Approximately 80% of occupational skin disease occurs as a result of nonimmunologic reaction to chemical irritants (irritant contact dermatitis) and 20% to allergic reactions (allergic contact dermatitis)(1). Among workers employed in machining operations that utilize water-soluble metalworking fluids (MWF), dermatitis is the most prevalent occupational disease. Dermatitis is inflammation (“itis”) of the skin characterized by red itchy rashes that may have well-delineated or diffuse patterns. Excessive and prolonged dermal exposures to straight oils (no water content) may cause keratoses, acne, and folliculitis. There is a wide range of individual susceptibilities and dermatological responses to MWF products and other industrial chemicals. The following discussion involves, (1) Some Common Causes of Dermatitis among Machinists; and (2) Prudent Measures to Reduce Incidences of Dermatitis (in machine shops).
SOME COMMON CAUSES OF DERMATITIS AMONG MACHINISTS
Water-based metalworking fluids (soluble oils, and semi-synthetic and synthetic fluids) are complex mixtures of chemicals and chemical additives. Dermal exposures to MWF over a period of time may deplete the epidermis (uppermost layer of skin) of natural lipids (a process called “defatting”). Although the epidermis is normally a very effective barrier against the intrusion of external substances, the defatting process can cause localized irritation and cracking of the skin which may lead to irritant dermatitis and subsequent infections. In cases of immunological susceptibility, some workers may experience allergic dermatitis which is characterized by delayed sensitivity reactions upon contact with fluids.
There are occasions when conscientious attempts to cleanse exposed skin of fluid deposits can actually cause or exacerbate dermal irritation. For example, workers who engage in excessive hand-washing may experience dry and damaged skin over a period of time. Also, removal of MWF residues from skin surfaces by rubbing with soiled shop cloths that contain dirt/grit and microscopic metal fines may cause nicks and abrasions of the skin. Minute cuts and bruises can provide niches for opportunistic bacteria to foment infections and, thus, impede normal healing mechanisms of the skin. It has been known for many years that MWF bacteria on the surface of uncompromised and intact skin are not a cause of dermatitis.(2)
Common causes of dermal disease involving metalworking fluids are summarized as follows:
Figures 1 and 2 show examples of hand and wrist dermatitis.(3)
Figure 1. Hand Dermatitis
Figure 2. Affected Hand and Wrist
PRUDENT MEASURES TO REDUCE INCIDENCES OF DERMATITIS
Incidences of dermatitis among machinists can be minimized by a combination of fairly easy and cost effective measures. In this regard, a major strategy is to reduce the frequency and extent of MWF exposures that workers experience during any given work shift. This goal can be accomplished in a variety of ways:
The reader is referred to the Independent Lubricant Manufacturers Association (ILMA) Dermal Assessment Guide and the OSHA Dermal Exposure websites for additional information on the evaluation and reduction of occupational dermatitis.(4,5)
Other articles in this issue: