Toxicology of Industrial Compounds

T.W.HESTERBERG ET AL. 109
Table 7.6 Representative airborne levels of fiber glass in workplace and rat
inhalation study
a Outdoor data from Tiesler and Draeger (1994). Product-related fibers counted
using NIOSH A Rules.
b Data from Jacob et al., (1993). Airborne levels resulting from manufacturing
operations using FG insulation.
c Data from Lees et al., (1993a). Installation of residential insulation.
d Jacob et al. (1992) reported that levels returned to background within hours after
Batt installation.
All other data are averages from the various studies herein cited.
and quantitative comparison was made of the aerosol and lung fibers in the
rat inhalation study with those in various human exposure situations
(Hesterberg and Hart, 1994). A comparison of the reported aerosol fiber
levels in various human settings with those used in the rat inhalation study
is shown in Table 7.6. FG levels in the rat aerosol were more than five
orders of magnitude higher than the reported level for outdoor air, and at
least three orders of magnitude higher than for average airborne levels for
many occupational settings (e.g. over 2000fold higher than FG batt
installation). The rat aerosol was 75-fold more concentrated than the
highest reported average TWA for airborne fiber levels in an occupational
setting, i.e. blowing installation of unbound fiber glass (the potential for
higher airborne levels has been recognized for some time, and
recommended work practices call for the use of respirators in such
circumstances). Despite the range in products and occupational settings,
fiber dimensions in most of the human exposures examined were fairly
similar to those found in the rat inhalation study aerosol (Hesterberg and
Hart, 1994). The fiber dimensions of aerosolized rock and slag wool
collected from workplace air during the installation of batts or blowing of
loose fibers have similar mean diameters to that of fiber glass (1.0–1.6
µm). However, the mean lengths appear to be greater (30–50 µm) than for
most workplace samples of fiber glass.
Hesterberg and Hart (1994) also compared the lung burdens of rats
exposed in the recent fiber glass inhalation study in rats with lung burdens
found in workers involved in MMMF (primarily FG) manufacturing
(McDonald et al. 1990). As shown in Table 7.7, rat fiber glass lung
burdens vastly exceeded that of the workers reported by McDonald et al.,