Using the thermal work limit as an environmental determinant of heat stress for construction workers

Construction workers are vulnerable to heat stress in summer as evidenced by deaths and injuries caused by heat stroke. Over the past centuries, many heat-stress indices have been developed to assist with the management of these problems. To address this pressing need of the industry, an enhanced model based on a multi-dimensional environmental indicator, the thermal work limit (TWL) index, is developed. Field studies were conducted between July and September 2010 in Hong Kong on ten apparently healthy and experienced construction rebar workers. Based upon 281 sets of synchronized meteorological and physiological data collected from four different construction sites, physiological, work-related, environmental, and personal parameters were measured to construct the heat-stress model. Multiple linear regression showed that a total of ten determining factors are able to predict the workers' subjective rating of perceived exertion (RPE) (adjusted R2=0.79, p<0.05). The accuracy of the TWL heat-stress model was found to be statistically acceptable (mean absolute percentage error = 4.3%, Theil's U inequality coefficient = 0.003). Alcohol-drinking habits, age, and work duration are the three most important predictors to determine the physiological responses of construction workers. The model reported in this paper provides a scientific prediction of the reality, which may benefit the construction industry to produce solid guidelines for workers working in hot weather.