Polychlorinated biphenyls (PCBs) and organochlorine pesticides have been associated with altered thyroid hormone levels in humans, but their relationship with thyroid cancer is unknown. The authors conducted a nested case-control study of thyroid cancer in the Norwegian Janus Serum Bank cohort using pre-diagnostic blood samples from 1972 to 1985. Incident thyroid cancer (n?=?108) was ascertained through 2008. Controls were matched 2:1 by age, date of blood draw, gender, and county. Gas chromatography/mass spectrometry was used to quantify 36 PCB congeners and metabolites of pesticides DDT, chlordane, hexachlorocyclohexane, and hexachlorobenzene. PCBs and pesticide metabolites were evaluated individually and summed by degree of chlorination and parent compound, respectively. Odds ratios (OR) and 95% confidence intervals (CI) were computed using conditional logistic regression per specified increase in lipid-adjusted concentration. The authors additionally stratified analyses by birth cohort (1923-1932, 1933-1942, 1943-1957). Increasing concentration of DDT metabolites (ORper 1000?ng/g = 0.80, 95%CI = 0.66-0.98) was inversely associated with thyroid cancer. Associations for PCBs were null or in inverse direction. Interactions for total PCBs, moderately-chlorinated PCBs, and chlordane metabolites with birth cohort (p???0.04) were observed. Among participants born 1943-1957, total PCBs (ORper 100?ng/g = 1.25, 95%CI = 1.00-1.56), moderately-chlorinated PCBs (ORper 100?ng/g = 1.31, 95%CI =1.01-1.70), and chlordane metabolites (ORper 10?ng/g = 1.78, 95%CI = 1.09-2.93) were positively associated with thyroid cancer. For individuals born before 1943, associations were generally null or in the inverse direction. Emissions of PCBs and OC pesticides varied over time. Different risk patterns by birth cohort suggest the potential importance of timing of exposure in thyroid cancer risk. Further evaluation of these associations is warranted.
Authors: Lerro CC, Jones RR, Langseth H, Grimsrud TK, Engel LS, Sjödin A, Choo-Wosoba H, Albert P, Ward MH. ; Full Source: Environmental Research. 2018 Apr 23; 165:125-132. doi: 10.1016/j.envres.2018.04.012. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][Epub ahead of print][/fusion_builder_column][/fusion_builder_row][/fusion_builder_container]