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Case Study in Environmental Chemistry....
Case Study 3: Photolysis of Terbufos
Authors: Sarunya Hengpraprom and Cindy Lee, Environmental Engineering and Science, Clemson University.
Abstract : This case study considers the rate at which exposure to sunlight can transform a pesticide known as terbufos. Transformation of a contaminant by photolysis will change its behavior in a given situation. In some cases, a product of photolysis is just as toxic or more toxic than the parent compound. In other cases, the products of photolysis are rendered nontoxic and the transformation can be considered beneficial. The experiment described in this case study produced some of the first basic kinetics data available to evaluate the importance of photolysis as a process to remove terbufos from the environment. For more detailed information about this research, see Lee, C. M.; Anderson, B.; and Elzerman, A. W. 1999. Photochemical oxidation of terbufos. Environmental Toxicology and Chemistry. 18(7):1349-1353.
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Why is Terbufos a Problem?
Terbufos is of environmental concern because it is extremely toxic to fish and aquatic invertebrates (4). The acute lethal concentration 50 (LC50) of terbufos to particular species of aquatic organisms ranges from 0.77 to 20 mg/L ( see Table 1). Terbufos is also expected to be toxic to mammals and reptiles (also see Table 1) (4); however, it is nontoxic to bees. Toxicity of this compound in general is based on its ability to inhibit the enzyme cholinesterase, a chemical vital to the normal function of the nervous system of living organisms ( 5). More details of terbufos toxicity are presented elsewhere (6, 7 ).