Researchers at the National Institute for Occupational Safety and Health (NIOSH) are studying how stone, sand, and gravel (SSG) mineworkers identify and understand hazards in their work environment. This is the last article in a three part series (see the December, 2016, and March, 2017, North American Quarry News issues). In this article, we discuss risk assessment, which is how an individual reports how risky a situation is. It is critical to study how mineworkers assess risk, because research shows that risk assessment influences safety related decisions on the job (Hunter, 2002). Understanding how mineworkers assess risk is an important step towards determining not only how they identify and evaluate hazards, but it is also critical to understanding how they make decisions about how and when to mitigate hazards at mine sites.
To study risk assessment, we asked mineworkers and safety professionals to assess the risks associated with numerous hazards found at a surface stone mine site. This article presents an overview of our risk assessment task, how safety professionals and mineworkers used it, and our suggestions for improving risk assessment at mine sites.
Risk assessment task and measure
The purpose of the risk assessment task was to determine whether experience affects how mineworkers assess risk. Thirty-five participants took part in the study; this included 11 new mineworkers (less than two years of experience), 11 experienced mineworkers (more than two years of experience), and 13 safety professionals (more than two years of experience in environmental, health, and safety positions). After completing the NIOSH hazard recognition task described in part two of this series, participants reviewed all 102 hazards with researchers during a debrief. Participants were given feedback on which hazards they had identified and missed. While going through this feedback, we asked participants to make a risk assessment for each hazard, regardless of whether they identified or missed it (see Figure 1).
To measure risk, we used a risk assessment measure previously used in the construction industry (Perlman et al., 2014). Using this measure, participants made a decision about the (1) accident severity, (2) accident probability, and (3) overall risk level for each hazard (see Figure 2). For each risk assessment, we instructed participants to use a scale from one to five to rate each component based on what was shown in the panoramic images. Participants were asked to go with their first instinct and make their decisions as quickly as possible. They were also given the following detailed explanation for each of the components:
- Accident Severity: For this component, participants were told that severity is how severe they thought the likely resulting accident would be;
- Accident Probability: For this component, participants were told that probability is the likelihood that an accident would occur; and
- Risk Level: For this component, participants were told that risk level is their overall risk assessment for a hazard.
Risk assessment results
The results of the risk assessment task show that there is a great deal of variability across ALL levels of mining experience and ALL components of risk. This was true even for safety professionals who have more experience and training in assessing risk. This variability is illustrated using electrical and material handling hazards as examples and is evident by the long length of the error bars in the graphs in Figures 3 and 4. Specifically, the two point range for electrical severity (see Figure 3) indicates that mineworkers’ ratings ranged from a minor injury with leave to a fatal injury. This variability suggests that there are differences in how mineworkers assess risk, independent of experience.
However, experience level was shown to affect risk assessment ratings for hazards in specific accident classifications. Electrical and material handling hazards provide a good comparison because of their differences in severity and accident probability, as represented in the MSHA fatal and non-fatal days lost (NFDL) data (incidence of metal/non-metal mining accidents by classification for years 2009-2015). Injuries attributed to electrical hazards do not happen frequently; however, when they do happen, they tend to cause fatal or more severe injuries (see Figure 5). In contrast, injuries attributed to handling materials hazards happen far more frequently, but typically do not lead to as-severe injuries.
For electrical hazards (see Figure 3), the relative difference in the risk assessment components agree with the trends in the MSHA data. On average, participants at all experience levels rated electrical hazards higher for accident severity than for probability. However, the severity and probability ratings for handling material hazards (see Figure 4) do not align with the MSHA data. While injuries from handling material are frequent in the MSHA data, participants’ accident probability assessments do not reflect that they understand just how often these injuries occur. Accident probability assessments were approximately the same as accident severity assessments for all participant groups. Interestingly, when comparing accident probability ratings across accident classifications, safety professionals rate handling material hazards higher than electrical hazards. These results indicate that, in general, ALL participants understand the potential consequences of an accident. For accident probability assessments, only the safety professionals are also able to recognize differences in the likelihood that an accident will occur.
Risk assessment summary
A mineworker’s ability to assess risk is critical for health and safety at the mine site because this ability has been shown to affect hazard mitigation, for instance when to use PPE or when to de-energize and lockout a piece of equipment (Hunter, 2002). The results of the risk assessment task indicate that not all mineworkers see and understand hazards in the same way. First, there is a great deal of variability found within the risk assessment scores, even across experience levels. One explanation for this finding is that there are differences between people. These individual differences can be attributed to varying knowledge of worksite hazards, specific experiences, or differences in how much risk they tolerate. One way to minimize the effect of mineworker differences on risk assessment ratings is to standardize the procedure they use when assessing the risk associated with a hazard. Whether it is MSHA’s SLAM Risks (https://arlweb.msha.gov/SLAMRisks/SLAMrisks.asp) or another risk assessment program, making sure all mineworkers are using the same procedure and scale should help reduce variability.
The results of the risk assessment task also suggest that, while all participants understand accident severity (the consequences of the hazard), only the safety professionals exhibited some understanding of accident probability (how likely it is that an injury will occur). While understanding severity is important, especially for hazards that can lead to fatal injuries, it is also important to recognize how often injuries can occur. Frequency increases the overall risk, especially for less severe hazards (e.g., handling material hazards). Increased risk may prompt workers to immediately mitigate the hazard or stop work as opposed to just reporting it to be fixed later. Overall, understanding severity and probability can affect how and when mineworkers mitigate hazards.
Finally, during the study, we asked participants whether they had received risk assessment training. Although the majority of the participants (29 out of 35) reported receiving some type of risk assessment training, it became evident during the debrief that most mineworkers did not have a lot of experience making these assessments. In order for experienced and inexperienced mineworkers to assess risk as effectively as safety professionals, especially for accident probability, it is critical for them to practice making risk assessments and understand how probability and severity affect overall risk.
What can you do now?
- Standardize your risk assessment procedure by using a risk assessment program such as MSHA’s SLAM Risks or the risk assessment measures included in this article.
- Make sure all mineworkers understand and use probability and severity to assess risk.
- Use MSHA fatal and NFDL data to talk about how often injuries occur to increase mineworkers’ understanding of probability.
- Have your mineworkers practice making risk assessments using probability and severity.
To practice making risk assessments, choose an accident category (e.g., slips and falls) and come up with ways that the work environment can change that would result in changes in accident severity or probability. For instance, debris on a walking path at ground level may result in minor injury. However, the probability of that injury occurring depends on where the debris is located. A mineworker is less likely to trip over debris if it is in a brightly lit walkway than if it is immediately behind a doorway they are entering.
Upcoming NIOSH work
NIOSH is using research related to hazard recognition and risk perception among stone, sand, and gravel mineworkers to develop a workplace examination training and assessment tool. This tool will be a Microsoft Windows® application that can help mine operators evaluate mineworkers’ ability to perform workplace exams as well as provide a platform to practice recognizing hazards and performing risk assessments. This training tool will be available to all stakeholders through the NIOSH website in the upcoming months. We will begin testing the training tool soon. If you are interested in evaluating the training tool, or if you have any questions, please contact Brianna Eiter (BEiter@cdc.gov). To learn about other ongoing NIOSH research studies, visit our website at www.cdc.gov/niosh/mining .
Disclaimer: The findings and conclusions in this article are those of the authors and do not necessarily represent the views of NIOSH.