Respirable Dust Exposure in Western Australian Mining: Trends, Variability, and Implications for Occupational Health.

Abstract

Background: Mining workers are exposed to a range of respiratory hazards, including respirable dust. While exposure to respirable crystalline silica in the mining industry has been found to be common, less is known about trends in measured levels of exposure to respirable dust overall.

Methods: This study analyzed 109,442 personal respirable dust measurements collected from Western Australian mines between 1986 and 2014. Data were sourced from an industry-wide monitoring database and modeled using mixed-effects regression, adjusting for sampling characteristics (year of measurement, duration, reason), mine type, and job title. Differences in trends over time between mine types were also examined.

Results: Overall geometric mean respirable dust concentrations declined from 0.393 mg/m³ in 1986-1990 to 0.181 mg/m³ in 2011-2014, representing an average annual decrease of 3.51% (95% confidence interval -3.63% to -3.39%). Modeled exposure levels varied by mine type, with the highest levels observed in iron ore mines (GM 0.489 mg/m³ in 1986 through to 0.197 mg/m³ in 2014) and exploration (GM 0.665 mg/m³ in 1994 through to 0.172 mg/m³ in 2014). Temporal trends varied by mine type, with a steeper decline in exposure levels seen in exploration activities in particular.

Conclusions: Exposure to respirable dust in Western Australian mines has decreased substantially over the past three decades, although higher levels persist in some jobs and activities. While this suggests that existing controls have been broadly effective, the presence of these higher exposures indicates that further measures may be required.