Highly carboxylated porphyrin concentration: a biochemical marker of PCB exposure in herring gulls

Our previous studies showed that the concentration of highly carboxylated porphyrins (HCPs) was higher in livers of herring gulls (Larus argentatus) from the Great Lakes than in livers of herring gulls from a relatively uncontaminated area of the Atlantic coast of Canada. Since there are relatively few causes of elevated HCPs other than exposure to certain halogenated aromatic hydrocarbons (HAHs), we suggested that HCP concentration might offer promise as a biochemical marker of HAH exposure in herring gulls. We did not confirm if, or identify which, HAHs were the cause of elevated HCPs. Here we provide evidence that polychlorinated biphenyls (PCBs) are a likely cause of HCP accumulation in herring gulls. HCP concentration was measured in livers of adult gulls that were collected from several sites on the Great Lakes and from two reference sites. Non-polar extracts prepared from the livers were assayed for porphyrinogenic potency in a chicken embryo hepatocyte (CEH) bioassay, and analyzed for concentrations of various HAHs, including PCBs. There was a good linear correlation between (a) liver HCP concentration and porphyrinogenic potency of liver extracts, and (b) liver HCP and PCB concentration. Congenerspecific analysis suggested that the mono-ortho substituted PCB congeners 2,3,3′,4,4′-pentachlorobiphenyl (PCB 105) and 2,3′,4,4′5-pentachlorobiphenyl (PCB 118) were the congeners which contributed most to elevated HCPs in gull livers. We conclude that HCP concentration is a good biochemical marker of PCB exposure in herring gulls.