Airborne asbestos in buildings

The concentration of airborne asbestos in buildings nationwide is reported in this study. A total of 3978 indoor samples from 752 buildings, representing nearly 32 man-years of sampling, have been analyzed by transmission electron microscopy. The buildings that were surveyed were the subject of litigation related to suits alleging the general building occupants were exposed to a potential health hazard as a result the presence of asbestos-containing materials (ACM). The average concentration of all airborne asbestos structures was 0.01 structures/ml (s/ml) and the average concentration of airborne asbestos ⩾5 μm long was 0.00012 fibers/ml (f/ml). For all samples, 99.9% of the samples were <0.01 f/ml for fibers longer than 5 μm; no building averaged above 0.004 f/ml for fibers longer than 5 μm. No asbestos was detected in 27% of the buildings and in 90% of the buildings no asbestos was detected that would have been seen optically (⩾5 μm long and ⩾0.25 μm wide). Background outdoor concentrations have been reported at 0.0003 f/ml ⩾5 μm. These results indicate that in-place ACM does not result in elevated airborne asbestos in building atmospheres approaching regulatory levels and that it does not result in a significantly increased risk to building occupants.