Environmental Health & Safety


Fiberglass is a man-made mineral fiber that is widely used in America. First produced in the 1920's, fiberglass became a popular substitute for asbestos in the 1950's when some of the deleterious health effects from asbestos were first becoming apparent. Due to the similarity in shape between the fiberglass and the asbestos fibers, fiberglass was able to effectively replace asbestos in many applications such as in electrical, thermal, and acoustic insulation and in adding structural reinforcement and heat resistance to a material.

The similarities to asbestos, which have allowed fiberglass to be so versatile, are also sources of concern for some who suggest that fiberglass may also exhibit similar deleterious health effects. There are three main types of fiberglass. Each type has different physical dimensions and properties which effect the suitability for specific applications and may also impact human health in different ways. These types are continuous fibers (used in electrical insulation, cement and plastics reinforcement), insulation wool (for thermal and acoustic insulation), and special purpose fibers (used for heat resistance and light-weight materials).

There is currently a great deal of debate concerning the health effects of fiberglass. It is, however, agreed that fiberglass is an irritant. Skin irritation is generally associated with thick fibers which can be found in insulation wools and filamentous glass. Fiberglass may also cause irritation of the eyes and throat. If the exposure is sufficient, fiberglass may produce irritation dermatitis and difficulty in breathing, which will go away once exposure has ceased.

There have been a variety of studies designed to determine whether fiberglass can have a carcinogenic effect in humans. Differing results have been attributed to problems determining exposure, achieving statistical power, and accounting for the type and size of fibers.

The larger continuous fibers, with diameters greater than 3µm (micrometers) and length greater than 10µm have been designated by the American Conference of Governmental Industrial Hygienists (ACGIH) as an "A4" substance meaning "Not Classifiable as a Human Carcinogen". This means that there is insufficient data to draw a conclusion either way about any cancer causing potential.

Glass wool which has diameters down to 0.05µm and lengths greater than 1µm have been designated by the ACGIH as an "A3" substance. This classifies the glass wool as an animal carcinogen, but indicated that the dose and the routes of exposure of the animal studies are not considered to be relevant to worker exposure. They go on to state that "Available evidence suggests that the agent is not likely to cause cancer in humans except under uncommon or unlikely routes or levels of exposure."

In October 2001, an international expert review by International Agency for Research on Cancer (IARC) re-evaluated the 1988 IARC assessment of glass fibers, rock and slag wool fibers from its list of substances "possibly carcinogenic to humans." All fiber glass and rock and slag wools that are commonly used for thermal and acoustical insulation are now considered not classifiable as to carcinogenicity to humans (Group 3). (International Agency for Research on Cancer, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Man-Made Vitreous Fibres, Vol. 81 (Lyon, France: WHO/IARC, 2002); http://monographs.iarc.fr/ENG/Monographs/vol81/volume81.pdf 

There are many ways to protect yourself and lower your exposure if you are working with fiberglass. Always wear goggles and appropriate work gloves. Be sure to cover all exposed skin with long sleeve shirts and long pants. During low level exposure to airborne fibers at least a dust mask should be worn to protect your throat and lungs. After the work is done always wash your hands and face thoroughly.

Fiberglass is extremely useful in workplace and residential applications, but it should be treated with care to avoid some of its irritating properties. In the future more scientific studies will be conducted to determine if there are truly any far reaching health effects. For now, safe handling and work practices will go a long way toward insuring a safe and healthy treatment of fiberglass.

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