The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated furan [110‐00‐9]. All toxicity endpoints have been considered and publications are described in detail.
Genotoxicity data show only a secondary genotoxic effect at high doses and no effect at low doses. Therefore, furan is classified as a primary non‐genotoxic carcinogen. As a maximum concentration at the workplace (MAK value) can be derived from available studies, furan was reclassified from Category 2 into Category 4 for carcinogens.
There are no long‐term inhalation studies available to derive a MAK value. In a 13‐week study with rats, subcapsular inflammation and apoptosis in the liver of unclear relevance for humans were observed at 0.12 mg/kg body weight/day with a NOAEL of 0.03 mg/kg body weight/day. These may be adaptive effects and were not observed in a two‐year study or its interim investigations. A physiologically based pharmacokinetic model predicted the burden in human livers to be about three‐fold lower compared with rats. The NOAEL of 0.03 mg/kg body weight/day was scaled to a concentration at the workplace and a MAK value of 0.02 ml/m3 was derived, also taking into account the lower liver dose in humans.
The MAK value was derived from a systemic NOAEL; therefore, furan is classified in Peak Limitation Category II with the default excursion factor of 2 as sufficient toxicokinetic data are not available, especially for the reactive metabolite cis‐2‐butene‐1,4‐dial.
Model calculations show that dermal absorption would contribute substantially to the systemic toxicity and furan continues to be designated with an „H“.
Because there are no studies on developmental toxicity, furan is assigned to Pregnancy Risk Group D.
There are no data on sensitization.