The Climate Centre and the Prudence Foundation have published a scoping review of academic literature from 2000 to 2023, involving more than 30 papers, to better understand the compound risk to human health of heat, humidity, and air pollution.

Extensive research has been conducted on their individual implications, but the compound effect of the three together has not been as closely studied.

Air pollution alone contributes to an estimated 9 million deaths a year globally, a 2022 study found, while heatwaves have for some time now been regarded as the silent killer of climate change.

The components of this triple threat interact in complex ways: heat contributes to the production of ozone and particulate matter, exacerbating air pollution and trapping heat in the atmosphere, increasing the risk of respiratory and cardiovascular problems.

Simultaneously, elevated humidity impedes the body’s ability to regulate temperature through sweating, making heat more lethal still.