There is a general consensus on dermatitis and respiratory illnesses: exposures to the metal removal environment are associated with both. But there is also a consensus that fluid management, appropriate personal protective equipment and good housekeeping will protect most workers from most exposures.

Ted Haines of McMaster University, Hamilton, Ont., highlighted his recent work on the association between asthma and metal removal fluid exposures. Working with General Motors and the CAW, McMasters and his colleagues have completed a new survey of more than 1,200 workers. They found 350 were positive for asthma, 386 had chronic bronchitis and 468 had rhinitis. Following up with the asthma group, Haines said that spraying coolant was the only exposure associated with proven asthma in the study. But he noted that both asthma levels and chronic bronchitis were higher in the departments in the plant that reported higher aerosol levels. His conclusion: higher average mist concentrations were associated with asthma and chronic bronchitis.

Cancer risks?
David Garabrant M.D., professor emeritus with the University of Michigan School of Public Health in Ann Arbor, described a cohort mortality study he and his colleagues conductedcovering 13Ford Motor Co.plants,to identify cancer risks associated with metalworking fluid exposures. The bottom line of his large and very complex study was asmall to moderate excess risk of lung cancer among nonskilled production workers – the workers with consistent exposure to metal removal fluids – in the transmission and chassis plants. But, cautioned Garabrant, In every analysis in which there was increased risk of lung cancer, there was also increased risk of heart disease, suggesting possible confounding by smoking.

Garabrant noted that other studies of metalworking fluid exposure have found excesses of stomach cancer. His study found a significant excess of stomach cancer among metal machining workers, but no significant excess of stomach cancer (or of any other gastrointestinal cancer) among workers exposed to straight cutting oils, water soluble machining fluids, or synthetic machining fluids.

There was no clear excess risk of leukemia or lymphoma among workers exposed to any type of machining fluid, Garabrant said. While other studies of metalworking fluid exposure have found excesses of pancreatic cancer in gear and axle workers, and associated with exposure to synthetic machining fluids, Garabrant found a non-significant excess of pancreas cancer among workers exposed to straight cutting oils and no appreciable excess of pancreas cancer among workers exposed to water soluble machining fluids or synthetic machining fluids or among metal machining workers.

Garabrant noted that he plans toperform additional analyses ofhis data with a focus on duration of exposure.

Other health issues
Mycobacteria are frequently cited as an evil actor in fluid sumps and mists, generating allergic responses up to and including hypersensitivity pneumonitis. But in a recent large HP outbreak in the United Kingdom, Brian Crook of the U.K.s Health & Safety Laboratory in Derbyshire told the symposium that they werent a factor. Mycobacterium is common. Its an immuno-stimulant. But no mycobacterium species were found in Europes largest case of work-related respiratory disease.

Michael Rocker of Germanys BG Metall Nord Sud, which insures large end-users of metal removal fluids, told about his discoveries of ultrafine particles generating during metal removal operations. Ultrafine particles of metal are known to induce radical reactions in cells, which can result in oxdative stress, which in turn induces DNA damage and may be followed by cancer, Rocker noted. After several years of study, Rocker has determined that the ultrafine particles generated in metal removal processes are a mix of the metal workpiece and of the fluid, with sizes ranging from seven nanometers to one micron.

Rocker has looked at ultrafine particle generation in dry machining, in minimum-quantity lubrication, and standard wet machining. The highest generation of ultrafine particles came with MQL, Rocker said. There were far more particles, 40 times more particles, than when working with oil.

Ultrafine particles do not automatically mean cancer, Rocker stressed. But the time for outbreak of cancer can be five to 40 years, and MQL is only about 12 to 15 years old. Rocker sees a lot more research ahead to better understand ultrafine particle formation and its effects.

Wally Dalbey, recently retired from ExxonMobil Biomedical Sciences, gave a clean bill of health to todays highly refined straight oils. Straight oils have low toxicity, low allergenicity, no pulmonary effect and are not carcinogenic, Dalbey asserted.

Its not the oil, John Howell of D.A. Stuart, a Houghton Co., concurred. Mineral oil is not responsible for observed health effects. Other entities such as endotoxins are more appropriate targets. There is growing evidence pointing at endotoxins plus chemical components, other microbiological entities, pH, hypotonicity, or some combination, he concluded.

The MRF symposium was presented by the Independent Lubricant Manufacturers Association, the Automotive Industry Action Group, the American Industrial Hygiene Association, and UEIL, the Union of European Independent Lubricant Manufacturers.