A Comparison of the CATHIA-T Sampler, the GK2.69 Cyclone and the Standard Cowled Sampler for Thoracic Fiber Concentrations at a Taconite (Iron Ore)-Processing Mill
1 Exposure Assessment Branch, Health Effects Laboratory Division (HELD), National Institute for Occupational Safety and Health (NIOSH), 1095 Willowdale Road, MS-3030, Morgantown, WV 26505, USA
2 Spokane Research Laboratory, NIOSH, 315 E. Montgomery Avenue, Spokane, WA 99207, USA
3 Biostatistics and Epidemiology Branch, HELD, NIOSH, 1095 Willowdale Road, MS-4020, Morgantown, WV 26505, USA
* Author to whom correspondence should be addressed. Tel: 1-304-285-6146; fax: 1-304-285-6041; e-mail: elee2{at}cdc.gov
Several recommendations have been made to the effect that the most appropriate health-based size-selective criterion for fibers is the thoracic convention of the International Organization for Standardization (ISO). The performance of two thoracic samplers, the CATHIA-T (37-mm filter) and the GK2.69 cyclone (37-mm filter), was investigated against the standard 25-mm cowled sampler (current NIOSH 7400 standard method) to determine the effect of thoracic sampling on field results. A total of 270 samples: 80 field and 10 field blank samples for each sampler type, were taken from seven stations in the processing mill of an iron ore mine whose ore contains amphibole minerals. Slides were prepared using the dimethyl formamide/Euparal technique and relocatable cover slips. Two counters examined the slides according to NIOSH 7400 counting A rules with phase contrast microscopes. Prior to counting the sample slides, four reference slides were randomly selected and counted three times on different days to compare the coefficient of variation (CV) between and within counters. Also, seven reference slides were chosen to explore variability between the two microscopes. The average CV between counters (0.148) showed slightly higher than the average CVs within counters (0.072 for Counter 1 and 0.119 for Counter 2). The average CV between the two microscopes was 0.147. Compared to the standard cowled sampler, the overall fiber concentration was lower for the CATHIA-T sampler (CATHIA-T/Cowled = 0.63) and higher for the GK2.69 cyclone (GK2.69/Cowled = 1.66). The result for the CATHIA-T sampler is as expected from laboratory trials, but the result for the GK2.69 cyclone is not as expected. In conclusion, the CATHIA-T sampler has a potential advantage as a high-flow static sampler for screening coarse particles. However, these findings resulted from one field sampling site that contains amphibole minerals, not all of which are asbestiform. Thus, additional field samples from other environments might be helpful to confirm the performance of these samplers.
Keywords: aerosol samples • CATHIA • fibers • GK2.69 • NIOSH 7400 method • thoracic sampling
Received June 26, 2007; in final form October 17, 2007