General

Metal working fluids (MWF) are fluids used during machining and grinding to prolong the life of the tool and protect the working surfaces of the work pieces. Workers are exposed to MWFs by inhaling mists and by skin contact with the fluid. Skin contact occurs by dipping the hands in the fluid, splashing, or handling the work pieces coated in the fluid. A substantial amount of scientific evidence indicates that workers routinely exposed to MWF mists have an increased risk of respiratory and skin diseases.

Types of Metal Working Fluids

There are four different classes of MWFs:

Straight Oil

These are solvent-refined petroleum oils or other animal, vegetable, or synthetic oils often used with additives.

Soluble Oil

These are combinations of 30% to 85% refined lubricant-based oils and emulsifiers with other performance additives. Soluble oils are diluted with water.

Semi-Synthetic

These contain a lower amount of lubricant-based oil and a higher proportion of emulsifiers and water.

Synthetic

These contain no petroleum oils and may be water soluble and water dispersible. The synthetic concentrate is diluted with water.

Exposure hazards

Exposure to hazardous contaminants in MWFs presents a health risk to workers. Contamination may occur from process chemicals, metals, and alloys from parts, water, cleaning agents, and chemicals introduced to control biological growth. Water-based MWFs are an excellent growth medium for many kinds of bacteria and fungi. Research has suggested that microorganisms and their by-products such as endo-toxins can cause respiratory effects seen in exposed workers.

Biocides

Biocides are chemicals used to limit bacterial growth, however, adaptation quickly causes bacteria to become used to the biocides and begin using it for nutrients. Some constituents in biocides are toxic to humans.

Health Risks

Dermatological Conditions

Workers exposed to MWFs suffer a high rate of skin diseases. Straight MWFs are linked to folliculitis, oil acne, and keratosis. Soluble semi-synthetic and synthetic MWFs have been linked to contact dermatitis and, in some cases, allergic contact dermatitis. The prognosis for dermatitis is poor. Some workers eventually have become disabled as a result of their skin disorders.

Cancer

Substantial evidence indicates some MWFs are associated with increased risk of larynx, pancreas, skin, scrotum, and bladder cancer. The time between initial exposure and appearance of most types of cancer is often 20 years or more.

Lung Disease

Exposure to MWF mists can cause a variety of respiratory conditions such as lipid pneumonia, hyper-sensitivity pneumonites, asthma, acute airways irritation, chronic bronchitis, and impaired lung function. While cases of deep lung-lipid pneumonia, hard metal disease, and legionellosis appear relatively unusual, hyper-sensitivity pneumonites, asthma, and other airway disorders have recently emerged as an important risk factor for workers exposed to MWF mists.

Prevention

Mist Inhalation

A breathing face mask must be mandatory. Mist collectors and exhausts should be installed over every machine that uses MWFs to prevent general inhaling of uncontrolled MWF mists.

Filtration

Continuous filtration of MWFs will remove microorganisms without having to add toxic biocides. A 0.5-micron fine solids filter will trap most bacteria as well as metal solids and debris.

The Allen Continuous Filter System extends fluid life by removing metal solids, dirt, and debris as well as bacterial solids and odors from metal working fluid. The system consists of a self-contained filter vessel suitable for one stacked-disc type filter element, and includes a differential pressure gauge that automatically shuts the motor down if the filter element clogs and needs to be changed. The vessel is provided with an automatic air vent. The Allen Continuous Filter System is available in larger capacities for large volumes of metal working fluid purification.
 

Terminology

Hyper-Sensitivity Pneumonites

Sometimes called “machine operator’s lung,” it is an allergic reaction caused by bacteria and chemicals found in machine working fluids. Symptoms include chills, fever, shortness of breath, and a deep cough.

Biocides

Biocides kill bacteria but are also highly toxic to humans if adsorbed through the skin or inhaled with mists.

Dermatitis

Dermatitis is a skin disease caused by contact with metal working fluids. Outbreaks involve dry, scaly, and cracked skin; pimples on the arms and hands; and raw sores.