Dust from cotton manufacture: changing from static to personal sampling.

Several designs of personal samplers were tested for use to collect cotton dust. The IOM personal inhalable-dust sampler was selected because: (1) collection of the whole inhalable fraction was preferred, since all inhaled sizes are under suspicion as contributing to respiratory symptoms in cotton exposure; (2) this sampler is well characterized; and (3) it was found to be practicable in the environments examined. Gauze shields to exclude 'fly' from the personal sampler were tried, but were rejected mainly because measurement of the whole inhalable fraction by a validated sampler was felt to be more appropriate. A range of processes at a representative selection of mills was assessed by a hygiene team, and classified as 'clean' or 'dirty' in terms of present standards of control. This classification agreed well with subsequent measurements using the present method, which uses a large static sampler. A personal sampling survey then showed that in about two-thirds of 'clean' processes personal exposure of at least 80% of those employed was less than about 2-2.5 mg m-3. Only one-tenth of 'dirty' processes met this standard. Personal exposure correlates poorly with the present static method, as expected, but comparison of the results suggested that a mean background level of 0.5 mg m-3 would correspond to a median personal exposure of about 2.2 mg m-3. Side-by-side measurements by the background method differed by less than 0.15 mg m-3 on about 95% of occasions. Niven et al. (to be published) have compared the IOM head used in this study with the Manchester University sampler previously used by Cinkotai et al. [Ann. occup. Hyg. 32, 103-113 (1988)] to derive a relationship between personal exposure and prevalence of byssinotic symptoms in spinners. According to Cinkotai et al.'s results the concentrations of 2-2.5 mg m-3 discussed would correspond to a prevalence of 3-5%. However, this prevalence probably reflects higher exposures in the past.

The human head as a dust sampler.

A life-size model human head and shoulders was exposed in a wind tunnel to winds between 0.75 and 2.75 ms/s and particles up to 30 micron aerodynamic diameter, and the weight of material entering the nose and mouth at various breathing rates was compared with that caught by isokinetic samplers. When aspirated at a constant rate, the head behaved like a blunt sampler, showing a ten-fold variation in entry efficiency for different windspeeds and directions, and a two-fold variation even at 5 micron. Detailed facial structure had little effect. The efficiencies for various breathing patterns and minute volumes were calculated, and when averages were taken for all wind directions, to simulate a worker randomly oriented to the wind, the efficiencies lay within a fairly small range, and were all substantially less than 100%. "Total" dust standards and samplers should take account of these efficiency curves.