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This study was carried out to evaluate the internal exposure to polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) of chimney sweeps in Bavaria compared to a control group without occupational exposure. The PCDD/PCDF concentrations in the blood fat of 227 chimney sweeps were compared with the concentrations in samples from 60 controls. Using an internal standard containing 17 13C12-labeled PCDD/F congeners, the samples were cleaned up after fat elution using standard methods. The statistical analysis was adjusted to account for demographic differences, dietary habits, smoking status, and both occupational and nonoccupational contact with chlorinated hydrocarbons. Detailed information on the type of heating in the households swept, the length of time the chimney sweeps had carried out the profession (min 34, med 195, max 466 months) and the protective measures employed, were used to examine the influence of the working conditions specific to chimney sweeps on the internal PCDD/PCDF exposure. The correlation between blood-fat PCB concentrations as well as urinary chlorophenol concentrations and the exposure to PCDDs/PCDFs was evaluated. The sum of PCDD/PCDF components in chimney sweeps, expressed by International Toxic Equivalents (I-TEQ), was significantly increased compared to the control group (median: 26.36 versus 20.75 pg I-TEQ/g blood fat). For 37 chimney sweeps (16.3%) the sum of PCDDs/PCDFs exceeded the 95th percentile of the control group, i.e., 38.23 pg I-TEQ/g blood fat. Multiple regression analysis revealed that in addition to occupation, the variables age, district, and proximity to a waste incineration plant seem to have an effect on the internal PCDD/PCDF exposure. An additional influence on the internal exposure could not be determined for any of the special aspects of the work. We identified no high correlations between the concentrations of PCBs and chlorophenols and PCDDs/PCDFs. This study revealed significantly higher internal exposure to PCDDs/PCDFs in chimney sweeps than in the control group. The differences are small and within the range of the internal exposure to PCDDs/PCDFs in blood found in the general population in Germany since 1989. Further investigations in to PCDD/PCDF-related diseases in these study groups were not carried out. [ABSTRACT FROM AUTHOR]