Pilot survey of urinary porphyrins from persons transiently exposed to a PCB transformer fire

In rats and humans chronically exposed to large amounts of PCB (polychlorinated biphenyls) and PCDF (polychlorinated dibenzofurans), the urinary excretion of uroporphyrin and coproporphyrin are altered. However, porphyrin excretion in humans after acute transient low level exposure has not been evaluated. Following such an exposure in which bystanders and firefighters were in contact with smoke from a PCB transformer fire, we surveyed 90 self-referred individuals by questionnaire and by determining single 24 hour urinary excretion of uroporphyrin and coproporphyrin 2-4 weeks after the fire. Questionnaire variables that assessed exposure were not associated with the magnitude of either uroporphyrin or coproporphyrin excretion. Uroporphyrin excretion was slightly elevated in nine subjects (range 66-106 micrograms/24 hours, normal less than 60), which is much less than in clinical cases of porphyria cutanea tarda. Uroporphyrin excretion was inversely correlated with coproporphyrin excretion (r = -0.3844, p = 0.0002). For 5 subjects (3 with elevated initial uroporphyrin excretion) retested at 3-4 weeks after the fire, all 5 showed increases in uroporphyrin and decreases in coproporphyrin excretion when compared to initial determinations. These two reciprocal relationships would be the expected result from inhibition of uroporphyrinogen decarboxylase, a known experimental effect of PCB and PCDF in mice. Overall, urinary porphyrin excretions were not altered or sensitive measures of exposure.