Singapore – A new study reveals a significant link between rising temperatures and heat-related illnesses among outdoor workers. Researchers found that each 1 degree Celsius increase in daily average temperature more than doubles an outdoor worker’s risk of heat stroke. If this temperature increase persists for three days, the likelihood of a worker experiencing a heat injury nearly quadruples.
Quantifying the Risk
Led by Adjunct Assistant Professor Joel Aik from the Duke-NUS Medical School, the study is the first local effort to quantify heat illness cases among outdoor workers over an extended period – between 2009 and 2023, approximately 40 cases were reported. Professor Aik noted that the actual number of cases may be underreported, as workers with milder symptoms like heat cramps may not seek medical attention.
The majority of reported cases – over 85 percent – involved more severe illnesses such as heat stroke and heat exhaustion. Symptoms of heat stroke include a high internal body temperature, delirium, and seizures, and can rapidly cause damage to vital organs if left untreated. The remaining cases involved moderate symptoms like fainting, dizziness, and muscle cramps.
Vulnerable Populations and Conditions
The study indicated that workers in the construction sector were most frequently affected, with over two-thirds of cases involving foreign workers. As of 2025, approximately 440,000 employees work in the construction, marine shipyard, and process sectors. Cases were more prevalent in the central and eastern regions of Singapore, which experience an average temperature of around 28 degrees Celsius.
Researchers found that the body’s ability to cool itself is hampered when air temperature approaches body temperature. Elevated humidity also poses a risk, slowing the evaporation of sweat, a key cooling mechanism.
Current and Future Measures
The Ministry of Manpower (MOM) has mandated heat stress measures since 2023, including acclimatizing new workers to the local climate and ensuring adequate hydration – at least 300ml of water per hour. Workers are also advised to rest in the shade for 15 minutes each hour during periods of high heat stress. Professor Aik suggests employers could further enhance worker safety by providing more cooling solutions.
With the El Niño climate phenomenon expected in the second half of 2026, the risk of a heatwave – defined as three consecutive days with a highest daily temperature of at least 35 degrees Celsius and a mean temperature of at least 29 degrees Celsius – could increase.
Frequently Asked Questions
What are the symptoms of heat stroke?
Heat stroke symptoms include a high internal body temperature, delirium and seizures. If not treated quickly, heat stroke can rapidly damage the brain, heart, kidneys and muscles.
Which workers are most affected by heat illness?
Most of the cases involved workers from the construction sector, and more than two-thirds of them were foreigners.
How does humidity affect the risk of heat illness?
When there is a lot of vapour in the air, the perspiration on the skin evaporates more slowly, and a few consecutive days of high humidity without sufficient cooling can negatively impact the body’s system.
How can workplaces best protect outdoor workers from the dangers of rising temperatures?
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