Air pollution haze over city skylineShare on Pinterest
A recent study shows a correlation between air pollution exposure and cardiovascular events. zxvisual/Getty Images
  • Researchers investigated the effects of air pollution on cardiovascular health.
  • They found that air pollution is linked to higher numbers of years of life lost, deaths, and years spent in disability.
  • The study found a correlation between air pollution and cardiovascular health, but not a causative link.

Around 91% of the world’s population lives in places where the air quality index exceeds limits set by the World Health Organization (WHO) guidelines.

Air pollution is one of the largest risk factors for disability, alongside high blood pressure, smoking, and high blood glucose levels. It is also a major risk factor for cardiovascular disease (CVD), which contribute to around 1 in 3 deaths globally.

Air pollution in the form of particulate matter (PM) is usually classified into three subgroups based on particle diameter:

  • Coarse particles: Fewer than 10μm but more than 2.5μm (i.e., dust, pollen, and fly ash).
  • Fine particles: Fewer than 2.5μm but more than 0.1μm (i.e., combustion particles and smoke).
  • Ultra-fine particles: Fewer than 0.1μm (i.e., diesel exhaust particles and wood burning).

Research shows fine particulate matter is the most influential environmental risk factor for cardiovascular disease mortality and disability.

Further study of the link between PM 2.5 and cardiovascular health over time could inform public health policy and recommendations.

Recently, researchers investigated the effects of PM 2.5 and cardiovascular-related deaths. They found that between 1990 and 2019, the number of premature cardiovascular disease deaths and years of disability linked to PM 2.5 increased by 31% globally.

Dr. Cheng-Han Chen, interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, not involved in the study, told MNT:

“The study shows on a global scale how the effect of PM on cardiovascular disease has been changing over time. Air pollution remains a significant risk factor for cardiovascular disease, and the problem appears to be worsening. There remain significant gender and geographical/sociodemographic disparities in the effects of air pollution, which present opportunities for us to better target pollution control in order to improve people’s health.”

The study was recently published in the Journal of the American Heart Association.

For the study, the researchers analyzed data from the Global Burden of Disease Study 2019, which contains health data from 204 countries. In particular, they examined data on particulate matter-attributed ischemic heart disease and stroke between 1990 and 2019.

Exposure to particulate matter pollution was estimated using information from satellites, ground-level monitoring, computer models of chemicals in the atmosphere, and land-use data.

In particular, the researchers assessed for changes over time in years of life lost due to premature death (YLLs), years lived with disability (YLDs), and disability-adjusted life years (DALYs), a time-based measure combining YLLs and YLDs.

The researchers noted that all-age deaths increased from 2.6 million in 1990 to 3.5 million in 2019.

The number of male deaths that occurred during the study period increased by 43%, whereas the number of female deaths increased by 28.2%.

The researchers additionally noted that all-age DALYs increased by 31% from 6.8 million in 1990 to 8.9 million in 2019, while YLLs decreased by 36.7% during the same period.

They further reported that regions with higher socioeconomic conditions had the least YLLs, and the highest number of DALYs, meaning that while people were less likely to die from particulate matter-related cardiovascular conditions, they were more likely to live with disability from them.

The inverse was true for countries with lower economic conditions; people were more likely to die from particulate matter-related cardiovascular conditions and less likely to live with a disability.

However, some countries saw declines in death and disability from particulate matter-related cardiovascular conditions.

“In Europe, death and disability from PM decreased, probably because of less exposure to PM by promoting air pollution control measures along with higher quality access to healthcare facilities and services,” said Dr. Zahir Rahman, a cardiologist at Staten Island University Hospital, who was not involved in the study.

MNT spoke with Dr. Wei Chung-Su, PhD, assistant professor and environmental science researcher with UTHealth Houston, not involved in the study, about how particulate matter air pollution contributes to heart disease risk.

“After being inhaled into the human respiratory system, coarse particles generally stop in the upper airways. However, fine and ultrafine particles can reach and deposit in [deeper areas in the lungs],” Dr. Chung-Su said.

Dr. Chung-su continued to explain that when particulate matter deposits in the pulmonary region, harmful substances from the particles can leech into the circulatory system. This may then cause oxidative stress and inflammation, which in turn induces harmful cardiovascular effects.

Dr. Sameer Chaudhari, a cardiologist with Novant Health Heart & Vascular Institute in Monroe, North Carolina, not involved in the study, told MNT more about these cardiovascular effects:

“Both inflammation and oxidation involve a complex chain of chemical reactions within the body. They eventually lead to adverse changes in the circulatory system, causing narrowing or spasming of the arteries, the buildup of ‘plaques’ (atherosclerosis), and the release of harmful byproducts, which ultimately lead to increased risk of stroke, coronary artery disease, heart attack, and death.”

The researchers examined exposure to both outdoor and indoor air pollution.

While outdoor air pollution exposure is more likely to lead to poor health outcomes, indoor air pollution exposure may also cause harm. For instance, using biomass fuels for indoor cooking without proper ventilation increases indoor air pollution levels.

Dr. Rahman said that while deaths linked to indoor pollution generally declined worldwide, they increased in sub-Saharan Africa, likely due to the use of solid fuel sources for cooking and heating. More research into the effects of indoor air pollution exposure may be warranted.

In addition, it is unclear why males were more likely to die of air pollution-related cardiovascular events than females. Further studies investigating the sex-based differences in air pollution-related deaths are needed.

Dr. Rahman noted that while the study shows an association between particulate matter pollution and cardiovascular health, no causal relationship can be deduced.

MNT also spoke with Dr. Chen about the study’s limitations. He noted that the study doesn’t distinguish between the effects of different types of particulate matter and that different types of particulate matter have different health effects.

He added that data from low and middle-income countries might be less reliable than that from countries with developed health care reporting systems, meaning that conclusions for these countries may be less robust.

“Also, the study is only able to examine ischemic heart disease and stroke, rather than the full spectrum of cardiovascular disease, and therefore likely underestimates the actual impact of PM on cardiovascular disease risk,” he continued.

MNT asked Dr. Chen how readers may protect their health when the air quality index reaches hazardous levels, such as during wildfires. He noted that it is important to keep an eye on the local air quality index.

“As air quality worsens, people in “sensitive groups” such as children, [people with asthma], or people with heart or lung conditions, should limit their time outside. When air quality reaches a “hazardous” level, we recommend that all people stay indoors with the windows closed,” Dr. Chen added.

MNT also asked Dr. Chaudhari about ways to protect against hazardous levels of air pollution. He recommended:

  • Avoiding exposure to visibly obvious particulate matter agents such as smoke, fumes dust, pollens, fires, chemicals, and potentially hazardous gases as much as possible.
  • Using protective equipment such as masks, shields, and protective covers.
  • Seeking medical attention for any health conditions potentially arising from particulate matter.

Lastly, he noted that appeals should be made to public health officials and policymakers to improve air quality and minimize pollution.