Highly hazardous pesticides in Nayarit, Mexico: a retrospective review

Abstract

According to the Food and Agriculture Organization of the United Nations (FAO), Mexico uses more than a quarter of Central America's agricultural pesticides. Furthermore, Mexican regulatory agencies still do not recognize the classification of highly hazardous pesticides (HHP) under the Regulations on Registrations, Import and Export Authorizations, and Export Certificates for Pesticides, Plant Nutrients, and Toxic or Hazardous Substances and Materials (PLAFEST) regulation; no explicit national HHP definition exists. The aim of this review was to identify active ingredients (a.i.) historically used in Nayarit that are classified as HHP by internationally accepted classification systems and highlight the differences between them. Seven bibliographic resources, identified through a literature search conducted between October 2024 and July 2025, reported the pesticide sales or use patterns in Nayarit between 1987 and 2021. One hundred and twenty-five different a.i. were observed, of which 44 (35.2%) are HHP according to criteria defined by the FAO and the World Health Organization (WHO). In comparison, 82 (65.6%) are HHP according to the Pesticide Action Network International (PAN). Although most pyrethroids are highly toxic to bees, most of them are not recognized as HHP by FAO/WHO. Organophosphorus and carbamates are the main chemical families of HHP used in Nayarit. Glyphosate, an individual a.i. rather than a chemical family, was also identified as HHP. Dicofol, an organochlorine listed in Annex A of the Stockholm Convention for the global elimination of its use, was reported in retailer sales records. This review demonstrates the differences in the selection of HHP at a state-level assessment revealing that the criteria proposed by PAN allow the inclusion of a greater number of pesticides, in terms of their environmental effects, and a broader understanding of the presence of multiple HHP identified across the available evidence, indicating the potential for mixed pesticide exposure. We consider that a transparent and nationally adopted HHP identification framework is the first step to develop risk prevention strategies and promotion of sustainable alternatives.