What is air pollution

Air pollution is a mixture of solid particles and gases in the air you breathe. Car emissions, chemicals from factories, dust, pollen and mold spores may be suspended as particles. Ozone, a gas, is a major part of air pollution in cities. When ozone forms air pollution, it’s also called smog.

Some air pollutants are poisonous. Inhaling them can increase the chance you’ll have health problems. People with heart or lung disease, older adults and children are at greater risk from air pollution. Air pollution isn’t just outside – the air inside buildings can also be polluted and affect your health.

Hazardous air pollutants, also known as toxic air pollutants or air toxics, are those pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental effects ¹. The United States Environmental Protection Agency (EPA) is working with state, local, and tribal governments to reduce air emissions of 187 toxic air pollutants (https://www.epa.gov/haps/initial-list-hazardous-air-pollutants-modifications) to the environment.

Toxic air pollutants or hazardous air pollutants tend to pose greater risks in urban areas because these areas have large populations and a higher concentration of emission sources. Combined exposures from all sources of air pollution, including major stationary sources, smaller area sources, indoor sources and mobile sources can increase public health risks from hazardous air pollutants. Low-income neighborhoods, tribal populations and communities of color that live in urban areas may be disproportionately exposed to air pollution, which is a barrier to economic opportunity and security.

Examples of toxic air pollutants include:

• benzene, which is found in gasoline;
• perchloroethylene, which is emitted from some dry cleaning facilities; and
• methylene chloride, which is used as a solvent and paint stripper by a number of industries.

Examples of other listed air toxics include dioxin, asbestos, toluene, and metals such as cadmium, mercury, chromium, and lead compounds.

Toxic air pollutants pose different risks to health depending on the specific pollutant, including:

• Cancer, including lung, kidney, bone, stomach
• Harm to the nervous system and brain
• Birth defects
• Irritation to the eyes, nose and throat
• Coughing and wheezing
• Impaired lung function
• Harm to the cardiovascular system
• Reduced fertility

How are people exposed to air pollutants?

People inhale many of these pollutants in the air where they live. But, since these pollutants also settle into waterways, streams, rivers and lakes, people can drink them in the water or eat them in the fish from these waters. Some hazardous pollutants settle into the dirt that children play in and may put in their mouths.

Types of air pollution

Air pollution is typically separated into two categories: outdoor air pollution and indoor air pollution.

Outdoor air pollution involves exposures that take place outside of the built environment. Examples include:

• Fine particles produced by the burning of fossil fuels (i.e. the coal and petroleum used in energy production)
• Noxious gases (sulfur dioxide, nitrogen oxides, carbon monoxide, chemical vapors, etc.)
• Ground-level ozone (a reactive form of oxygen and a primary component of urban smog)
• Tobacco Smoke
• Motor vehicle traffic
• Pollen from flowers, trees and shrubbery
• Wind-blown dust
• Burning wood
• Construction
• Agricultural operations, including raising animals and clearing land
• Power plants

Indoor air pollution involves exposures to particulates, carbon oxides, and other pollutants carried by indoor air or dust. Examples include:

• Gases (carbon monoxide, radon, etc.)
• Household products and chemicals
• Building materials (asbestos, formaldehyde, lead, etc.)
• Outdoor indoor allergens (cockroach and mouse dropping, etc.)
• Tobacco smoke
• Mold and pollen

In some instances, outdoor air pollution can make its way indoors by way of open windows, doors, ventilation, etc.

Health effects of air pollution

Over the past 30 years, researchers have unearthed a wide array of health effects which are believed to be associated with air pollution exposure. Among them are respiratory diseases (including asthma and changes in lung function), cardiovascular diseases, adverse pregnancy outcomes (such as preterm birth), and even death.

In 2013, the World Health Organization ² concluded that outdoor air pollution is carcinogen to humans.

Health problems associated with air pollution include:

• Headaches
• Irritation of the eyes, nose and throat
• Damage to airways of the lungs
• Increased risk of asthma development
• Worsening of existing asthma or other lung conditions
• Increased risk of heart attacks and strokes
• Increased risk of death from lung cancer and cardiovascular disease

How can I reduce my risk for air pollution exposure?

