By Ben Hoffman, MD, MPH
Chief Medical Officer, WorkSTEPS
Key Insights
- Heat injury is one of the leading causes of death worldwide.
- Upcoming OSHA regulations will increase requirements to mitigate heat risks and improve heat injury prevention.
- Implementing more rigorous protocols now can help prepare and protect workers.
Rising temperatures are increasing the risk of heat injury for both indoor and outdoor workers across industries. As one of the leading causes of death worldwide, heat is an industrial hygiene hazard and must be included in risk assessments. Awareness of heat-related illnesses, risk factors, and regulatory requirements is key to reducing instances of heat injury in the workplace.
Heat-Related Illnesses
Heat stress is the buildup of body heat generated internally by muscle use or externally by the environment. It impacts workers in both outdoor and indoor settings, with the most severe heat-related illnesses resulting in death if not treated properly. There are four stages of heat-related illness, by increasing severity:
- Heat rash: small, itchy bumps or blisters that develop when sweat glands become blocked
- Heat cramps: painful muscle spasms due to excessive sweating and electrolyte loss
- Heat exhaustion: symptoms include dizziness, headache, excessive sweating, rapid heartbeat, nausea or vomiting, and weakness
- Heat stroke: total breakdown of the body’s cooling system. Sweating stops. Skin becomes hot, red, and dry. Mental confusion or loss of consciousness is common, with possible seizures or convulsions. Heat stroke is a life-threatening medical emergency and requires immediate medical attention.
The accompanying heat stress infographic provides a visual summary of the four stages of heat stress and offers actionable steps to help teams stay safe in hot conditions.
Risk Factors
Multiple factors increase the risk of heat-related injury. They include:
- Individual elements such as pregnancy, disability, lack of heat acclimatization (the body’s gradual adjustment to working in hot conditions), low physical fitness, age, and high BMI
- Environmental factors like heavy or impermeable clothing, physically demanding work, high temperatures, high humidity, little air movement, and radiant heat (heat transferred directly from the sun or hot surfaces such as machinery)
- Pharmacological sources like antiepileptics, antipsychotics, antidepressants, heart medications, hormone therapy (including insulin), alcohol, and recreational drugs
- Pathological issues including acute illness, nervous system or cardiovascular diseases, diabetes, liver disease, respiratory disease, and skin conditions (including rashes or burns)
Prevention Strategies
Heat-related injury prevention requires a three-pronged approach.
- Engineering controls add needed ventilation and cooling systems to reduce the temperature. This includes air conditioning in closed spaces or cool rooms created as a recovery area near hot jobs. Fans increase air flow but are only effective when air temperature is lower than skin temperature. Heat conduction is reduced by insulating heat‑generating surfaces with shields or insulation.
- Administrative controls focus on process development, including work scheduling to avoid the hottest times, recovery breaks, and hydration guidelines. Worker acclimatization is another important element—current National Institute for Occupational Safety and Health (NIOSH) guidelines recommend ramping up exposure over the course of a week.
- Personal protective equipment (PPE) commonly includes reflective clothing, cooling vests, and clothing wetted with cold water.
Proposed OSHA Regulations
At the federal level, the Occupational Safety and Health Administration (OSHA) heat stress regulations have been light, but upcoming changes will make them more significant. OSHA has proposed a Heat Injury and Illness Prevention standard that would require employers to evaluate and control heat hazards through a formal prevention program. Although the new standard is not yet final, the General Duty Clause already provides significant scope for citations. In addition, OSHA’s expanded enforcement focus, including its Heat National Emphasis Program, signals greater scrutiny of both indoor and outdoor heat exposures. As a result, employers are well served by strengthening heat injury prevention protocols now rather than waiting for a finalized standard.
The proposed elements of the new heat standard include:
- Heat Injury and Illness Prevention Plan (HIIPP)
- Identifying heat hazards
- Requirements at or above initial heat trigger
- Requirements at or above high heat trigger
- Heat illness and emergency response and planning
- Training
- Recordkeeping
Heat Injury and Illness Prevention Plans (HIIPP)
The HIIPP includes all policies and procedures necessary to comply with the standard. It also requires a designated heat safety coordinator to implement and monitor the HIIPP. Employee input during development and review of the plan is key to capturing work scenarios and needs accurately. Once developed, the HIIPP must be reviewed and evaluated annually and made readily available to all employees at the work site.
Criteria for Heat Hazards
Heat hazards are measured by tracking either the local heat index (i.e., temperature and humidity) forecasts or measuring wet bulb globe temperature (WBGT), which also considers the radiant effects of the sun or other heat source. Heat indexes are used to determine initial heat triggers and high heat triggers, both of which call for different protocols and levels of precaution.
Initial heat triggers occur at a heat index of 80°F or a WBGT equal to the NIOSH Recommended Alert Limit (RAL). At or above the initial heat trigger, employees should be provided with cool drinking water—at least 1 quart per employee per hour—and paid rest breaks. Break areas with shade, or air-conditioning and dehumidification in enclosed spaces, are necessary. Indoor work areas should have fans or natural ventilation at a minimum, with air-conditioning or controls for radiant heat sources being preferable.
High heat triggers are set at a heat index of 90°F or a WBGT equal to the NIOSH Recommended Exposure Limit (REL) and have additional requirements. Paid 15-minute rest breaks every 2 hours are a minimum, although unpaid meal breaks may count as a rest break. Additional observation is necessary, either via a buddy system or oversight by the heat safety coordinator (or site supervisor) for up to 20 employees. Employees working solo at a site need two-way communication at least every 2 hours. Hazard alert information must also be posted, highlighting standards for drinking water, rest breaks, and emergency response procedures.
Emergency Response
Emergency response protocols should be clearly defined in accordance with OSHA’s guidance on heat-related illnesses and first aid.
Training and Recordkeeping
Initial and annual refresher training for supervisors, heat safety coordinators, and employees must be developed and provided. Supplemental training is appropriate after changes in exposure to heat hazards, policy and procedure changes, and occurrence of heat injury or illness at the work site.
Recordkeeping best practice includes retaining onsite measurements at indoor work areas in written or electronic form for 6 months
Conclusion
Proactive measures to remain aware of heat-related illnesses, risk factors, and regulatory requirements are necessary to reduce heat injuries in the workplace. The importance of this industrial hygiene hazard increases as average temperatures continue to rise globally, driving regulatory and industry urgency to protect workers.
Dr. Ben Hoffman is a highly seasoned physician executive with an extensive background in occupational and environmental health, clinical medicine, and transportation safety. He has been employed by government agencies, non-profits, and multinational corporations including GE, Waste Management, Anheuser-Busch, and DuPont. Dr. Hoffman trained at Yale, Brown, and Mt. Sinai School of Medicine and is board certified in internal medicine, preventive medicine, and environmental/occupational health.
He has published widely and holds a Professorship (Adjunct) at the University of Texas School of Public Health. He has held professorships at Tufts University Friedman School of Nutrition, Dartmouth School of Medicine, Boston University, and the University of New Hampshire. He is active on numerous committees and boards, including Global Health at the National Academy of Sciences/Institute of Medicine, IPIECA, the International Association of Oil & Gas Producers (OGP), and is a former chair of the U.S. DOT/FMCSA Medical Review Board.
