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Pollution, Strokes, and Heart Disease: Exploring the Links

Linda Crampton is a science writer who is interested in environmental issues. She is very concerned about the harmful effects of pollution.

A city covered by smog is a bad environment for people with circulatory or respiratory problems.

A city covered by smog is a bad environment for people with circulatory or respiratory problems.

Health Problems Caused by Air Pollution

Air pollution is harmful in many ways. Evidence indicates that it can increase the risk of some potentially dangerous cardiovascular problems, including a heart attack and a stroke. Someone who is at risk for developing one of these disorders is usually advised to follow a diet that is low in sugar, salt, and unhealthy fats. Their doctor will likely recommend that the person lowers the amount of LDL cholesterol in their blood, exercises regularly and safely, avoids smoking, and limits their alcohol consumption. There's another aspect of our daily lives that may affect the risk of a heart attack or stroke however—the air that we breathe.

Outdoor and indoor air pollution consists of both gases and fine particles. Luckily, there are steps that we can take to reduce (but perhaps not eliminate) our exposure to the contaminants. These steps are important for all us, but they are especially important for people who already have a cardiovascular problem. They are also important for people with chronic respiratory problems, such as COPD (chronic obstructive pulmonary disease) and asthma.

Seek Medical Advice

The information in this article is given for general interest. It describes observed relationships and strong possibilities but not certainties. Anyone who is concerned about the effect of air pollution on their health or about heart disease or strokes in their specific situation should consult a doctor.

Heart Disease and Strokes

It has been known for some time that air quality can influence the chance of developing cardiovascular problems. In the United States, the EPA (Environmental Protection Agency) has published a report describing the relationship between outdoor air pollution, heart disease, and circulatory system disorders. A link to this report is provided in the "References" section below.

In people with certain pre-existing medical or physical conditions, air pollution may trigger irregular heart rhythms (arrhythmia), a heart attack, or a stroke. There is also a small risk that apparently healthy people will develop cardiovascular problems due to inhalation of pollutants.

An extensive body of scientific evidence shows that short- or long-term exposures to fine particles can cause adverse cardiovascular effects, including heart attacks and strokes resulting in hospitalizations and, in some cases, premature death.

— Environmental Protection Agency (with respect to particulate matter in air)

Factors That May Increase Risk

Minute Particles in the Air

The EPA says that the most dangerous pollutants with respect to circulatory heath are the tiny particles that are present in smoke, smog, dust, and haze. People who have a higher risk of being affected by these particles include those who have already suffered from a heart attack or a stroke, people who have had heart surgery, people with angina or other heart problems, and people with blocked arteries, diabetes, or COPD.

Health, Age, and Heredity

Other factors that may increase the chance of cardiovascular damage due to air pollution include having a high blood cholesterol level (as explained below) or a high blood pressure, smoking, being overweight, not exercising, and being a woman aged 55 or older or a man aged 45 or older. Having a family member who experienced heart disease or a stroke at a relatively early age (younger than 55 in a father or brother and younger than 65 in a mother or sister) also increases the risk.

One of the possible implications is the finding that individuals with higher LDL (cholesterol) levels may be more susceptible to the health impacts of air pollution.

— Dr. Laura McGuinn, United States Environmental Protection Agency

LDL Cholesterol and Air Pollution Damage

Cholesterol sometimes has a bad reputation, but it’s an essential substance for us. The two main types are the HDL form and the LDL one. An HDL cholesterol molecule consists of a high-density lipoprotein and cholesterol. An LDL one is made of a low-density lipoprotein and cholesterol. The ratio of total cholesterol to HDL cholesterol is often used when assessing someone's health. If the ratio is high, the person is said to have a high blood cholesterol level. This is not considered to be good for health.

If the level of the LDL molecule is too high, it may deposit cholesterol on the inner wall of arteries, forming plaque. Plaque contains both cholesterol and fatty material. It can block the arteries and trigger the production of blood clots. HDL cholesterol removes plaque from the arteries. Therefore a low total cholesterol to HDL cholesterol ratio is desirable.

Researchers from the Environmental Protection Agency have discovered that there seems to be a link between the effects of air pollution and LDL cholesterol. A high level of the LDL form may increase the harm done by air pollution. It’s also possible that inhaling polluted air may increase the amount of LDL cholesterol in some people’s bodies.

Research Results: Air Pollution and Health

The observation that air pollution increases the chance of heart disease and strokes has been made many times, but some scientists are trying to get quantitative data to support this observation. The projects mentioned below were performed in the recent past to the near present. The reports linking air pollution to heart and blood vessel problems appear to be increasing.