Indoor air pollution can be reduced by making sure that a building is well-ventilated and cleaned regularly to prevent the buildup of agents like dust and mold. Occupants would also be wise to remove any known pollutants and or irritants (aerosols, stringent cleaning supplies, etc.) whenever possible.

Outdoor air pollution exposures can be reduced by checking your area’s Air Quality Index (AQI) (https://www.airnow.gov/), avoiding heavy traffic when possible, and avoiding secondhand tobacco smoke.

How is air pollution linked to climate change?

While climate change is a global process, it has very local impacts that can profoundly affect communities, not the least of which is air pollution.

Increasing temperatures are directly linked to poor air quality which, in turn, can affect the heart and exacerbate cardiovascular disease. Examples of this may include a rise in pollen, due to increased plant growth, or a rise in molds, due to severe storms — both of which can worsen allergies and other lung diseases, such as asthma.

Scientists say an increasing rise in ozone levels are also a concern.

Does air pollution make outdoor exercise risky?

While aerobic activity is one of the keys to a healthy lifestyle, air pollution and exercise can be an unhealthy combination. This is especially true if you have asthma, diabetes, or heart or lung conditions. Young children, older people, and people who work or exercise outdoors can be especially susceptible to the effects of outdoor air pollution.

Even when you’re not exercising, exposure to air pollution can cause health problems. But with the combination of air pollution and exercise, the potential health problems are increased.

One reason for this increased risk may be that during aerobic activity, you usually inhale more air and breathe it more deeply into your lungs. And because you’re more likely to breathe deeply through your mouth during exercise, the air you breathe in generally bypasses your nasal passages, which normally filter airborne pollution particles.

People living in many areas of the world, especially large cities, are regularly exposed to air pollution levels far beyond the limit recommended by the World Health Organization. What’s not clear with air pollution and exercise is how much exposure is a danger, how long you have to be exposed, or which types of outdoor air pollution are the most harmful over time.

However, because exercise has clear health benefits, don’t give up on exercise entirely, unless your doctor has instructed you to stop. Research has shown that the long-term benefits of regular exercise outweigh the risks associated with exposure to air pollution.

To stay as healthy as possible while you exercise, focus on ways to minimize your exposure to air pollution. You can limit the effects of air pollution when you exercise in many ways, including:

• Monitoring air pollution levels by using the Air Quality Index (AQI) (https://www.airnow.gov/). Most communities have a system for air pollution alerts. Contact your local or state air pollution control agency, a local hospital, or your doctor for information. Certain websites provide information about air quality from organizations such as the Environmental Protection Agency, and these sites can be accessed at any time. Local radio and television stations as well as newspapers also often report on air quality.
• Timing your workouts carefully. Avoid outdoor physical activity or reduce the intensity and duration of your outdoor exercise when an air quality alert has been issued. Air pollution levels tend to be highest near midday or in the afternoon, so try to avoid outdoor exercise during these times of the day. Exercising during rush hour can expose you to higher amounts of pollution. If you can, avoid exercising near roadways where there is heavy traffic.
• Avoiding high-pollution areas. Pollution levels are likely to be highest within 1/4 mile (400 meters) of a road. Urban environments and outdoor smoking areas also have higher pollution levels. If possible, avoid these kinds of areas when exercising.
• Exercising indoors. Vary your routine with occasional indoor activities, especially on poor air quality days. Take a fitness class, check out a local gym or run laps on an indoor track.

If you have asthma, diabetes or another condition, check with your doctor about when it’s safe for you to exercise.

Outdoor air pollution

Outdoor air pollution is a major environmental health problem affecting everyone in low, middle, and high-income countries.

Ambient (outdoor) air pollution in both cities and rural areas was estimated to cause 4.2 million premature deaths worldwide per year in 2016 ²; this mortality is due to exposure to small particulate matter of 2.5 microns or less in diameter (PM_2.5), which cause cardiovascular and respiratory disease, and cancers.

Particulate matter also called particle pollution, is a common proxy indicator for air pollution. Particulate matter (particle pollution) is made up of particles (tiny pieces) of solids or liquids that are in the air. Particulate matter (particle pollution) affects more people than any other pollutant. The major components of particulate matter are sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water.

