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

Abstract

Background: Insufficient heat acclimatization is a risk factor for heat-related illness (HRI) morbidity, particularly during periods of sudden temperature increase. We sought to characterize heat exposure on days before, and days of, occupational HRIs.Methods: A total of 1241 Washington State workers' compensation State Fund HRI claims from 2006 to 2021 were linked with modeled parameter-elevation regressions on independent slopes model (PRISM) meteorological data. We determined location-specific maximum temperatures (T max,PRISM ) on the day of illness (DOI) and prior days, and whether the T max,PRISM was ≥10.0°F (~5.6°C) higher than the average of past 5 days ("sudden increase") for each HRI claim. Claims occurring on days with ≥10 HRI claims ("clusters") were compared with "non-cluster" claims using t tests and χ 2 tests.Results: Seventy-six percent of analyzed HRI claims occurred on days with a T max,PRISM ≥ 80°F. Claims occurring on "cluster" days, compared to "non-cluster" days, had both a significantly higher mean DOI T max,PRISM (99.3°F vs. 85.8°F [37.4°C vs. 29.9°C], t(148) = −18, p < 0.001) and a higher proportion of "sudden increase" claims (80.2% vs. 24.3%, χ 2 [1] = 132.9, p < 0.001). Compared to "cluster" days, HRI claims occurring during the 2021 Pacific Northwest "heat dome" had a similar increased trajectory of mean T max,PRISM on the days before the DOI, but with higher mean T max,PRISM.Conclusions: Occupational HRI risk assessments should consider both current temperatures and changes in temperatures relative to prior days. Heat prevention programs should include provisions to address acclimatization and, when increases in temperature occur too quickly to allow for sufficient acclimatization, additional precautions.

A Novel Conceptual Model for Human Heat Tolerance

“…Heat stress also has a temporal spectrum of exposures both within a day and serial heat stress exposures over multiple days ( e.g. , carryover effects) (10–12). In defining heat tolerance, the exposure conditions are specified as constant with a short exposure time on the order of an hour to avoid drift over longer periods (13).…”

“…, perceived exertion, thermal sensation, and thermal comfort). At some point, the heat strain leads to deleterious outcomes including heat-related illness (11), acute injury (14,15), and decreased performance with lost productivity (16,17). The probability associated with the deleterious outcomes increases with heat stress, but the levels of de minimus or acceptable probability are not well defined.…”

“…In addition, situational factors such as performance expectations, voluntary and forced overtime, work practices, and incentives can affect heat tolerance. Another situational factor is the pattern of exposures over days, in which high heat exposures on a previous day (12) or days (10,11) influence the risk of heat disorders on the current day. Among personal factors, acclimatization and hydration are easily managed by policies and practices with some cooperation from the individual.…”

Editorial: Acute and long-term health issues of occupational exposure to heat and high physical loads

“…In the case of heat, some of this attention is driven by increased awareness of climate change, making us more conscious of heat events, which are projected to continue to be more frequent and severe ( Intergovernmental Panel on Climate Change, 2023 ). Unfortunately, some of our awareness also comes from the fact that undesired health outcomes have been documented in working populations ( Arbury et al, 2014 ; Heinzerling et al, 2020 ; Spector et al, 2023 ). The same is true for heavy or repetitive movements in the workplace where, despite clear evidence that these exposures can cause severe acute ( Lucas et al, 2020 ) or chronic health outcomes ( López-Ruiz et al, 2015 ), workers continue to be exposed in alarming numbers ( Lucas et al, 2020 ).…”