The Impact of Contract Operations on Safety in Underground Coal Mines.

OBJECTIVE The aim of this study was to test for differences in injury rates for contractor-operated underground coal mines relative to owner-operated mines in Kentucky, controlling for other covariates. METHODS We used disparities between MSHA contractor data and surface reclamation permit data to identify mines operated by contractors. We then used negative binomial regression to estimate injury rates from 1999 to 2013, controlling for mine and controller characteristics available from MSHA and the Energy Information Administration (EIA). RESULTS Contractor-operated mines with 15 or fewer full-time equivalent workers (FTEs) had a statistically significant 57% higher covariate-adjusted reported traumatic injury rate than similar mines without contract operators. Larger contractor-operated mines did not have a statistically significant elevated rate. CONCLUSIONS We detected a significant elevation of traumatic injury rates only among the smallest contractor-operated mines. This increase appears substantial enough to warrant attention.