The level of heat stress at construction sites in different districts across Hong Kong varied significantly, making the current heatstroke warning system inefficient at representing the risk faced by workers, a survey by Greenpeace has found.
According to a Thursday press release, over the past month, Greenpeace sent 14 researchers to measure heat stress data outside seven construction sites located in Hong Kong Island, Kowloon, the New Territories and Islands District.
The researchers measured the WetBulb Globe Temperature (WBGT) data, which indicates heat stress in direct sunlight, taking temperature, humidity, wind speed, sun angle and cloud cover into account.
They collected data on three very hot days, and every day they started measuring for 2.5 hours from noon. The survey found that the largest difference between the sites’ WGBT values was eight, representing a significant difference between the heat stress levels at each site.
Chao Ren, an expert in urban climate and associate professor of the faculty of architecture at the University of Hong Kong said in a press release in Cantonese: “Due to influence factors including the built environment, topography and water bodies, there will be microclimatic variations even within the same city.”
A three-tier warning system designed to help protect Hong Kong workers from heatstroke went into effect on May 15, but was not made mandatory. The system consists of amber, red and black warnings, indicating three levels of heat stress, based on the Hong Kong Heat Index, which is measured at King’s Park Meteorological Station.
However, Chao said that “relying on the data of King’s Park Meteorological Station alone to issue heatstroke prevention [warnings] cannot adequately represent the heat conditions in different parts of the territory.”
Not specific to outdoor workers
Greenpeace also said that the Hong Kong Heat Index was not specific to those working outdoors.
“Labourers working outdoors are directly exposed to the sun. The Hong Kong Heat Index is not designated for their actual working environment and it is not an appropriate measure for their heat stress. The Labour Department should directly adopt the WGBT, which is commonly used internationally to measure heat stress for construction workers,” Yu Tak-sun, the chairperson of the Hong Kong Workers’ Health Centre said in Cantonese.
Greenpeace urged the Labour Department to directly adopt the WBGT to measure heat stress and also to set up monitoring spots at different construction sites.
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