Proposal for reference concentrations (RfC) for inhalation exposure to methanol

A tentative reference concentration (RfC) for methanol in ambient air, i.e. an exposure concentration below which adverse effects are not expected to occur, was derived from the analysis of the toxicological data available in the literature. Well-documented studies that correlate environmental level s of methanol with observed toxic effects have not been found in the litera ture, nor have any long-term epidemiological studies of chronic low-level o ccupational exposure been found. Assessment of RfC for acute inhalation exp osure is based on a human study (n = 26 subjects) with a 'tentative' NOAEL of 262 mg/m(3). The calculated RfC for 1 h exposure is 104.8 mg/m(3). The R fC is given a low confidence rating as there was only one methanol concentr ation used. A well designed study on monkeys served as the basis for the as sessment of RfC for chronic inhalation exposure. In this study, 13.1 and 13 1 mg/m(3) were considered as NOAEL and LOAEL, respectively. The calculated RfC is 0.38 mg/m(3). The overall database is weak, lacking data on reproduc tive and developmental endpoints in human or non-human primates. Neverthele ss, the RfC is given a medium confidence rating because of the strength of the principal study. (C) 2000 Elsevier Science B.V. All rights reserved.