A review of the occurrence, toxicity, and biodegradation of condensed thiophenes found in petroleum

Condensed thiophenes comprise a significant portion of the organosulfur compounds in petroleum and in other products from fossil fuels. Dibenzothiophene (DBT) has served as a model compound in biodegradation studies for over two decades. However, until quite recently, few other organosulfur compounds were studied, and their fates in petroleum-contaminated environments are largely unknown. This paper presents a review of the types of organosulfur compounds found in petroleum and summarizes the scant literature on toxicity studies with condensed thiophenes. Reports on the biodegradation of benzothiophene, alkylbenzothiophenes, DBT, alkylDBTs, and naphthothiophenes are reviewed with a focus on the identification of metabolites detected in laboratory cultures. In addition, recent reports on quantitative studies with DBT and naphtho[2,1-b]thiophene indicate the existence of polar sulfur-containing metabolites that have escaped detection and identification.