Particulate matter particles may include ³:

• Dust
• Dirt
• Soot
• Smoke
• Drops of liquid

Some particles are big enough (or appear dark enough) to see — for example, you can often see smoke in the air. Others are so small that you can’t see them in the air.

Particulate matter (particle pollution) consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. While particles with a diameter of 10 microns (PM₁₀) or less, (≤ PM₁₀) can penetrate and lodge deep inside the lungs, the even more health-damaging particles are those with a diameter of 2.5 microns (PM_2.5) or less, (≤ PM_2.5). Particulate matter 2.5 (PM_2.5) can penetrate the lung barrier and enter the blood system. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer.

Air quality measurements are typically reported in terms of daily or annual mean concentrations of particulate matter 10 (PM₁₀) particles per cubic meter of air volume (m³). Routine air quality measurements typically describe such particulate matter concentrations in terms of micrograms per cubic meter (μg/m³). When sufficiently sensitive measurement tools are available, concentrations of fine particles (PM_2.5 or smaller), are also reported.

Particle pollution and your health

Breathing in particle pollution can be harmful to your health. Coarse (bigger) particles, called PM₁₀, can irritate your eyes, nose, and throat. Dust from roads, farms, dry riverbeds, construction sites, and mines are types of PM₁₀.

Fine (smaller) particles, called PM_2.5, are more dangerous because they can get into the deep parts of your lungs — or even into your blood.

There is a close, quantitative relationship between exposure to high concentrations of small particulates (PM₁₀ and PM_2.5) and increased mortality or morbidity, both daily and over time. Conversely, when concentrations of small and fine particulates are reduced, related mortality will also go down – presuming other factors remain the same. This allows policymakers to project the population health improvements that could be expected if particulate air pollution is reduced.

Small particulate pollution have health impacts even at very low concentrations – indeed no threshold has been identified below which no damage to health is observed.

How can particle pollution affect my health?

Particle pollution can affect anyone, but it bothers some people more than others. People most likely to experience health effects caused by particle pollution include:

• People with heart or lung diseases (for example, asthma)
• Older adults
• Babies and children

If you have asthma, particle pollution can make your symptoms worse. Carefully follow your asthma management plan on days when pollution levels are high.

Particle pollution has also been linked to:

• Eye irritation
• Lung and throat irritation
• Trouble breathing
• Lung cancer
• Problems with babies at birth (for example, low birth weight)

Heart disease

If you have heart disease, breathing in particle pollution can cause serious problems like a heart attack.

Symptoms include:

• Chest pain or tightness
• Fast heartbeat
• Feeling out of breath
• Being more tired than usual

If you have any of these signs, contact your doctor. Be sure to let your doctor know if the symptoms get worse or last longer than usual.

Where does particle pollution come from?

Particle pollution can come from two different kinds of sources — primary or secondary.

Primary sources cause particle pollution on their own. For example, wood stoves and forest fires are primary sources.

Secondary sources let off gases that can form particles. Power plants and coal fires are examples of secondary sources. Some other common sources of particle pollution can be either primary or secondary — for example, factories, cars and trucks, and construction sites.

Smoke from fires and emissions (releases) from power plants, industrial facilities, and cars and trucks contain PM_2.5.

How to protect yourself and your family from air particle pollution?

The good news is there’s a lot you can do to protect yourself and your family from the health effects caused by particle pollution. Start by learning about the Air Quality Index from the U.S. Environmental Protection Agency (https://www.airnow.gov/).

What is Air Quality Index?

The EPA Air Quality Index (AQI) (https://www.airnow.gov/) is an index for reporting daily air quality. The Air Quality Index (AQI) (https://www.airnow.gov/) tells you how clean or polluted your air is, and what associated health effects might be a concern for you. The Air Quality Index (AQI) focuses on health effects you may experience within a few hours or days after breathing polluted air. EPA calculates the Air Quality Index (AQI) for five major air pollutants regulated by the Clean Air Act:

1. Ground-level ozone,
2. Particle pollution (also known as particulate matter),
3. Carbon monoxide,
4. Sulfur dioxide, and
5. Nitrogen dioxide.

For each of these pollutants, EPA has established national air quality standards to protect public health .Ground-level ozone and airborne particles are the two pollutants that pose the greatest threat to human health in this country.

