Are Metalworking Fluids a Threat to Health?

Author Robert Eade
August 01, 1998 - 12:00pm

Members of an OSHA advisory committee hint at changes to current regulations to reduce metalworking fluid mist. What remedies are available?

Metalworking fluids - cutting oils and coolants - have been around since the dawn of the Industrial Age. Most people view them as a messy, unavoidable nuisance. Until recently, few thought they might constitute a health hazard.

Spurred by the urgings of the United Auto Workers (UAW) union, the Occupational Safety and Health Administration (OSHA) recently established the Metalworking Fluids Standards Advisory Committee to look into the fluids’ impact on worker health, if there are any. The committee held its first meeting in September 1997, and its final report and recommendations are due by mid-1999.

The report could make any of several recommendations. It could advocate a national control standard (which the UAW supports) or merely suggest the development of guidelines on the use and handling of possibly hazardous fluids. It could suggest, but not require, that companies adopt preventive programs when they think a problem exists. The committee may also report that no action is required.

The 15-member committee represents the full spectrum of parties interested in metalworking fluids and their impact on workers’ health. Five members represent workers, five represent employers, and five come from such organizations as the National Institute of Occupational Safety and Health and manufacturers of metalworking fluids. Several members of the committee are physicians.

Peter Infante, director of OSHA’s Office of Standards Review, oversees the work of the committee. He says the panel is delving into every aspect of how and where metalworking fluids are used in modern manufacturing. "We’re looking at the scope of fluid use and the exposure levels workers are subjected to," he says. "What actually are the health risks? Are all metalworking fluids potentially harmful, or just certain fluids?"

Infante says that the committee has already seen evidence that exposure to certain fluids may cause dermatitis. Exposure may also trigger asthma or cause stomach cancer and various kinds of lung disease. "One of the things the committee is looking at is fluid management," Infante says. "Does the growth of bacteria in the fluids affect health and, if so, what’s the best way to control it?"

Frank Mirer, director of the UAW’s Health and Safety Department in Detroit, is a member of the advisory committee. He says that several years ago, the UAW began to notice pockets of disease and illness in scattered groups of its members. The evidence was at first anecdotal but sufficiently alarming for the UAW to petition OSHA in 1993 for an industry standard covering the manufacture and use of metalworking fluids. The union also asked that the Environmental Protection Agency (EPA) promulgate a ruling under the Toxic Substance Control Act to eliminate any possible hazard to workers. The formation of the OSHA advisory committee last year is one of the results of that effort.

New Information
"We have more data now than we had five years ago," the UAW’s Mirer says. "Since then, more than a dozen studies have shown a higher-than-expected incidence of stomach cancer in some of our locals. Also, we’re seeing an increase in respiratory illnesses, such as asthma and bronchitis. We’ve had 12 outbreaks of multiple cases among our membership. Five years ago, none had been documented."

Mirer and many others believe that part of the problem comes from the increasing use of synthetic cutting fluids, plus higher cutting tool speeds that increase the amount of particulate matter in the atmosphere. "Bacteria tend to live in the newer fluids, and that could be causing some of the problem," he says. "In our view, we can’t presently control the growth of microbes and bacteria. More research is needed. But we can control the amount of mist emanating from the machines. OSHA’s standard is currently a maximum of 5.0mg/m3 . We want to see that reduced to 0.5mg/m3. We believe the 0.5 level can be reached at a relatively small cost."

Mirer points out that the Big Three automakers have long been concerned about the possible harmful effects of metalworking fluids, and each has already set exposure limits far lower than OSHA’s 5.0mg/m3.

Hank Lick, manager of industrial hygiene for Ford Motor Co., Dearborn, MI, and a member of the committee, says that his company began studying the issue as far back as the 1970s and that Ford has a standing committee that seeks ways to reduce workers’ exposure to metalworking fluids. He reports that the average contaminant level for the Big Three, including Ford, is now 1.0mg/m3. Ford, he says, has reduced the concentration of metalworking-fluid contaminants in its machine tool areas to below 1.0mg/m3 - and in many cases much lower.

"If you’re a heavy user of the new synthetic oils," Lick says, "1.0mg isn’t good enough, because those fluids are more irritating to workers. The new machines, most of which are fully enclosed, are a big help. When a new line comes in at Ford, it’s almost always 0.5mg/m3 or lower. And many lines are fed by robots and other automatic parts-handling equipment, meaning the doors are opened less frequently. This helps alleviate the problem even more."

