Trimethylamine [MAK Value Documentation, 2016]

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 work place (MAK value) of trimethylamine [ 75‐50‐3 ] of 2 ml/m 3 , considering the endpoints local and systemic toxicity as well as developmental toxicity. Available publications are described in detail. Daily exposure of rats to trimethylamine for 14 days resulted in inflammation of the respiratory epithelium at 74 ml/m 3 , the lowest concentration tested. Since 2014, the Commission uses an empirical approach to set MAK values for substances with critical effects on the upper respiratory tract or the eyes. According to this approach, the MAK value would have to be lowered to 1 ml/m 3 . However, several data show, that the previous MAK value can be retained. Workers reported no irritation at 5 ml trimethylamine/m 3 . In addition cyclohexylamine and dimethylamine with a MAK value of 2 ml/m 3 are used as a read‐across due to similar alkalinity and RD50 values, and in a recent volunteer study a NOAEC of 2 ml cyclohexylamine/m 3 is found. The MAK value will also protect from possible blue hazy vision which is caused by other tertiary amines since trimethylamine is assumed to be less effective than N,N‐dimethylethylamine with a MAK value of 2 ml/m 3 . The assignment is to Peak Limitation Category I, because local effects are critical, and the excursion factor of 2 is confirmed. Developmental toxicity studies with trimethylamine show that damage to the embryo or foetus is unlikely if the MAK value is observed, and the assignment to Pregnancy Risk Group C is retained.