Consequences and mitigations of hyperthermia in Industrial Environments

About This Grant

PROJECT ABSTRACT Extreme heat exposure in the US caused over 120,000 heat-related emergency room visits in 2024; heat stroke leads to organ damage, including acute kidney injury, and even death. The health effects of recurrent, asymptomatic hyperthermia, however, remain unknown. Kidney disease disproportionately affects working-age persons living in hot regions of the world, including California’s Central Valley and Texas’ Rio Grande Valley and repetitive heat stress is posited to be the cause. If heat exposure is linked to kidney injury, a broad swath of heat-exposed workers—outdoor workers (farm workers, construction workers, and firefighters) and indoor industrial workers (warehouse workers, shipyard welders, and food truck operators)—are at risk. Since several individual-level factors contribute to heat stress—e.g., age, comorbidities, physical fitness, and acclimatization, heat stress itself can be challenging to quantify, particularly in large population studies. Consequently, systematic investigations on the causal effects of heat stress, and of mitigation strategies have also lagged. In this study, we propose two aims. In aim one, we will develop measures of heat stress using non-invasive proxies. In controlled climactic chambers experiments, we will conduct high frequency physiologic monitoring and biosampling during exercise in persons of working age (30-50 years) with varied temperature conditions. We plan to agnostically identify markers that correlate with changes in core temperature and kidney injury. In aim two, using a case-cross over randomized control trial design at the work site, we will implement and assess two active cooling interventions in 72 workers, accounting for individual response to heat and underlying comorbidities. Over sequential weeks, we will measure rate of core temperature change (primary outcome) and changes in kidney injury markers and worker acceptability (secondary outcomes). Testing and quantifying the effects of active cooling interventions on kidney injury markers not only helps to build the case for investment in a specific cooling technology, it will also provide supporting or refuting causal evidence for the link between heat stress and kidney injury. In future work, we can 1) apply a non-invasive heat stress marker in broader population-based studies on the health effects of heat, and 2) assess the cost-effectiveness of heat mitigation strategies and specifically their impact on worker productivity and satisfaction.