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One statistical survey was completed by researchers at the Sackler Faculty of Medicine at Tel Aviv university. Dr. Yariv Gerber and his colleagues examined the records of patients admitted to hospital after suffering a myocardial infarction (heart attack) and then followed their medical progress for nineteen years. Air quality was also monitored in the areas where the patients lived. The researchers found that patients living in the most polluted areas were 43% more likely to experience a second heart attack or congestive heart failure and 46% more likely to experience a stroke. They were also 35% more likely to die in the nineteen-year study period.

Dr. Hazrije Mustafic and colleagues at the Paris Descartes University examined data from the general population. They found that short-term exposure to air pollution (no more than seven days in length) produced a statistically significant increase in the risk of a heart attack. The pollutants included particulate matter, sulfur dioxide, nitrogen dioxide, and carbon monoxide. Exposure to ozone didn't increase the risk of a heart attack. Ozone is known to cause breathing problems, however.

An Interesting Relationship

In the video below, a doctor and researcher from the University of Washington discusses the relationship between air pollutants and cardiovascular changes.

Strokes and Air Quality

In the USA, researchers analyzed ten years of data from a Boston stroke center. The records of 1,705 patients were studied. The researchers found that strokes were more likely to occur after a twenty-four hour period in which the air quality had dropped into the "moderate' range, as classified by the EPA. There was a 34% increase in stroke risk after a day of moderate air quality as compared to the risk after a day of good air quality. The air quality did not need to be as bad as that shown in the photo at the top of this page in order to have a detrimental effect.

Two Types of Strokes

A stroke is a disorder in which the blood flow to part of the brain is stopped or severely reduced. The condition may be caused by a blocked artery (ischemic stroke) or by a broken blood vessel (hemorrhagic stroke). Both situations are medical emergencies.

Results of a Large Study in the United States

In 2021, researchers published an analysis of health records from 63 million patients who had signed up for Medicare. The records covered the years 2000 to 2016. All of the records were of people aged 65 and older. The researchers looked for reports of specific diseases in the records. They also looked at environmental records showing three aspects of air pollution that the people were exposed to: particulate matter, nitrogen dioxide, and ozone.

  • The scientists found a significant link between increased particulate matter and the increased incidence of heart attacks, atrial fibrillation and flutter, strokes, and pneumonia.
  • Exposure to nitrogen dioxide increased the risk of stroke and atrial fibrillation.
  • Pneumonia was the only health outcome increased by ozone concentration in the air.

According to the TCTMD reference below, the pollutants and the concentration that the people in the project were exposed were derived at least in part from ”a range of machine-learning algorithms based on land use, chemical transport, meteorological factors, and satellite measurements”. This analysis gave an estimate of daily pollutants per square kilometer. The American Heart Association reference also describes the project.

Data also showed there were surges in hospital admissions for all of the health outcomes studied with each additional unit of increase in particulate matter. Specifically, stroke rates increased by 2,536 for each additional ug/m3 (micrograms per cubic meter of air) increase in fine particulate matter each year.

— American Heart Association

Indoor Air Quality and Heart Disease

Indoor air pollution can also increase the risk of heart disease. The pollution may consist of cigarette smoke, particles released from wood-burning stoves, fireplaces, candles, or incense, vapors from household cleaning products, painting products, and pesticides, carbon monoxide, and outdoor pollution that finds its way indoors. Formaldehyde, radon, and mold spores may also be present inside buildings.

Health Problems Caused by Indoor Pollutants

Secondhand smoke is especially dangerous for cardiovascular health, since cigarette smoke increases the risk of both heart attacks and strokes. Burning wood releases tiny carbon particles which may cause shortness of breath and contribute to circulatory and heart problems, especially in older people. The vapor from paint solvents and some pesticides can cause an irregular heartbeat. Exposure to dust from paints containing lead can cause high blood pressure.

Carbon Monoxide (CO) and Heart Disease

Carbon monoxide joins to hemoglobin, the red pigment in our blood that normally attaches to oxygen and transports it around the body to all the tissues. The carbon monoxide prevents oxygen from binding to hemoglobin molecules, which means that the body's cells won't receive the oxygen that they need to survive. Even a small amount of CO will interfere with the blood's ability to transport oxygen and can lead to chest pain and heart arrhythmia.

Carbon monoxide may be emitted from space heaters, ranges, dryers, fireplaces, and wood stoves. It's also released from the exhaust of motor vehicles. The gas can build up when a vehicle is left in a garage or other enclosed space with its engine running. This can be true even if the garage door is open. Carbon monoxide in the surrounding air is a serious problem for everyone, even if they are healthy, because if it's sufficiently concentrated it can cause fatalities.

A Possible Mechanism of Pollution's Effects

There are several suspected reasons why exposure to air pollution can increase the risk of a heart attack or stroke. Some studies have shown an increased heart rate after inhalation of polluted air. In addition, studies have shown detrimental blood vessel changes in people chronically exposed to air pollution. In atherosclerosis, plaque in the lining of arteries causes the blood vessels to become stiff. Air pollution speeds up the progression of atherosclerosis.

