Heat stress and strain in commercial construction workers in the summer: A pilot study

Construction workers are 13 times more likely to die from heat-related illnesses than workers in other job industries. This elevated risk is attributed to excessive heat stress from environmental exposure, metabolic heat generated from physical labor, and the insulating effects of protective clothing. Levels of heat stress may vary across job types, reflecting the diversity of tasks performed and the work environment. Despite elevated risks, heat strain assessed by core temperature (Tcore) in construction workers during summertime in the United States has not been evaluated previously. Thirty-two construction workers (three females) were monitored over 3 summer workdays. Participants were categorized by job type (carpenter, concrete, laborer, roofer) and work environment (covered, uncovered). Heat index (HI), heart rate (HR), and Tcore were measured throughout the workday, while hydration was assessed through pre- and post-shift measurements of urine specific gravity (USG). Peak HI over the 3 days was 27.3, 35.2, and 33.7 °C, indicating the potential for low to moderate heat stress. Roofers experienced a higher peak HI compared to other job types (p < 0.01), but no differences were observed between workers in covered (28.8 ± 3.7 °C) and uncovered (32.1 ± 4.2 °C) areas (p = 0.37). The estimated peak metabolic rate was higher in workers in uncovered areas (868 ± 238 W) compared to covered (632 ± 130 W) (p < 0.01), with no differences among job types (p = 0.23). Forty-three percent of workers had Tcore exceeding 38.0 °C, with 4% exceeding 38.5 °C. Based on USG, 63% of workers began work dehydrated (1.022 ± 0.005), but urine did not become more concentrated during the workday (post-shift USG; 1.022 ± 0.007) (p = 0.78). Forward stepwise regression identified that peak metabolic rate plus post-shift USG were the combined variables most associated with peak Tcore (r² = 0.55, p < 0.01). Construction workers, even in low to moderate environmental heat exposure, experienced significant heat strain, primarily due to an elevated metabolic rate. Environmental heat exposure and metabolic rate vary by job type and work environment.