Intra-individual variations and time trends 1991–2001 in human serum levels of PCB, DDE and hexachlorobenzene

Background: An important question is whether human serum levels of persistent organic pollutants has continued to decrease during the last decades. The aim of this study was to assess intra-individual variations over time of serum levels of 2,2′,4,4′,5,5′-hexachlorobiphenyl (CB-153), 1,1-dichloro-2,2-bis(4-chlorophenyl)-ethene (p,p′-DDE) and hexachlorobenzene (HCB), considering the impact of a number of possible determinants. Methods: Blood samples were drawn for the same 39 subjects in 1991 and 2001. Interviews were made at both occasions. Lipid adjusted serum concentrations of CB-153, p,p′-DDE and HCB were determined in both sets of blood samples using gas chromatography–mass spectrometry. The fatty acid composition of the serum lipids was analyzed by means of gas–liquid chromatography. Result: The CB-153 concentrations in serum had averagely decreased with 34% in between 1991 and 2001 (p < 0.001). Of individual determinants only increasing BMI was associated with decreasing CB-153 levels (β = −1.0, 95% CI −1.8, −0.2, p = 0.01), explaining 13% of the variation. The average decrease of p,p′-DDE was 55%, and could only weakly be associated with a relative increase of BMI (β = −1.0, 95% CI −2.3, 0.2, p = 0.09), explaining only 5% of the variation. The average decrease of HCB was 53%, and was associated only with high fish consumption in 1991, explaining 12% of the variation. Conclusions: The results support a continuing decrease in human body burdens of PCBs, DDE and HCB during the 1990s. The explanatory factors relative change of BMI and fish consumption explained only a minor part of the time-related variations in serum levels.