Methanol
MAK-Begründung, Nachtrag
Andrea Hartwig1MAK Commission2
1 Institut für Angewandte Biowissenschaften, Abteilung Lebensmittelchemie und Toxikologie, Karlsruher Institut für Technologie (KIT), Adenauerring 20a, Geb. 50.41, 76131 Karlsruhe, Deutschland
2 Ständige Senatskommission zur Prüfung gesundheitsschädlicher Arbeitsstoffe, Deutsche Forschungsgemeinschaft, Kennedyallee 40, 53175 Bonn, Deutschland
Abstract
The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the workplace (MAK value) of methanol [67‐56‐1] of 200 ml/m3, considering all toxicity endpoints. Available publications and unpublished study reports are described in detail.
Uptake of larger amounts of methanol depresses the central nervous system and leads to developmental toxicity as direct effects of methanol followed by metabolic acidosis and ocular toxicity as formate effects.
No neurobehavioral effects were observed in subjects exposed 4 hours to 200 ml/m3 at rest leading to a concentration of 6.5 mg methanol/l blood. The steady state concentration of methanol after exposure to 100 ml/m3 with physical activity is calculated to be 6 mg methanol/l blood and is reached after 8 hours. Therefore, taking into account the increased respiratory volume at the workplace (see List of MAK‐ and BAT Values, Sections I b and I c), the MAK value has been lowered to 100 ml/m3. Due to the half‐life for methanol of 1.4 hours in humans, no accumulation of methanol is expected during the work week.
Since a systemic effect is critical, Peak Limitation Category II is retained. As the half‐life in humans is 1.4 hours, the excursion factor has been set to 2. No irritation was observed in volunteers at 200 ml/m3, the permissible peak concentration.
Taking into consideration the data for methanol and the metabolite formate, damage to the embryo and fetus is unlikely when the MAK value for methanol is not exceeded. Therefore, methanol remains classified in Pregnancy Risk Group C.
Methanol is not genotoxic in vitro at concentrations which are not cytotoxic. No clastogenic effects were observed in vivo. No increased tumour incidence occurred in long‐term inhalation studies in mice and rats as well as in a long‐term study in rats with administration in the drinking water.
Uptake via the skin can lead to systemic effects and methanol remains designated with “H”.
