Extreme Heat's True Cost Revealed by Study of 1,000 Women Workers

A recent United Nations report indicates the world has failed to limit global warming to 1.5°C above pre-industrial levels, a threshold considered critical for avoiding the most severe climate impacts. Concurrently, an NPR investigation revealed that extreme heat in the United States is significantly deadlier than previously recorded, with nearly five times more fatalities than official estimates suggest.

These findings follow two consecutive years of intense heatwaves. Europe experienced widespread reporting on heat-related deaths as its infrastructure strained under record temperatures. In the U.S., "heat domes" settled over large areas, affecting over 100 million people. The impacts extended beyond direct fatalities, affecting a diverse range of individuals including construction and outdoor workers, delivery drivers, agricultural laborers, the unhoused, those unable to afford air conditioning, individuals on certain medications, and people with mental health conditions or limited access to healthcare.

Globally, billions of workers face extreme heat annually, according to the International Labor Organization. While many survive, they often endure long-term physical and mental strain. Quantifying the full impact of heat on mental health, physical well-being, wages, food security, and infrastructure remains a complex challenge.

To address this, a study involving 1,000 women in India's informal labor economy is working to quantify the burden of heat and humidity on their health, earnings, and overall well-being. The Community Heat Adaptation and Treatment Strategies (CommHATS) project, a collaboration between Harvard University and the Self Employed Women’s Association (SEWA) in India, has recruited participants from various trades, including street vendors, waste recyclers, home-based artisans, and farmers. Over 13 months, each woman is equipped with wearable sensors to measure heat and humidity in their homes and workplaces, and undergoes lab tests for critical biomarkers. Surveys collect data on their living and working conditions, as well as their well-being and wages. This data is forming one of the world's largest databases on heat's impact on human health.

The project aims to answer critical questions about adaptation to extreme heat, such as the effectiveness of interventions like cool roofs and appropriate metrics for success. It also seeks to understand subjective experiences, like whether a slight temperature drop is meaningful if sleep quality remains poor, and what threshold should define a new heat insurance product – airport temperature or actual household temperature.

Early findings, set to be shared at New York Climate Week, indicate significant wage losses on hot days, reduced sleep duration, and heightened cardiac stress among participants. In India, where approximately 90% of workers are informally employed, accountability often falls on the individual. These workers adapt by altering work hours, reallocating savings, and investing in personal cooling and water solutions. Existing global financial instruments for heat adaptation are often underfunded and lack mechanisms to reach the most vulnerable, leaving them to bear the costs themselves.

The CommHATS project utilizes a grassroots approach with field workers monitoring sensors, wearables, and the participating workers. The active involvement of participants in the study's questions, tools, and analysis ensures its relevance and scalability. The methodology is designed to help communities worldwide understand their environmental exposures at a scale actionable for decision-making and to measure the efficacy of interventions.

The study underscores that the costs of climate inaction are disproportionately borne by those already facing precarious conditions. While human resilience is notable, relentless heat diminishes the capacity for individuals to thrive, even if they survive.