The rise in hospitalizations for heart disease is linked to air pollution by ozone, according to a large study in China made public on Friday, the latest illustration of the risks posed by greenhouse gas emissions.
This study, published in the European Heart Journal and covering 258 million people in 70 Chinese cities, compared hospital admission data over the period 2015-2017 with the live evolution of the quality of the air in these cities.
These data show that, independently of other pollutants, ozone was associated with more than 3% of hospitalizations related to coronary heart disease, heart failure and strokes.
In addition, every increase of 10 micrograms of ozone per cubic meter of air has been shown to be linked to a 0.75% increase in hospitalizations for heart attacks and a 0.4% increase for accidents. cerebrovascular.
“Although these increases seem modest”, the impact would be “magnified more than 20 times” when ozone levels exceed 200 micrograms during the summer, study author Shaowei Wu told AFP. from Xi’an Jiaotong University, and his colleagues. In this extreme example, exposure to ozone would be linked to 15% of heart attacks and 8% of strokes, the researchers estimate.
While ozone in the upper layers of the atmosphere helps block harmful ultraviolet (UV) rays from reaching Earth, at ground level, this gas is a major component of the smog that pollutes most major cities. .
Ozone is created in the atmosphere by a chemical reaction when two pollutants, often emitted by cars or industry, combine in the presence of sunlight, and has been shown to interfere with photosynthesis and plant growth.
The study claims to be the first to assess the risk of hospitalization for heart disease when ozone levels exceed the daily recommendation of 100 micrograms per cubic meter of air issued by the World Health Organization.
Researchers call for stronger public action to reduce fossil fuel consumption, as well as implementing an alert system so people can limit their exposure on days when ozone levels are low. pupil.
Since the study was observational, however, it was unable to directly show that ozone pollution causes heart disease.