Lick says that enclosing existing machines is an excellent aid to preventing contamination, but it’s very expensive. Retrofitting is always difficult, he says. A far better way is to ensure that all new equipment is fully enclosed.

According to Lick, the advisory committee originally concentrated on the airborne aspects of the fluids but has now expanded its inquiry to include all aspects of machining. "We’re looking at a systems approach to fluid management," he says. "This covers anything associated with the fluids, including operator training, ventilation, filtration and overall control of the oils. We also are looking at how the machines are operated to see if there’s anything there that might cut down on unnecessary operator exposure."

Lick says that it’s clear even at this early date that something needs to be done. The evidence, he says, shows a need for improvement not only in large companies but in small machine shops as well.

The big automakers, as well as their larger suppliers, already know a problem exists, Lick says. "As many as 30% of the small shops already have a serious problem with metalworking fluids, but many of them won’t admit it. They haven’t seen what we’ve seen. It’s conceivable that some smaller shops will sue to block any new regulations that might be promulgated, particularly when they start adding up the costs of correcting the problem."

The Cost Factor
Estimates of the cost of fixing the problem nationwide vary widely, because, at present, the tab is based on speculation about what the committee might recommend and the type and scope of the regulations OSHA might eventually issue.

"Some people say that a remedial program to reduce metalworking emissions might total $15 billion for the nation’s small shops," Ford’s Lick says. "By small, I mean shops with under 100 people. For the auto industry and its first-tier suppliers, you have to add another $6 to $7 billion. But right now, that’s based only on guesswork."

The UAW’s Mirer points out that it’s harder to control fluid emissions in big facilities than in small ones. The mist levels in small shops are usually far less severe. As a rule of thumb, he cites some industry estimates that put the cost of remedial work at some $10,000 per machining station. "That’s based on a fully enclosed machine with an exhaust system," he says.

"But," Mirer adds, "we think the actual costs can be a lot cheaper. You wouldn’t have to enclose every machine because many of them are already operating below the 0.5mg/m3 level. But even where emissions are low, enclosing a machine entirely can give you benefits in addition to the health factor. For one thing, it’s an effective method of noise control. For another, you get immediate machine guarding, which obviously provides its own health benefits."

Whether or not the advisory committee recommends that OSHA issue new regulations, many devices already exist to control and remove the mists of metalworking fluids. Sales of this kind of equipment in machine shops are experiencing steady growth, often for reasons not primarily associated with workers’ health.

Fig. 1: A Trion air cleaner removes water-soluable coolant mist from a Mazak CNC machining center.Trion Inc., Sanford, NC, offers various types of air-cleaning equipment (Figure 1). Craig Ellis, director of sales and marketing for the company’s engineered products, says there has been a sharp increase in the use of air cleaners among machine-shop owners. More see an OSHA or EPA crackdown coming and want to be prepared. "There have been lots of studies lately," he says, "and even though there are many gray areas of uncertainty, most people acknowledge that this stuff [metalworking fluid] is not good for you."

Ellis adds that shops are turning to air-cleaning systems for other reasons as well. The mist generated by metalworking fluids can penetrate sensitive areas of a machine, especially the CNC, causing damage that is often difficult to detect. By the same token, it can settle on the shop’s finished inventory, causing problems with parts that have been machined to very tight tolerances.

Choosing Equipment
Since no two shops have exactly the same requirements, all of Trion’s installations are custom engineered. Ellis points out that the size of the plant and its physical layout determine what kind of equipment can be installed. For example, in a shop with 50 machines, it’s cheaper to mount a central air cleaner on the roof and connect the machines to it via ducts than it is to provide each machine with its own individual unit. However, he says, in a plant with overhead cranes, ductwork may be out of the question. Also, fixed ducts remove the inherent flexibility where manufacturing cells are widely used.

Ellis says that people planning to buy air-cleaning equipment should first ask themselves these questions:

bullet.GIF What are the plant’s current and future requirements?
bullet.GIF How is the mist being generated?
bullet.GIF How is it being released into the air?
bullet.GIF Are the pArticles wet or dry?
bullet.GIF Are the pArticles submicron or larger?

As for making the final purchase, Ellis says that the biggest mistake a company can make is to buy solely on the basis of price. "People will sometimes take the least-expensive way rather than the correct way," he says. "They end up with equipment that doesn’t do the necessary job. The most important factor in buying any air-cleaning system is choosing a supplier with application-engineering experience. The system must be designed correctly from the beginning. You seldom get a second chance."

