Personal exposure to heat amongst older adult women in Tamil Nadu, India

Background & Aim: In 2019, 127,000 deaths were attributed to heat exposure globally, with over 40% in India, where a substantial portion of the population has limited access to cooling technologies. This substantial burden is expected to worsen with climate change, but little is known about personal exposure to outdoor temperatures in India We leverage data collected as part of the Household Air Pollution Intervention Network (HAPIN) randomized controlled trial to describe personal temperature exposure of older adult women in Tamil Nadu. We compare personal exposure to ambient monitoring stations and modelled temperature products. Methods: As part of HAPIN, older adult women in Tamil Nadu periodically wore instrumentation for a 24-hr period to measure air pollution; these instruments also measure temperature. We analyzed temperature measurements taken between 2018 and 2021 and compared them to the nearest identified ambient monitoring stations, and to the ERA5 and GLDAS meteorological products. Results: Personal measurements were recorded from 105 different participants for a total of 1.7 million datapoints. The mean temperature recorded was 28.6 °C with a standard deviation of 3.5 °C. Differences of ≥5 °C across individuals on the same day were not uncommon, nor were intra-individual exposures that varied by several degrees within an hour -- potentially a result of elevated heat while cooking. ERA5 estimates were more positively correlated with personal exposure than with GLDAS or ambient monitors. Correlations varied by season, with best performance across all products during the monsoon season. Conclusions: Accurate exposure assessment is important for assessing health effects of heat – a growing problem. There is substantial variability in how well public datasets correlate with personal experience, not only by product type but also location and season. It is important to quantify these differences to appropriately estimate health effects. Keywords: Heat, India, Remote Sensing, Exposure Assessment