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Abstract Paraquat (1,1′-dimethyl-4,4′-dipyridinium chloride), also known as methyl viologen, is frequently used as a quaternary ammonium herbicide (broadleaf weed killer) around the world due to its excellent effect within plant cells in crop protection and horticultural use. However, it has caused many cases of human poisoning, with the lungs being the primary targeted organ. Recently, an investigation on paraquat toxicity has revealed that it might be an environmental factor contributing to the Parkinson's disease in humans. From the ecotoxicology, human health, and regulatory aspects, it is essential to restrict the emissions and release of the highly acutely toxic chemical from the industrial processes and agricultural applications. This article reviews paraquat in the current literature in terms of physicochemical properties, agricultural/commercial uses, residual contribution in the aqueous environment, possible human exposure, and toxicity, as well as its exposure standards and safety limits. Emphasis was put on the most significant distribution in the aquatic environment, occupational, and non-occupational human exposures. Comprehensively, it is strongly convincing that paraquat is not a carcinogenic, and is rapidly excreted through the urinary system during normal spraying. Keywords: paraquatenvironmental propertyresidual contributionexposure riskhealth hazard Notes aThreshold limit value (ACGIH Citation2009). The critical effect of paraquat is lung damage on a TLV basis. bPermissible exposure limit (OSHA Citation2012). cRecommended exposure limit (NIOSH Citation2012b). dImmediately Dangerous to Life or Health (NIOSH Citation2012a). eMaximum allowable concentration (DFG Citation2002; Lewis Citation2004). fPermissible Concentration Standard (Council of Labor Affairs, Taiwan). gListed as one of respirable dusts and skin-sensitive chemicals.
Wen‐Tien Tsai (Tue,) studied this question.