KINETIC STUDY OF THE PHOTOCHEMICAL PERSISTENCE OF THE LARVICIDES TEMEPHOS AND N-TOSYLINDOL

• Grant number: 24/12649-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2024
• End date: August 31, 2025
• Field of knowledge: Engineering - Chemical Engineering
• Principal Investigator: Antonio Carlos Silva Costa Teixeira
• Grantee: Amanda Velho Guimarães
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

On the world stage, mosquito-borne diseases, in particular dengue fever, represent a major public health issue today and are mainly spread by Aedes aegypti, whose larval development takes place in aquatic environments. In view of the still limited vaccine prophylaxis coverage for the disease, it is understood that the ideal control measure available is larval elimination. Thus, the use of larvicides, such as the commercial product temephos, appears to be the most efficient containment option. In turn, larvicides based on N-tosylindol have been presented as an innovative alternative for control, considering the evidence of resistance of A. aegypit larvae to commercial products. It should be emphasized that an effective larvicide is based on the balance between its sufficient environmental persistence to act against the larvae and its possible damage to aquatic ecosystems and human health in the long term, if not degraded. In this context, the aim of this project is to study the photo-oxidative degradation kinetics of the larvicides temephos and N-tosylindol in aqueous media under simulated sunlight, as a result of photolytic processes and reactions mediated by photoproduced reactive intermediates-PPRI (HO*, 3CDOM*, 1O2). We hope to obtain fundamental kinetic parameters (direct photolysis quantum yield, second-order kinetic rate constants of the reactions of larvicides with PPRI), as well as elucidate the role of each reactive intermediate in the degradation of target compounds and evaluate the effect of different aqueous matrices. The results obtained will allow us to understand whether the photochemical persistence of larvicides in surface water (assessed from their half-lives) is sufficient to combat mosquito larvae, as well as generating information to help assess their potential environmental risks.