Potential Impacts of Different Occupational Outdoor Heat Exposure Thresholds among Washington State Crop and Construction Workers and Implications for Other Jurisdictions

Abstract

Occupational heat exposure is associated with substantial morbidity and mortality among outdoor workers. We sought to descriptively evaluate spatiotemporal variability in heat threshold exceedances and describe potential impacts of these exposures for crop and construction workers. We also present general considerations for approaching heat policy-relevant analyses. We analyzed county-level 2011–2020 monthly employment (Bureau of Labor Statistics Quarterly Census of Employment and Wages) and environmental exposure (Parameter-elevation Relationships on Independent Slopes Model (PRISM)) data for Washington State (WA), USA, crop (North American Industry Classification System (NAICS) 111 and 1151) and construction (NAICS 23) sectors. Days exceeding maximum daily temperature thresholds, averaged per county, were linked with employment estimates to generate employment days of exceedances. We found spatiotemporal variability in WA temperature threshold exceedances and crop and construction employment. Maximum temperature exceedances peaked in July and August and were most numerous in Central WA counties. Counties with high employment and/or high numbers of threshold exceedance days, led by Yakima and King Counties, experienced the greatest total employment days of exceedances. Crop employment contributed to the largest proportion of total state-wide employment days of exceedances with Central WA counties experiencing the greatest potential workforce burden of exposure. Considerations from this analysis can help inform decision-making regarding thresholds, timing of provisions for heat rules, and tailoring of best practices in different industries and areas.

Occupational heat‐related illness in Washington State: A descriptive study of day of illness and prior day ambient temperatures among cases and clusters, 2006–2021

“…We found higher proportions of HRI claims occurring on “cluster” days in Western WA and higher proportions of HRI claims occurring on days at or above 80°F (27°C) in Central WA. We found similar geographic patterns for the frequency of HRI claims across WA as previous research that identified the average number of days and employment days at or above PRISM maximum daily temperature thresholds of 80°F (27°C) in WA 19 . The concordance of these findings underlines the importance of both the geographical distribution of the workforce and ambient temperature exposures on the risk of occupational HRI.…”

“…Finally, we used an exposure assessment approach based on modeled meteorological data. Different heat exposure assessment approaches have different strengths and limitations 19 . Although gridded meteorological data are efficient and provide reasonable spatial resolution, they may not reflect smaller‐scale microclimates.…”

“…We found similar geographic patterns for the frequency of HRI claims across WA as previous research that identified the average number of days and employment days at or above PRISM maximum daily temperature thresholds of 80°F (27°C) in WA. 19 The concordance of these Heat prevention programs should include provisions to optimize workers' acclimatization status. Acclimatization allows for protection from about an additional ~2.5-3°C WBGT of heat exposure.…”

“…In the summer of 2021, the Pacific Northwest experienced unprecedented increases in temperature and temperature extremes during a “heat dome” event, in which heat was trapped by high‐pressure atmospheric circulation. Although existing research in WA has separately demonstrated spatiotemporal variability in heat exposure 19 and characterized HRI workers' compensation claims, 3,6 there is a gap in the characterization of spatiotemporal variability in changes in heat exposure on days leading up to HRIs among workers. Given the potential physiological and occupational health significance of insufficient acclimatization and the projected increase in the frequency and intensity of heat events in the future, 20 we sought to characterize heat exposure on days leading up to the day of illness (DOI), including “sudden increase,” lagged, and cumulative exposure, among WA HRI workers' compensation claims and clusters over space and time and by claim characteristics, including during the 2021 Pacific Northwest heat dome event.…”

“…6 In the summer of 2021, the Pacific Northwest experienced unprecedented increases in temperature and temperature extremes during a "heat dome" event, in which heat was trapped by highpressure atmospheric circulation. Although existing research in WA has separately demonstrated spatiotemporal variability in heat exposure 19 and characterized HRI workers' compensation claims, 3,6 there is a gap in the characterization of spatiotemporal variability in changes in heat exposure on days leading up to HRIs among workers.…”