Studies related to the chemistry and environmental persistence of methoxychlor and its derivatives

Abstract

An Investigation of some of the chemical and biological factors Influencing the environmental fate of methoxychlor ( 1 , 1, 1-trichloro-2,2-bis (p-methoxyphenyl) ethane) has been conducted. Methoxychlor is an organochlorine insecticide which is used extensively in Canada and has been proposed as a potential DDT replacement. It has been reported in the literature that methoxychlor exhibits a low toxicity towards most mammals and is also partially degraded by these organisms. Although much information exists on the interaction of this insecticide with higher animals, less information is available on the interaction between this compound and organisms at lower tropic levels, especially the microorganisms. Methoxychlor, because of its use as a larviclde in and around natural water systems, has the potential to interact directly with nontarget aquatic biota. Therefore an investigation concerning the interaction between methoxychlor and aquatic microorganisms was initiated. The microorganisms chosen for this study were common species of green algae, Chlorella pyrenoidosa and Chlorella vulgaris. The biological effects of methoxychlor have been studied in vitro using axenic cultures of the test algae . Known metabolites and derivatives of methoxychlor required for this study were synthesized. The extensive modification of the literature methods for the preparation of these compounds has resulted in improved yields and purer products for virtually all compounds synthesized. The synthesis of 1-monochloro-2,2-bis (p-hydroxyphenyl) ethylene, a known methoxychlor metabolite, has been developed and almost completed. The synthesis of this compound has not been reported in the literature before. The product of the previously reported base-promoted rearrangement of 1,1-dichloro-2,2-bis (p-hydroxyphenyl) ethane has been identified and a mechanism for its formation postulated. Also, to aid in the selection of solvents used for the extraction of the polar metabolites of methoxychlor from aqueous samples, the p-values (ie. extractability) and solubilities (in water and organic solvents) of these compounds have been determined. The toxicity of methoxychlor and hydroxychlor (1,1,1- trichloro-2,2-bis(p-hydroxyphenyl)ethane) towards both species of algae was assessed. Although both species are tolerant of relatively high concentrations of these compounds, the hydroxy analogue was much more toxic than the parent insecticide. Growth rate studies revealed that both methoxychlor and hydroxychlor had little effect on the overall growth of Chlorella pyrenoidosa, The growth of Chlorella vulgaris was however, significantly depressed by methoxychlor, while on the other hand hydroxychlor stimulated the growth of this alga. Recovery experiments indicated that the uptake of methoxychlor and hydroxychlor by Chlorella pyrenoidosa is mainly due to physical adsorption. In the case of Chlorella vulgaris very little of the added methoxychlor could be recovered. Recovery experiments conducted with Chlorella vulgaris and hydroxychlor suggest that at least some of this compound is reductively dechlorinated by this organism.