Food delivery driver John Jay Chan has had no protections from the record-breaking heat waves that have hit the Philippines in recent months, but he must continue to work nine-hour days to provide for his family.
"We understand that the nature of our work means we're exposed to extreme heat," said Chan, a 30-year-old father of two, who has been a motorbike gig worker for six years.
Some of Chan's colleagues have experienced mild heatstroke or elevated blood pressure while working in temperatures that have exceeded 45 degrees Celsius.
"But until now, we haven't been monitored by the government for heat-related illnesses or deaths, so the lack of data means we're not a priority," said Chan.
From the Philippines to India and Mali, a lack of reliable data on heat-related deaths is undermining efforts to mitigate the risk of extreme heat and provide better protection for the most vulnerable, like outdoor migrant and gig workers.
Globally, 2.41 billion workers, or 70% of the world's workforce, are exposed to excessive heat, with people in Africa, Arab states and the Asia and Pacific region facing the highest exposure, according to a July report by the International Labour Organization (ILO). This causes nearly 19,000 deaths a year, the ILO said.
"The number of workers suffering the consequences of excessive heat is alarming, and occupational safety and health protections have struggled to keep up," the ILO said.
Collecting accurate data to inform government policy on reducing exposure to extreme heat is more urgent than ever as climate change pushes global temperatures and heat death tolls higher.
Last year was the hottest on record, and July 21, 2024, was the hottest day ever recorded as heat waves scorched large swaths of the United States, Europe and Russia.
"In the context of climate change, we see longer extreme-heat days that last longer through the night, and so people won't have a break," said Tarik Benmarhnia, an environmental epidemiologist at the University of California San Diego. "Health professionals don't fully realize how this is a big issue," he said.
In the Philippines, where a two-week heat wave in April forced schools to shut, seven heat-related deaths and 77 heat-related illnesses were reported from January to May this year, according to health ministry data.
Labor union activist Lucas Ortega said such figures do not reflect the risk of heat stress that workers face.
"We know we have thousands of delivery riders, construction and maintenance workers, street cleaners and workers from different industries," said Ortega, a spokesperson for the Center of United and Progressive Workers in the Philippines. "But we don't know how many of them were exposed to extreme heat," he said.
'Sneaky, silent killer'
Accurate data on heat-related mortality is difficult to obtain because health authorities do not attribute deaths to heat specifically, but rather to the illnesses exacerbated by high temperatures, such as cardiovascular and kidney issues.
This makes heat a "sneaky and silent killer," said Benmarhnia. "In the vast majority of situations, heat is going to actually trigger a lot of complications, and that would be the case for people who already have some sort of comorbidity (or) underlying chronic diseases," he explained.
Death certificates stating heat as a direct cause are rare, according to health researcher Barrak Alahmad.
"Gathering data typically involves identifying indirect causes and correlating this with temperature on very hot days and seeing excess deaths on a typical day," said Alahmad, a research fellow at the Department of Environmental Health at Harvard T.H. Chan School of Public Health.
But in many low-income countries, mortality data is often reported on a weekly or monthly basis and not daily, he said.
It means heat-related deaths are undercounted, typically overlooking thousands, if not tens of thousands, of deaths.
"Even countries with massive resources still struggle to identify heat deaths," said Alahmad.
'Public health failure'
In India, the lack of accurate recording of heat-related mortality is a "public health failure," said Dileep Mavalankar, a professor and former head of the Indian Institute of Public Health, a private university in Gandhinagar city.
It is projected that more than 1.5 million Indians will die each year from extreme heat by 2100, according to 2019 research by the Climate Impact Lab.
Since the start of India's summer on March 1 through June 18, at least 110 confirmed heat-related deaths occurred, when temperatures in the capital, Delhi, soared to almost 50 C.
That figure is only "the tip of the iceberg," said Mavalankar, who helped implement South Asia's first Heat Action Plan in Ahmedabad in 2013, after the city saw more than 1,300 deaths in a 2010 heat wave.
"Political will and understanding are totally missing at the moment. There is also no public pressure or accountability pressure or auditing pressure," he said. Without data, "no public action will be taken ... This is long-standing neglect."
The National Center for Disease Control (NCDC) at India's health ministry, which records heat-related deaths, did not respond to repeated requests for comment.
While the NCDC published a set of guidelines to help hospitals identify and categorize heat-related deaths, Mavalankar wants the NCDC to require all hospitals to report all deaths daily on its online portal, rather than leaving it as a voluntary practice.
Heat officers should be assigned to every city to record daily deaths from crematoriums and cemeteries and publish them with comparative data, he said.
"These fixes, including the all-cause mortality data, are easily doable at no major costs," said Mavalankar.
Deadly heat waves
At Mali's Gabriel Toure Hospital in the capital Bamako, doctors said some 102 patients died over four days in April compared with 130 deaths recorded in the entire month of 2023.
They linked the spike to a deadly heat wave, and resulting power cuts, that hit Mali and other countries in the African Sahel, including Senegal, Guinea, Mali, Burkina Faso, Niger, Nigeria and Chad.
Official death tolls from the heat wave across the Sahel region are undercounts, according to World Weather Attribution (WWA), a group of researchers who study the link between heat and climate change.
"Many places lack good record keeping of heat-related deaths, therefore currently available figures are likely an underestimate," the WWA said in a statement after the heat wave. Tunde Ajayi, a Nigerian epidemiology and environmental health expert, said heatstroke in hospital records and death certificates is often reported as a secondary cause of death in African health settings.
"We need to mine the data for the cause of death right from hospital records to inform data for the health ministry and other agencies," Ajayi said.
Currently most of the research on heat-related deaths is being conducted in the United States, Europe and Australia.
Benmarhnia sees "a paradox," in which most heat-related deaths are occurring in places with the least data, especially Sub-Saharan and northern Africa.
"These heat days are just going to become the norm. We shouldn't be surprised when there is another heat event or another record that is broken," said Benmarhnia.