Air pollution to blame for alarming rise in heart attacks and strokes, study shows

XI’AN, China — Air pollution is contributing to a concerning increase in heart attacks and strokes, according to recent research. Scientists in China argue that inhaling ozone, also known as smog, accelerates the hardening of arteries, thereby leading to cardiovascular disease. Smog is created in the atmosphere when emissions from vehicles and industries interact with sunlight, forming harmful nitrogen oxides and volatile organic compounds.

Cardiovascular disease is the leading cause of death worldwide, taking approximately 18 million lives each year. It is estimated that air pollution is responsible for 1.8 million of these global deaths annually.

“During this three-year study, ozone was responsible for an increasing proportion of admissions for cardiovascular disease as time progressed. It is believed that climate change, by creating atmospheric conditions favoring ozone formation, will continue to raise concentrations in many parts of the world,” says the lead author of the study, professor Shaowei Wu from Xi’an Jiaotong University, in a media release. “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.”

Smog over Shanghai, China
New research shows air pollution is linked to increased hospital admissions for heart attack and stroke. (Photo by Holger Link on Unsplash)

Linking smog to heart problems

The study, which is the largest of its kind, is based on data from national health insurance systems covering 70 cities and 258 million people in China, nearly a fifth of the country’s population. The research supports earlier evidence suggesting that smog negatively impacts the heart and blood vessels. From 2015 to 2017, hospital admissions for cardiovascular disease increased when ozone levels rose.

The researchers compared almost 6.5 million cases with pollution data from each city. They found that each increase of 10 micrograms per cubic meter (µg/m3) in the two-day average eight-hour maximum concentration was linked to more heart attacks and strokes, as well as other cardiovascular diseases.

“It’s important to note that ozone levels can surge to over 200 µg/m3 in the summer. These increases would result in over an 8% increase in hospitalizations for stroke and a 15% increase for acute myocardial infarction,” says Wu.

Ozone levels below 70 µg/m3 are generally naturally occurring and not due to human activity. However, levels of 100 µg/m3 or higher were associated with significant increases in cases, ranging from 3.38% for stroke to 6.52% for heart attack. Even lower concentrations of 70 to 99 µg/m3 were linked to increased hospital admissions.

Blame it on the air

The study found that 3.42%, 3.74%, and 3.02% of hospitalizations for coronary heart disease, heart failure, and stroke, respectively, were attributable to ozone pollution.

“This study suggests that a significant number of hospital admissions for cardiovascular disease could be avoided if ozone concentrations were below 100 µg/m3, with even more reductions at lower concentrations,” concludes professor Wu.

An earlier U.K. study involving 4,000 participants suggested that even low levels of air pollution can cause changes to the heart similar to those in the early stages of heart failure. Individuals living near busy, noisy roads had larger hearts on average than those in less polluted areas, despite air quality being within guidelines. The Queen Mary University of London team compared these changes to the effects of being consistently inactive or having elevated blood pressure.

This study is published in the European Heart Journal.

South West News Service writer Mark Waghorn contributed to this report.