How does air quality affect our cardiovascular health? – 10/10/2021

In late September, the WHO (World Health Organization) announced stricter limits for major air pollutants, the first update of the air quality guidelines since 2005. And it’s not hard to imagine why.

The data reveal that pollution has only grown and continues to expand its influence on different aspects of health, being responsible for about 7 million premature deaths per year, in addition to causing serious damage to the body and reducing the lifespan of healthy individuals.

Thresholds refer, above all, to the so-called classic pollutants: airborne particles (particulate matter), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. The fact is that every time you breathe in a big city, you take a combination of pollutants into your body, which can enter your lungs and even reach your bloodstream.

And anyone who imagines that this reflects only in deaths from respiratory complications is mistaken. The heart is among the main causes. According to the WHO, in the adult population, ischemic heart disease and stroke (stroke) are the most frequent causes of premature death attributed to air pollution.

Evidence is also emerging for other effects, such as neurodegenerative diseases and diabetes, another factor that has a strong influence on the cardiovascular system. For children, the impacts include decreased growth and lung function, respiratory infections and severe asthma.

Therefore, the morbidity attributed to air pollution is today on the same level as other serious health risks, such as an unhealthy diet and smoking.

Pollution and the cardiovascular system

The most significant consequences of exposure to different pollutants for the heart involve pulmonary inflammatory response, changes in coagulation, cardiac ischemia (reduced blood flow to the heart preventing it from receiving enough oxygen), increased blood pressure, changes in heart rate (arrhythmias ) and organ anatomy dysfunction. These generated changes even increase the risk of a heart attack or acute myocardial infarction. And for that we have some possible scenarios.

Once in the respiratory system, inhaled pollutants can cause intense inflammation in the lungs and constrict the lungs. The consequence continues in a cascade effect: narrower vessels reduce the entry of oxygen into the blood; the heart then receives less oxygen and starts working harder to compensate; if overloaded continuously, the chances of a heart attack grow.

The probability of a heart attack is also greater when the substance enters the bloodstream. First, it makes the blood more viscous, increasing the risk of formation of small thrombi (clots) in the vessels. These clots can block the coronary artery, thereby increasing the threat of a heart attack.

There is yet another strong possibility. In response to the foreign element in the current, the blood’s defense cells begin to act. This, in turn, favors atherosclerosis —the accumulation of fatty plaques inside the coronary arteries—, which can cause a reduction in their caliber or even interruption of blood flow, thus triggering an acute myocardial infarction.

Held for a decade at the University of Washington, with funding from the EPA (US Environmental Protection Agency), the Multiethnic Study of Air Atherosclerosis (MESA Air), provided even more evidence of the link between air pollution and the acceleration of the process of atherosclerosis—and thus the likelihood of cardiovascular events.

According to the survey, healthy individuals exposed to airborne particle pollution for a prolonged period have premature aging of blood vessels, a faster accumulation of calcium in the coronary artery and thus accelerated atherosclerosis, to the point that some participants have the possibility of infarction increased. Researchers have found that the higher the level of exposure, the faster atherosclerosis progresses.

And the problems don’t stop there. Recent studies point to an alteration in the size of cardiac structures in individuals exposed to pollution at high concentrations. Exposure to pollutants—mainly from gasoline or diesel-powered cars—such as nitrogen dioxide or carbon monoxide causes the two ventricular cavities, left and right, to increase in size.

Located at the bottom of the organ, the ventricles are responsible for pumping blood to the aorta artery (left ventricle) and to the pulmonary artery (right ventricle). Although the changes may be small, we should not rule them out, since combined with other factors, including genetic characteristics, eating habits and stress, this change in the size of the ventricles can lead to heart failure.

Fires: a risk factor that deserves attention

Although most of the problems when we talk about air pollution are due to the burning of fuels used in various sectors — transport, energy, industry, agriculture, in addition to homes — it is also necessary to highlight fires: fires are another relevant source of pollution.

According to UCLA Medical Center – University of California/USA, the smoke from these fires is potentially dangerous and exacerbates heart and lung conditions. The pollutants present in smoke are highly toxic and have both acute and chronic effects.

Smoke from fires contains not only harmful gases like carbon monoxide, but also fine particles, components small enough to travel to the lungs and bloodstream. And as we’ve seen above, a scenario that can result in inflammation, blood clots and heart attacks, among other problems. In addition, it motivates the release of stress hormone in the body, which raises blood pressure, affects the metabolism of glucose, lipids and insulin.

A study by California Department of Health and Environmental Protection Agency Researchers, published in Journal of the American Heart Association, analyzed more than 1 million emergency room visits during 2015. They found a significant link between exposure to smoke and the risk of heart attacks, strokes, worsening heart failure and pulmonary embolisms.

In Brazil, a survey coordinated by Fiocruz and the NGO WWF assessed the impact of pollution emitted by fires on the population’s health. According to the survey, 70% of hospital admissions recorded from 2010 to 2020 in Mato Grosso, Pará, Amazonas, Rondônia and Acre are related to the high concentrations of pollutant particles from burning in the Amazon. According to the survey, air pollution doubled the risk of hospitalization (for different complications).

Without heavy rain, we still have low air humidity

And added to the already known pollution of cities and the increase in fires (especially due to accelerated deforestation), we are facing what is already considered the worst drought in the last 91 years. Then the scenario becomes a snowball: the drought only worsens the dispersion of pollutants.

When we face long periods of low humidity, our health suffers more than we realize. There are risks of dehydration, especially when outdoor humidity levels get too low—according to the WHO, the ideal humidity is in the 50-80% range. Dry air combined with pollution makes the body even more susceptible to viral and respiratory diseases such as flu and pneumonia. Infection caused by these diseases can alter the heart rate, overloading the heart’s pumping of blood.

In addition, as soon as the body detects the presence of infectious agents, it starts to produce substances to try to react. The problem is that these substances are inflammatory and harmful to the cardiovascular system. They end up in the bloodstream and, if the patient already has some cardiac vulnerability, such as a coronary compromise, the process is faster and more severe.

There is also the possibility that a viral disease generates an aggression process to the heart muscle and thus causes cardiomyopathy, one of the most common causes of heart failure (when the heart is no longer able to pump enough blood to the rest of the body) — a condition that it can also culminate in a heart attack or stroke. For this reason, flu vaccination is so important, not only to prevent respiratory infections, but also to protect people from cardiovascular events.

Required actions

As said, for those who already have a predisposition or heart disease, the probability of problems arising from exposure to pollutants is greater, but there are records of cases of cardiovascular events even in individuals without symptoms or associated factors.

The fact is, none of us are completely protected from exposure to air pollution. It is present, in greater or lesser concentration, in the most different environments. Therefore, Brazil has major challenges to reduce air pollution: controlling fires, generating clean energy and investing in reducing pollutant emissions.

This is just to name a few actions. Now it’s up to us to contribute and demand that this be done. The health risks, as we have seen, if nothing is done going forward, are great!