Occupational heat exposure and injury risk in Washington State construction workers

Abstract

Introduction: The primary objectives of this research were to: 1) assess the relationship between heat exposure and occupational traumatic injuries in Washington State; and 2) assess heat exposure and the relationship between heat stress and psychomotor vigilance and balance in a population at high risk for injuries and heat related illness. Methods: We conducted an epidemiologic study and a field study. First, we assessed the relationship between maximum daily humidex and Washington State Fund workers’ compensation injuries in outdoor construction workers from 2000-2012 using a case-crossover design and high-resolution meteorological data. Second, we collected full-shift measurements of heat exposure and tests of psychomotor vigilance and balance in a sample of 22 commercial roofing workers in the Greater Seattle area in a repeated-measures study during the summer and fall of 2016. Heat exposure was compared across three spatial resolutions (regional, area, and personal). The association between heat stress, specifically the mean one-hour difference between the worksite wet bulb globe temperature and the recommended exposure limit (ΔREL), and PVT and balance outcomes were modeled using linear GEE. Results: We observed a traumatic injury odds ratio (OR) in outdoor WA construction workers of 1.0053 (95% CI 1.003, 1.007) per °C change in humidex. We report a positive mean (95% confidence interval) difference between personal- and area-level temperature of 4.4 (4.1, 4.7)°C. The direction of the difference between regional and area monitors varied by site. We observed a positive (detrimental) association (0.3; 95% CI -3.0, 3.5) and a negative association (-0.9; 95% CI -1.7, -0.1) between heat stress and PVT and balance, respectively. Post hoc interaction analyses of heat stress and dehydration yielded positive associations of heat stress with psychomotor outcomes. Conclusion: In the case-crossover study, increasing humidex was associated with increasing traumatic injury risk. In the field study of commercial roofing workers, personal temperature measurements were consistently higher than area temperature measurements, and the difference between regional and area temperatures varied in direction by site. No decrements in psychomotor vigilance or postural sway were observed with the low levels of heat stress measured in this study, however dehydration may modify this effect.