More than 70 million gallons of metal-working fluids (MWFs) - the most complex material to evaluate and control for employee exposure purposes - are produced annually in the U.S. Other generic classes of materials such as welding fumes, heated rubber and plastic, and some solvent-based paints also are complex. But MWFs hold the top spot, mostly because their composition is constantly changing.

The only way to effectively deal with the health risks from MWFs is by taking a comprehensive approach to preventing and controlling problems caused by the changing composition of the material. Consider what happens when a specific type of MWF is first put to use:

  • The metal and tools being machined add metallic fines and corrosion-resistant materials, such as oils, to the fluid. The metallic fines may include small amounts (below the cut-off limit for reporting in a MSDS) of lead or other toxic materials added to the metal by the manufacturer to make the metal softer to machine.
  • The MWF may also become contaminated by hydraulic oils, seal greases, and machine paint.
  • Temperature of the MWF depends upon conditions such as tool speed, tool sharpness, and volume of fluid flow.
  • As the fluid is used, evaporation and chemical changes alter the MWF's concentration and properties such as pH.
  • Biological growth starts to occur. Biocides are added. The fluid starts to foam. Anti-foaming agents are added.
  • The fluid stinks - turning rancid. Then a Rreodorant' or masking agent may be added.
  • The first-shift operator cuts his finger and bleeds into the fluid.
  • The second-shift operator spits chewing tobacco into the fluid.
  • And you don't want to know what the third-shift operator puts into the fluid.

More challenges

Changing composition for a specific MWF is only the beginning of the problem. Consider these issues:

Different types of fluids are often tried from time to time. The aim is to increase tool life, reduce disposal costs, or eliminate problems and poor performance caused by prior MWFs.

There's a macho element involved with using the fluid. Self-proclaimed top-notch machinists insist you need to bathe yourself in the fluid to understand it. By rubbing the fluid between their fingers and thumb (without gloves), machinists claim they can tell when the fluid is breaking down, is too dirty, or is too warm for good use. They also claim they can tell by odor and sight when biological growth is unacceptable.

A lot of machinists don't like wearing gloves because they say it makes it too difficult to hold onto small and slippery parts. They also don't like wearing hearing protection because they need to listen to the sound of the tool working against the metal. Apparently, there is some subtle change in the pitch of the noise that alerts them to the need to use a sharper tool or adjust the flow or composition of the MWF.

MWFs used today are different from MWFs used in the past. This makes epidemiological studies difficult to apply to today's exposures. For example, prior to 1976, some water-based MWFs included sodium nitrite as a corrosion inhibitor. Under alkaline conditions and when in contact with secondary amines, the sodium nitrite could permit cancer-causing nitrosamines to form.

Older MWFs may also have contained, or created, cancer-causing polycyclic aromatic compounds, chlorinated paraffins, or ethanolamines. For the most part, but not completely, these very bad chemical actors have been removed from modern MWFs.

Solving the problem

Though changes have been made to make MWFs safer, significant health risks still exist. Lung and skin disease, cancer, and other serious problems may be caused by excessive exposure. To help address health concerns with MWFs, NIOSH issued a criteria document for a recommended standard, symposiums are being held, new and beefed up Internet sites are now available, and other actions and recommendations are being taken by interested groups and the government.

To effectively solve complex problems, you need to see and address the whole picture. Unfortunately, when a problem arises with a MWF we usually see just the part of the problem that needs to be immediately fixed. For example, if employees contract a rash while handling MWFs, the employer generally just wants to know what to do to get rid of the rash.

But the problem is complex, as we've discussed. Could the rash be caused by the pH of fluid reaching an undesirable level? Or was it due to bacteria, fungus, or some other microbes? What about contaminants in the fluid? Poor personal hygiene practices? Lack of, or improper use of, PPE? Ineffective engineering controls?

These are only a few of the questions that could be asked. It's extremely difficult, and maybe nearly impossible, to solve some problems with MWFs by addressing just one piece of the puzzle. Particularly with MWFs, prevention far outweighs cures.

To prevent problems, EHS pros need to be in the complete loop of the fluid, which we often affectionately refer to as the cradle-to-grave approach.

Practical guidelines

If you provide EHS support to operations that use MWFs, you should initiate or ensure that the following practices or actions are being used:

1) Establish a multi-disciplinary team (include the outside MWF salesperson, engineering, production employees, and the EHS representative) to review and offer recommendations on MWFs issues;

2) Develop a written procedure for acquiring, using, maintaining, and disposing of MWFs;

3) Implement a verification system to ensure that procedures are followed;

4) Create metrics that track deviations from the Rideal' condition of the MWF;

5) Provide ready solutions and controls to maintain the MWF near ideal conditions;

6) Install, maintain and monitor the performance of engineering controls;

7) Ensure that employees use PPE and follow good personal hygiene practices as necessary; and,

8) Ensure that all practices and actions meet or exceed NIOSH recommendations.

By Dan Markiewicz, CIH, CSP, CHMM, senior industrial hygienist with Aeroquip Vickers, Inc., Maumee, Ohio.

For more information

There are some new and improved web sites that offer information and recommendations on working with MWFs. The most comprehensive is the NIOSH site that houses the criteria for a recommended standard for MWFs. The NIOSH Web site address is

The Organization Resources Counselors, Inc., and the Metal Working Fluids Product Stewardship Group developed "Metal Removal Fluids - A Guide to Their Management and Control." This guidance document can be found at

There is an online "Metal Working Fluid Magazine." The magazine is not only technically informative but is spiced with real-world experience and a little humor that coaxes a smile. The magazine can be located on the Web at