Herbicides PCDD contamination

PCDDs have been released into the environment in a number of different ways. Sometimes this has been due to the use of a pesticide that is contaminated with them. 2,4,5-T and related phenoxyalkanoic herbicides have been contaminated with them as a consequence of the interaction of chlorophenols used in the manufacturing... 

Polychlorinated dibenzo-p-dioxins, or PCDDs, are highly toxic substances that are present in trace amounts as byproducts of some chemical manufacturing processes. They have been implicated in a number of environmental incidents—for example, the chemical contamination at Love Canal and the herbicide spraying in Vietnam. The structure of dibenzo-p-dioxin, along with the customary numbering convention, is... 

In many industrialized countries the use of products contaminated by PCDDs and PCDFs is nowadays highly reduced. For instance 2,U,5-T, earlier a major herbicide in most countries, is now only produced and used in New Zealand and PCB is being phased out as dielectric fluid in transformers and capacitors in most countries during the 1980 s. 

We have used the human tissue levels of PCDDs and PCDFs in the north of Vietnam as a reference value, believing that this area has had little environmental contamination from synthetic, industrial, and agricultural chemicals. The United States, Canada, and Europe represent highly industrialized areas with a substantial use, disposal, and combustion of a variety of synthetic, especially halogenated chemicals. The south of Vietnam, because of the herbicides used for military purposes during the 1960 s and 1970 s, has had a significant contamination with 2,3,7,8-TCDD as well as other PCDD and PCDF isomers. 

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