Abstract

Using blue light as a preventive measure to counteract drowsiness in mining operators

Background: Night shift mining operators often face cumulative fatigue and drowsiness, which can impair performance and compromise safety. This study explores the efficacy of blue stimulating light in mitigating these issues. Blue light, known to directly activate brain alertness centers via melanopsin-sensitive retinal cells, was tested on night shift operators in dimly lit work environments. The light technology used is based on a discovery at CERVO Brain Research Center, that pulsing blue light at 70 Hz can double its biological effect compared to continuous blue light (patent US 11,259,738). This discovery makes it possible to test low-intensity blue light for night shift workers operating in dim lighting environments. This research goal was to evaluate objectively the impact of adding blue light on alertness in real night workers.  To do so, we used the Psychomotor Vigilance Test (PVT) which is recognize as the gold standard for assessing alertness.

Methods: Thirteen fly-in/fly-out rotating shift workers engaged in computer and screen-monitoring tasks at the Raglan mine (Glencore) concentrator/smelter in Northern Quebec (61°69’N) participated. They worked twelve consecutive 12-hour night shifts (7 PM-7 AM) under two conditions: one rotation using blue light (mounted above the computer screen) and one without blue light (counterbalanced conditions).  PVT was performed both at the beginning and end of each night shifts in both conditions. This test requires participants to tap a portable screen upon detecting a visual stimulus (randomly appearing every 2-10 seconds), measuring reaction speed which is also an indicator of performance. Testing (5-min) was conducted in isolated rooms to minimize distractions. The daily mean (all workers) median reaction time over 5-min was used for the analysis.

Results: In the baseline (no blue light) condition, mean median reaction time (RT) at the beginning of each shift increased by 3.5 ms with each successive shift from days 1 to 12 (p<0.01), indicating a daily performance decline. In the blue light condition, the daily RT increase was only 1.1 ms over the same period, and there was even some improvement in RT at the end of the shift after 12 nights (p<0.05). These results demonstrate a significant reduction or even elimination of RT increase (performance decrement) with blue light. Following this study, an open-pit mine implemented a portable in-cabin blue light device for operators of F793 Caterpillar 250-ton trucks. A survey of 61 operators found that 85% reported enhanced alertness, and 94% noted improved sleep.

Conclusion: Night shift operators typically experience performance declines and cumulative fatigue over 12 consecutive night shifts. The PVT confirmed this decline in the absence of blue light, whereas blue light significantly mitigated fatigue buildup and was even reported by operators to improve sleep quality. Acting as a stimulant, blue light directly targets brain centers for alertness, countering night-time drowsiness and enhancing operator safety. Given the high priority on safety in the mining industry, incorporating blue light could be considered as a proactive measure in fatigue management programs.