Alert for Occupational Heatstroke Among Workers Exposed to High Temperatures

Heatstroke is a commonly known condition, which most people associate exclusively with summer. However, few fully understand the body’s normal heat production and heat dissipation mechanisms. Many also hold unanswered questions: Is every case of heatstroke occupational? What clinical manifestations does occupational heatstroke present? How can it be prevented and treated?

1. Human Heat Production and Heat Dissipation Mechanisms

Under physiological normal conditions, the human body maintains a dynamic balance between heat generation and heat loss to stabilize core body temperature. When working in hot environments or high-temperature posts, workers absorb environmental heat while generating extra metabolic heat from physical labor, leading to an increased total heat load. The body compensates by activating thermoregulation, water-electrolyte metabolism and other physiological functions to boost heat dissipation and sustain thermal equilibrium.

No thermal metabolic disturbance or organ dysfunction will occur if the rate of heat loss equals the combined heat gained via endogenous metabolism, radiation and convection, or when deep body temperature stays around 38°C. Nevertheless, human thermoregulation has a limited capacity. Persistent excess heat gain over heat loss leads to cumulative heat storage and elevated body temperature. The resulting disorders of thermal balance and/or water-salt metabolism trigger heat-related illnesses characterized primarily by central nervous system and cardiovascular dysfunction.

2. Classification and Etiology of Heat-Related Illnesses

Rapid-onset conditions induced by heat exposure in hot environments, namely heat stroke, heat cramps and heat exhaustion, are collectively defined as heat-related illnesses.

Heat stroke: Strenuous labor under high temperatures generates far more endogenous and environmental heat (via convection and radiation) than the body can dissipate through evaporation. Accumulated heat raises body temperature and impairs the hypothalamic thermoregulatory center, causing disease onset.

Heat cramps: Heavy sweating during high-temperature work induces excessive sodium and potassium depletion, disrupting water-electrolyte balance and triggering painful muscle spasms.

Heat exhaustion: In hot and humid settings, peripheral vasodilation increases cutaneous blood flow, while profuse sweating reduces circulating blood volume, resulting in insufficient cerebral perfusion. It predominantly affects the elderly and patients with underlying cardiovascular diseases.

3. High-Risk Occupations Prone to Heat-Related Illnesses

High-temperature and high-radiation work: Coking, ironmaking and steelmaking workshops in metallurgy; casting workshops in machinery manufacturing; kiln workshops for ceramics, glass and brick production; boiler rooms in power plants, gas plants and ships.

High-temperature and high-humidity work: Textile printing and dyeing factories, deep coal mines.

Outdoor summer work: Construction sites, dock cargo handling and other field operations.

4. Predisposing Risk Factors for Heat-Related Illnesses

Workplace ambient temperature above 34°C, compounded by high humidity, intense thermal radiation and poor ventilation.

Excessive labor intensity, prolonged working hours, insufficient rest intervals, chronic fatigue and sleep deprivation.

Impaired sweat secretion: congenital anhidrosis, sweat gland damage, extensive skin lesions, sedative medication use.

Poor physical condition: chronic underlying diseases, malnutrition, advanced age and frailty.

Heavy alcohol intake, which disrupts the body’s heat acclimatization capacity and precipitates heatstroke.

5. Diagnosis Criteria for Occupational Heatstroke

Occupational heatstroke is diagnosed based on the worker’s high-temperature exposure history (meteorological conditions at work), clinical manifestations including hyperthermia, muscle cramps or syncope, and exclusion of other differential disorders. It is categorized into impending heatstroke, mild heatstroke and severe heatstroke with distinct diagnostic standards:

Impending heatstroke

After prolonged labor in high-temperature workplaces, symptoms include dizziness, headache, thirst, profuse sweating, general fatigue, palpitations, poor concentration and uncoordinated movements; body temperature remains normal or slightly elevated.

Mild heatstroke

All symptoms of impending heatstroke worsen, accompanied by flushing, heavy perspiration and tachycardia; body temperature rises above 38.5°C.

Severe heatstroke

Three subtypes (heat stroke, heat cramps, heat exhaustion) may occur individually or in mixed forms:

Heat stroke (including sunstroke): Sudden onset in hot environments with core temperature exceeding 40°C.

Heat cramps: Prominent painful sustained muscle spasms.

Heat exhaustion: Rapid onset with dizziness, headache, sweating, thirst, nausea and vomiting, progressing to clammy skin, hypotension, arrhythmia and mild dehydration; body temperature is slightly elevated or normal.

6. Standard First Aid Interventions

Core emergency procedures for heatstroke: Remove the patient from the high-temperature workplace to a cool, well-ventilated rest area; supply salt-containing cool drinks and deliver symptomatic supportive care. Physical cooling modalities include ice water immersion, full-body cold compress combined with fan ventilation, or whole-body wiping with cold towels and ice pack cooling in air-conditioned spaces.

For severe heatstroke, continue constant cold water spraying and towel friction over the scalp, bilateral axillae and groin while maintaining physical cooling, and arrange urgent hospital transfer for definitive treatment.

7. Preventive Strategies and Dietary Guidance for Heat-Related Illnesses

Enterprise-level Prevention

Optimize production processes and operating workflows to minimize direct worker contact with heat sources; install thermal insulation materials, water curtains, circulating water gates and air interlayer walls; upgrade natural or mechanical ventilation systems, or install air conditioning in insulated enclosed workshops.

Establish rational work-rest schedules tailored to production conditions, adjusting summer high-temperature shifts to guarantee adequate sleep and rest for heat-exposed staff.

Conduct pre-employment physical examinations and heat acclimatization training for high-temperature workers. Employees with heat contraindications shall receive targeted intervention and undergo occupational capacity assessment by professional institutions to determine fitness for hot work.

Strengthen safety awareness and personal protective equipment (PPE) compliance for frontline heat workers: supply heat-resistant full sets including hoods, face shields, overalls, footwear and specialized protective goggles.

Individual Dietary & Hydration Guidelines

Timely balanced nutrition and rational meal planning; consume heat-adapted electrolyte drinks in small, frequent sips.

Match fluid intake to sweat volume: limit single serving to 150–200 mL. Daily water demand reaches 3–4 L under moderate heat and labor intensity, and exceeds 5 L for heavy work in extreme heat.

Supplement sodium appropriately: sodium requirements increase in the initial days of high-temperature work. Concurrent potassium and magnesium supplementation is essential via high-potassium and high-calcium foods such as fresh fruits, vegetables, soybean products, kelp, eggs and poultry.