A comparison of airborne man-made vitreous fiber concentrations before and after installation of insulation in new construction housing

Airborne fiber concentrations were measured before and after installation of man-made vitreous fiber (MMVF) insulation products in 14 homes. Gravimetric, phase contrast microscopic (PCM), and scanning electron microscopic (SEM) methods were used to measure total dust, fiber, and MMVF concentrations, respectively. Preinstallation and postinstallation total dust concentrations, ranging from 0.01 to 1.17 and 0.03 to 0.96 mg/m3, respectively, were not statistically different. PCM analysis of preinstallation fiber concentrations calculated from the use of the National Institute for Occupational Safety and Health (NIOSH) Method 7400 A rules ranged from 0.002 to 0.011 fibers/cm3 (f/cm3); postinstallation concentrations ranged from 0.003 to 0.015 f/cm3. Fiber concentrations calculated from the use of the NIOSH 7400 Method B rules were slightly lower. Comparison of preinstallation and postinstallation concentrations using a one-sided, paired t-test indicated that there was no statistically significant difference for fiber concentrations calculated by either A or B rules. Airborne MMVF concentrations determined using SEM were all <0.01 f/cm3. Eleven of 14 preinstallation samples and 7 of 14 postinstallation samples were below the analytical limit of quantification (LOQ). SEM data are difficult to interpret because of the large number of samples <LOQ. Initially airborne fiber concentrations resulting from fiber counts <LOQ were calculated in the traditional manner by substituting 5.5 fibers for the actual number of fibers counted. This is termed the “LOQ-substituted” concentration. Nonparametric statistical analyses indicate that the postinstallation LOQ-substituted SEM airborne MMVF concentrations were significantly elevated as a result of insulation activities. Comparison of the pooled preinstallation and postinstallation concentrations, however, indicates that in both cases the concentration is low and the difference is slight. All airborne fiber concentrations detected and determined by the two methods used in this study were two to three orders of magnitude below occupational exposure limits proposed by the Occupational Safety and Health Administration and those recommended in industry guidelines.