Annals of Occupational Hygiene Advance Access originally published online on October 31, 2008
Annals of Occupational Hygiene 2009 53(1):19-25; doi:10.1093/annhyg/men068
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Application of PUF Foam Inserts for Respirable Dust Measurements in the Brick-Manufacturing Industry
1 Occupational and Environmental Health Research Group, School of Translational Medicine, Faculty of Medical and Human Sciences, The University of Manchester, Room C4.4, Ellen Wilkinson Building, Oxford Road, Manchester M13 9PL, UK
2 Gardner Baker Limited, Dronfield, Derbyshire S18 1YB, UK
* Author to whom correspondence should be addressed. Tel: +44-161-275-8500; fax: +44-161-275-5595; e-mail: Frank.deVocht{at}manchester.ac.uk
Institute of Occupational Medicine dual-fraction samplers equipped with porous polyurethane foam inserts have been introduced as a cheaper alternative to cyclone pre-selectors for measuring respirable dust. Initial data from a variety of industries suggested that the dual-fraction sampler yielded similar results as personal cyclones and that the respirable selection of the foam was not adversely affected by particle loading. We conducted a similar study, but specifically in the brick industry to assess the validity of this dual-fraction sampler as an alternative to personal cyclones in this industry. A total of 72 side-by-side samples using Higgins–Dewell cyclones and dual-fraction samplers were taken in seven UK factories manufacturing a variety of bricks. A priori measurements were assigned to any of the three groups based on the dominant source of the particulates in the exposure matrix (clay, sand or mixed) at the location in the factories where the measurements were taken. After log transformation, Higgins–Dewell cyclone-measured concentrations were on average 1.9 times higher than the concentrations measured by the dual-fraction samplers, with a Pearson correlation of 0.78 (95% confidence interval 0.66–0.85). Stratified analysis by main source of exposure suggested that the correlation was best for silica dust-based exposures rp = 0.88 (0.63–0.96), but decreased with the relative importance of clay particulates in the exposure matrix to rp = 0.82 (0.59–0.93) in the ‘mixed-source’ group and rp = 0.74 (0.55–0.85) in the ‘clay particulates’ group. Similarly, performance of the dual-fraction sampler relative to the cyclone sampler was negatively associated with increased relative importance of clay particulates in the exposure matrix and ranged from similar measured concentration β = 0.96 (0.54–1.39) for silica to 50% under sampling β = 0.50 (0.33–0.67) for clay particulates. These results suggested that the overall performance of the dual-fraction sampler in the brick industry depends on the relative importance of clay particulates in the exposure matrix. As such, results from occupational hygiene compliance surveys close to the occupational exposure limit can lead to erroneous decisions on compliance.
Keywords: brick industry • dual-fraction sampler • foam inserts • respirable dust
Received March 19, 2008; in final form September 10, 2008