Program > Saturday > 14:00 > Session symposium. Symposium: Asbestos

Paper: An asbestos exposure database for asbestos mine/mill workers (1977-1994)
Author(s) and Affiliation(s):
Tina Giles Murphy, Safety Net – Centre for Occupational Health & Safety Research, Memorial University of Newfoundland
John Oudyk, Occupational Health Clinic for Ontario Workers
Paul Demers, School of Environmental Health, University of British Columbia
Stephen Bornstein, Safety Net – Centre for Occupational Health & Safety Research, Memorial University of Newfoundland
Session : symposium. Symposium: Asbestos
Day/Time: Saturday at 14:00
Room: Armoury Suite, 2nd Floor
Objectives:

As part of the creation of the Baie Verte, Newfoundland Asbestos Miners Registry, the results from over 7000 asbestos personal and area air samples collected at the Baie Verte open pit asbestos mine and mill between years of 1976 and 1994 are described. Patterns of variance are explored within- and between-sampling units (persons, shifts, jobs within departments).

Methods:

Over 6000 personal and area sampling data were extracted from monthly lists of routine air sampling results for asbestos taken at the asbestos mine and mill near Baie Verte in Newfoundland between the years of 1976 to 1994. For the years 1991 to 1994, actual individual sampling results including raw fibre counts were available for over 250 of these personal samples. In addition, data for just under 1000 personal samples were extracted from an intensive four-month government study carried out in 1981. The data were evaluated for log-normal distribution fit and descriptive statistics. For the data from the years 1991-1994, a mixed model analysis was performed to determine the between- and within-worker proportion of the total variance. The data from the intensive 1981 sampling campaign was used to ascertain the within- and between-shift variance.

Results:

The distribution for most job categories could adequately be described as fitting a log-normal distribution. For almost 100 different job codes, mean exposures ranged from 0.1–5 f/mL (averaging around 0.5 f/mL). Variability with job categories was quite significant often exceeding a geometric standard deviation of 2.5. The between worker portion of the total variance was usually negligible. Within-shift variation accounted for more than 75% of the total variation in fibre counts. A slight downward trend over time could be detected in most groupings however, a slight increase was observed in the last few years before the mine shut down.

Conclusions:

Personal exposures to asbestos fibres in the Baie Verte asbestos mine and mill were generally below 2 f/mL but greater than 0.1 f/mL. Exposures were greater in the mill than in the mine. Most of the variation in the personal air sampling results could be attributed to the within-worker/shift component, however, some of this may be due to the significant variation in asbestos fibre counting techniques. The exposure database represents a comprehensive picture of worker exposures in the Baie Verte asbestos mine and mill for the years from 1976-1994.