Analysis of the Time-Dependent Acute Aquatic Toxicity of Organophosphorus Pesticides: The Critical Target Occupation Model

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• 作者：Karin C. H. M. Legierse ; Henk J. M. Verhaar ; Wouter H. J. Vaes ; Jack H. M. De Bruijn ; and Joop L. M. Hermens
• 刊名：Environmental Science & Technology
• 出版年：1999
• 出版时间：March 15, 1999
• 年：1999
• 卷：33
• 期：6
• 页码：917 - 925
• 全文大小：174K
• 年卷期：v.33,no.6(March 15, 1999)
• ISSN：1520-5851

文摘

A model is presented for the acute toxicity of organophosphorus (OP) pesticides belonging to the class ofphosphorothionates. The acute toxicity of these pesticidesis governed by the irreversible inhibition of the enzymeacetylcholinesterase (AChE), after their metabolic activationto oxon analogues. The model is based on the idea that,for chemicals exhibiting an irreversible receptor interaction,mortality is associated with a critical amount of "covalentlyoccupied" target sites, i.e., the "critical target occupation"(CTO). For a given compound and species, this CTO isassociated with a critical time-integrated concentration ofthe oxon analogue in the target tissue, which can bemodeled by the critical area under the curve (CAUC) thatdescribes the time-concentration course of the phosphorothionate in the aqueous phase or in the entire aquaticorganism. In contrast to the classical critical bodyresidue (CBR) model, the CTO model successfully describesthe 1-14-d LC₅₀(t) data of several phosphorothionates inthe pond snail and guppy. Furthermore, the time dependencyof lethal body burdens (LBBs) of phosphorothionates isexplained by the model. Although the CTO model is specificallyderived for OP pesticides, it can be applied to analyzethe acute toxicity and to estimate incipient LC₅₀ values oforganic chemicals that exert an irreversible receptorinteraction in general.