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While air pollution is often linked to respiratory issues like asthma and coughing, can it also have an adverse effect on the heart?
George Marks/Retrofile/Getty ImagesFor many years, scientists have understood that air pollution leads to various health problems. The focus has largely been on lung-related issues such as asthma, developmental concerns in children's lungs, and even lung cancer. It makes sense: When harmful chemicals like sulfur dioxide, carbon monoxide, and hydrocarbons are present in the air, along with tiny particles, our lungs are the first to feel the effects.
These pollutants come from a range of sources, some natural, like volcanic eruptions and plant-based chemical reactions, and others are man-made. Factories and vehicles burning fossil fuels emit large amounts of pollutants into the air every day. The production of plastics releases chemicals like chlorine, sulfuric acid, and vinyl chloride (in the case of PVC). The use of aerosol sprays, cigarette smoke, and the burning of waste all contribute to poorer air quality.
Some of these pollutants form ground-level ozone. Others fall to the Earth as acid rain, while some linger in the air, clouding the skies of densely populated cities as smog.
In today's world, it's almost impossible to avoid polluted air. Just stepping outside means inhaling particles that our lungs would rather not encounter, and sitting in traffic -- if only we all had air purifiers in our cars, our lungs would certainly thank us. But what about the rest of our bodies? After all, the lungs and the heart are so intricately connected, the damage likely doesn't stop with our lungs.
Medical research has long known that exposure to high levels of air pollution, especially fine particulate matter, can worsen or even trigger heart disease. However, until recently, the exact mechanism of how this happens remained somewhat of a mystery. Now, scientists have uncovered substantial evidence showing that air pollution negatively impacts heart health.
In this article, we will explore the connection between air pollution and heart disease. We'll look at how various pollutants impact the cardiovascular system and discuss ways to reduce the risks of damage.
Let's begin with a brief overview of the cardiopulmonary (heart-lung) system to better understand how breathing in polluted air affects the heart directly.
The Impact of Particulate Matter on Cardiovascular Health
This image of air pollution over China could be enough to make anyone lose their breath.
Image courtesy of NASAOur bodies cannot function without oxygen. Every single one of our cells depends on it, and our lungs and heart work together to provide it.
Each time we inhale, oxygen enters our lungs, the first place where the blood pumped by the heart travels. As the right atrium contracts, it pushes blood into the lungs to gather oxygen from the air. This enriched blood then flows into the left atrium, which sends it throughout the body.
But what occurs when substances like carbon monoxide, particulates, or sulfur oxides join the oxygen in our lungs? The blood absorbs these pollutants too, and they enter the bloodstream, reaching the heart and spreading to every part of our body.
The issue lies in the fact that everything is interconnected. Sadly, the heart suffers just as much from air pollution as the lungs do. While factors such as poor diet, genetics, obesity, diabetes, and smoking are primary causes of heart disease, growing evidence suggests that pollution plays a significant role in exacerbating heart problems. For example, carbon monoxide from secondhand smoke reduces the amount of oxygen that our blood can carry, depriving the heart muscle of the oxygen it needs to function correctly. Additionally, particulates found in diesel exhaust can cause blood vessels to constrict, reducing blood flow.
These particulates seem to be particularly harmful when it comes to heart health.
Particulates are minuscule particles of liquid or solid matter. In the context of air pollution affecting the heart, we often refer to PM2.5 -- particulate matter smaller than 2.5 micrometers in diameter. To put it into perspective, that's roughly 1/10,000th of an inch, or about one-tenth the thickness of a human hair. These tiny particles are small enough to penetrate deep into the lungs. The American Heart Association reports that for every 10 micrograms of particulates per cubic foot of air, there is a 1.4 percent increase in heart-related deaths [source: AHA]. And 10 micrograms is not a large amount. The U.S. Environmental Protection Agency (EPA) deems a concentration of 35.5 micrograms (measured over a 24-hour period) to be within acceptable health standards [source: GADNR].
Some researchers have discovered that even those EPA-approved levels can still cause harm to the heart and blood vessels, particularly in individuals already suffering from heart disease. And now, they may have uncovered the reason why.
Impact of Pollution on ST-Segment Depression
Both our hearts and lungs face significant challenges when dealing with particulate matter, like the pollution that lingers in cities such as Beijing.
AP Photo/Greg BakerA study published in 2008 sheds light on why hearts may respond so negatively to air pollution: Particulate matter disrupts the heart's electrical system [source: Science Daily].
The heart muscle pumps blood through contractions, pushing it into the body's arteries. Like all muscles, the heart's contraction is triggered by an electrical impulse generated by the SA node, located in the right atrium. The heart's rhythm and pulse are dictated by the rate and pattern of this impulse (see What determines the rhythm of your heart? for more details).
Harvard University researchers studied 48 heart patients after they were discharged from the hospital and tested their heart function after exposure to the air in Boston over weeks and months. They discovered a change in heart conductivity, known as ST-segment depression. This condition is essentially a reduction in the heart's electrical conductivity.
In addition to particulate matter, black carbon, which refers to traffic exhaust, has been linked to ST-segment depression. As the levels of black carbon and particulates in the air rise, an increase in ST-segment depression among the test subjects was also observed.
What does this mean for those of us exposed to polluted air?
The key takeaway is that an already weakened heart is more vulnerable to these effects. For individuals with atherosclerosis (clogged arteries), air pollution has been shown to accelerate plaque buildup on artery walls. However, while those with healthy hearts face a lower risk of heart-related issues due to air pollution, the consequences are still felt by everyone. The AHA estimates that, on average, we may all lose one to three years of life expectancy due to pollution-induced heart problems [source: AHA].
The positive aspect is that we can still take action to protect our health while governments work on addressing the air-pollution crisis. We can follow heart patient guidelines: avoid high-traffic areas when possible, stay indoors on days with poor air quality, and, of course, get away from L.A.
