Air Pollution And Asthma: Is There A Link?

Air pollution is a mixture of solid particles and gases in the air. It contains pollutants that have harmful effects on human health and the environment. These pollutants are released through car emissions, industrial emissions, wildfires, and more.

Air pollution can cause and worsen asthma, a chronic respiratory disease that affects the quality of life of millions of people worldwide. Pollutants in the air can irritate the airways, making them swell and tighten up, and cause breathing problems. They can also make individuals more likely to catch upper respiratory infections, which can bring on asthma symptoms.

Ground-level ozone, a harmful pollutant formed when chemicals from cars, power plants, and factories mix with sunlight, is a main part of smog. Particle pollution, created when tiny bits of dust, dirt, smoke, soot, and other substances hang in the air, can also cause breathing problems. Other pollutants include gases such as carbon monoxide, nitrogen dioxide, and sulfur dioxide, which come from the burning of different types of fuels.

Children are especially vulnerable to air pollution, as they have developing lungs, immature metabolic pathways, and increased time spent outdoors.

Asthma and air pollution: the basics

Air pollution is the presence in the air of substances harmful to humans. It is associated with a high risk of premature deaths due to cardiovascular diseases, chronic obstructive pulmonary disease, asthma, lower respiratory infections, and lung cancer. Air pollution can be defined by the presence of gaseous and particulate matter (PM) in the air. The main gaseous pollutants include nitrogen dioxide, sulphur dioxide, ozone, carbon monoxide, carbon dioxide, and heavy metals such as lead or chromium. PM is a complex mixture of dirt, soot, smoke, and liquid droplets from both natural and man-made sources.

Air pollution can trigger asthma symptoms and attacks, and make symptoms worse. It can also cause asthma in people who don't already have it. Pollutants in the air can irritate the airways, making them swell and tighten up, and cause breathing problems. Pollutants can also make people more likely to catch upper respiratory infections (like colds), which can bring on asthma symptoms. If allergens in the air are an asthma trigger, pollutants can make the lungs even more sensitive to them.

Ground-level ozone, particle pollution, and gases (such as carbon monoxide, nitrogen dioxide, and sulfur dioxide) are the main pollutants that affect breathing. Ground-level ozone is formed by photochemical reactions between sunlight and pollutant precursors, such as nitrogen oxides and volatile organic compounds, especially in warm conditions and peak summer temperatures. Particle pollution includes tiny bits of dust, dirt, smoke, soot, and other stuff that hang in the air. The smaller the particles, the deeper they can get into the lungs and cause breathing problems.

People with asthma should ideally live at least 300m from major roadways, especially those with heavy truck traffic. On days when air quality is poor, it is recommended to run the air conditioning and limit outdoor activities. It is also important to avoid unnecessary outdoor activity, especially if it entails vigorous exercise that increases minute ventilation and thus the total inhaled dose.

Air pollution and asthma triggers

Air pollution can cause and exacerbate asthma. It is estimated that there are six million children in the United States with asthma, who are especially vulnerable to air pollution.

Ozone, nitrogen dioxide, and sulphur dioxide

Ground-level ozone is formed by photochemical reactions between sunlight and pollutant precursors, such as nitrogen oxides and volatile organic compounds, especially in warm conditions and peaks in summer temperatures. Nitrogen oxides, including nitrogen dioxide, are formed primarily by the reaction of ozone with nitric oxide emitted during fossil fuel combustion. Sulphur dioxide is a reductant and probably causes asthma symptoms through a different mechanism.

Particulate matter

Particulate matter (PM) is categorised on the basis of its aerodynamic diameter, with implications for its typical site of deposition when inhaled. Coarse PM, with an aerodynamic diameter of 2.5–10 μm, deposits mainly in the head and large conducting airways. Fine PM or PM2.5 deposits throughout the respiratory tract, particularly in small airways and alveoli. Ultrafine PM (<0·1 μm) deposits in the alveoli.

Traffic-related air pollution

Traffic-related air pollution (TRAP) is a complex mixture of PM derived from combustion and non-combustion sources and primary gaseous emissions including nitrogen oxides. These primary emissions lead to the generation of secondary pollutants such as ozone, nitrates, and organic aerosol.

Risk modifiers

Young children with asthma have long been regarded as a group who are very susceptible to adverse effects from air pollution because of their developing lungs, immature metabolic pathways, high ventilation rates per bodyweight, and increased time exercising outdoors.

Clinical implications

One strategy to reduce exacerbations of asthma related to air pollution is for local governments to issue smog alerts on days when ozone or PM2·5 levels are forecast to be high. Individuals with asthma and other pre-existing cardiopulmonary disorders are urged to stay indoors on such days. Clinicians should encourage patients with asthma (and advise parents of children with asthma), to avoid unnecessary outdoor activity, especially if it entails vigorous exercise that increases minute ventilation and thus the total inhaled dose, on days when air pollution levels are high.