You can use the Air Quality Index (AQI) (https://www.airnow.gov/) as a tool to help you avoid air particle pollution. Local TV stations, radio programs, and newspapers report the Air Quality Index (AQI). Try checking it when you’re planning your daily activities.

How does the Air Quality Index Work?

Think of the Air Quality Index (AQI) (https://www.airnow.gov/) as a yardstick that runs from 0 to 500. The higher the Air Quality Index (AQI) (https://www.airnow.gov/) value, the greater the level of air pollution and the greater the health concern. For example, an Air Quality Index (AQI) value of 50 represents good air quality with little potential to affect public health, while an Air Quality Index value over 300 represents hazardous air quality.

An Air Quality Index (AQI) value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. An Air Quality Index (AQI) values below 100 are generally thought of as satisfactory. When Air Quality Index values are above 100, air quality is considered to be unhealthy — at first for certain sensitive groups of people, then for everyone as Air Quality Index values get higher.

Understanding the Air Quality Index

The purpose of the Air Quality Index is to help you understand what local air quality means to your health. To make it easier to understand, the Air Quality Index  is divided into six categories:

Footnote: Values above 500 are considered Beyond the Air Quality Index (AQI). Follow recommendations for the Hazardous category.

[Source ⁴ ]

Each category corresponds to a different level of health concern.

The six levels of health concern and what they mean are:

1. “Good” Air Quality Index is 0 to 50. Air quality is considered satisfactory, and air pollution poses little or no risk.
2. “Moderate” Air Quality Index is 51 to 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.
3. “Unhealthy for Sensitive Groups” Air Quality Index is 101 to 150. Although general public is not likely to be affected at this AQI range, people with lung disease, older adults and children are at a greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.
4. “Unhealthy” Air Quality Index is 151 to 200. Everyone may begin to experience some adverse health effects, and members of the sensitive groups may experience more serious effects.
5. “Very Unhealthy” Air Quality Index is 201 to 300. This would trigger a health alert signifying that everyone may experience more serious health effects.
6. “Hazardous” Air Quality Index greater than 300. This would trigger a health warnings of emergency conditions. The entire population is more likely to be affected.

Take Action

When particle pollution levels are high, take steps to limit the amount of air you breathe in while you’re outside. For example:

• Think about spending more time indoors, where particle pollution levels are usually lower.
• Choose easier outdoor activities (like walking instead of running) so you don’t breathe as hard.
• Avoid busy roads and highways where particulate matter is usually worse because of emissions from cars and trucks.

What can I do to reduce my exposure to fine particle pollution when levels are extremely high?

• Stay indoors in an area with filtered air. Particle pollution can get indoors, so consider purchasing an air cleaner if you live in an area with high levels of particle pollution. (See information on selecting an air cleaner below.)
  • Air cleaners that remove particles include high-efficiency mechanical filters and electronic air cleaners, such as electrostatic precipitators. Avoid using an air cleaner that works by generating ozone, which will increase the pollution in your home.
  • If you do not have air cleaners in your home, try to go somewhere that does have air filtration. This could, for example, be a friend’s home, if it has air filtration.
• Keep your activity levels low.
  • Avoid activities that make you breathe faster or more deeply. This is a good day for indoor activities, such as reading or watching TV.
• If you cannot buy filters for your entire home, create a clean room for sleeping.
  • A good choice is a room with as few windows and doors as possible, such as a bedroom.
  • If the room has windows, keep them closed.
    • Run an air conditioner or central air conditioning system if you are certain your air conditioner does not draw air from outdoors and has a filter. If the air conditioner provides a fresh air option, keep the fresh-air intake closed. Make sure that the filter is clean enough to allow good air flow indoors.
  • Use an air filter in that room. Avoid using an air cleaner that works by generating ozone. Those types of cleaners will increase the pollution in your home.
  • Follow steps for keeping pollution in your home low.
• Take additional steps to keep pollution in your home low. Air cleaners alone may not be enough. Because particle pollution from the outdoor air can easily get inside, take steps to avoid adding even more pollution indoors when outdoor PM_2.5 levels are high:
  • Avoid using anything that burns, such as wood fireplaces, gas logs and even candles or incense.
  • Keep the room clean – but don’t vacuum unless your vacuum has a HEPA filter. That stirs up particles already inside your home. Wet mopping can help reduce dust.
  • Don’t smoke.
  • Be cautious when the weather is hot. If it is too hot to stay inside with the windows closed, or if you are in an at-risk group, go somewhere else with filtered air.
  • When air quality improves, open the windows and air out your home or office.
• Selecting an air cleaner:
  • Air cleaners that remove particles include high-efficiency mechanical filters and electronic air cleaners, such as electrostatic precipitators. Avoid using an air cleaner that works by generating ozone, which will increase the pollution in your home.
  • The California Air Resources Board has information on selecting portable and central air cleaners– including information on choosing the correct size for your room(s). Go to https://www.arb.ca.gov/research/indoor/acdsumm.pdf
  • EPA also provides detailed technical information on air cleaners in the home. See https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home

