Exposure to persistent organic pollutants (POPs) such as dioxins, furans, and polychlorinated biphenyls (PCBs) may influence leukocyte telomere length (LTL), a biomarker associated with chronic disease. In vitro research suggests dioxins may bind to the AhR (aryl hydrocarbon receptor) and induce telomerase activity, which elongates LTL. However, few epidemiologic studies have investigated associations between POPs and LTL.
We examined the association between 18 PCBs, 7 dioxins, 9 furans, and LTL among 1,330 US adults from NHANES 2001-2002.
We created 3 summed POP metrics based on toxic equivalency factor (TEF), a potency measure including affinity to the AhR: 1) non-dioxin-like PCBs (comprised of 10 non-dioxin-like PCBs; no AhR affinity and no TEF); 2) non-ortho PCBs (comprised of 2 non-ortho-substituted PCBs with high TEF); 3) and toxic equivalency (TEQ) (comprised of 7 dioxins, 9 furans, 2 non-ortho-substituted PCBs, and 6 mono-ortho-substituted PCBs; weighted by TEF). We tested the association between each metric and LTL using linear regression, adjusting for demographics, blood cell count and distribution, and another metric with a different TEF (i.e., non-ortho PCBs and TEQ adjusted for non-dioxin-like PCBs; non-dioxin-like PCBs adjusted for non-ortho PCBs).
In adjusted models, each doubling of serum concentrations of non-ortho PCBs and TEQ was associated with 3.74% (95% CI: 2.10, 5.40) and 5.29% (95% CI: 1.66, 9.05) longer LTLs, respectively. Compared to the lowest quartile, the highest quartile of exposure was associated with 9.16% (95% CI: 2.96, 15.73) and 7.84% (95% CI: -0.53, 16.92) longer LTLs, respectively. Non-dioxin-like PCBs were not associated with LTL.
POPs with high TEFs and AhR affinity were associated with longer LTL. Because many dioxin-associated cancers are also associated with longer LTL, these results may provide insight into the mechanisms underlying PCB and dioxin-related carcinogenesis.