When PCBs enter the human body, many are converted by enzymatic processes to derivative compounds, or "metabolites," called hydroxylated PCBs (OH-PCBs). OH-PCBs can be significantly more powerful biologically than the original PCB from which they are derived.

Courtney et al. compared blood levels of PCBs and OH-PCBs, in Inuit living in the Canadian arctic (Nunavik, Quebec) with blood sampled in the general Canadian population living in the south of the country.

Their work is of high interest because of:

• the known transport of persistent organic pollutants, including PCBs into arctic ecosystems (OSF chapter 7);
• the Inuit diet, which often contains significant proportions of fat-laden meat from seals, whales, polar bears and other species near the top of the food chain and thus often burdened with high levels of bioaccumulative contaminants; and
• the potency of certain PCBs and related compounds in interfering with thyroid and retinoid hormone systems. Some of these contaminants are more powerful than even thyroxin, the natural thyroid prohormon, at binding with thyroid hormone transport proteins.

They found that arctic living Inuit carried blood levels of contaminants ranged widely among individuals but that the arctic people's PCB and OH-PCB concentrations overall were up to 70x greater than the pooled sample from the southern part of Canada. This pattern did not hold for all compounds measured. "The geometric mean PCB [pentachlorophenol] concentration in the Inuit samples was 2.02 ng/g, approximately 3 times lower than in the southern Quebec pooled sample."

"Women had lower mean concentrations of all phenolic compounds quantitated than men. The generally lower levels in women may result from the loss of OH-PCBs and PCBs through lactation because both have been identified in milk (36-38). Both OH-PCBs and PCBs were significantly correlated with age (r = 0.68 and 0.78, respectively; p < 0.05). The increase of both PCB and OH-PCB concentrations with age may be due to the increased exposure with age (elders' preference for traditional foods), a slow excretion rate of PCBs that prevents steady state from being achieved, or both."

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