Absence of conflict of interest.
Wilson, L. A. (2015). Evaluation of automated vs. manual bagger exposures related to ergonomics, dust, and noise at a sand mine processing plant (Unpublished master’s thesis). Montana Tech of the University of Montana, Butte, MT.
- The study’s objective was to examine the impact of an automated bagging system on mine worker health and safety outcomes.
- Using data from a sand mining plant, the author used an interrupted time series design to compare the rates of mine worker injuries and health issues before and after implementing an automated bagging system.
- The study found that implementation of an automated bagging system is significantly associated with a reduction in noise exposure.
- The quality of causal evidence presented in this report is low because the authors did not observe outcomes for multiple periods before and after the intervention. This means we are not confident that the estimated effects are attributable to the automated bagging system; other factors are likely to have contributed.
Features of the Study
The nonexperimental study was conducted at a sand mining plant in the United States. The author compared the health and safety outcomes before and after the implementation of the automated bagging system using statistical analyses. Outcomes included the number of injuries per year, exposure to respirable dust or crystalline silica, and exposure to noise. The study used data provided by the sand mining plant including injury data specific to the bagging location (1995 to 2015), samples of dust and silica (1979 to 2015), and noise samples (1996 to 2015).
Health and safety
- The study found that implementation of an automated bagging system was significantly associated with a decrease in noise exposure, with noise exposure decreasing from 69 to 54 A-weighted decibels.
- The automated bagging system was also associated with a reduction in injuries from 2.76 per year to .72 per year, although tests of significance were not reported for this outcome.
- The study found no significant relationships between the automated bagging system and exposure to respirable dust or crystalline silica.
Considerations for Interpreting the Findings
The study only reviews data at two time points, "before" the implementation of the automated bagging system and "after." The data were collected between 1979 and 2015; however, the study does not indicate at what intervals the data were collected or when in time the automated bagging system was introduced. CLEAR’s guidelines require that the author observe outcomes for multiple periods before the intervention to rule out the possibility that the sand mining plant had increasing or decreasing trends in the outcomes examined before implementing the automated bagging system. Without knowing the trends before enrollment, we cannot rule this out. Therefore, the study is not eligible for a moderate causal evidence rating, the highest rating available for nonexperimental designs.
Causal Evidence Rating
The quality of causal evidence presented in this report is low because author did not observe outcomes for multiple periods before or after the intervention. This means we are not confident that the estimated effects are attributable to the automated bagging system; other factors are likely to have contributed.