Glass Fiber - Safety

Safety

Glass fiber has increased in popularity since the discovery that asbestos causes cancer and its subsequent removal from most products. However, the safety of glass fiber is also being called into question, as research shows that the composition of this material (asbestos and glass fiber are both silicate fibers) can cause similar toxicity as asbestos.

1970s studies on rats found that fibrous glass of less than 3 micrometers in diameter and greater than 20 micrometers in length is a "potent carcinogen". Likewise, the International Agency for Research on Cancer found it "may reasonably be anticipated to be a carcinogen" in 1990. The American Conference of Governmental Industrial Hygienists, on the other hand, says that there is insufficient evidence, and that glass fiber is in group A4: "Not classifiable as a human carcinogen".

The North American Insulation Manufacturers Association (NAIMA) claims that glass fiber is fundamentally different from asbestos, since it is man-made instead of naturally-occurring. They claim that glass fiber "dissolves in the lungs", while asbestos remains in the body for life. Although both glass fiber and asbestos are made from silica filaments, NAIMA claims that asbestos is more dangerous because of its crystalline structure, which causes it to cleave into smaller, more dangerous pieces, citing the U.S. Department of Health and Human Services:

Synthetic vitreous fibers differ from asbestos in two ways that may provide at least partial explanations for their lower toxicity. Because most synthetic vitreous fibers are not crystalline like asbestos, they do not split longitudinally to form thinner fibers. They also generally have markedly less biopersistence in biological tissues than asbestos fibers because they can undergo dissolution and transverse breakage.

A 1998 study using rats found that the biopersistence of synthetic fibers after one year was 0.04–10%, but 27% for amosite asbestos. Fibers that persisted longer were found to be more carcinogenic.