Ground-level ozone to become an increasingly deadly threat without action

Scientists who examined short-term exposure to ground-level ozone and daily mortality in 406 cities across 20 countries, have warned that ozone-related deaths will rise significantly over the next two decades years unless air quality regulations are tightened.

Ground-level ozone is a major component of air pollution that is produced when atmospheric pollution from car exhaust, industrial processes, and volatile chemicals like paint thinner and other solvents interact with sunlight.

The research, undertaken by a team from the Yale School of Public Health is believed to be the geographically largest and most comprehensive investigation of this issue to date.

The research set out four scenarios, based on the hypothetical existence or strong or weak policies relating to firstly, climate and secondly air quality. Using advanced modelling, the increase in ozone-related deaths between 2010-2014 and 2050-2054 was estimated, producing the following results:

• Strong climate and strong air quality controls: deaths to increase by 0.7%
• Weak climate but strong air controls: deaths to increase by 56%.
• Weak climate and weak air pollution controls: deaths to increase by 94%.

In real terms, this would mean the additional deaths of between 45 and 6,200 people a year in the cities studied, between 2010-2014 and 2050-2054. 

Only one scenario produced results that projected a decrease in ozone-related mortality fraction and that was the one that adopted climate and air quality controls consistent with the international Paris Climate Agreement.

The problem, according to the scientists, is the global vagaries that surround safe levels of ozone. In this study, the scientists set 70 µg/m³ as the threshold for maximum allowable exposure. However, the WHO limit is 100µg/m³ while in the U.S. it is approximately 137µg/m³, Europe 120µg/m³, Mexico 137µg/m³, and China 160µg/m³.  

Kai Chen, a senior author of the study and an assistant professor of public health at the Yale School of Public Health. said: ‘This paper is further evidence of the health benefits that can be achieved if more countries adhered to the Paris Climate Agreement’s goals.

‘In all four of the climate scenarios we studied, only the scenario that aligns with the Paris Agreement would see a reduction in ozone-related mortality fraction in the future.’