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An impact evaluation of a federal mine safety training regulation on injury rates among US stone, sand, and gravel mine workers: An interrupted time-series analysis (Monforton & Windsor 2010)

Absence of conflict of interest.

Citation

Monforton, C., & Windsor, R. (2010). An impact evaluation of a federal mine safety training regulation on injury rates among US stone, sand, and gravel mine workers: An interrupted time-series analysis. American Journal of Public Health, 100(7), 1334-1340. https://dx.doi.org/10.2105%2FAJPH.2009.178301

Highlights

  • The study’s objective was to examine the impact of the Mine Safety and Health Administration (MSHA) Policy Part 46 on mine workers’ injury rates.
  • The study used an interrupted time series design to compare injury rates before and after the policy implementation using injury rate data that is reported to MSHA by individual mining companies.
  • The study found that policy implementation was associated with a significant decrease in mine workers’ likelihood of permanent disabling injuries.
  • The quality of causal evidence presented in this report is low because the authors did not account for anticipation of the policy before it was implemented. This means we are not confident that the estimated effects are attributable to MSHA Policy Part 46; other factors are likely to have contributed.

Intervention Examined

Mine Safety and Health Administration (MSHA) Policy Part 46

Features of the Intervention

In 1976, the Mine Safety and Health Administration (MSHA) required health and safety training for any worker employed at a mine. This included at least 24 hours of training for new mine workers and at least 8 hours of refresher training for experienced miners annually. About 10,000 surface mines were exempt from this requirement. In 1999, a congressional directive (Part 46) dictated that previously exempt mines would no longer be exempt from health and safety training requirements. Mine operators were given one year to comply, and the nationally mandated training requirements took effect on October 1, 2000.

The MSHA Policy Part 46 rule stated that mines must create and implement a written plan for developing effective training programs for new and newly hired experienced miners, for new tasks, for hazard awareness, and for refresher courses. To be MSHA approved, the training plans had to contain mine operator or contractor names and identification numbers, information on the person responsible for health and safety training at the mine, a general description of the teaching methods and the course materials used in training, a list of persons and/or organizations who provide the training and their subject areas, and the evaluation procedures used to assess training effectiveness.

Features of the Study

The interrupted time series study included 7,998 mine sites across the United States. To be included in the study, mines needed to have been previously exempt from MSHA training regulations, be in operation from 1995 to 2006, and have employed mineworkers eight or more quarters before and after the policy's initiation. The preintervention period ran from January 1, 1995 to September 30, 2000 (when the new regulation took effect). The post-intervention period ran from October 1, 2000 to December 31, 2006. Outcomes included quarterly serious injury rates, defined as the total of permanently disabling, lost-time, and restricted-duty injuries. The author also examined lost-time, medical-treatment-only, restricted-duty, and permanently disabling injuries separately. Using MSHA’s Office of Injury and Employment Information databases, the authors used statistical models to examine the change in injury rates over 12 years, comparing the rates before and after the policy began.

Findings

Health and safety

  • The study found that MSHA Policy Part 46 was significantly associated with a 41% decrease in the likelihood of a permanently disabling injury.
  • The study found no significant relationships between the MSHA policy and severe, quarterly lost-time, restricted-duty, or medical treatment-only injury rates.

Considerations for Interpreting the Findings

MSHA Policy Part 46 was announced a year prior to when it took effect. The analysis included this one-year lag during the pre-intervention period instead of controlling for it in the model. Thus, the reduction in injury rates might reflect that the mines in the study anticipated the intervention and adjusted accordingly rather than the true impact of the policy.

Causal Evidence Rating

The quality of causal evidence presented in this report is low because the authors did not account for anticipation of the policy before it was implemented. This means we are not confident that the estimated effects are attributable to MSHA Policy Part 46; other factors are likely to have contributed.

Reviewed by CLEAR

August 2020