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J.Health Sci., 50(1), 58-65, 2004
Comparison of Compositions of Polychlorinated
Dibenzo-p-dioxins (PCDDs) and Dibenzofurans
(PCDFs) in Air and Soil Samples Collected in Ishikawa
Hitoshi Kakimoto,*, a Hideo
Oka,a Yumiko
Harada,a Shigeru
Ushijima,a Akira
Toriba,b
Ryoichi Kizu,b and Kazuichi
Hayakawab
aIshikawa Prefectural Institute of Public Health and Environmental Science, Taiyogaoka 1-11, Kanazawa 920-1154, Japan and
bGraduate School of Natural Science and Technology, Kanazawa University, Takara-machi 13-1, Kanazawa 920-0934, Japan
Dioxins are present as impurities in agrochemicals applied to the soil. To examine the possibility that dioxins
end up in the atmosphere, we compare the homologue composition and some characteristic isomer distributions of
polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in air and soil samples
collected at sites in Ishikawa Prefecture, Japan. Tetrachloro
dibenzo-p-dioxin (TeCDD) was the most abundant
PCDD homologue in the air samples, while octachloro
dibenzo-p-dioxin (OCDD) was the most abundant PCDD
homologue in the soil samples. However, at several site, the most predominant homologue in the soil sample was not
OCDD but TeCDD. The mean ratio of TeCDDs to PCDDs in the air samples was significantly smaller in winter than
in other seasons, but no such seasonal variation was observed in the distribution of PCDF homologues. The
abundance of PCDF homologues was inversely related to the number of chlorine substitutions in the air samples. The
contribution of each toxic isomer (2,3,7,8-chlorine-substituted) to the total toxicity equivalency quantity (TEQ) in
the air samples tended to be intermediate between their contributions to the TEQs in the soil and cinder samples.
This result suggested that the air samples were influenced by both soil/dust suspension and combustion.
In order to clarify the contributions of agrochemicals to dioxins in the air, we focused on the ratios of several characteristic
isomers that are indicators of agrochemicals (chloronitrophen: CNP and pentachlorophenol: PCP) to their
homologues. Significant decreases in the ratios of the isomers to their homologues in the air samples were observed only
in winter, probably as a result of suppression of dust suspension by the snow cover. Therefore, the contribution of
combustion to the dioxin concentration in the air was thought to be relatively large in winter.
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