Four controls that save lives: A simple approach to preventing heat illness in mining

Last summer, I hiked into a remote drill site in the warm, humid Sierra Madre mountains of central Mexico with one of our exploration teams. Within the first hour, I could feel it — my pace slowing, my heart rate climbing faster and the humidity making every step heavier. Nothing dramatic, just a clear signal: You are not used to this environment yet. The crew I was with moved efficiently and comfortably. They had adapted. I had not.That experience reinforced something I have seen across mining operations: Heat does not just challenge the unfit, it challenges the unacclimatized. And if we do not respect that, it can be deadly. From an occupational health and industrial hygiene perspective, we can model heat stress. But in the field, the most effective protections come down to four simple controls that work: (1) water, (2) rest, (3) shade and (4) acclimatization. Why this matters: A predictable and preventable risk Heat is the leading cause of weather-related deaths worldwide, accounting for about 546,000 deaths annually [1]. In the United States, heat-related deaths have more than doubled since 1999 [2]. In the workplace, at least 999 U.S. worker deaths from heat exposure were documented between 1992 and 2021 [3]. But the most important and actionable statistic is this: Around 70 percent of occupational heat-related fatalities occur during a worker’s first week on the job [4]. Heat illnesses — including heat rash, heat exhaustion, heat syncope, heat stroke and death — are most common among new or returning workers who are not familiar with the work and whose bodies have not yet acclimatized.The four controls that matter most: Water — Hydration is the first line of defense. Provide continuous access to cool, potable water near the job. A practical target is 250 to 500 mL every 15 to 20 minutes, not just “drink when thirsty” [5]. Consider electrolytes for extended work or heavy sweating. Rest — Allow time for the body to cool. Work-rest cycles can be an important control when done right. Adjust frequency based on heat index or wet-bulb globe temperature (WBGT), workload and personal protective equipment (PPE), and work with your industrial hygiene professional for site-specific guidance. Short, frequent breaks are often most effective [5]. Shade — Reduce the heat load. Shade reduces radiant heat exposure and supports recovery. Create shade near/where work is happening. It is simple and highly effective. Acclimatization — A control that saves lives. Acclimatization is the body’s adaptation to heat through repeated exposure and on-the-job experience. Over seven to 14 days, workers’ bodies can physiologically adjust, to a degree, to working conditions [6]. It must be planned and managed especially for new and returning workers. A common rule of thumb is the “20 percent rule”: Start at approximately 20 percent of normal workload on day one. Increase by approximately 20 percent each day. This is a helpful starting point but not one-size-fits-all. Conditions like extreme heat, humidity, clothing, work intensity, PPE and altitude require adjustments. Industrial hygiene professionals can help design and validate effective acclimatization programs by using tools to assess metabolic rates, measure WBGT and conduct heat stress evaluations, depending on job-specific details. Without acclimatization, risk is highest in the first few days on the job [4]. What this means for mine operators and leaders Heat-related illness is preventable. To reduce risk: Be especially careful with new workers. They are less likely to speak up if they do not feel well. Create a culture where employees speak up, especially new ones. Implement structured acclimatization programs. Ensure water, rest and shade are available and used. Train supervisors on the four controls and the signs of heat stress. Plan work around environmental conditions. Verify controls in the field. A final thought Across different countries, climates and cultures, when mine sites focus on water, rest, shade and acclimatization, they protect their people — and performance follows. Four controls. One goal: every person goes home safe. n References Romanello M, et al. The Lancet Countdown on Health and Climate Change (2023–2025). Centers for Disease Control and Prevention (CDC). Heat-Related Mortality — United States, 1999–2023. Bureau of Labor Statistics (BLS). Census of Fatal Occupational Injuries (CFOI); OSHA data. Occupational Safety and Health Administration (OSHA); Tustin AW et al. (2018), NIOSH-supported analysis. National Institute for Occupational Safety and Health (NIOSH). Criteria for a Recommended Standard: Occupational Exposure to Heat (2016). Sawka MN et al. Physiological Adaptation to Heat Stress and Heat Acclimation. Helpful resources American Industrial Hygiene Association Heat Stress App (mobile WBGT-based guidance).National Institute for Occupational Safety and Health Heat Stress Topic Page.Australian Bureau of Meteorology Extreme Heat Guidance (Extreme heat is Australia’s deadliest natural hazard).

Four controls that save lives: A simple approach to preventing heat illness in mining

Authored by: Kyle Naylor

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