According to a large study conducted in China, the rise in hospitalizations for cardiovascular diseases is linked to ozone pollution of the air, the most recent example of the risks posed by greenhouse gas emissions.
This study, published in the journal European Heart Journal and involving 258 million people in 70 Chinese cities, compared hospital admission data from 2015 to 2017 with the direct evolution of air quality in these cities.
Hospitalizations skyrocket during ozone depletion events.
These data show that, independent of other pollutants, ozone is linked to more than 3% of hospitalizations for cardiovascular diseases, cardiac insufficiencies, and cerebral vasculopathies. Furthermore, it has been demonstrated that every increase of 10 micrograms of ozone per meter cube of air is associated with a 0.75% increase in hospitalizations for cardiac crises and a 0.4% increase in cerebrovascular accidents.
"Although these increases appear minor," the impact will be "multiplied by more than 20 times" when ozone levels exceed 200 micrograms during the summer, according to the study's author, Shaowei Wu of Xi'an Jiaotong University, and colleagues.
While ozone in the upper layers of the atmosphere helps to prevent harmful ultraviolet (UV) rays from reaching Earth, this gas is a major component of the smog that pollutes the majority of major cities.
Ozone is formed in the atmosphere by a chemical reaction that occurs when two pollutants, often emitted by automobiles or industry, combine in the presence of sunlight, and it has been demonstrated that it interferes with photosynthesis and plant growth.
The study calls for the involvement of public authorities.
The study claims to be the first to assess the risk of hospitalization for cardiovascular disease when ozone levels exceed the World Health Organization's daily recommendation of 100 micrograms per meter cube of air.
The researchers call for more vigorous public action to reduce the use of fossil fuels, as well as the implementation of an alert system to allow people to limit their exposure on days when the ozone level is high.
However, because the study was observational, it was unable to demonstrate directly that ozone pollution causes cardiovascular diseases.
