New research has found that exceeding the World Health Organization’s (WHO) ozone pollution limit can significantly increase the risk of hospitalisation for cardiac disease.
A new study, ‘Ozone pollution and hospital admissions for cardiovascular events,’ has been published in the European Heart Journal. The paper describes how ozone pollution can increase the risk of heart attack, heart failure and stroke in the population.
“During this three-year study, ozone was responsible for an increasing proportion of admissions for cardiovascular disease as time progressed,” said study author Professor Shaowei Wu.
“It is believed that climate change, by creating atmospheric conditions favouring ozone formation, will continue to raise concentrations in many parts of the world. Our results indicate that older people are particularly vulnerable to the adverse cardiovascular effects of ozone, meaning that worsening ozone pollution with climate change and the rapid ageing of the global population may produce even greater risks of cardiovascular disease in the future,” he continued.
What is ozone pollution?
Ozone pollution and the ozone layer are different; the ozone layer absorbs ultraviolet radiation from the Sun, whereas ozone pollution is formed by pollutants that react in the presence of sunlight.
Ozone pollutants can be emitted by motor vehicles, power plants, industrial boilers, refineries, chemical plants, and biomass and fossil fuel burning facilities. Past research has suggested that these pollutants can damage blood vessels and the heart; however, studies have been inconclusive.
In this study, the researchers examined the link between ambient ozone pollution and hospital admissions for cardiovascular disease. They studied hospital admission data from 2015 to 2017 in 70 cities across China, covering around 258 million people. Admissions for coronary heart disease, stroke and heart failure, and subtypes such as angina, acute myocardial infarction, acute coronary syndrome, ischaemic stroke and haemorrhagic stroke were all included in the study.
Measuring air pollution
Ozone pollution was measured by calculating the maximum average concentrations of ozone pollutants in the air, such as sulphur dioxide, nitrogen dioxide and carbon monoxide. A total of 6,444,441 patients were admitted to hospitals with cardiovascular disease during the study period. The average daily maximum ozone concentration in the study period was 79.2 μg/m3. Each 10 μg/m3 rise in average ozone concentration led to a 0.40% increase in hospital admissions for stroke and 0.75% for acute myocardial infarction.
“Although these increments look modest, it should be noted that ozone levels may surge to higher than 200 μg/m3 in summer, and these increases in hospitalisations would be amplified by more than 20 times to over 8% for stroke and 15% for acute myocardial infarction,” said Professor Wu.
Between 2015 and 2017, hospitalisations for coronary heart disease, heart failure and stroke caused by ozone pollution rose by 3.42%, 3.74% and 3.02%.
According to the researchers, ozone pollution was responsible for 109,400 of 3,194,577 coronary heart disease admissions in this period.
“This suggests that 109,400 coronary heart disease admissions could have been avoided if ozone concentrations were 0 µg/m3. This may be impossible to achieve given the presence of ozone from natural sources. However, we can conclude that considerable numbers of hospital admissions for cardiovascular disease could be avoided if levels were below 100 μg/m3, with further reductions at lower concentrations,” explained Professor Wu.
“Projections for Europe suggest that ozone will play a more dominant role as a health risk factor in the future due to climate change with rising temperature and, accordingly, increasing photochemical formation of ozone. The strong link between climate change and air quality means that reducing emissions in the long term to tackle global warming will play a key role in alleviating ozone pollution and improving the air that we breathe,” concluded co-author of the study, Professor Thomas Münzel.