On-line CEUs

TIP OF THE MONTH: February/March 2006
Fiberglass Dust and its Potential as a Health Hazard During Cast Removal
David Witmer, BFA, MS

With the continuing growth of the synthetic casting tape market worldwide and the introduction of new products and manufacturers, the issue of health risks associated with the use of traditional fiberglass casting tape has again come into question. Specifically, there is rising concern about the potential health hazards of dust produced during the removal of fiberglass casts. The purpose of this article is to provide some general information about fiberglass and about the potential health hazards of dust produced during the removal of fiberglass casts.

Background on fiberglass

Fiberglass is one of the most useful manufactured products in industry, with numerous commercial applications. It is a man-made fiber composed of natural ingredients such as sand and recycled products such as window glass and bottles. There are two primary types of fiberglass: wool fiberglass and textile fiberglass. The structure and size of their glass fibers vary.  Wool fiberglass, which is made up of thin, small diameter (less than 5 microns thickness) strands of glass, is used extensively in the building construction, and appliance industries as an insulating product.

In comparison, textile fiberglass is made of much thicker and stronger strands of glass (10 microns or more thickness) which are woven into a mesh-like fabric. The fabric is then impregnated with a moisture-curing resin. This fabric is used for reinforcing plastics and composites to construct automotive bodies and boat hulls, bathroom fixtures, and numerous other products such as auto body repair kits and orthopedic casting tape. 

Fiberglass casting tape was originally introduced in the 1950’s as an alternative to plaster of Paris for use in treating orthopedic injuries. In the late 1970’s and early 1980’s, significant improvements in application technologies were made and fiberglass casting tape received widespread acceptance by the orthopedics community.

Fiberglass, asbestos, and lung cancer

There has been an on-going association between asbestos and lung cancer. Since some forms of asbestos are similar in appearance to fiberglass fibers, questions have been posed as to whether working with fiberglass could also result in the development of lung cancer or other health hazards. The scientific community has made over 400 studies of fiberglass in an attempt to answer that question. The conclusion is that it will not, because its properties are very different from asbestos. The United States Occupational Safety and Health Administration (OSHA) confirmed these findings in 1991 when it decided to regulate fiberglass as a nuisance dust and not as a cancer causing agent. In 2001, the International Agency on Cancer Research (AIRC) considered fiberglass not classifiable as a human carcinogen or cancer-causing agent. There are no known chronic health effects connected with long term use or contact with fiberglass.

The principal difference between glass fibers and asbestos fibers is their size and the way the fibers break down. Glass fibers are cylindrical single fibers that never split lengthwise; they only break across the fiber. As they break, they form tiny fragments that no longer have the properties of a fiber. Asbestos fibers, on the other hand, are always present as bundles, never as a single fiber. Asbestos fibers tend to fracture only lengthwise when the bundles break apart, releasing thousands of long, tiny fibers.

When asbestos fibers are inhaled, they become trapped in the small sacs of the lungs known as alveoli. Because asbestos fibers are long, sharp, and irritating to lung tissue, the alveoli close up and trap them in the lungs. This eventually results in asbestosis, a condition where the lungs become hard, fibrous, and inelastic. Although the mechanism has not yet been explained, the epidemiological evidence is clear that in certain individuals exposed to asbestos, lung cancer will result. Because fiberglass breaks across the fiber to form tiny fragments, the tissue response is very different when these particles are inhaled. When fiberglass fragments are inhaled and deposited into the small air sacs of the lung, the alveoli do not close and trap the particles. The particles are expelled from the alveoli and there is a rapid clearance of fiberglass dust particles from the lungs.

Respiratory and inhalation hazards

The dust produced during the removal of fiberglass casts with a cast saw could represent a respiratory hazard depending on the size and concentration of the airborne dust particles generated. Respirable fibers are defined as being greater than 5 microns in length and less than 3 microns in diameter. 

Particle size

Textile fiberglass mesh is made with larger diameter fiberglass strands to increase strength and durability. Orthopedic casting tapes use a fiberglass mesh with strand diameters of 1000 microns or larger. As noted previously, when these strands are cut or broken, they break across the fiber, so the smallest dust particulate would still be 1000 microns in size and therefore generally not capable of remaining airborne as an inhalation hazard, but instead settle as surface particulate dust. For those particles that do make it into the breathing zone of an individual, particles this size typically become trapped in the upper respiratory tract (i.e.; nasal passages). In order to make it into the aveolar part of the lungs, particles must be less than 10 microns in size.

Particle concentration

Cast cutters fitted with vacuum systems are now standard equipment in most cast rooms. The most recent models are equipped with large (6.5 amp) vacuum systems that compare to shop vacs and provide exceptional dust particulate capture capabilities when properly used and maintained. Using a sharp cutting blade and keeping the vacuum filter clean improve the vacuum system efficiency. Using the correct cutting blade also had an impact on the amount of dust produced. A stainless steel blade produces the least dust, a carbide blade a little more, and a tempered blade the most.

