Chemistry, Environmental Fate, Toxicological Implications, and Sustainable Management of Pesticides and Herbicides in Commercial Agriculture in Nigeria: A Review

Abstract

Pesticides and herbicides play a critical role in commercial agriculture by enhancing crop productivity, reducing pest- and weed-related losses, and supporting food security. In Nigeria, increasing agricultural intensification has led to widespread use of diverse agrochemical classes, including organophosphates, carbamates, pyrethroids, organochlorines, neonicotinoids, glyphosate, atrazine, and 2,4-dichlorophenoxyacetic acid (2,4-D). This review examines the chemistry of these agrochemicals, with emphasis on their molecular structures, physicochemical properties, mechanisms of action, environmental behaviour, residue dynamics, toxicological effects, and management challenges within Nigerian agricultural systems. The biological activity of pesticides and herbicides is fundamentally determined by specific chemical interactions with enzymes, receptors, ion channels, and metabolic pathways, while their environmental fate is influenced by hydrolysis, photolysis, oxidation–reduction reactions, sorption, volatilisation, leaching, and runoff processes. Evidence from Nigerian agricultural regions indicates intensive agrochemical application in vegetable production systems, irrigated farming areas, and cocoa plantations, often resulting in detectable residues in soils, water bodies, and agricultural commodities. Analytical chemistry techniques such as gas chromatography–mass spectrometry (GC–MS), liquid chromatography–tandem mass spectrometry (LC–MS/MS), and QuEChERS-based extraction methods have significantly improved residue detection and monitoring capabilities, although analytical infrastructure and surveillance systems remain inadequate in many parts of the country. Human exposure occurs primarily through dermal contact, inhalation, and dietary intake, with toxicological consequences including cholinesterase inhibition, oxidative stress, endocrine disruption, neurological impairment, and developmental toxicity. Persistent challenges such as weak regulatory enforcement, counterfeit pesticide circulation, poor storage practices, limited farmer training, low adoption of Integrated Pest Management (IPM), and insufficient residue monitoring continue to compromise sustainable agrochemical use. Future directions should focus on expanding IPM implementation, developing biopesticides, adopting precision agriculture technologies, strengthening regulatory frameworks, enhancing analytical chemistry capacity, and improving public health education. A comprehensive understanding of agrochemical chemistry is essential for balancing agricultural productivity with environmental protection and human health, thereby promoting sustainable agricultural development in Nigeria.