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Assessing Fitness-for-Duty of Shift Workers at Underground Mine

Study demonstrates the value of using the Druid Fitness-for-Duty App

Safety Manager Inspecting Mine Operations

Impairment Science, Inc. released the results of a study done with Impala Canada Ltd.’s Lac des Illes Mine Operation, demonstrating the effectiveness of the Druid Impairment App to monitor worker fitness-for-duty. Worker safety is a significant area of focus for all companies in the mining industry, particularly with regard to the threat posed by workers’ cognitive and motor impairment. As in many safety-sensitive industries, a single mistake can have serious, even fatal, consequences. While on the job, miners are expected to operate heavy, dangerous machinery in hazardous and high-stress situations.

Mining and Substance Abuse

The mining industry is particularly vulnerable to substance abuse-based impairment. According to a 2022 report by the Substance Abuse and Mental Health Services Administration (SAMHSA), workers in the mining industry consistently report some of the highest rates of heavy alcohol use, illicit drug use, and substance abuse disorder, both in the United States and worldwide. Rotating shifts, isolation, separation from family, boredom, exhaustion, and pressure from colleagues also contribute to a work culture that often normalizes unhealthy and dangerous substance use patterns. Therefore, it is critical for mining companies to have an effective, proactive approach to impairment testing in order to combat the cultural norms of the industry and to protect the safety and security of workers and work sites.

Lac des Iles Mine, Thunder Bay, Ontario

Impala Canada Ltd.

Impala operates six mining locations for the Implats group, a world-class premier producer of nickel, palladium, and copper. The company has mined in the Northwestern Ontario region for twenty five years. It maintains a staff of approximately 700 individuals and has made extensive strides towards becoming Canada’s largest, lowest-cost, and safest underground mining operation.

In 2019, shortly after the advent of the legalization of cannabis for recreational use in Canada, one of Impala’s mines, Lac des Iles Mine, began steps to increase its drug testing practice. This proposed increase sparked considerable objection by the mine’s union, United Steel Workers Canada. At the same time, Lac des Iles Mine observed a concerning rise in positive drug test results. In response, its management began working with representatives from the United Steelworkers Canada to craft a new substance abuse policy that included oral swab testing, random testing, and the requirement for self-declaration of drug use. Local union representatives, however, were uncomfortable with random drug testing, indicating that they would fight it at the national union level.

In search of a compromise, mine management investigated alternate tools for deterring substance abuse. Ultimately, the mine chose to pilot the Druid app from Impairment Science. After union and management discussion about the nature of the Druid test, the union responded positively and agreed to participate. Druid presented an ideal solution: the precision and scientific validation of the Druid test gave Impala the ability to detect impairment, while the fact that Druid cannot determine the cause of the impairment helped union members feel more comfortable with technology.

The Druid Test

The Druid fit-for-duty test is a mobile app that determines levels of cognitive and motor impairment via four game-like tasks that assess decision-making accuracy, eye-hand coordination, reaction time, time estimation, and balance. The test takes one minute. Over the course of the test, the Druid app collects and integrates hundreds of measures across the four tasks to create an impairment score on a scale from 25-75, with high scores showing more impairment. The accuracy of Druid has been validated and confirmed in three peer-reviewed, published, scientific studies and is used by dozens of leading impairment researchers.

Implementation of Druid at the Mine

The Druid pilot was conducted over several months beginning in early 2020. Two different mine crews across four sites – Earthworks, Mill Operations, UG Development, and Mobile Maintenance - were chosen to participate. The identities of the crews’ participants were kept anonymous from both Impairment Science and from mine management. Participation in the assessment was mandatory, and participants were incentivized with gift cards. Participants were also informed that there would be no consequences for poor scores.

Testing was performed at both the beginning and end of each shift every day over the course of a 14-day rotation. Each test contributed to the formation of a personal Druid “baseline” score for that individual. Scores more than five points above baseline were marked as potentially indicating impairment.

During the first phase of testing, participants were not shown their scores, but thereafter, participants were shown their scores.

Representatives from Impairment Science visited the mine to observe the testing first hand and to support data analysis.


In total, 84 participants completed a total of 1,774 tests over the course of the pilot. The data was organized by participant group (Crew A/Crew B), by shift time, and by threshold of impairment (either five or seven points above baseline). Test scores ranged from 32.5 to 77.6, with a whole group averaging 41.1. (Any Druid score above 45 indicates some level of impairment, and the higher the score, the greater the impairment.)

Mine management used reports, several of which are reproduced below, to view the scores by shift over time. Workers scores were tracked and compared to their individual baseline scores. Scores 5 points or more above baseline triggered an alert for the supervisor.

The mine’s safety protocol was to have a supervisor pull any worker with an elevated score aside for a brief interview in order to understand if the worker presented any other indications of impairment. If there was such an indication of impairment, an on-staff nurse would interview the worker to determine if a blood or urine test for drugs was advisable. If not, on most occasions, workers with elevated scores were reassigned to different, less risky duty. The plant manager noted that there was always work to do if they were not fit to operate machinery.

Figure 1, below, is a graph of test score results plotted over time, with dots representing individual tests; green, yellow, orange, and red dot colors representing unimpaired, slightly impaired, moderately impaired and severely impaired scores, respectively; and lines representing participants.

Figure 1

Figure 2, below, is a graph of the deviation of test scores from baseline scores, with the zero horizontal line representing all the participants’ baselines.

Figure 2

Figure 3, below, is a timeline of the testing protocol followed.

Figure 3


Key takeaways by mine management:

  • Regardless of their baseline score, nearly all participants’ Druid scores were consistent from day-to-day, within a point or two, demonstrating Druid’s reliability.

  • Test scores at the beginning and end of each miner’s 10-hour shift were also generally consistent with each other. Given the physical nature of work in the mine, it was beneficial to learn that the vast majority of workers did not exhibit any substantial impairment either before or at the end of their shifts.

  • Providing performance feedback to participants had a positive impact on results, with Druid scores trending slightly lower once participants got access to their scores.

  • Management was able to assess aggregate fatigue levels for the shift as a whole when comparing the mine’s two 10-hour shifts, with the night work shift showing slightly more fatigue than the other shifts.

  • Management was pleased to have found a means of testing acceptable to its union and that, even though it was not a drug test for cannabis, it detects and measures impairment due to cannabis.

  • Mine management acknowledged that using Druid caused it to enlarge its concept of fitness for duty from the narrow, conventional focus on alcohol and drugs to the much broader focus on cognitive and psychomotor impairment regardless of cause, whether due to fatigue, illness, injury, chronic condition, severe emotional stress, or drugs and alcohol.

  • Finally, and most importantly, Druid did detect some level of significant impairment in approximately 10% of the tests, flagging those individuals for additional, follow-on scrutiny.

The Lac des Illes Mines’ Druid study permitted mine management to evaluate - methodically, objectively, and scientifically - its miners’ current fitness for duty, both by individual and shift. The Druid app proved to be a quick, accurate, non-invasive, easily to use, and inexpensive contribution to mine management’s effort to improve productivity and prevent dangerous, costly impairment-related accidents.

Lac des Iles Mine Main Facility



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