In addition, improved nozzle vacuum assemblies can now capture almost all dust particulate generated during cast removal. Despite the name cast cutter, the mechanical action of the blade, which oscillates about 1/4 of an inch, actually rips through the cast during removal. This action significantly reduces the amount of particulate dust that would be thrown if a circular cutting motion were used.  Recent tests of dust production associated with fiberglass cast removals found that fiberglass casts produced very low concentrations of airborne dust. The maximum allowable respirable limit for fiberglass dust concentration is 5 milligrams per cubic meter (5mg/m3). Laboratory tests using a cast saw generated fiberglass dust concentrations between one and three tenths of a milligram (0.1 and 0.3 mg/m3), well below the allowable limit.

For situations where cast cutters equipped with vacuum systems are not available, and with inadequate ventilation where airborne concentrations may exceed the limits recommended, approved respirators (such as NIOSH N95 or better) may be used. However, respirators must be properly fitted to function properly, and while that may be easily accomplished for castroom personnel, it can be a challenge for patients, especially small children. To date, there are no definitive studies that show the effectiveness of vacuum-equipped cast saws in reducing and eliminating airborne fiberglass particulate dust in the cast room. However, the use of a properly maintained cast cutting system with vacuum attachment is highly recommended and undoubtedly has the potential to capture and control fiberglass particulate dust.

Mechanical hazards

Skin irritation

Although vacuum-equipped cast cutters have the potential to capture fiberglass particulate dust, some large residual dust particulate can cling to the soft under-padding materials used in cast construction. These particles can be transferred to clothing or gloves and could inadvertently come in contact with skin or eyes.

The primary health effect and hazard associated with large fiberglass particulate dust involves temporary skin and eye irritation. Most skin problems arise from direct contact with fiberglass through handling rather than from airborne fibers or dust. The irritation is primarily due to the mechanical abrasion of fiberglass on exposed skin. Skin irritation occurs chiefly at the pressure points such as around the neck, the wrist, and between the fingers. Repeated exposure to the skin causes additional irritation, redness and itchiness. The mechanical action of the fibers or fragments scraping against the skin may cause a condition known as dermatitis.

Contacting fiberglass splinters is another type of skin irritation. When fiberglass tape is cut, fractured, or frayed, small fiber slivers that can puncture the skin are sometimes formed. Much like wood splinters from cut lumber, these sliver punctures can become infected if not removed and treated.  In general, wearing nitrile gloves and other items of protective clothing such as long-sleeved shirts or clinical smocks will prevent fiberglass dust from contacting exposed skin surfaces or street clothes worn underneath. Mild soap and cold water can be used to remove fibers that do get on exposed skin. Do not wash with warm water as this will open up the pores of the skin which will cause further penetration of the fibers. To avoid further irritation, do not rub or scratch affected areas. Rubbing or scratching may force fibers into the skin.

Fiberglass dust can and does adhere to work clothes and shoes where it is retained in fabrics. If this dust is not removed from clothes and shoes, it can be brought home and in turn will contaminate household family laundry.

Eye irritation

Eye irritation is another potential hazard associated with removing casts made with fiberglass casting tape. Large particulate clinging to the cast under-padding or to clothing can inadvertently be transferred to the eyes if they are accidentally touched or rubbed. Safety glasses or goggles will prevent contact with the eye and alleviate potential eye injuries. If dust does get into the eyes, immediately flush with plenty of running water for at least 15 minutes.

Biological Hazards

In additional to potential respiratory and mechanical hazards caused by fiberglass, particulate dust or splinters from removed casts could also pose a biological hazard. Diseases such as Hepatitis B and C, and HIV/AIDS are caused by microorganisms that are transmitted through blood and other bodily fluids such as urine and feces. Other diseases also spread by bloodborne pathogens include malaria, syphilis and viral hemorrhagic fever.

Fiberglass dust from casts that have become contaminated by blood and other body fluids could be inhaled or ingested if airborne, or injected into exposed hands, arms, and eyes as splinters. Although inhalation and ingestion have not been shown to transmit these diseases, injection and abrasion injuries accompanying eye, throat or skin irritation from contaminated fiberglass particles or splinters are much more dangerous.  Wearing rubber or nitrile gloves, avoiding skin and eye contact, and washing hands and skin following cast removal can reduce the exposure hazard from contaminated fibers.

Conclusion

There are potential health hazards with exposure to all forms of dust. At this point however, the evidence indicates that the dust generated while removing fiberglass casts is primarily a nuisance type dust that has little potential for impact on the health of those exposed. Fears about the hazards of fiberglass dust is scientifically unsubstantiated and is often the byproduct of careless or inaccurate information. A basic understanding of the physical properties of fiberglass and the institution of some basic castroom safety practices can reduce and eliminate the hazards associated with exposure to fiberglass dust. Such practices include:

·      Use a cast cutter with an attached vacuum system that is properly operated and maintained.

·      Wear nitrile gloves, long-sleeved clothing, and eye protection when removing fiberglass casts.

·      Avoid rubbing eyes or skin during cast removal.

·      Do not handle removed fiberglass casts more than necessary. Have a trash bin nearby for quick disposal.

·      Clean work clothes of fiberglass residual prior to going home.

·      Keep the castroom clean.

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