Ozone pollution has been linked to a variety of health problems, including cardiovascular disease. While ozone in the upper atmosphere (stratospheric ozone) is beneficial in that it blocks harmful ultraviolet (UV) radiation, ozone at ground level (tropospheric ozone) is a harmful air pollutant.
According to new research, exceeding the World Health Organization’s (WHO) ozone limit is linked to significant increases in hospital admissions for heart attack, heart failure, and stroke. Even ozone levels lower than the WHO maximum have been linked to worsened health.
The European Heart Journal, a journal of the European Society of Cardiology (ESC), published the first evidence that exceeding the World Health Organization (WHO) ozone limit is associated with significant increases in hospital admissions for heart attack, heart failure, and stroke today. Even ozone levels lower than the WHO maximum have been linked to worsened health.
“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 of Xi’an Jiaotong University, China. “It is believed that climate change, by creating atmospheric conditions favoring 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 aging of the global population may produce even greater risks of cardiovascular disease in the future.”
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 aging of the global population may produce even greater risks of cardiovascular disease in the future.
Professor Shaowei Wu
Ozone is a gas that is the most prevalent air pollutant in photochemical smog. The ozone layer, which absorbs the majority of the sun’s ultraviolet radiation, is not the same as ozone pollution. When other pollutants react in the presence of sunlight, ozone is formed. Other pollutants include volatile organic compounds and nitrogen oxides emitted by automobiles, power plants, industrial boilers, refineries, chemical plants, and biomass and fossil fuel burning facilities. Previous research has suggested that ozone pollution is harmful to the heart and blood vessels, but there is limited and inconclusive evidence about its impact on the risk of cardiovascular disease.
This study looked at the relationship between ozone pollution in the environment and hospitalizations for cardiovascular disease. Data on daily hospital admissions for cardiovascular disease in 70 Chinese cities from 2015 to 2017 were gathered from the two major national health insurance systems. During the study period, the two databases covered approximately 258 million people in 70 cities, or more than 18% of China’s population. Coronary heart disease, stroke, and heart failure were among the cardiovascular diseases studied, as were subtypes such as angina, acute myocardial infarction, acute coronary syndrome, ischaemic stroke, and hemorrhagic stroke.
Ozone pollution is linked with increased hospitalizations for cardiovascular disease
Daily eight-hour maximum average concentrations of ozone, fine particulate matter (PM2.5), inhalable particles (PM10), sulfur dioxide, nitrogen dioxide and carbon monoxide were obtained for each city from the China National Urban Air Quality Real-time Publishing Platform.*
During the study period, there were 6,444,441 hospital admissions for cardiovascular disease in the 70 cities and the average daily eight-hour maximum ozone concentration was 79.2 μg/m3. Exposure to ambient ozone was associated with increased hospital admissions for all cardiovascular diseases studied except hemorrhagic stroke, independent of other air pollutants. For example, each 10 μg/m3 rise in the two-day average eight-hour maximum ozone concentration was associated with a 0.40% increase in hospital admissions for stroke and 0.75% for acute myocardial infarction.**
Professor Wu said: “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 hospitalizations would be amplified by more than 20 times to over 8% for stroke and 15% for acute myocardial infarction.”
The researchers also estimated the excessive admission risk for cardiovascular disease associated with ozone concentrations at or above the WHO air quality guideline (100 µg/m3) compared to levels below 70 μg/m3. Ozone levels below 70 μg/m3 are mostly naturally occurring and not due to human activity. Compared to two-day average eight-hour maximum concentrations below 70 μg/m3, levels of 100 µg/m3 or higher were associated with substantial increases in hospital admissions for cardiovascular disease, ranging from 3.38% for stroke to 6.52% for acute myocardial infarction. Nevertheless, lower concentrations of 70 to 99 µg/m3 (vs. below 70 μg/m3) were also linked with increases in hospital admissions, ranging from 2.26% for heart failure to 3.21% for coronary heart disease.
From 2015 to 2017, ozone pollution was responsible for 3.42%, 3.74%, and 3.02% of hospitalizations for coronary heart disease, heart failure, and stroke, respectively. When each year was examined individually, the proportions increased over time. Over a three-year period, ozone was responsible for 109,400 of 3,194,577 admissions for coronary heart disease. “This suggests that 109,400 coronary heart disease admissions could have been avoided if ozone concentrations were 0 µg/m3,” Professor Wu said. Given the presence of ozone from natural sources, this may be impossible to achieve. However, we can conclude that if levels were below 100 µg/m3, significant numbers of hospital admissions for cardiovascular disease could be avoided, with further reductions at lower concentrations.”
Professor Thomas Münzel and co-authors wrote in an accompanying editorial, “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, consequently, increasing photochemical formation of ozone.” Because of the strong link between climate change and air quality, reducing emissions in the long term to combat global warming will play a critical role in reducing ozone pollution and improving the air we breathe.”
