Abstract
The purpose of the study was to determine whether hexahydrotriazine (“triazine”) bactericides increase the likelihood of elevated mycobacteria growth in metal removal fluids (MRFs). In reaction to an outbreak of hypersensitivity pneumonitis (HP) at a transmission manufacturing facility, machining plants of a large automobile manufacturer were directed to increase the testing of MRF, especially testing for mycobacteria. A working hypothesis was developed that triazine bactericides cause an increase in mycobacteria contamination, which in turn may lead to an increased risk of HP for workers exposed to MRF aerosols. Test results for 277 central MRF systems from nine machining facilities were analyzed for various MRF properties including the presence and type of both bactericide in the MRF formula and bacterial contamination of the MRF. The study included data reflecting usual operating conditions of all of the 277 large MRF systems in the company. The study does not evaluate the effect of tank-side biocide addition. The results show that soluble oils, semi-synthetic, and synthetic MRFs are all capable of supporting mycobacterial growth. The results also demonstrate a highly significant association between routine use of triazine bactericides and mycobacterial contamination of MRF. Based on the hypothesis that mycobacteria are a likely causative agent of hypersensitivity pneumonitis from MRF exposure, it is concluded that elimination of triazines from MRF formulae may be protective against HP in the machining environment.