According to a new report from the World Heart Federation (WHF), of the 4.2 million deaths caused by air pollution in 2019, almost 70% were due to cardiovascular disease, particularly ischemic heart disease (1.9 million) and stroke (0.9 million).
The report highlights the significant contribution that air pollution has to the global cardiovascular disease (CVD) epidemic.
Meanwhile, air pollution has surpassed even high blood pressure as the leading risk factor for the overall global disease burden, according to a recently published Lancet study of 88 environmental and health risk factors in 204 countries and territories. The analysis is part of the 2021 Global Burden of Disease (GBD) study conducted by the Seattle-based Institute for Health Metrics and Evaluation (IHME).
The GBD study is published every two years, but the release of the 2021 data was delayed until now due to the pandemic. A range of risk factors were taken into account, from environmental and occupational hazards such as air pollution to behavioural factors such as smoking, physical inactivity, unsafe sex and poor nutrition.
Air pollution was also one of the leading risk factors in the latest GBD study published in 2020, but the methodology was different and the disease burden was calculated separately for ambient and household pollution.
Most deaths from air pollution are due to cardiovascular disease, not lung disease
But a new report from the WHF shows that of the diseases most closely associated with air pollution-related exposures, cardiovascular disease accounts for the majority – a surprising new finding.
“When most people think of air pollution, they think of people coughing and lung diseases such as asthma and pulmonary disease, but in fact it's cardiovascular disease that's probably the biggest concern,” Dr Mark Miller, chair of the World Health Forum's Air Pollution and Climate Change Expert Group, from the University of Edinburgh, told Health Policy Watch.
“The report is essentially a re-evaluation of the latest data from the World Health Organisation to highlight just how bad the cardiovascular effects of air pollution are,” he said.
The report, titled “Clearing the Air to Address the Cardiovascular Health Crisis from Air Pollution,” was released this weekend at the World Heart Summit in Geneva, Switzerland. It is one of the most comprehensive reports ever published by a global coalition on risk factors that many cardiologists are not fully aware of.
For household air pollution, the association with CVD is also clear, but less pronounced.
Of the 3.2 million deaths due to household air pollution in 2019, 53% were due to CVD, including 1 million deaths due to ischemic heart disease and 700,000 deaths due to stroke.
From a disease perspective, the report found that around 37% of global CVD deaths in 2019 were attributable to air pollution, of which 22% were due to ischemic heart disease and 15% were due to stroke.
Air pollution – the biggest environmental health risk
The report calls air pollution the “biggest environmental health risk,” noting that in some areas air pollution is 10 times higher than the WHO recommended limit.
Cardiovascular disease claims more than 20 million lives worldwide each year, and air pollution has the greatest impact on those who suffer from cardiovascular disease, the report said.
The report warned that unless appropriate policies are implemented, there will be further increases in deaths and disabilities from cardiovascular disease caused or exacerbated by air pollution.
“These two reports highlight how important it is for governments to prioritise rapid air quality measures to save lives and reduce the toll and cost of cardiovascular disease, the world's biggest killer,” said Nina Renshaw, Health Director at the Clean Air Fund. “The fact that air pollution is the number one risk factor for the global disease burden must also be brought to the attention of health donors. Air pollution efforts have been chronically underfunded, receiving just 1% of global development funding in recent years. Air pollution must urgently become a global health priority.”
Why air pollution increases CVD mortality
In fact, although counterintuitive, there are clear physiological reasons why air pollution, particularly fine particles, is so closely linked to heart disease and stroke.
Air pollution particles are absorbed into tissues deep in the lungs, causing inflammation that contributes to chronic lung disease and cancer. But particulates at or below PM2.5 can penetrate the lung walls and enter the bloodstream. These particles circulate through the arteries and veins of the body and brain, not only exacerbating plaque buildup over time, but also contributing to the narrowing of arteries, creating the perfect conditions for heart disease and stroke.
Air pollution-related CVD deaths surge in Southeast Asia and the eastern Mediterranean
The report also found that deaths from heart disease attributable to air pollution have increased by as much as 27 percent in some areas over the past decade.
Experts say the main reason for rising air pollution levels in several countries in Southeast Asia and the eastern Mediterranean is that average concentrations of air pollution are almost 10 times higher than the WHO recommended levels.