Should I wear a dust mask if I have to go outside?

Do not rely on dust masks for protection. Paper “comfort” or “dust” masks are designed to trap large particles, such as sawdust. These masks will not protect your lungs from small particles such as PM_2.5. Scarves or bandanas won’t help either.

Disposable respirators known as N-95 or P-100 respirators will help if you have to be outdoors for a period of time. It’s important that you wear the respirator correctly. For information on how to use one, see (https://oehha.ca.gov/media/downloads/public-information/document/wildfirev8.pdf)

How will I know when conditions are better?

When the air clears, and Air Quality Index (AQI) (https://www.airnow.gov/) readings are low, take advantage of these times to get outdoors.

Air quality conditions in Beijing can change rapidly. Check the U.S. Embassy or Chinese government air quality monitoring web pages for the most recent hourly PM_2.5 readings. These readings can help you determine when to take steps to reduce your exposure. Also pay attention to weather forecasts; these can help you plan your activities for times when air quality improves, such as when winds are forecast that clear the air.

How can ozone affect my health?

Ozone at ground level – not to be confused with the ozone layer in the upper atmosphere – is one of the major constituents of photochemical smog. Ozone at ground level is formed by the reaction with sunlight (photochemical reaction) of pollutants such as nitrogen oxides (NOx) from vehicle and industry emissions and volatile organic compounds emitted by vehicles, solvents and industry. As a result, the highest levels of ozone pollution occur during periods of sunny weather.

If you have asthma, bronchitis, or emphysema, ozone at ground level can make your symptoms worse. Carefully follow your asthma management plan on days when ozone levels are high.

Ozone at ground level can cause the muscles in the airways to constrict, trapping air in the alveoli. This leads to wheezing and shortness of breath.

Ozone at ground level can:

• Make it more difficult to breathe deeply and vigorously.
• Cause shortness of breath, and pain when taking a deep breath.
• Cause coughing and sore or scratchy throat.
• Inflame and damage the airways.
• Wheezing and trouble breathing during exercise or outdoor activities.
• Aggravate lung diseases such as asthma, emphysema, and chronic bronchitis.
• Increase the frequency of asthma attacks.
• Make the lungs more susceptible to infection.
• Continue to damage the lungs even when the symptoms have disappeared.
• Cause chronic obstructive pulmonary disease (COPD).

These effects have been found even in healthy people, but can be more serious in people with lung diseases such as asthma. They may lead to increased school absences, medication use, visits to doctors and emergency rooms, and hospital admissions.

Long-term exposure to ozone is linked to aggravation of asthma, and is likely to be one of many causes of asthma development. Long-term exposures to higher concentrations of ozone may also be linked to permanent lung damage, such as abnormal lung development in children.

Recent studies consistently report associations between short-term ozone exposures and total non-accidental mortality, which includes deaths from respiratory causes. Studies suggest that long-term exposure to ozone also may increase the risk of death from respiratory causes, but the evidence is not as strong as the evidence for short-term exposure.

Who is most at risk of ozone at ground level?

Ozone at ground level can affect anyone, but it bothers some people more than others. People most likely to experience health effects caused by ozone include:

• People with asthma or other lung diseases
• Older adults
• People of all ages who exercise or work hard outside
• Babies and children. Children are at greatest risk from exposure to ozone because their lungs are still developing and they are more likely to be active outdoors when ozone levels are high, which increases their exposure. Children are also more likely than adults to have asthma.

