The Hidden Risk of Underreporting — Part 2: When Heat Overexposure Goes Unrecognized

By: | June 16, 2026

Dr. Ronda McCarthy is the senior director of Medical Operations, Medical Surveillance, and Telebehavioral Health Services at Concentra®. She chairs a panel of medical experts who advise on hazardous chemicals and physical exposure standards. A recognized industry speaker and published researcher, McCarthy has testified before Congress on the prevention of heat stress. Board-certified in occupational medicine, she earned her medical degree from the University of Texas Health Science Center in Houston and completed her residency training at the University of Pennsylvania Perelman School of Medicine.

The second and final installment in the series explores how unrecognized and underdocumented signs and symptoms of heat overexposure can obscure workplace risk and contribute to heat-related illness.

On the manufacturing floor where workers are stationed near furnaces, presses, or molten materials, no one calls it heat overexposure. It’s considered routine fatigue and heavy sweating from a long shift, so they push through. And somewhere in that normalcy, risk compounds quietly, steadily, and undocumented. The worker didn’t collapse dramatically, so no alarms sounded. No one rushed in. Instead, it started quietly — slower reaction times, mental lapses — nothing that looked actionable or medically urgent. By the time anyone calls it a heat-related illness, it’s too late. The symptoms may be documented, but the heat exposure that contributed to them often isn’t. This is how heat overexposure risks can take hold.

When Heat Is a Hidden Contributor

A heat-related illness rarely presents all at once; it can build gradually. If clinicians treat acute conditions (e.g., dehydration, dizziness, fainting) without documenting heat exposure as a contributing factor, the result can be systemic underreporting driven by:

  • Delayed recognition by workers and supervisors
  • Reluctance to report, especially among new hires or machine-paced teams
  • Clinical documentation gaps
  • Coding and reporting variations that obscure heat as an occupational cause

When heat overexposure is inadequately documented, employers can’t see the full picture. This makes it easier to underestimate the danger and miss the chance to act early. Connecting the dots between these “routine” incidents and heat overexposure isn’t just about better documentation; it’s about recognizing patterns early enough to prevent a heat-related medical emergency.

Heat Safety Regulators Step In

Employers aren’t the only ones paying closer attention to heat exposure and its role in workplace incidents. On April 10, 2026, the Occupational Safety and Health Administration (OSHA) announced a five‑year extension and expansion of its National Emphasis Program for outdoor and indoor heat-related hazards. This is a clear signal that heat risk is broader, more persistent, and more underestimated than employers assume.

The updated program explicitly covers indoor and outdoor work and allows OSHA to intervene before a fatality occurs. This matters since heat is often listed as a secondary factor on incident reports or death certificates, even though it’s debatable whether it was the actual trigger. In short, regulators are no longer waiting for worst‑case scenarios to act. For employers, this means recognizing and documenting early warning signs before they develop into more serious events.

The Overlooked Indoor Risk

Many employers still associate heat illness with outdoor labor. That assumption can lead to indoor heat exposure risks being overlooked until symptoms become more severe. Yet, some indoor work environments are among the most hazardous for heat overexposure:

  • Manufacturing floors with radiant heat
  • Warehouses without ventilation
  • Facilities where personal protective equipment (PPE) or uniforms trap body heat
  • Operations that rely on mandatory overtime during peak months

Workers in a non-air-conditioned warehouse during a summer heatwave may face indoor temperatures well above 100°F while lifting, moving, and wearing gear that limits cooling — creating dangerous heat stress even without direct sun exposure.

Common missteps in indoor environments can actually increase heat load rather than reduce it. A prime example would be the use of high-powered fans in certain indoor environments. Once the room temperature exceeds normal body temperature, strong airflow can trap heat on the body, reducing sweating’s effectiveness. Because these conditions don’t feel immediately alarming, they can be especially dangerous.

Underreporting Is a Risk Management Issue

When early heat-related illness signs and symptoms are underreported in the workplace:

  • Cognitive impairment increases the likelihood of secondary accidents
  • Minor cases escalate into medical emergencies
  • Claims grow more severe and costly
  • Employers lose the chance to intervene early

The cumulative effect is reduced visibility that may affect safety, productivity, and workforce health more than incident records suggest. Organizations that encourage early symptom reporting and work with occupational health providers often see quicker employee recovery from illness and lower workers’ compensation costs. Occupational health providers can also help identify recurring symptom patterns that might otherwise be viewed as isolated incidents.

The Bottom Line

Heat overexposure is a safety issue that can act as a catalyst influencing data accuracy, claims costs, and regulatory risk, particularly when early signs are missed. As OSHA’s expanded focus makes clear, waiting for heat-related illness to look obvious is no longer an effective risk management strategy.

The most effective risk management strategies focus on equipping supervisors and employees to recognize early signs and symptoms and to act on them promptly. They reinforce the importance of following heat stress prevention measures tailored to the specific hazard, helping reduce the risk of heat-related first-aid cases, illnesses, and injuries.

Heat exposure rarely becomes a serious event without warning signs first. And when overexposure isn’t recognized or reported, it doesn’t disappear; it escalates. &

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