Particles less than 2.5 microns in diameter are especially worrying for researchers. (A micron is a millionth of a meter, or a thousandth of a millimeter.) These tiny particles easily enter the human body and irritate both the lungs and the arteries serving the heart muscle.

Researchers have discovered that the level of C-reactive protein (or CRP) increases in at least some people exposed to air pollutants. A high level of this protein is an indication of inflammation inside the body, sometimes including inflammation of arteries, and has been linked to heart disease. In fact, the blood level of the protein is sometimes tested in order to assess a person's risk of cardiovascular problems.

A Marker for Inflammation

C-reactive protein is made by the liver. It's a "marker" for inflammation—that is, a substance that indicates that inflammation is present. It has sometimes been suggested that the protein is also a cause of inflammation, but the evidence obtained so far doesn't support this idea.

Avoiding Outdoor Air Pollutants

Besides maintaining a healthy diet and lifestyle and seeking a doctor's advice about the amount of exercise that is appropriate for a specific medical condition, there are a number of steps that we can take to protect ourselves from injury caused by outside air pollution.

First, it's a good idea to follow the daily reports of air pollution levels. Pollution doesn't have to be visible to be harmful. In some cities, news programs on the television or radio describe the air quality each day. Websites that do the same thing exist. A useful site for people living in the United States is the AirNow website, which describes the current air quality. There's a link to international versions of the site on the AirNow home page.

Even when the air quality is reported to be good, there are some precautions that are useful for people who have serious cardiovascular problems. It's a good idea to do outdoor exercise away from traffic, or at least to avoid busy traffic, since the exhaust released by vehicles contributes to air pollution. Areas near industries that release products into the air should also be avoided. It's also advisable to stop outdoor exercise when there is a forest fire producing smoke. If someone does exercise in polluted air, it's good to do a gentler form of exercise that involves slower and shallower breathing than a more energetic exercise.

Potential symptoms of carbon monoxide poisoning

Potential symptoms of carbon monoxide poisoning

Avoiding Indoor Air Pollutants

Indoor air pollution can be greatly reduced by not allowing smoking in a home. Containers of cleaning materials and pesticides should be kept tightly closed and far away from the living area. It's a good idea to use fragrance-free products to reduce the release of volatile compounds into the environment. Furnaces, heat-producing devices, and devices that use fuel should be serviced regularly to make sure that they're operating correctly and aren't releasing dangerous fumes. They should also be well ventilated.

Installing carbon monoxide alarms is a great idea, especially next to a sleeping area. CO is a sneaky poison. It's invisible and has no odor, so people are usually unaware that they are inhaling it. It produces symptoms that may be confused with the flu, such as a headache, dizziness, nausea, weakness, tiredness, and confusion. An affected person may eventually lose consciousness if the concentration of carbon monoxide is high enough.

Clean air is wonderful for nature and for our health.

Clean air is wonderful for nature and for our health.

These health problems that are affected by air pollution are health problems that also have other things contributing to them ... At the end of the day, we can never say whether it was your diet or air pollution that was the straw that broke the camel’s back.

— Michael Brauer, University of British Columbia School of Population and Public Health

A Multifaceted Problem

It's very important that countries and communities take steps to reduce air pollution. It's also important that we as individuals try to reduce both our production of substances that reduce air quality and our exposure to polluted air. I’ve described a few research projects linking environmental pollution with heart disease and strokes, but others exist.

Several factors can cause cardiovascular problems. An unhealthy diet is one of them, as the quote above mentions. Air pollution appears to be another one. Either factor on its own could cause problems. The combination of both factors may increase the probability of a cardiovascular problem.

Even if someone has reservations about the procedures used in a particular air quality analysis or in a survey, the many reports about harmful air pollution emerging from different institutions suggest that the situation is very likely significant. Our health may depend on reducing the heart disease and stroke risk created by all factors, including the detrimental quality of the air that we inhale.

References and Resources

  • Air pollution information from the National Institute of Environmental Health Sciences (a division of the NIH)
  • "Air pollution linked to chronic heart disease" from the ScienceDaily news service
  • A possible link between LDL cholesterol and heart disease from the EPA
  • "Short-term exposure to most major air pollutants associated with increased risk of heart attack" from ScienceDaily
  • "The Emerging Role of Outdoor and Indoor Air Pollution in Cardiovascular Disease" from the North American Journal of Medical Sciences
  • Air pollution and the heart from Global News Canada
  • ”Large US Study Links Air Pollution to Heart, Lung Diseases” from TCTMD
  • Effects of air pollution on heart and lung disease from the American Heart Association
  • Particulate matter found in air and its possible effects from the Environmental Protection Agency (EPA)
  • A report about outdoor air quality from the EPA
  • AirNow website run by the United States Government

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2012 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on September 13, 2016:

Thank you very much for the interesting comment, Sundip. Air pollution is worrying for a number of reasons. Awareness is definitely important, as you say.