In addition, people with certain genetic characteristics, and people with reduced intake of certain nutrients, such as vitamins C and E, are at greater risk from ozone exposure.

Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and airway inflammation. It also can reduce lung function and harm lung tissue. Ozone can worsen bronchitis, emphysema, and asthma, leading to increased medical care.

How can I reduce these health risks?

The AirNow web site (https://www.airnow.gov/) provides daily air quality reports for many areas. These reports use the Air Quality Index (AQI) to tell you how clean or polluted the air is.

When ground-level ozone levels are high, take steps to limit the amount of air you breathe in while you’re outside. For example:

• Think about spending more time indoors, where ozone levels are usually lower.
• Choose easier outdoor activities (like walking instead of running) so you don’t breathe as hard.
• Plan outdoor activities at times when ozone levels are lower (usually in the morning and evening).

What are the environmental effects of ozone?

Ozone affects sensitive vegetation and ecosystems, including forests, parks, wildlife refuges and wilderness areas. In particular, ozone harms sensitive vegetation during the growing season.

When sufficient ozone enters the leaves of a sensitive plant, it can:

• Reduce photosynthesis, which is the process that plants use to convert sunlight to energy to live and grow.
• Slow the plant’s growth.
• Increase sensitive plants’ risk of:
  • disease
  • damage from insects
  • effects of other pollutants
  • harm from severe weather.

Also, some plants can show visible marks on their leaves when ozone is present under certain conditions.

Plant species that are sensitive to the effects of ozone on their growth include trees found in many areas of the U.S., such as:

• black cherry
• quaking aspen
• tulip poplar
• white pine
• ponderosa pine
• red alder.

The effects of ozone on individual plants can then have negative impacts on ecosystems, including:

• loss of species diversity (less variety of plants, animals, insects, and fish)
• changes to the specific assortment of plants present in a forest
• changes to habitat quality
• changes to water and nutrient cycles.

What are health effects of nitrogen dioxide?

Nitrogen dioxide (NO₂) is one of a group of highly reactive gases known as oxides of nitrogen or nitrogen oxides (NOx). Other nitrogen oxides include nitrous acid and nitric acid. Nitrogen dioxide (NO₂) is used as the indicator for the larger group of nitrogen oxides.

Nitrogen dioxide (NO₂) primarily gets in the air from the burning of fuel. Nitrogen dioxide (NO₂) forms from emissions from cars, trucks and buses, power plants, and off-road equipment.

Breathing air with a high concentration of nitrogen dioxide (NO₂) can irritate airways in the human respiratory system. Such exposures over short periods can aggravate respiratory diseases, particularly asthma, leading to respiratory symptoms (such as coughing, wheezing or difficulty breathing), hospital admissions and visits to emergency rooms. Longer exposures to elevated concentrations of nitrogen dioxide (NO₂) may contribute to the development of asthma and potentially increase susceptibility to respiratory infections. People with asthma, as well as children and the elderly are generally at greater risk for the health effects of nitrogen dioxide (NO₂).

Nitrogen dioxide (NO₂) along with other nitrogen oxides (NOx) reacts with other chemicals in the air to form both particulate matter and ozone. Both of these are also harmful when inhaled due to effects on the respiratory system.

Nitrogen dioxide environmental effects

Nitrogen dioxide (NO₂) and other nitrogen oxides (NOx) interact with water, oxygen and other chemicals in the atmosphere to form acid rain. Acid rain results when sulfur dioxide (SO₂) and nitrogen oxides (NOx) are emitted into the atmosphere and transported by wind and air currents. The sulfur dioxide (SO₂) and nitrogen oxides (NOx) react with water, oxygen and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials before falling to the ground.

Acid rain or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic.  Acid rain harms sensitive ecosystems such as lakes and forests.

While a small portion of the sulfur dioxide (SO₂) and nitrogen oxides (NOx) that cause acid rain is from natural sources such as volcanoes, most of it comes from the burning of fossil fuels. The major sources of sulfur dioxide (SO₂) and nitrogen oxides (NOx) in the atmosphere are:

• Burning of fossil fuels to generate electricity. Two thirds of sulfur dioxide (SO₂) and one fourth of nitrogen oxides (NOx) in the atmosphere come from electric power generators.
• Vehicles and heavy equipment.
• Manufacturing, oil refineries and other industries.

