Heat Stress And Strain In Construction Workers During Work In The Summer

Construction workers are at high risk of heat-related illnesses. This elevated risk is likely due to excessive heat stress, defined as the combination of metabolic heat production and excessive environmental heat exposure, which results in heat strain [i.e., increases in core temperature(Tcore)]. Excessive heat stress may vary across job types, reflecting the diversity of tasks performed. Heat stress may also vary for workers based on whether they operate in covered or uncovered work areas. Despite these elevated risks, no previous study has assessed heat strain via Tcore in construction workers during the summer in the United States. PURPOSE: To measure heat stress and strain in construction workers during work in the summer. METHODS: Over 3 days, 32 construction workers (3 females) were monitored during a summer workday in a commercial building work site. Participants were identified by both job type (4 carpenters, 15 concrete, 8 laborers, and 5 roofer workers) and work environment (covered, uncovered). Heat index (HI), heart rate (HR), and Tcore (intestinal, n = 28) were measured throughout the workday. Urine specific gravity (USG) was used to assess hydration status pre- and post-shift. RESULTS: Peak HI over the three days were 27.3, 35.2, and 33.7 °C. Roofers were exposed to a higher HI compared to other job types (p < 0.001), but no overall differences were observed between covered (28.8 ± 3.7 °C) and uncovered (32.1 ± 4.2 °C) areas (p = 0.366). Metabolic rate (MR) calculated from HR and corrected for Tcore was higher in workers in uncovered (423 ± 127 W/m2) compared to covered (316 ± 50 W/m2) (p = 0.006) areas, but not different among job types (p = 0.227). Peak Tcore exceeded 38.0 °C in 43% of the participants, with 4% exceeding 38.5 °C. There was no change in USG from pre- (1.022 ± 0.005) to post-shift (1.022 ± 0.007) (p = 0.846). Notably, 63% of workers began their shift dehydrated (USG > 1.020). A significant positive correlation was found between peak MR and peak Tcore (R = 0.62, p = 0.001). A positive, non-significant correlation was noted between peak HI and peak Tcore (R = 0.36, p = 0.06). CONCLUSIONS: Even during low to moderate environmental heat stress, construction workers experience significant heat strain, which is associated with peak MR. Environmental heat exposure and metabolic work vary by job type and work environment. This study was supported by CPWR (#22-5-PS) and NIOSH (R01OH011528).