Formation of N-nitrosodiethanolamine when using monoethanolamine and diethanolamine in water-mixable cooling lubricants for metal processing - Results of a measurement program

In the Federal Republic of Germany a special set of technical regulations ( TRGS 611) deals with the use of cooling lubricants containing diethanolamin e. Thus, the latter substance has often been substituted by monoethanolamin e which lead to an increased number of complaints relating to irritations o f the skin and the respiratory tract. Some extensive test series were condu cted to compare a top-class inhibited lubricant containing diethanolamine w ith the usual secondary amine-free cooling lubricants. One of the test seri es, including machining centres with an individual lubricant supply, showed a slowly but permanently increasing concentration of N-nitrosodiethanolami ne (NDELA) in the emulsions; nevertheless, limit values were not exceeded. In a second test series the diethanolamine-containing cooling lubricant was employed in two centrally-fed plants for more than two years. Again, limit values applying to NDELA were not exceeded but a regular check of the micr obiological situation turned out to be essential. The use of products conta ining diethanolamine makes sense whenever there are medical problems. It is however necessary to take accompanying measure for each new application. T he results cannot be transferred to other conditions of use nor to other co oling lubricants.