tert‐Butyl acetate

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) and the Pregnancy Risk Group for tert‐butyl acetate [540‐88‐5]. Critical effects are transient acute neurotoxic symptoms which are observed in a 90‐day‐study with mice with a NOAEC of 100 ml/m3. From this concentration the former MAK value of 50 ml/m3 was derived. It is now lowered to 20 ml/m3 taking into account the increased respiratory volume at the workplace because the blood:air partition coefficient of tert‐butyl acetate is > 5 (see List of MAK and BAT Values, Sections I b and I c). This value also provides protection from irritation. Since a systemic effect is critical, Peak Limitation Category II is retained. The excursion factor of 2 is set in spite of the short half‐life of tert‐butyl acetate in blood as it is an acute effect for which an adaptation during subchronic exposure has been noticed. Therefore, peaks of exposure will not enhance the effect at chronic exposure. Furthermore, since the incidences after 90 days at 400 ml/m3 are low, the true NAEC might have been higher than 100 ml/m3. tert‐Butyl acetate had been classified in Pregnancy Risk Group C because the NOAEC for fetotoxicity is 1600 ml/m3 in a screening study in rats and taking into consideration the data for the metabolite tert‐butyl alcohol. There is no new data on developmental toxicity. This classification is retained even considering the increased respiratory volume at the workplace.