Temephos, an organophosphate larvicide for residential use: a review of its toxicity

Abstract

Temephos (O,O,O',O′-tetramethyl O,O′-thiodi-p-phenylene bis(phosphorothioate)) is a larvicide belonging to the family of organophosphate pesticides used for the control of different vectors of diseases, such as dengue, Zika, chikungunya, and dracunculiasis. The aim of this review was to discuss the available published information about temephos toxicokinetics and toxicity in mammals. Temephos is quickly absorbed in the gastrointestinal tract, distributed to all organs, and then it accumulates mainly in adipose tissue. It is metabolized by S-oxidation, oxidative desulfuration, and hydrolysis reactions, with the possible participation of cytochrome P450 (CYP). Temephos is mainly eliminated by feces, whereas some of its metabolites are eliminated by urine. The World Health Organization classifies it as class III: slightly dangerous with a NOAEL (no-observed adverse effect level) of 2.3 mg/kg/day for up to 90 days in rats, based on brain acetylcholinesterase (AChE) inhibition. A LOAEL (lowest observable adverse effect level) of 100 mg/kg/day for up to 44 days in rats was proposed based on cholinergic symptoms. However, some studies have shown that temephos causes toxic effects in mammals. The inhibition of the enzyme acetylcholinesterase (AChE) is one of its main demonstrated effects; however, this larvicide has also shown genotoxic effects and some adverse effects on male reproduction and fertility, as well as liver damage, even at low doses. We performed an extensive review through several databases of the literature about temephos toxicokinetics, and we recommend to revisit current assessment of temephos with the new available data.

Keywords:

• Temephos
• organophosphate pesticides
• disease vectors
• larvicides
• pesticide toxicity

Acknowledgments

The authors want to thank Dr. Isabel Hernández-Ochoa from the Department of Toxicology and Dr. Enrique Othon Hernández-González from the Department of Cell Biology at Cinvestav for their critical revision of the document. The authors are grateful to the anonymous reviewers who kindly reviewed the document, their valuable comments improved the quality of this paper. JPMM had a scholarship from The Consejo Nacional de Ciencia y Tecnología-México (CONACYT).

Declaration of interest

The authors’ affiliations are academic public institutions in Mexico, the Center for Research and Advanced Studies from the National Polytechnic Institute (Cinvestav) and the Autonomous University of Nayarit. All authors belong to the Pesticide Toxicology Network in Mexico, who have identified the need to study the toxicity of this widely used larvicide as well as other pesticides. Each author participated in the search of literature, review process and preparation of this paper and gave the final approval. The authors declare that there are no conflicts of interest to declare. No funding was received to assist the preparation of this manuscript.