ABSTRACT
INTRODUCTION Origins and Environmental Impact of PCDDs and PCDFs Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are formed as by-products in a number of industrial processes and during combustion (Hutzinger and Fiedler, 1993; Rappe, 1993b; Fiedler, 1996). For example, PCDDs/PCDFs (Fig. 1) have been identified as contaminants in the production of chlorinated phenols and their derived products as well as other chlorinated industrial compounds. These compounds have also been detected as by-products in sewage sludge, pulp and paper mill effluents, in diverse high-temperature industrial processes, and as by-products of incineration of diverse organic materials including municipal and industrial waste, wood, and coal. The mass balance of industrial and anthropogenic inputs of PCDDs/PCDFs into the environment is unknown and depends on specific local and regional sources. Regulatory decisions in most industrialized countries have resulted in significantly decreased emissions of these compounds from many of the identified industrial sources.