The Western Pacific region had the highest number of deaths from heart disease and stroke due to outdoor air pollution in 2019, at nearly 1 million, with South-East Asia coming in a close second with 762,000 deaths.
In Southeast Asia, Africa and the Eastern Mediterranean, air pollution levels are about 10 times higher than recommended levels. Countries facing the most serious air pollution problems include Kuwait, Egypt and Afghanistan in the Eastern Mediterranean.
Actual number of CVD deaths linked to air pollution likely higher
Furthermore, the actual number of CVD deaths attributable to air pollution is likely much higher: currently, mortality has only been assessed for a single air pollutant, namely PM2.5, and only for ischemic heart disease and stroke, despite a wide range of other cardiovascular diseases that may be exacerbated by air pollution.
“The reality is that there is a real lack of reliable, detailed data, mainly due to the lack of ground monitoring systems. This is particularly true in low-income areas, where millions of people live in unmonitored areas,” said Mariachiara Di Cesare from the University of Essex, who worked on the WHF report.
“To give just one example, IQAir's 2023 World Air Quality Report provides a comprehensive overview of PM2.5 data for almost 8,000 cities in 134 countries, regions and territories. Looking at Africa, only 24 out of 54 countries have some form of air quality monitoring, and most of the existing stations are concentrated in the western and southern parts of the continent,” Di Cesare said.
Because of this, the report's findings are an underestimate, Cesare told Health Policy Watch, and he said improved monitoring of air pollution in both rural and urban areas would allow for more accurate estimates of air pollution levels and trends.
WHF study relies on 2019 data – Lancet updates that air pollution is now the biggest cause of death
Notably, the new WHF report relies on 2019 data on the impact of air pollution on cardiovascular health; the latest IHME Global Burden of Disease study, published in The Lancet, provides slightly updated data linked to 2021. And while the WHF report focuses its analysis primarily on air pollution-related CVD deaths, the Lancet study looks at both mortality and morbidity. But the overall message about the deadly effects of air pollution is the same.
More than 11,000 participants participated in the IHME GBD study. After air pollution, high blood pressure and smoking were the second and third highest risk factors leading to excess disease and disability, or disability-adjusted life years (DALYS).
“These are groups that are increasingly exposed to risk factors, and this is only exacerbated by demographic factors like population growth and aging,” Michael Brauer, lead author of the study from the Institute for Health Metrics and Evaluation (IHME), said in a podcast discussing the findings.
The 2021 study also looks at how health risks have changed over the past two decades, comparing the latest findings with those from the year 2000, when the World Health Organization published the first-ever GBD study, which quantified deaths and illnesses associated with 25 environmental, occupational and behavioral health risks. The comparison between the two reveals some risk factors that have stagnated or become more significant, as well as some that have moved down the list as conditions have improved, particularly safe water, sanitation and sanitation.
Climate change is having a growing impact
WHF experts note that climate change is an additional stressor as global temperatures continue to rise unabated, increasing the risks from air pollution.
Already this year, heatwaves have caused temperatures to soar from Mali to India, and climate scientists say that heatwaves are becoming more frequent and intense due to climate change. Heatwaves are also known to worsen underlying non-communicable diseases, such as diabetes and heart disease, as previously reported by Health Policy Watch.
“That's kind of the main message that the science is telling us right now is that we're starting to see all these environmental stressors intertwine with each other in complex ways,” Miller said, “and so, for example, if you have a heatwave in the context of increased air pollution, you would expect cardiovascular disease to worsen.”
Global health costs related to air pollution are already projected to soar from $21 billion in 2015 to $176 billion in 2060, and annual workday losses could rise to 3.7 billion by 2060. Additional stressors would make health costs even worse, the WHF report noted.
But the key message, Miller said, is that action makes a difference: “We're highlighting some really scary numbers here — huge numbers of deaths around the world — but we call these preventable deaths, because air pollution is preventable. So there's also an opportunity here: if we can address these issues, and we know some of the steps to do so, then hopefully we'll see improvements in cardiovascular health.”
Image credit: Unsplash, Clean Air Report to Address the Cardiovascular Health Crisis from Air Pollution. , Clean Air Report to Address the Cardiovascular Health Crisis from Air Pollution, Global Burden of Disease Study 2021.
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