Exposure to fine airborne fibrous dust amongst processors of para-aramid

Laboratory studies with animals exposed to high concentrations of fine fibrous dust (fibrils) derived from para-aramid fibres suggest that it may cause lung damage. Based on the information from such studies there is an initiative in the U.K. to regulate workplace exposure. Para-aramid fibres are used in textiles, friction products, composite materials 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 para-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 electron 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 expected to exceed 0.5 fibres ml^-1 and about 0.002% would be above 2 fibres ml^-1. Analysis of a selection of samples by fluorescence microscopy suggests that most of the fibrils in the majority of sites surveyed were para-aramid. At some sites a significant proportion of asbestos fibres were also found.