N-Nitrosodi-n-butylamine (NDBA)

NDBA forms by the nitrosation of dibutylamine, a secondary amine used as a corrosion inhibitor in metalworking cutting fluids and as a component of rubber accelerators and vulcanization agents [1]. In metalworking fluids, dibutylamine can coexist with nitrite (used as a corrosion inhibitor for iron surfaces), creating the conditions for nitrosamine formation [2]. Similar formation occurs in rubber manufacturing where dibutylamine-based accelerators are present alongside nitrogen-containing curing agents [1]. NDBA has also been detected in some beer and cured meat products where dibutylamine may be present as a trace impurity [2].

Machinists and metalworkers using cutting fluids containing dibutylamine and nitrite have skin contact and inhalation exposure to metalworking fluid mist containing NDBA [1]. Workers in rubber manufacturing face similar exposure [2]. Trace dietary exposure has been documented from some fermented and cured food products [1].

NDBA undergoes alpha-hydroxylation to reactive intermediates that form DNA adducts at guanine and adenine in esophageal and bladder urothelial cells [1]. Esophageal tumors and bladder tumors were induced in rat studies. EPA classifies it as a B2 probable carcinogen [2].

Machinists using nitrite-containing cutting fluids, rubber manufacturing workers [1].

1. Use nitrite-free cutting fluid formulations — eliminate the nitrosamine-forming conditions [1]. 2. Minimize skin contact with metalworking fluids [2]. 3. Regular changing of metalworking fluid to prevent bacterial buildup that may produce nitrite [1].