What do we know about the effectiveness of mine health and safety interventions?
Mining is a potentially dangerous occupation with hazards and risks that can lead to injuries, illnesses, and death. To ensure the safety of the miners and the mine sites, the mining industry is regulated by government agencies, including the Mine Safety and Health Administration (MSHA) at the U.S. Department of Labor. These agencies develop safety regulations and conduct inspections to enforce the regulations, administering sanctions and penalties for violations. Workplace safety is also promoted through outreach, education, and training.
Engineering controls are physical manipulations of the sources of the hazard or the manner of exposure to the hazard. Examples include atmospheric monitoring, explosion suppression, fire warning and fire suppression, ground control, hearing protection, proximity detection systems, and respiratory devices.
Government agencies develop safety regulations to keep workers safe and healthy. Regulations may include directives for mine operations and exposure regulations (e.g., maximum noise levels).
Government agencies conduct inspections to enforce the established regulations and administer sanctions and penalties for violations of safety standards.
Workplace safety is promoted through education and training. Training includes both classroom-based and on-the-job training.
Studies receiving a low causal evidence rating provide valuable information about the intervention.
Causal evidence ratings are based on the quality of the study, not the intervention. A low rating does not mean that the intervention was ineffective or had unfavorable outcomes. Low-rated studies often reflect the most rigorous methods authors could use given the circumstances. Six studies received a low causal evidence rating based on their study design, but all found favorable impacts on health and safety outcomes. When interpreting the findings from low-rated studies, we cannot attribute the findings solely to the intervention as other factors are likely to have contributed to the observed outcomes.
Table 3 at the end of the synthesis report lists all studies included in the review with information about the intervention, study design, rating and impact(s), with links to profiles that summarize each study on the CLEAR website.
Engineering controls prevented injuries or improved safety practices that could prevent injuries.
All but one high-rated study examining engineering controls found favorable health and safety outcomes. The studies found that engineering controls increased steering accuracy of underground coal mine shuttle cars (Burgess-Limerick et al., 2013), improved detection speed for continuous mining machine movements (Sammarco et al., 2012), reduced operator errors while using roof-bolting machines (Steiner & Burgess-Limerick, 2013; Steiner et al., 2014), and reduced whole body vibration exposure (Kim et al., 2018).
Two low-rated studies of engineering controls also found improved safety practices that could prevent injuries. One study found that engineering controls prevented injury by reducing noise exposure (Wilson, 2010), while another found they improved error rates over time (Steiner & Burgess-Limerick, 2013). However, these findings should be interpreted with caution.
Enforcement activities improved health and safety outcomes but the evidence base is small.
The moderate-rated studies found significant reductions in worker injuries due to enforcement activities, with one study showing a significantly lower likelihood of injury with higher penalties per violation (Gernand, 2016) and the other finding reduced citations and worker injuries with mine safety disclosures in financial reports (Christensen et al., 2017). The studies provide a small body of credible, quality evidence of promising interventions to improve health and safety outcomes.
The only moderate-rated study on safety regulations showed no significant impact on health and safety outcomes.
This study found that exposure regulations were associated with lower mortality rates, but the author did not provide tests of statistical significance that would indicate that the findings were not due to chance (Edwards et al., 2014). However, one low-rated study of a safety regulation found a decrease in injury rates (Monforton & Windsor, 2010). More evidence is needed to draw stronger conclusions on the effectiveness of safety regulations.
Training interventions may increase knowledge and skills that could improve health and safety outcomes.
The studies found improvements in knowledge and skills that could reduce injuries, such as higher health and safety knowledge scores (Cherniack, 2016) and higher belief in successfully completing a virtual mine rescue (Hoebbel et al., 2015). Only one study looked at the effects of training on actual injury rates, finding a lower lost time injury rate at one mine (Burgess, 2016). This small body of literature shows promise to potentially reduce injuries but the studies received a low causal evidence rating.
Where are the gaps in the research on mine health and safety interventions?
Little higher-rated evidence exists on the effectiveness of training interventions to increase health and safety outcomes. The systematic review found three studies that tested the impacts of training interventions on health and safety outcomes. All three studies found favorable impacts on health and safety. However, none of the studies received a high or moderate causal evidence rating due to methodological issues with the studies. More rigorous, credible research would enable us to draw stronger conclusions about the effectiveness of training interventions.
Exploring the context of the safety violations would further explain the effects of enforcement activities on health and safety outcomes. One study of enforcement activities in the review examined the effect of the amount of the penalty on future rates of injuries or illnesses. However, the study did not identify if the violations for receipt of the penalty were obvious nor did it look at a reduction of fatality rates which are the most important measure regarding mine safety. More research about the violation types and subsequent sanctions due to the violations as well as characteristics of the mines would provide more contextual information about the effectiveness of specific penalties for different types of mines and levels of violation.
More research is required to determine the effects of engineering controls on rates of injuries and illnesses. The systematic review included outcomes that prevent injury or illness and enhance safety practices (e.g., increased reaction time or reduction of respirable dust). While all but one study of the impact of engineering controls found favorable health and safety outcomes, the findings did not directly pertain to rates of injuries or illnesses. Also, 17 studies of engineering controls were identified during the systematic search process but could not be reviewed using the CLEAR Causal Evidence Guidelines. CLEAR reviews studies that use specific research methodologies that are found in the behavioral sciences, such as randomized controlled trials and comparison group designs that compare those who participated in an intervention to those who did not, and interrupted time series designs that examine trends before and after an intervention. However, many studies of engineering controls used scientific experimental designs that did not include a comparison group or examine trends over time. Alternate research methods could provide stronger evidence on the effects of engineering controls on rates of injuries and illnesses.
Additional research is needed to determine the effects of safety regulations on health and safety outcomes. Only two of the 15 studies examined the impact of safety regulations on outcomes. Also, the studies look at aggregate changes in rates of injuries/illnesses before and after the implementation of the regulation. More research could explore the implementation of the safety regulation at the individual mine level to further identify challenges and solutions to implementation in the mines, providing context for the changes in health and safety outcomes.