RFC paper informs views of asbestos

A side debate in the particle and lung cancer world is whether there is something special about asbestos fibers, or whether all fibers are equally dangerous. This debate arose when BrooklynDodger was being taught that asbestos caused fibrosis and lung cancer, while silica only fibrosis. That's no longer true, but the long fiber-short fiber-durable fiber paradigm continues.

This population overall suffered exposures pretty much in the line of asbestos standards of the time, although definitely elevated compared to the current 0.1 fiber/cc limit. The current asbestos rule is aimed at a cumulative exposure of about 4.5 fiber years.

The study found that 8% of workers with 20 year latency had pleural changes, compared to 2.7 % overall. This suggests that the under 20 year latency group must have a prevalence of 1.3% or nearly a 6 fold risk for 20 year latency compared to under 20 years.

Cumulative exposure was dichotomized at 135 fiber/months, which is a bit more than 10 fiber-years. It yielded a 6-fold risk of pleural changes, which backs down to a signficant risk of pleural changes down to vanishing levels of exposure.

Had BrooklynDodger been reviewing this paper, the Dodger would have ballisticed over "irregular opacities...showed a nonsignificant elevated OR in regard to cumulative fiber exposure of 4.7 (95% CI, 0.97 to 23.5). CONCLUSIONS: RCF are significantly associated with pleural changes that were predominantly pleural plaques, but have not resulted in a statistically significant increase in interstitial changes." To the contrary, there is a big odds ratio and a huge upper bound discounted because of reached a lower CI of 0.03 less than 1.00.

Quoting exposure data, for those who join the Dodger in thinking this is an important detail:

From 1987 to 1988, the range of time-weighted average exposure
estimates were 0.01 to 1.04 fibers per cubic centimeter for the
blanket line, 0.03 to 0.61 fibers per cubic centimeter for dry
fabrication, 0.01 to 0.27 fibers per cubic centimeter for wet
fabrication, 0.01 to 0.47 fibers per cubic centimeter for furnace
operations, and 0.02 to 0.62 fibers per cubic centimeter for
maintenance.
...Historical exposure data were available at two plants for calculating pre-1987 in-plant exposures.1...Overall, exposures over time have decreased.
The maximum exposure estimate was 10 fibers per cubic centimeter
in the 1950s for carding in a textile operation;
subsequent engineering changes reduced this estimated exposure to 1
fiber per cubic centimeter.

Chest. 2002 Jun;121(6):2044-51.

A longitudinal study of chest radiographic changes of workers in the refractory ceramic fiber industry.

Lockey JE, LeMasters GK, Levin L, Rice C, Yiin J, Reutman S, Papes D.Division of Occupational and Environmental Medicine, Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA.

...Chest radiographs were obtained every 3 years... Exposure metrics were ... duration and latency in a production job, and cumulative exposure (fiber-months per cubic centimeter). .. The ... survey included 625 current workers at five manufacturing sites and 383 former workers at two of the five sites. ... Pleural changes were seen in 27 workers (2.7%). Of workers with > 20 years of latency from initial production job or 20 years of duration in a production job, 16 workers (8.0%) and 5 workers (8.1%) demonstrated pleural changes, respectively. Results from the cumulative exposure analysis (> 135 fiber-months per cubic centimeter) demonstrated a significant elevated odds ratio (OR) of 6.0 (95% confidence interval [CI], 1.4 to 31.0). The incidence of irregular opacities at profusion categories > or = 1/0 was similar to other nonspecified dust-exposed worker populations at 1.0%, and showed a nonsignificant elevated OR in regard to cumulative fiber exposure of 4.7 (95% CI, 0.97 to 23.5). CONCLUSIONS: RCF are significantly associated with pleural changes that were predominantly pleural plaques, but have not resulted in a statistically significant increase in interstitial changes.