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Explore the compound structure, production history, uses, and toxic effects of Methoxychlor in aquatic environments. Understand its physical and chemical properties, mode of entry into water systems, biochemical metabolism, and defense mechanisms in animals.
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Methoxychlor Aquatic ToxicologySpring 2011Karen Chow
Methoxychlor • Compound structure • Production history • Uses and Application • Physical Properties • Chemical Properties • Physical half-life • Mode of entry to aquatic environment • Biochemical metabolism • Toxic effect • Defense mechanisms for animals
Production History • Replacement for DDT DDT Methoxychlor
Production History • Synthesized in 1893 • 1948: Registered as a pesticide • Formulated as wettable powders, dusts, ready-to-use products, pressurized liquids • Suspended in 2000Methoxychlor is not eligible for re-registration all registered technical source of methoxychlor were cancelled in 2003, all tolerances have been revoked. • It is not necessary to assess the risks of methoxychlor products because there are no tolerances for methoxychlor
Uses and Application • Used to kill cockroaches, mosquitoes, flies, arthropods • Found on field crops, vegetables, fruits, ornamentals, stored grain, livestock, domestic pets.
Physical Property • Melecular weight: 345.65 g/mol • Color: pale yellow • Odor: slightly fruity; musty; chlorine-like • Physical state: Crystalline solid • Melting point: 89oC • Density: 1.41g/cm2
Chemical Properties • Organic solvents: soluble in chlorinated aromatic solvents, ketonic solvents, ethanol, methylene chloride, methlated naphalene, carbon tetrachloride, chloroform, xylene, methanol, petroleum ether, benzene • Chemical reactivity with water: soluable • Solubility in water:
Physical Half-life • In soil: ~120 days • Distilled water: 130days • Natural water: 2-5 hours • In atmosphere: 7 hours • When degraded in water: 1 year • Within some organisms: less than 2 weeks
Mode of Entry to Aquatic Environment • Released to air settles to the ground • Sticks strongly to particles in soil • Runoff from soil that contains methoxychlor • Industrial sewage • Leaks at storage and waste sites • Can be released directly to surface water on farm as a pesticide • Harp seals had detectable concentration of methoxychlor in various tissue. (Zitko 1998)
What happens when it enters the environment? • Does not dissolve in water easily • In water: Binds to sediments and settles to the bottom • Breaks down slowly in air, water, soil by sunlight and microscopic organisms • Harmful breakdown products of methoxychlor
Biochemical metabolism • Breakdown in water and sediment: Methoxychlor degraded to dechlorinated, dehydrochlorinated, and demethylated products by chemical, photochemical, and biological processes. • Rapidly metabolized to phenolic derivatives • In animals: methoxychlor is rapidly metabolized and eliminated
Toxicity to aquatic life • Toxic for aquatic animal by ingestion, contact with skin • For freshwater invertebrate: 0.0005 mg/L • For Marine birds: non toxic (LD50 >2000 mg/kg)
Toxic effect • Affect the hypothalamic-pituitary-gonadal axis • Developmental effect • Thyroid toxic effect • Irritate skin, eyes, • Affect human nervous system • Group D carcinogen • Group 3 carcinogen • 1978: NCI concluded Insufficient evidence to classify as a carcinogen
Defense mechanism for organisms • Antibodies is important to the defense strategy of the organisms. • Integration in number of cells that produce antibody • Methoxychlor undergoes oxidative metabolism by cytochromes P450, yielding 1,1,1-trichloro-2-(4-hydroxyphenyl)-2-(4-methoxyphenyl)ethane (mono-OH-M) and 1,1,1-trichloro-2,2-bis(4-hydroxyphenyl)ethane (bis-OH-M) as main metabolites.
References • ATSDR. 2002. Methoxychlor CAS #72-43-5. Toxicological Profile for Methoxychlor. U.S. Department of Health and Human Service, Public Health Service. • ATSDR. 2009. Addendum to the toxicological profile for methoxychlor. U.S. Department of Health and Human Service, Public Health Service. • EPA. 2000. Toxicological Reviewfor Chloral hydrate (CAS No. 302-17-0). U.S. Washington, DC: Environmental Protection Agency. • Gray, L.E. Jr., J. Ostby, J. Ferrell et al. 1989. A dose- response analysis of methoxychlor-induced alterations of reproductive development and function in the rat. Fund. Appl. Toxicol. 12(1): 92- 108. • Goldman, J.M., R.L. Cooper, G.L. Rehnberg, J.F. Hein, W.K. McElroy, and L.E. Gray Jr. 1986. Effects of low subchronic doses of methoxychlor on the rat hypothalamic-pituitary reproductive axis. Toxicol. Appl. Pharmacol. 86(3): 474-483.
References • Kapoor IP, Metcalf RL, Nystrom RF, et al. 1970. Comparative metabolism of methoxychlor, methiochlor and DDT in mouse, insects, and in a model ecosystem. J Agric Food Chem 18:1145-1152. • Kupfer, D. and W.H. Bulger. 1987. Metabolic activation of pesticides with proestrogenic activity. Fed. Proc. 46(5): 1864-1869. 6. Ware, G.W. 1982. Fundamentals of Pesticides, Thompson Publications. • Shea, D. Transport and fate of toxicants in the environment. New York: Academic Press, 1994 • Stoltz RL, Pollock GA. 1982. Methoxychlor residues in treated irrigation canal water in Southcentral • Idaho. Bull Environ ContamToxicol 28:473–476. • Zitko V, Stenson G, Hellou J. 1998. Levels of organochlorine and polycyclic aromatic compounds in harp seal beaters (Phocagroenlandica). Sci Total Environ 221:11-29.
