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Blood samples from 34 workers at a pulp and paper mill and from 14 control persons were analysed for 2,3,7,8-substituted PCDDs and PCDFs. There were no statistically significant differences in total lipid-adjusted PCDD/PCDF concentrations, expressed as toxic equivalents, in blood plasma between the potentially exposed bleaching plant or paper mill workers and the controls. The mean level was 61 pg/g I-TEQ in bleaching plant workers, 60 pg/g I-TEQ in paper mill workers and 49 I-TEQ pg/g in controls. Regarding the concentrations of individual isomers, however, there was an indication that the blood plasma concentrations might be affected by the living and working environment.

The concentrations of airborne 2,3,7,8-substituted polychlorinated dibenzo- p -dioxins and dibenzofurans measured at a pulp and paper mill ranged from 0.04 to 1.9 pg/m 3 . The paper mill used softwood and hardwood pulp which was bleached with solely chlorine dioxinde in the first chlorination stage. The chlorinated furans dominated in all samples, while very few dioxins were detected. No 2,3,7,8-tetrachlorodibenzo- p -dioxin was detected. The highest concentration was measured for 1,2,3,4,6,7,8-heptachlorodibenzofuran, which was present in all samples. The toxic equivalent concentrations varied between 0.002 and 0.2 pg/m 3 using the international toxic equivalency factors. The congener profile of a paper dust sample was similar to that of the corresponding air samples.

A softwood and hardwood kraft pulp mill, utilizing chlorine-containing bleaching agents, was monitored for 40 organohalogen compounds in the workplace air. Low levels of chloroform, carbon tetrachloride, tetrachloroethene, 1,1,1-trichloroethane, 1,4-dichlorobenzene, methanesulphonyl chloride, 2,5-dichlorothiophene and pentachlorophenol were detected. The workplace air at the bleaching plant was found to be slightly genotoxic in an on-site bacterial mutagenicity test.