Increase in urinary porphyrin excretion in workers exposed to polychlorinated biphenyls

Urinary porphyrin excretion was investigated in 67 workers occupationally exposed to commercial mixtures of polychlorinated biphenyls (PCBs) by determining the concentration of uro‐, hepta‐, hexa‐, penta‐, and coproporphyrin homologues. The workers had a mean blood PCB concentration of 386 ± 257 ppb (mean ± SD; range 162–1319 ppb). These values are at least ten‐fold higher than that expected in a population not occupationally exposed to PCBs. No qualitative alterations of the urinary porphyrin excretion were found and the uroporphyrin: coproporphyrin ratio remained normal. There was a definite increase in the excretion of all the porphyrinic homologues, so that the average concentration of total porphyrins in urine was 94.5 μg 1−1 in the exposed group versus 48.3 μg 1−1 in the control group. This excretory pattern of porphyrins corresponds to that usually observed in the first stage of chemical porphyria induced by polyhalogenated aromatic hydrocarbons. In accordance with current knowledge, this should be interpreted as a consequence of the specific inductive properties of PCBs on liver microsomal enzymes. The results of this investigation show that, as already observed in experimental animals, commercial mixtures of PCBs have a porphyrinogenic activity in man, as well.