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Q.As a home inspector, I'm exposed to fiberglass insulation almost every day, and although I wear a dust mask, I'm concerned that this may not provide enough protection. I also am concerned about the possible health hazards to the occupants of these homes, particularly when there's exposed fiberglass in basement areas used as shop space or as play areas for children. It seems to me that fibers could become airborne when someone walks on the floor above these rooms. What are the real risks?

A.Jeffrey May, principal scientist at May Indoor Air Investigations in Cambridge, Mass., responds: Because the exposed fibers in fiberglass batts are largely glued together, they are only aerosolized (broken up and suspended in the air) when there is a direct physical disturbance, such as during installation or while mechanical work is being performed in an insulated area. Even then, these fibers don't stay in the air long, and eventually they accumulate in the floor dust. Otherwise, the number of fiberglass fibers in the air is probably rather low, with most of them too large to be inhaled into the lungs.

Occasionally, there are a few respirable fibers (ones that are short and thin enough to be inhaled), but the theory is that — unlike highly stable asbestos fibers — they ultimately dissolve in the lung fluids. Fiberglass fibers are still considered to be "possible" carcinogens, but they have remained in this category for some time and have not advanced to actual carcinogen status. So I would say that the risk to both you and the home's occupants is quite low.

Actually, drop ceiling tiles mounted in a grid system suspended from the ceiling or fastened directly to the ceiling joists also contain glass fibers and glass particulates; they may pose a greater risk than insulation, which is usually covered by ceiling and wall finishes. When installed over carpeting, for example, the glass particles and fibers that collect in the fabric can be released by foot traffic, causing irritation in some cases when there is skin contact.

For home inspectors, a NIOSH-rated N95 particle mask should be fine for eliminating most inhalation exposure. Of course, fibers that accumulate on clothing could cause additional exposure even when away from the source, which is a good reason to wear coveralls in crawlspaces while doing inspections.