We present in this paper a review of the toxicological and environmental hazards, exposures and risks of tetrahydrofuran (THF; CASRN 109-99-9). THF is a polar solvent and monomer that is easily absorbed by all routes of exposure. The acute toxicity of THF is low to moderate by all routes. Irreversible corrosive damage to the eye can result from direct contact. However, THF is neither a skin irritant, nor sensitizer. Studies in vitro and in vivo have shown that THF is not mutagenic. Chronic studies have found benign tumors in the kidneys of male rats and in the livers of female mice. These findings have been examined, and although a mode of action is not known, the weight of evidence suggests that these tumors are likely not relevant to human health, but instead secondary to rodent-specific modes of action. THF produces transient sedative effects in rats at high concentrations but no significant neurobehavioral changes or neuropathology in sub-chronic studies. There were no specific effects reported on reproduction or developmental toxicity in rats or mice, with non-specific developmental toxicity observed only in the presence of significant maternal toxicity. The log K(ow) value for THF is less than 3, indicating a low potential for bioaccumulation. THF is inherently biodegradable, thus is not expected to be environmentally persistent. THF does not present an ecotoxicity hazard based on test results in fish, aquatic invertebrates and plants. Exposures to THF in the workplace, to consumers and via environmental releases were modeled and all found to fall below the derived toxicity thresholds.

As a contribution to the second round of rodent carcinogenesis prediction organised by the U.S. National Institute of Environmental Health Sciences (NIEHS), speculative predictions for 30 chemicals currently under evaluation in U.S. National Toxicology Program (NTP) rodent bioassays are presented. Core chemical data received from NIEHS were supplemented by relevant information from commercially available scientific databases to provide input for reasoned assessment. For each chemical, carcinogenesis by a genotoxic or nongenotoxic mechanism or noncarcinogenesis is predicted; species-and target organ-specific predictions are also presented, together with arbitrary indices of confidence in each such prediction. In all or nearly all cases, an element of informed speculation was a necessary part of the prediction process, but the rationale for each decision is briefly described. It is predicted that ten chemicals will prove noncarcinogenic, five will be carcinogenic to mice only, and 15 will induce tumours in both species.

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