How does air quality affect asthma?

Poor air quality can have a detrimental effect on people with asthma. Pollutants in the air can irritate the airways, causing them to swell and tighten up, and trigger breathing problems. Pollutants can also make people more likely to catch upper respiratory infections, which can bring on asthma symptoms. If allergens in the air are an asthma trigger, pollutants can make the lungs even more sensitive to them.

Ground-level ozone, which forms when chemicals from cars, power plants, and factories mix with sunlight, is a main part of smog. Particle pollution, created when tiny bits of dust, dirt, smoke, soot, and other stuff hang in the air, can also cause breathing problems. Other pollutants include gases (such as carbon monoxide, nitrogen dioxide, and sulfur dioxide) that come from the burning of different types of fuels. High levels can affect lung function.

People with asthma should ideally live at least 300 meters from major roadways, especially those with heavy truck traffic. On days when air quality is poor, it is recommended to run the air conditioning and limit outdoor activities, if possible.

What pollutants affect breathing?

Air pollution can affect everyone’s health. When we breathe in air pollutants, they can enter our bloodstream and contribute to coughing or itchy eyes and cause or worsen many breathing and lung diseases, leading to hospitalizations, cancer, or even premature death.

Ozone and Particle Pollution

Ozone and particle pollution are the two dominant types of pollution in the US. Both of these pollutants are tracked in the American Lung Association's annual "State of the Air" report. They threaten the health and lives of millions of Americans.

Pollutants That Affect Breathing

• Premature death: Short-term and long-term exposure to unhealthy air can shorten your life and lead to premature death.
• Asthma attacks: Breathing ozone and particle pollution can lead to increased asthma attacks, which can result in visits to the emergency room and hospital admissions, not to mention missed work and school.
• Cardiovascular disease: Air pollution can increase the risk of both heart attacks and stroke.
• Lung cancer: Particle pollution can cause lung cancer, which is the leading cause of cancer-related death in the US.
• Developmental damage: Exposure to air pollution can slow and stunt lung development in growing children, harming their health now and reducing their lung function as adults.
• Susceptibility to infections: Air pollution increases the risk of lung infections, especially in children.
• Worsened COPD symptoms: Exposure to air pollution can make it even harder for people with chronic obstructive pulmonary disease (COPD) to breathe. Severe symptoms can lead to hospitalization and even death.
• Lung tissue swelling and irritation: Even people with healthy lungs are susceptible to irritation and swelling. For those living with chronic lung diseases, such as asthma and COPD, these effects can be especially harmful.
• Low infant birth weight: Exposure to air pollution may increase the risk of low infant birth weight and infant mortality.
• Wheezing, coughing and shortness of breath: These can be caused by both long-term exposure and short-term exposure to high levels of air pollutants.

Other Pollutants

In addition to ozone and particle pollution, other pollutants that affect breathing include:

• Nitrogen dioxide
• Sulphur dioxide
• Carbon monoxide
• Carbon dioxide
• Heavy metals such as lead or chromium
• Volatile organic compounds (VOCs)
• Polycyclic aromatic hydrocarbons (PAHs)

Improving the air quality in your home

Improve Ventilation:

• Open windows and doors to increase natural ventilation and allow fresh air to circulate throughout your home.
• Use window or attic fans, or air conditioning with the vent control open, to enhance air circulation.
• Consider installing a mechanical system that brings outdoor air into your home, such as an energy-efficient heat recovery ventilator.
• Ensure proper ventilation during activities that can generate high levels of pollutants, such as painting, cooking, or welding. If possible, perform these activities outdoors.

Reduce Sources of Pollution:

• Identify and eliminate individual sources of pollution or reduce their emissions.
• Seal or enclose sources that contain asbestos.
• Adjust gas stoves or other combustion sources to decrease emissions.
• Ensure your home is smoke-free, and avoid burning fireplaces, wood stoves, or candles.
• Avoid using air fresheners, sprays, and chemical cleaning products, or opt for healthier alternatives.

Use Air Cleaners and Filters:

• Consider investing in an air purifier, especially if you have pets or are unable to eliminate allergy triggers. Place them in commonly used areas of the house.
• Use air cleaners with filters to capture pollutants. Look for models with high efficiency in particle removal and adequate air circulation rates.
• If necessary, use a dehumidifier in damp areas, such as basements, to prevent mold growth.

Maintain Cleanliness:

• Vacuum carpets and area rugs regularly, preferably with a vacuum cleaner equipped with a HEAP filter.
• Opt for hard-surface flooring instead of wall-to-wall carpeting to reduce allergens.
• Wash bedding, drapes, and other items that attract allergens frequently, using hot water (at least 130° F).
• Clear clutter, as it can trap and hold dust.
• Keep indoor plants to a minimum, as they can collect and foster mold growth.
• Change filters in your heating and cooling systems regularly to trap dust and other airborne irritants.

Frequently asked questions