[Occurrence of symptomatic liver porphyria in workers at risk for exposure to free SiO2 during subway construction].

Symptomatic hepatic porphyria was followed up in workers exposed to the risk of free SiO2. This disease was found in 12 out of 998 workers engaged in the construction of the underground and exposed to SiO2 (group I), and in 12 at-risk persons out of 440 patients from different workplaces who were hospitalized for SiO2 exposure (group II). The average age of the workers of group I was 40.6 +/- 7.7, that of the group II 54.9 +/- 13.3. In both these high-risk groups, porphyria was found to be significantly more frequent than in the control group not exposed to free SiO2. The authors discuss the long-lasting effects of free SiO2 on the occurrence of symptomatic hepatic porphyria.