Cutting Fluid - Safety Concerns

Safety Concerns

Cutting fluids present some mechanisms for causing illness or injury in workers. These mechanisms are based on the external (skin) or internal contact involved in machining work, including touching the parts and tooling; being splattered or splashed by the fluid; or having mist settle on the skin or enter the mouth and nose in the normal course of breathing.

The mechanisms include the chemical toxicity or physical irritating ability of:

• the fluid itself
• the metal particles (from previous cutting) that are borne in the fluid
• the bacterial or fungal populations that naturally tend to grow in the fluid over time
• the biocides that are added to inhibit those life forms
• the corrosion inhibitors that are added to protect the machine and tooling
• the tramp oils that result from the way oils (the lubricants for the slideways) inevitably finding their way into the coolant

The toxicity or irritating ability is usually not high, but it is sometimes enough to cause problems for the skin or for the tissues of the respiratory tract or alimentary tract (e.g., the mouth, larynx, esophagus, trachea, or lungs).

Some of the diagnoses that can result from the mechanisms explained above include irritant contact dermatitis; allergic contact dermatitis; occupational acne; tracheitis; esophagitis; bronchitis; asthma; allergy; hypersensitivity pneumonitis (HP); and worsening of pre-existing respiratory problems.

Safer cutting fluid formulations provide a resistance to tramp oils, allowing improved filtration separation without removing the base additive package. Room ventilation, splash guards on machines, and personal protective equipment (PPE) (such as safety glasses, respirator masks, and gloves) can mitigate hazards related to cutting fluids.

Bacterial growth is predominant in petroleum-based cutting fluids. Tramp oil along with human hair or skin oil are some of the debris during cutting which accumulates and forms a layer on the top of the liquid; anaerobic bacteria proliferate due to a number of factors. An early sign of the need for replacement is the "Monday-morning smell" (due to lack of usage from Friday to Monday). Antiseptics are sometimes added to the fluid to kill bacteria. Such use must be balanced against whether the antiseptics will harm the cutting performance, workers' health, or the environment. Maintaining as low a fluid temperature as practical will slow the growth of microorganisms.

The discussion above could leave a reader with the mistaken idea that cutting fluid is "often extremely dangerous". That would be an exaggeration. In reality, cutting fluid exposure is like many exposures in life, such as second-hand tobacco smoke; ethanol ingestion; paint and thinner fumes; kitchen or bakery smoke; contact with animal manure in farming or veterinary work, or contact with sewage in plumbing or sewer work. Such exposures only cause acute illness or injury in occasional cases where some situational factor was "out of normal bounds". Rather, the main health risk is that of chronic illness from long-term occupational exposure. Most machinists work around cutting fluids for years without adverse effects. They generally don't worry about casual contact, and they use PPE to minimize it.