Polychlorinated dibenzo- p-dioxins and dibenzofurans in plywood combustion gas

Polychlorinated dibenzo- p-dioxin and dibenzofuran (PCDD/DF) levels in plywood combustion gas were investigated for the effects of ammonium chloride (NH 4Cl) and paint. For combustion systems in which neither NH 4Cl nor paint were present in the plywood samples, total amounts of PCDD/DFs in the combustion gas were in the order of 35–529 ng/Nm 3, and were higher in the systems with softwood trees than broadleaf ones, depending on the Cl concentrations. For the systems with added NH 4Cl and no paint, and those without NH 4Cl but were painted, higher PCDD/DF rates were observed at combustion temperatures of 270°C and 500°C, respectively. However, for the systems with both NH 4Cl and paint, their amounts in the range of 0.6–13 ng/Nm 3 were the lowest in all systems. The PCDD/DF abundance profiles were similar to their patterns in pentachlorophenol (PCP). Furthermore, it was found that the 2,3,7,8-chlorine substituted penta- and hexa-CDDs contributed more than other 2,3,7,8-chlorine substitutes to toxicity equivalency (TEQ).