By Ollie Jay, Professor of Heat and Health, University of Sydney
Professor Ollie Jay is Founding Director of the Heat and Health Research Centre at The University of Sydney, driving global efforts to protect people from extreme heat. His work has helped shape heatwave policies and heat alerts across multiple continents. He advises major sporting bodies, including the Australian Open, and was the Lead Heat Consultant for the Australian Olympic Team (Paris 2024). Ollie’s research has been featured in leading scientific journals such as Science, Nature, and The Lancet.
Integrating a Physiological Approach in Problem-Solving: Insights from Bangladesh’s RMG Sector
Established in 2022, the Heat and Health Research Centre at the University of Sydney is a multidisciplinary research group focussed on understanding and mitigating the negative effects of extreme heat and hot weather on human health and wellbeing across the lifespan. Our goal is to build resilience to a warming world by generating rigorous evidence that informs health-centred policies, practices and recommendations for individuals, public health authorities, government organisations, and sporting bodies.
An essential element of our methodology for creating evidence-based solutions involves integrating our understanding of human physiology at every phase of the problem-to-solution cycle (see Fig.1).
Fig.1. The problem-to-solution cycle with physiology embedded at each stage
Drawing on our recent collaborative research evaluating scalable cooling strategies for workers in Bangladesh’s ready-made garment industry as an example, the cycle begins with systematically identifying and quantifying the heat-health problem. This initial phase is critical to ensure that resources are allocated to address issues with the most significant impact. Partnering with an RMG factory in Dhaka, we measured human heat stress potential by considering not only air temperature – as is common in meteorological and epidemiological studies – but also incorporating humidity, air movement, and mean radiant temperature, which collectively define the potential for physiological heat strain. Additionally, worker interviews were conducted to establish the presence experienced symptoms of heat illness or exhaustion, whose physiological mechanisms are well documented.
Upon completion of this step, it became apparent that the primary underlying mechanism of the heat-health problem was exposure to air temperatures reaching up to 40˚C, coupled with elevated humidity and limited air movement, which together hinder effective sweat evaporation. Additionally, workers produced significant metabolic heat due to routine ironing and sewing activities, and standard workplace attire further restricted the evaporation of sweat.
Based on our understanding of how various workplace environmental features influence physiological heat strain, several potential solutions were collaboratively developed with the factory owners. This approach ensured that only interventions capable of being scaled up in real-world settings would be evaluated for effectiveness. Accordingly, selected measures aimed to mitigate the effects of elevated humidity and stagnant air on sweat evaporation (fans), alleviate dehydration-related limitations on sweat production (fans plus drinking water), and address aspects of the built environment – specifically, the potential benefits of installing a reflective insulated white roof. Computer simulations showed that this modification could lower indoor temperatures by ~2.5˚C. The critical question remained though whether such a decrease in air temperature would sufficiently relieve physiological heat strain.
Next, we conducted a proof-of-principle test in a climate chamber (Fig.2) to evaluate our proposed interventions by replicating the factory environment in Dhaka as closely as possible, including representative work tasks such as ironing (for men) and sewing (for women). Participants with matching physiological profiles (age and sex) were selected, and each underwent pre-conditioning in a hot, humid setting to facilitate early physiological adaptation to heat. The primary outcomes for this trial were physiological: core temperature increases, heart rate responses, and fluid loss due to sweating, which collectively informed the potential effectiveness of each intervention. Findings indicated that, during peak heat stress conditions, fans alone only mitigate physiological heat strain if combined with an appropriate hydration strategy, whereas the benefit of an insulated white roof was further enhanced when supplemented with additional air-flow from fans.
Fig.2. An example of the chamber trial assessment potential cooling solutions for worker in the Bangladesh RMG industry
While the chamber trial utilising physiological metrics does not yield definitive conclusions, it represents a critical step in establishing which interventions should be prioritised in the subsequent phase of our cycle: comprehensive field testing. Conducting the physiology-focused chamber trial beforehand is essential for identifying viable interventions for field evaluation, thereby minimising unnecessary costs and avoiding potential disruptions. For instance, assessing the impact of lowering air temperature by 2.5˚C in a climate chamber – such as would result from modifications to a factory roof – and comparing these results with and without increased air movement is significantly more practical than implementing such changes directly within an operational factory and installing additional fans, hoping to achieve supplementary cooling effects.
After field tests have been conducted and have produced Class A evidence supporting the effectiveness of these interventions, the concluding phase will involve collaborating with policy-makers in the RMG industry to enact changes in policy and practice, thereby addressing the initial heat-health issue.
Professor Ollie Jay was a member of our 2025 Global Climate and Health Summit Steering Group. Learn more about the Summit and how physiology can drive faster, fairer climate action.