PCDD/DF and co-planar PCB emissions from crematories in Japan

Abstract

Japan implemented dioxin emission guidelines for crematories in 2000, but the effects of the new guidelines have not been fully evaluated. In this study, concentrations of polychlorinated dibenzodioxins/dibenzofurans (PCDDs/DFs) and co-planar polychlorinated biphenyls (co-PCBs) were measured in flue gas, fly ash, and bottom ash (mainly bone) from several crematories as a follow-up investigation. Total concentrations (O2 12% normalized) of PCDDs/DFs and co-PCBs in flue gas ranged from 4.2to540ng/mN3, and toxic equivalent concentrations ranged from 0.000053 to 11ng-TEQ/mN3. Based on these measurements, the average emission factor was estimated to be 1400ng-TEQ/body. This is approximately one-third the emission factor recorded in 1999. The emission factor distributions from 1999 and our study in 2007 were log-normally distributed. Emission factors were significantly lower in 2007 than in 1999, which suggests that the guidelines have been effective in reducing dioxin emissions. Meanwhile, toxic equivalent concentrations in fly ash ranged from 0.014 to 13ng-TEQg−1. Higher dioxin concentrations in fly ash were observed in facilities that used a heat exchanger as a flue-gas cooling device. Because the concentrations of PCDDs/DFs and co-PCBs in flue gas were also elevated after heat exchangers during the investigation of PCDD/DF- and co-PCB-removal behaviors, secondary formation of PCDDs/DFs and co-PCBs on heat exchanger surfaces unambiguously occurred.