Laboratory studies with animals exposed to high concentrations of fine
fibrous dust (fibrils) derived from pai a-aramid fibres suggest that
it may cause lung damage. Based on the information from such studies t
here is an initiative in the U.K. to regulate workplace exposure. Para
-aramid fibres are used in textiles, friction products, composite mate
rials and other applications, but little is known about the extent or
intensity of fibre dust exposure during these manufacturing operations
. A survey has been undertaken in a selection of manufacturers of pala
-aramid containing products to assess their 8-h time-weighted average
exposure to respirable fibrils. Concentrations were measured using the
membrane filter technique with analysis by phase-contrast microscopy.
Measurements of airborne fibril size were also made by scanning elect
ron microscopy. Geometric mean concentrations for different jobs were
generally low, ranging from 0.005 to 0.4 fibres ml(-1). Assuming a log
-normal distribution, less than 1% of the exposure levels would be exp
ected to exceed 0.5 fibres ml(-1) and about 0.002% would be above 2 fi
bres ml(-1). Analysis of a selection of samples by fluorescence micros
copy suggests that most of the fibrils in the majority of sites survey
ed were para-aramid. At some sites a significant proportion of asbesto
s fibres were also found.