Fig. 2: This line of turning centers has been equipped with Airflow Systems; individual Mist-PAC mist collectors.
Another manufacturer of air-cleaning equipment is Airflow Systems Inc. of Dallas. One of its customers, Dodge/ Rockwell Automation in Marion, NC, is a 200-employee shop that produces mounted roller bearings. All of the company’s 40 milling machines and lathes are equipped with individual mist collectors (Figure 2).

Jerry Carroll, plant engineer, says that the units offer two chief advantages: They improve the air the workers breathe and they remove plant contamination. "Our operators say that when they open the machine doors, there’s no mist to irritate them," Carroll says. "It’s so important to them that when a unit goes down or needs a new filter, the operators tell us about it right away."

According to Carroll, the units cost between $2500 and $3000 each but are well worth it for several reasons. "Besides the workers’ health and comfort, they help prolong machine life," he says. "Because there’s a slightly negative pressure inside the enclosure, we’ve noticed that we’re getting better bearing and seal life. Also, the mist collectors help keep the whole plant a lot cleaner. There’s no oil dripping off things, which is good for everybody."

Carroll points out that installing the air cleaner on a machine is usually a simple matter, providing a few precautions are taken. "The units have to be sized correctly, according to the amount of airflow you have in the work area. A good manufacturer’s rep can do that for you. And where you cut the duct into the machine housing is important. You have to make sure it’s not in a position where liquid and chips are being thrown right into the filter. Other than that, installation is seldom anything to worry about."
Many shops around the country are taking steps to control the mist coming from their metalworking machinery before it becomes a health problem. In many cases, the result is improved worker morale and higher productivity.

C&P Machine Co., a 24-worker job shop in South Windsor, CT, produces a variety of parts for the aerospace industry on four CNC turning centers. General manager Charles Agreda says that the heavy roughing cuts the machines take caused a thick mist to deposit a scum on just about every surface in the shop. "More importantly," he says, "the workers began to complain. The machine operators would get a rush of heavy mist every time they opened the machine door, which they naturally found objectionable."

About a year ago, C&P installed mist collectors on the turning centers and eliminated the problem. "The shop’s a lot cleaner now and so are the workers," says Agreda. "And they’re a lot happier than they used to be."

Engineered Machine Products, Escanaba, MI, had a similar experience. It produces water and oil pumps and other products for the auto industry using 47 lathes and other equipment. In addition to mist, the machines also produced a form of smoke at the spindles, the result of high spindle speeds and the 1/8" depth of cut.

David Hamelin, the company’s maintenance supervisor, says that the machine operators used to complain that the smoke was highly irritating. "We didn’t actually have any obvious health problems, but the potential was there."

About four years ago, Engineered Machine Products installed a mist collector on each machine, and the complaints disappeared. "The operators love the units," says Hamelin. "They want them installed on any new machines we get. There’s no mist and no smoke, just a lot of happy workers. And they’re probably a lot healthier, too."

About the Author
Robert Eade has been reporting on trends and issues in metalworking and manufacturing for 35 years. His Articles have appeared in numerous publications in the United States and abroad.

Related Glossary Terms

  • centers


    Cone-shaped pins that support a workpiece by one or two ends during machining. The centers fit into holes drilled in the workpiece ends. Centers that turn with the workpiece are called “live” centers; those that do not are called “dead” centers.

  • computer numerical control ( CNC)

    computer numerical control ( CNC)

    Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.

  • coolant


    Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

  • depth of cut

    depth of cut

    Distance between the bottom of the cut and the uncut surface of the workpiece, measured in a direction at right angles to the machined surface of the workpiece.

  • gang cutting ( milling)

    gang cutting ( milling)

    Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.

  • machining center

    machining center

    CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.

  • metalworking


    Any manufacturing process in which metal is processed or machined such that the workpiece is given a new shape. Broadly defined, the term includes processes such as design and layout, heat-treating, material handling and inspection.

  • milling


    Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

  • numerical control ( NC)

    numerical control ( NC)

    Any controlled equipment that allows an operator to program its movement by entering a series of coded numbers and symbols. See CNC, computer numerical control; DNC, direct numerical control.

  • turning


    Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.


Robert Eade is a Waterbury, Connecticut-based business writer who has been reporting on trends and issues in metalworking and manufacturing for 35 years.