New scientific publication on carcinogenicity of methylene chloride

In December 2020, a high-level scientific paper evaluating the carcinogenicity of dichloromethane (DCM) in animals and humans was accepted by the journal Regulatory Toxicology and Pharmacology. The peer-reviewed paper is freely available here and as a PDF below. The paper discusses the current information on DCM carcinogenicity in view of a current re-classification proposal for DCM and the most recent assessment by the International Agency for Research on Cancer (IARC).

In short, the paper concluded that carcinogenicity studies in rats, mice and hamsters have demonstrated a malignant tumour-inducing potential of DCM only in the mouse (lung and liver) at air concentrations of 1000 - 4000 ppm, whereas human data do not support a conclusion of cancer risk. Dose-dependent toxico-kinetics of DCM suggest that DCM is a threshold carcinogen in mice, initiating carcinogenicity via a biotransformation pathway that becomes relevant only at high exposure concentrations. Rats and hamsters have very low activities of this DCM-metabolising enzyme and humans have even lower activities. Based on these aspects, the mouse is considered a less relevant animal model. As such, the current classification of DCM as a possible human carcinogen category 2 remains appropriate.