Open burning as a source of dioxins

This review critically collates data on the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like biphenyls (dl-PCBs), or in brief dioxins from a wide range of open burning sources. Open burning started raising attention in the nineties and has then been identified as one of the major global sources of dioxins, especially since evident guided emissions-principally from waste incineration and metallurgy-have been drastically curtailed. During combustion, dioxin emissions appear related to the proximate and ultimate analysis of the materials burning, to different combustion parameters (temperature, turbulence oxygen, etc.), to the successive phases in the development of a fire (flaming vs. smoldering), and to other factors influencing upon dioxins formation, such as heating, halogens, soot, ash, and catalytic transition metals. Although the roles of these factors are analyzed and discussed, they still remain difficult to evaluate and quantify, resulting in emission factor values ranging over several orders of magnitude, even after carefully controlled, repetitive experiments. Comprehensive comparisons of dioxins emission data are presented for both biogenic and anthropogenic sources, as well as some possible countermeasures toward reduction of dioxins from open burning.