Assessment of Heat Stress Exposure on Construction Workers in Warm and Humid Environments

Abstract

Construction workers are at high risk of heat stress, due to the demanding nature of their work and the high temperature work condition. Open field workers such as construction workers have to carry out physical works in warm and humid conditions hence they are more vulnerable to heat stress. The objectives of the study were: to assess occupational factors affecting construction workers that are related to heat stress on site during construction; to measure the heat levels of construction sites in warm and humid environment; and to assess heat stress risk on construction workers using the Wet Bulb Globe Thermometer (WBGT) index and Humidex Index. Construction workers were identified using stratified sampling in the 6 constituencies of Mombasa County. Field studies were conducted in January and February 2022 whereby 463 sampled construction workers were observed during construction work. Workers were classified into 6 job categories namely steel Reinforcement works, walling, form work construction, concreting, plumbing and electrical works and roofing works. The levels of exposure of construction workers to direct sunlight was recorded, perceived exertion recorded using the Borg CR10 perceived exertion scale and workload was classified based on the ACGIH workload classification. Majority of workers who were unskilled (67%) and undertaking Concreting works (heavy work) and Steel reinforcement jobs (moderate work) were at high risk of heat stress based on their occupational activities. Both the WBGT and Humidex index used to assess the heat stress risk found out that construction workers exposed to the open sun and working between 12pm and 2pm were at the highest risk of heat stress followed by 10am-12pm and 2pm-4pm time periods. Construction work carried out between 10am-12pm and 2pm-4pm presented similar high risk environmental conditions felt by construction workers. Work-ability (productivity) levels were significantly reduced by 37% for light works, 62% for moderate works and 72% for heavy works between 12pm and 2pm. It was further noted that temperatures on construction sites could reach higher levels than the reported meteorological data. A One Way ANOVA test was performed on the environmental data collected for hypothesis testing. At p=0.00, using a Significance level , the null hypothesis was rejected. Construction managers and contractors are therefore recommended to measure the levels of WBGT on construction sites in warm and humid environments and issue alerts to construction workers working in the open environment to protect them from the likelihood of heat stress. Provision of shaded rest areas on site, worker rotation and flexible working hours were also to be adopted. It was concluded that the findings in this study should be adopted by stakeholders such as National Construction v Authority (NCA), and the Directorate of Occupational Safety & Health Services (DOSHS) in the development of heat exposure guidelines for construction workers in hot and humid environments in Kenya. Lastly, further studies can be undertaken by taking into account heat strain on construction workers in relation to heat stress studied in this research project. A similar study can also be undertaken for a longer period of time to give a better assessment because heat stress effects may appear later in the long-term.