operations

Paraquat (PQ) is widely used as a herbicide in Thailand. The aim of this study was to evaluate the health risk and protective effect of respirators during simulated PQ spraying operations in an experimental chamber. Additional data were collected from the interviews of PQ sprayers. Airborne PQ concentrations were collected from an experimental spray chamber employing controlled-rate sprayers of solutions (paraquat dichloride in water) and were lower than 50 µg/m3 (the standard regulation). Air sampling through a polytetrafluoroethylene filter membrane was performed under the conditional settings of inside and outside respirators, and analysed by using a HPLC-UV detector following NIOSH method 5003. The average PQ concentrations inside the certified respirators (cartridge, cup-shaped mask, surgical mask) were significantly lower than those outside of the respirators (4.30 ± 2.63 µg/m3 vs. 19.12 ± 16.65 µg/m3), which was not found with convenient sponge masks. Human health risk assessment on short-term and long-term exposure following US.EPA guide estimation showed that cartridge respirators and cup-shaped masks significantly decreased the risk (hazard quotient) of adverse health effects (p-value < 0.05) among the PQ sprayers. As a result, the PQ sprayers should be aware of preventive action and use a qualified mask/respirator to protect against exposure to airborne PQ and chronic health effects. HIGHLIGHTS The estimated human health risk from paraquat (PQ) exposure lower than the occupational exposure limit (OEL: 50 µg/m3) during the spraying operation was unacceptable for some sprayers The average PQ concentrations inside the certified respirators (cartridge respirator and cup-shaped mask) were significantly lower than outside of the respirators that was not seen with the convenient sponge mask, a common type used by the sprayers The cartridge respirator and cup-shaped mask significantly decreased the risk estimation of the PQ sprayers with regard to adverse health effects both from short-term and long-term PQ exposure It is important for preventive action on exposure to PQ of the sprayers by the use of qualified respirators or masks to protect against inhalation of PQ and decrease health risks GRAPHICAL ABSTRACT