Urinary excretion of porphyrins by smelter workers chronically exposed to arsenic dust

Urinary arsenic (inorganic arsenic and methylated metabolites), uroporphyrin and coproporphyrin I and III isomers were determined in 84 smelter workers exposed to arsenic trioxide and in 22 non-exposed controls. Both 'high' and 'low' exposure groups were defined, based on individual's work area (arsenic recovery plant and maintenance) and mean urinary excretion of arsenic was compared to the control group (257 and 129 micrograms/g creatinine against 9.9 micrograms/g creatinine). Total coproporphyrin (I+III) increased in each exposure group as compared to control (63.3 and 59 micrograms/g creatinine against 27.2 micrograms/g creatinine), as a consequence of a 2-fold increase in each coproporphyrin isomer. The mean concentration of uroporphyrin in each exposure group was very similar to that of the non-exposed controls (9.5 and 8.8 micrograms/g creatinine against 10.7 micrograms/g creatinine). These results suggest that long-term occupational exposure of humans to arsenic is associated with coproporphyrinuria and raise the question of the use of this parameter in addition to urinary arsenic for biological monitoring.