Sundip Doshi from California on September 13, 2016:

Enjoyed your in depth article on air pollution and its potential impact on heart disease and of cour a myriad of other potential disorders including respiratory diseases, Asthma, COPD and others. I know more and more research is being conducted in various institutions on other areas such as impact on moms to be. Unfortunately the problem is awareness but also for people to know what's exactly in the air and how it's impacting them personally. And on that subject people are hard at work with nanotechnology and its ability to sense airborne toxins. Thanks for a great article!


Linda Crampton (author) from British Columbia, Canada on September 05, 2012:

Thank you so much for the lovely comment, the vote and the share, Mama Kim 8. I enjoy reading your hubs too!

Aloe Kim on September 05, 2012:

I'm so grateful to live in Oregon... we have nice air here -- although allergies are a big problem ^_^ This was a fascinating article Alicia I enjoy your hubs so much! Voted and shared

Linda Crampton (author) from British Columbia, Canada on September 01, 2012:

Hi, Mary. Carbon monoxide detectors are so important to prevent us from being poisoned. I'm looking forward to reading your hub about this topic soon. I never use spray air fresheners - or any air fresheners - either, and I try to use fragrance-free cleaning products. They all release chemicals into the air, and I don't want my family or I to inhale them! Thank you for the votes.

Mary Hyatt from Florida on September 01, 2012:

You raise some valid points with this Hub. I wrote a Hub about carbon monoxide killing people, and that can be preventable through the use of detectors. You know these "air fresheners" that are sprays? I always think of the danger of those. I won't use them.

I voted this Hub UP, etc.

Linda Crampton (author) from British Columbia, Canada on September 01, 2012:

Hi, drbj. Yes. it's a great shame that we have to worry about what's in the air as well as what's in our food! Thanks for the visit.

drbj and sherry from south Florida on September 01, 2012:

So, Alicia, it's not just the food we eat that is full of dangerous stuff but also the air we breathe. Thanks for this additional information about air pollution and the increased risk of heart disease. Who knew?

Linda Crampton (author) from British Columbia, Canada on September 01, 2012:

Hi, Nell. That's a sad comment about the air quality in London! I always walk along a trail to go shopping instead of beside the road, too - except when it's starting to get dark. I take that route because I'd rather be surrounded by nature than houses, although there are houses fairly near the trail. I'm sure that I'm exposed to less air pollution on the trail, though! Thank you very much for the vote and the share, Nell.

Linda Crampton (author) from British Columbia, Canada on September 01, 2012:

Thanks for the comment and the vote, teaches! Yes, air pollution is a problem in many areas. It is so sad that we are altering the air that we breathe is such a damaging way.

Nell Rose from England on September 01, 2012:

Hi Alicia, its very rare that we get a warning where I live, but I do know that London is very polluted, in fact most people who ride a bike to work actually wear mouth covers. I am asthmatic so I have to be careful of that as well as the pollutants, in fact I never ever walk up to the high street along the road, but cut through a small park on the way, its so much better, great points and something we should all take notice off, its our health at the end of the day, wonderful stuff, voted up and shared! nell

Dianna Mendez on September 01, 2012:

Great topic and well written. The increase of pollution around the nation and world has caused many to acquire serious health problems and allergies. I lived in a midwest area where smog was a concern. Voted up!

Linda Crampton (author) from British Columbia, Canada on September 01, 2012:

Thank you very much for the comment and the votes, Tom. I think many people may be aware that air pollution is bad for our health, but they may not realize how dangerous it can actually be. Air quality can have a very important effect on our well-being!

Thomas Silvia from Massachusetts on September 01, 2012:

A very interesting and informative hub . The impact at which air pollution has on our world and health is a major problem. Thanks for making all aware of these problems that pollution brings in our lives.

Awesome,useful and vote up !!!

Linda Crampton (author) from British Columbia, Canada on September 01, 2012:

I agree, unknown spy. Reducing air pollution has to become a major effort in our communities.

Life Under Construction from Neverland on September 01, 2012:

couldn't agree more. the air is becoming a poison to use.we have to reduce this pollution.

Linda Crampton (author) from British Columbia, Canada on September 01, 2012:

Thank you for the comment, unknown spy. I appreciate your visit. I think it's very sad that air pollution - a lot of it created by humans - can make us ill. We are poisoning ourselves.

Life Under Construction from Neverland on September 01, 2012:

like the term "smog". Air pollution is one of the major problems attacking our world. these problems can result to serious illnesses like heart disease and stroke as you mentioned. Interesting and very informative.

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