Evaluation of porphyria cutanea tarda in U.S. workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

A cross-sectional medical study was performed to evaluate whether occupational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-contaminated substances is associated with porphyria cutanea tarda or porphyrinuria. The exposed participants were employed more than 15 years earlier in the manufacture of sodium trichlorophenol and its derivatives. The referent group consisted of individuals with no occupational exposure to phenoxy herbicides. A total of 281 workers and 260 referents participated. The pattern of urinary porphyrin excretion for each participant was assessed to determine if symptomatic or subclinical porphyria cutanea tarda was present. None of the participants were found to have symptomatic porphyria cutanea tarda. No difference was found between workers and referents in the prevalence of subclinical porphyria cutanea tarda (odds ratio [OR] = 0.93, 95% confidence interval [CI] 0.19, 4.54). There were also no differences in the risk between workers and referents for an out-of-range urinary uroporphyrin or coproporphyrin concentration. In conclusion, this study did not find an elevated risk for porphyria cutanea tarda or porphyrinuria among workers with high serum TCDD levels. Our review of the literature indicates that there is insufficient evidence available to convincingly support or refute an association in humans between TCDD exposure and porphyria cutanea tarda or porphyrinuria.