The first evidence that exceeding the World Health Organization (WHO) ozone limit is linked to significant increases in hospital admissions for heart attacks, heart failure and stroke is published today in european heart journal, Journal of the European Society of Cardiology (ESC). Even ozone levels below the WHO limit have been associated with poor health.
“During this three-year study, ozone was responsible for an increasing proportion of admissions for cardiovascular disease as time progressed,” said study author Shaoyi Wu of Xi’an Jiaotong University, China. “It is believed that climate change, by creating favorable atmospheric conditions for ozone formation, will continue to increase concentrations in many parts of the world. Our results indicate that the elderly are particularly vulnerable to the cardiovascular effects of ozone, which means worsening ozone pollution with climate change and rapid aging of the world population may result in a higher risk of cardiovascular disease in the future.”
Ozone is a gas and the main air pollutant in photochemical smog. Ozone pollution differs from the ozone layer, which absorbs most of the sun’s ultraviolet rays. Ozone pollution is formed when other pollutants react in the presence of sunlight. These other pollutants are volatile organic compounds and nitrogen oxides that are emitted from automobiles, power plants, industrial boilers, refineries, chemical plants, and biomass and fossil fuel burning facilities. Previous studies have indicated that ozone pollution harms the heart and blood vessels, but there is limited and inconclusive evidence about its effect on cardiovascular disease risk.
This study examined the relationship between ambient ozone pollution and hospital admissions for cardiovascular disease. Data on daily hospitalizations for cardiovascular disease during the period 2015–2017 in 70 cities in China were collected from the two major national health insurance systems. During the study period, the two databases covered nearly 258 million people in 70 cities, which amounts to more than 18% of China’s population. Types of cardiovascular disease included coronary heart disease, stroke, and heart failure as well as subtypes such as angina pectoris, acute myocardial infarction, acute coronary syndrome, stroke, and hemorrhagic stroke.
The maximum average concentrations of ozone, fine particulate matter (PM2.5), respirable particulate matter (PM10), sulfur dioxide, nitrogen dioxide and carbon monoxide for each city were obtained from the China National Urban Air Quality Real-time Publication Platform . .*
During the study period, there were 6,444,441 hospital admissions for cardiovascular diseases in 70 cities and the average maximum ozone concentration for eight hours per day was 79.2 μg/m.3. Exposure to ambient ozone was associated with increased hospitalizations for all studied cardiovascular diseases except hemorrhagic stroke, independent of other air pollutants. For example, every 10 μg/m3 A rise in the average of the two days’ eight-hour maximum ozone concentration was associated with an increase of 0.40% in hospitalizations for stroke and 0.75% for acute myocardial infarction.**
Professor Wu said: “Although these increases seem modest, it should be noted that ozone levels may rise above 200 μg/m.3 In the summer, those increases in hospitalizations will increase more than 20-fold to more than 8% for stroke and 15% for acute myocardial infarction.”
The researchers also estimated excessive admission risks for cardiovascular disease associated with ozone concentrations at or above WHO air quality guidelines (100 μg/m).3) compared to levels below 70 μg/m3. Ozone levels are less than 70 µg/m3 They mostly occur naturally and are not caused by human activity. compared to a two-day average for eight-hour maximum concentrations of less than 70 μg/m3levels of 100 µg/m3 or higher with significant increases in hospital admissions for cardiovascular disease, ranging from 3.38% for stroke to 6.52% for acute myocardial infarction. However, concentrations as low as 70 to 99 μg/m3 (For less than 70 µg/m3) also with increases in hospital admissions ranging from 2.26% for heart failure to 3.21% for coronary heart disease.
During the period from 2015 to 2017, 3.42%, 3.74%, and 3.02% of hospitalizations due to coronary heart disease, heart failure, and stroke, respectively, were attributed to ozone pollution. When each year was analyzed separately, the proportions increased over time. For coronary heart disease, ozone was responsible for 109,400 cases out of 3,194,577 admissions over a three-year period. Professor Wu said: “This indicates that 109,400 admissions for coronary heart disease could have been avoided if ozone concentrations had been 0 μg/m.3. This may be impossible to achieve due to the presence of ozone from natural sources. However, we can conclude that large numbers of hospital admissions for cardiovascular disease could be avoided if levels were below 100 μg/m.3with further reductions at lower concentrations.”
In an accompanying editorial, Professor Thomas Münzel and co-authors said: “Projections for Europe indicate that ozone will play a dominant role as a future health risk factor due to climate change with warming and, consequently, increased photochemical formation of ozone. The strong link between climate change And air quality means that in the long term, reducing emissions to combat global warming will play a major role in mitigating ozone pollution and improving the air we breathe.”
Notes:
*Eight-hour average concentrations were calculated from hourly average concentrations. The maximum eight-hour average is the highest value between 00:00 and 23:59 hours. **The mean of the two days refers to the day of hospital admission and the day before.
