Trends in coal miners' exposure to coal mine dust before and after implementation of the continuous personal dust monitor and reduced exposure limit

Background: Coal worker’s pneumoconiosis (CWP) is a lung disease caused by overexposure to respirable coal mine dust (CMD). Since the 1990s, CWP prevalence increased. In response, the National Institute for Occupational Safety and Health (NIOSH), with external partners, created the Continuous Personal Dust Monitor (CPDM), and the Mine Safety and Health Administration (MSHA) reduced the CMD exposure limit. Due to recent increases in CWP and regulatory changes in mining practice, it is imperative to understand miners’ current exposure. Objectives: The primary objective of this report is to describe trends in U.S. underground coal miners’ CMD exposure during three intervals; 1) before implementation of the CPDM; 2) after CPDM implementation but before establishing a lower CMD exposure limit; 3) after both the implementation of the CPDM and lower CMD exposure limit. The secondary objective is to describe CMD exposure trends by state, mine size, and occupation title. Methods: CMD exposure and mine data were downloaded from MSHA’s website. Data were restricted from August 1, 2015 to January 31, 2017 and divided into three six-month intervals. 111,002 CMD samples were included. Median concentration of CMD and CMD exposure limit exceedances were computed for each month and six-month interval. The Kruskal-Wallis test was used to determine differences in median CMD concentrations, and the Chi-Square and Cochran-Armitage tests were used to determine differences and trends, respectively, in CMD exposure limit exceedances among the six-month intervals. Results: Median concentrations of CMD significantly differed among the six-month intervals (p-value