Indoor airborne fiber levels of MMVF in residential and commercial buildings.

Man-made vitreous fibers (MMVF) have been used widely in commercial and residential buildings for over 50 years. Concerns have been expressed since the late 1960s that MMVF products may erode and contribute to fiber levels in the indoor environment. This cooperative investigation was undertaken to quantify indoor respirable fiber levels by phase contrast optical microscopy (PCOM) and to differentiate between fiber types using scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX). A total of 205 stationary samples were collected using standard industrial hygiene methods in 51 residential and commercial buildings. Twenty-one simultaneous outdoor samples were collected at 19 buildings. All samples were analyzed by PCOM following the NIOSH 7400 Fiber method, "B" counting rules, and 50 randomly selected samples were analyzed by SEM-EDX. The PCOM mean value for all respirable fiber levels was 0.008 f/cc with a median value of 0.007 f/cc and a maximum value of 0.029 f/cc. Ninety-seven percent of the respirable fibers identified by SEM-EDX were determined to be organic. MMVF were detected on only two samples. Airborne fiber levels were very low and the respirable fibers present were primarily organic. The inorganic fiber levels determined by SEM-EDX which included MMVF were less than 0.0001 f/cc.