Worker exposures to nitrosamines in a rubber vehicle sealing plant

Occupational nitrosamine exposures were measured during a National Institute for Occupational Safety and Health (NIOSH) health hazard evaluation at a rubber vehicle sealing plant. All of the 28 personal breathing zone samples had detectable concentrations of nitrosodimethylamine (NDMA), nitrosodiethylamine, nitrosopiperidine (NPIP), and nitrosomorpholine; and 27 of the 28 samples had detectable concentrations of nitrosopyrrolidine. The NDMA exposures were the highest, ranging from 0.47 to 11.44 micrograms/m3. The next highest exposures were to NPIP, ranging from 0.20 to 4.39 micrograms/m3. Several general area air samples were also collected, which revealed concentrations of NDMA ranging from 2.29 to 88.47 micrograms/m3 at the drills along the salt bath lines. The salt bath curing process appears to be the primary source of nitrosamine formation, and personal exposures were highest for the salt bath line operators and assistant operators. Although there are no numerical occupational nitrosamine standards in the United States to reference, the exposures in this plant were much higher than the German standard of 1 micrograms/m3 total nitrosamines for general industry and 2.5 micrograms/m3 total nitrosamines for certain processes such as vulcanization. NIOSH investigators recommended that the ventilation systems be improved to reduce the exposures to the lowest feasible concentrations until the process can be redesigned so that nitrosamines are not formed.