[The effect of exposure to silicon dioxide on the occurrence of porphyria tarda].

The incidence of porphyria cutanea tarda was studied in two groups of silicon dioxide risk workers and compared to that in a control group. In the group with higher exposure to SiO2 the illness occurred in 12 out of 440 workers, in the group with lower exposure in 12 out of 1000 workers. In the control group porphyria was found in 18 out of 12,100 individuals examined. The difference in the incidence of the illness between the SiO2 risk individuals and the control group is statistically significant (p less than 0.01), while the difference between the group with variously high SiO2 exposure is on the level of statistically significance (p less than 0.05). The causes of the higher incidence rate of porphyria cutanea tarda in free SiO2 risk workers are discussed.