Climate change is making more people around the world vulnerable to heat exposure, putting them at greater risk of heart and kidney disease, heat stress, and other heat-related killers, scientists warned on Wednesday.

Global warming’s effects look most serious for ageing and urban populations and people with chronic health conditions. And Europe and the eastern Mediterranean are more vulnerable than Africa and southeast Asia due to many older people living in densely populated cities, the researchers said in an analysis in The Lancet medical journal.

“Trends in the impacts of climate change, exposures and vulnerabilities show unacceptably high risk for health, now and in the future,” said Hilary Graham, a professor at Britain’s York University who co-led the work.

The Lancet Countdown on Health and Climate Change involved work from 27 academic institutions in disciplines from health to engineering to ecology, plus expertise from the United Nations and intergovernmental agencies across the world.

According to the World Health Organization (WHO), climate change affects many factors influencing health, including clean air and water, food and shelter. It estimates that between 2030 and 2050, climate change could cause an additional 250,000 deaths a year due to malnutrition, diarrhoea, malaria and heat stress.

The report found that in 2017, some 157 million vulnerable people were exposed to heatwaves. Some 153 billion hours of labor were lost last year due to heat exposure, it said.

It also found that small changes in temperature and rainfall can result in large changes in the transmission of certain infectious diseases spread via water and mosquitoes, such as cholera, malaria and dengue fever.

Howard Frumkin, a climate and health specialist at the Wellcome Trust which part-funded the work, said the findings were clear.

“Climate change is directly impacting our health, with extreme heat, for example, driving wildfires, crop failures, infectious diseases and costing lives all around the world,” he said, and urged all sectors to act more swiftly to curb climate change and “reduce the potentially devastating impact on our planet and our health”.