Fiberglass Insulation & Cancer

Manufacturers began using fiberglass in the 1920's. The material used to create it--rock, slag and sand combinations--is plentiful and cheap. Use of fiberglass expanded when suspicions began to surface about the safety of asbestos. Fiberglass' similarity in shape and size to asbestos made it equally useful for insulation, and for adding strength and fire safety to products. The same similarity made researchers wonder about the safety of fiberglass.

Fiberglass Types

• One value of fiberglass is the ability to create many different size and shape fibers that then have different properties and uses. E-glass fiberglass serves electrical uses. Its continuous fibers make it perfect for increasing the strength of other materials. Glass wool fiberglass strands are extremely fine and form a wool-like mass. It works well for insulation and to add fire resistance and sound proofing. Manufacturers can also create "special purpose" fibers using combinations of fibers with specific properties such as higher heat resistance or strength.

Larger Fiber Glass Fibers

• Fibers with diameters greater than three micrometers and longer than 10 micrometers--one micrometer being one millionth of a meter-- are considered safe according to the American Conference of Governmental Industrial Hygienists (ACGIH) in a report dated 2004. The Environmental Protection Agency says fibers must be smaller than five micrometers to be inhaled. The ACGIH fact sheet says workers in fiberglass factories did not have increased rates of lung cancer.

Warning

• The ACGIH does consider fiberglass wool as a carcinogen in animals, but the report says that the animal studies did not apply to humans. The researchers' method of exposing the animals--injecting fibers into airways rather than the animals breathing naturally--meant that humans would not likely receive the same kind of exposure that caused cancer in lab experiments.

2010 Report

• A report in 2010 by the National Toxicology Program notes that inhaling fibers did increase lung cancers in laboratory animals, and fiberglass wool has diameters as tiny as .05 micrometers, so can be inhaled. Longer, thinner fibers, and "biopersistence"--the ability to stay in the lung tissues--were strong indicators of a fiber's potential to make tumors grow, along with the degree of exposure. The "longer" fibers were more than 20 micrometers.

Fiber Types of Most Concern

• According to the National Toxicology Program report, the fiberglass most associated with possible cancer is glass wool fibers made into special purpose fiberglass. Two of the many types mentioned are "type 475" and Man-Made Vitreous Fiber (MMVF) 33, which combines type 475 with other types and sizes of glass fiber. Additionally, when lab animals inhaled E-glass fibers, researches found significant increases in tumors, both malignant and non-malignant.

Possible DNA Changes

• The report from the National Toxicology Program cited a study done in 2008 (Nguea et al.) that discovered glass wool fibers damaged DNA in cells from mammals, and caused chromosomal abnormalities.

Still Great Disagreement

• Reports and opinions by government agencies still have not found proof of cancer in humans related to fiberglass wool, the type used for insulation. All agencies agree that fiberglass is an irritant that can cause temporary skin and eye irritation and difficulty breathing for people exposed. Caution is warranted, but the report from the National Toxicology Program did find reassuringly that fiberglass insulation does not cause appreciable increases in fiberglass exposure in homes.