Increasing international concern is being expressed regarding the contamination of the environment with polychlorinated dibenzo-p- dioxins (PCDDs) and polychlorinated dibenzofurans because certain of these chemicals have been shown to be highly toxic to animals and are ubiquitous in the environment. They are known to be distributed as contaminants of commercial products and as by-products from com- bustion processes. A considerable volume of information has accumulated on these chemicals in the past two decades, particularly for the most toxic of them, 2,3,7,8-tetrach1orodibenzo-p-dioxin...