n‐Butylamine, sec‐Butylamine, iso‐Butylamine, tert‐Butylamine

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 n‐, sec‐, iso‐ and tert‐butylamine, considering local and systemic toxicity as well as developmental toxicity. Daily exposure of rats to n‐butylamine for 14 days resulted in inflammation of respiratory epithelium at 17 ml/m3. 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, which would result in lowering the MAK value for n‐butylamine. However, workers reported no irritation at 1 to 2 ml n‐butylamine/m3. Therefore, the MAK value of 2 ml/m3 is confirmed, also for sec‐ and iso‐butylamine due to similar structure, pKa and RD50 values. With tert‐butylamine the LOAEC of 66 ml/m3 in rats in a 13‐week study resulted in nasal tissue inflammation and liver weight increase. Following the empirical approach, the same MAK value of 2 ml/m3 is set for tert‐butylamine. As local effects might be or are critical, Peak Limitation Category I and an excursion factor of 2 and a momentary value of 5 ml/m3 are assigned for all butylamine isomers. Developmental toxicity studies with n‐butylamine show that damage to the embryo or foetus is unlikely if the MAK value is not exceeded and thus n‐butylamine is assigned to Pregnancy Risk Group C. Due to the lack of developmental toxicity studies, sec‐, iso‐ and tert‐butylamine are assigned to Pregnancy Risk Group D.