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Chlorodioxins in Pesticides, Soils, and Plants

ABSTRACT

Chlorodioxins, such as 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), are highly toxic impurities found in certain pesticides. A review is made of (i) the sources and toxicology of TCDD and its relationship to the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), and (ii) pesticide analyses and soil-related environmental studies of TCDD conducted by the U. S. Department of Agriculture. TCDD was persistent and immobile in soils. The dioxin was not detected, however, 6 years after abnormally high applications of 2,4,5-T to Lakeland sand. TCDD was not photodegraded on soil and only slightly, in aqueous suspension. Plants grown in soil containing 0.06 ppm TCDD had no detectable quantity ( 1 ppb) at maturity. It was not translocated when applied to leaves, but wash-off or volatilization occurred. TCDD was undetected (< 50 ppb) in 19 bald eagle (Haliaeetus leucocephalus) carcasses.

Key Words: 2,4,7,8-tetrachlorodibenzo-p-dioxin • 2,4,5-T • herbicides • soil-pesticide relationships • environmental contamination

² Soil Scientist, Plant Physiologist, Chemist, Agricultural Research Technician, Chemist, Chemist, and Investigations Leader, Agricultural Environmental Quality Inst., ARS, USDA, Beltsville, Md. 20705.

Received for publication June 7, 1972.