Evaluation of Alachlor Herbicide Impacts on Nile Tilapia (Oreochromis niloticus) using Biochemical Biomarkers

Abstract

Herbicide application as a part of agricultural processes may have impacts on nontarget organisms, especially aquatic lives and their environment. Often as a component of sustainable agriculture in tropical countries, fish farming is practiced on farmlands. Thus, to supplement risk assessment studies, it is important to obtain information on the effects these xenobiotics have on local species. Alachlor (2-chloro-N-[2,6-diethyphenyl]-N-[methoxymethyl)acetamide]) is one of the most widely used chloroacetanilide herbicides for the control of annual grasses and many broadleaf weeds. Its extensive use and its persistence in ground and surface water have posed potential risks for human exposure, not only to professional applicators and farmers, but also to general populations. There have been numerous studies on alachlor, but much less investigation of its effects on fish and aquatic species. Alachlor has been listed as carcinogenic and highly toxic to humans despite slight acute toxicity (Orme and Kegley, 2005). Thus, many countries have banned alachlor from their markets. The main objective of this study was to evaluate the effects of alachlor herbicides on relative activities of acetylcholinesterase (AChE) and glutathione-S-transferase (GST) in various tissues of Nile tilapia (Oreochromis niloticus). Nile tilapia, a local fish species of high economic importance, is a benthic omnivorous cichlid commonly found in fish ponds and streams of tropical countries, including Thailand. The effects of short-term contaminant exposure, measured as the biochemical and physiologic responses in Nile tilapia, may be used to assess and monitor alachlor contamination in agricultural settings.