Winds can blow sulfur dioxide (SO₂) and nitrogen oxides (NOx) over long distances and across borders making acid rain a problem for everyone and not just those who live close to these sources.

The nitrate particles that result from nitrogen oxides (NOx) make the air hazy and difficult to see though. This affects the many national parks that you visit for the view.

Nitrogen oxides (NOx) in the atmosphere contributes to nutrient pollution in coastal waters. Nitrogen and phosphorus are nutrients that are natural parts of aquatic ecosystems. Nitrogen is also the most abundant element in the air you breathe. Nitrogen and phosphorus support the growth of algae and aquatic plants, which provide food and habitat for fish, shellfish and smaller organisms that live in water.

But when too much nitrogen and phosphorus enter the environment – usually from a wide range of human activities – the air and water can become polluted. Nutrient pollution has impacted many streams, rivers, lakes, bays and coastal waters for the past several decades, resulting in serious environmental and human health issues, and impacting the economy.

Too much nitrogen and phosphorus in the water causes algae to grow faster than ecosystems can handle. Significant increases in algae harm water quality, food resources and habitats, and decrease the oxygen that fish and other aquatic life need to survive. Large growths of algae are called algal blooms and they can severely reduce or eliminate oxygen in the water, leading to illnesses in fish and the death of large numbers of fish. Some algal blooms are harmful to humans because they produce elevated toxins and bacterial growth that can make people sick if they come into contact with polluted water, consume tainted fish or shellfish, or drink contaminated water.

Nutrient pollution in ground water – which millions of people in the United States use as their drinking water source – can be harmful, even at low levels. Infants are vulnerable to a nitrogen-based compound called nitrates in drinking water. Excess nitrogen in the atmosphere can produce pollutants such as ammonia and ozone, which can impair our ability to breathe, limit visibility and alter plant growth. When excess nitrogen comes back to earth from the atmosphere, it can harm the health of forests, soils and waterways.

What are the health effects of sulfur dioxide air pollution?

Sulfur dioxide (SO₂) is a gaseous air pollutant composed of sulfur and oxygen. Sulfur dioxide (SO₂) forms when sulfur-containing fuel such as coal, oil, or diesel is burned. Sulfur dioxide also converts in the atmosphere to sulfates, a major part of fine particle pollution in the eastern U.S.

Sulfur dioxide causes a range of harmful effects on the lungs, as the EPA’s most recent review of the science concluded:

• Wheezing, shortness of breath and chest tightness and other problems, especially during exercise or physical activity.
• Continued exposure at high levels increases respiratory symptoms and reduces the ability of the lungs to function.
• Short exposures to peak levels of sulfur dioxide (SO₂) in the air can make it difficult for people with asthma to breathe when they are active outdoors.
• Rapid breathing during exercise helps sulfur dioxide (SO₂) reach the lower respiratory tract, as does breathing through the mouth.
• Increased risk of hospital admissions or emergency room visits, especially among children, older adults and people with asthma ⁵.

What are the sources of sulfur dioxide emissions?

Manmade sources in the U.S. emitted more than 6.4 million tons of sulfur dioxide in the most recent reports ⁶. The largest sources of sulfur dioxide emissions are electricity generation, industrial boilers, and other industrial processes such as petroleum refining and metal processing. Diesel engines are another major source, including old buses and trucks, locomotives, ships, and off-road diesel equipment.

What causes high concentrations of sulfur dioxide?

Coal-fired power plants remain one of the biggest sources of sulfur dioxide in the U.S., particularly in the eastern states. The plume from a coal-fired power plant touches down at ground level during high wind conditions or gets trapped by inversions in the atmosphere. High levels can happen during start-up, shutdown, upsets, and malfunctions of pollution control equipment.

Ports, smelters, and other sources of sulfur dioxide also cause high concentrations of emissions nearby.

People who live and work nearby these large sources get the highest exposure to sulfur dioxide (SO₂). After sulfur dioxide (SO₂) gets into the air, it changes chemically into sulfate particles, which can blow hundreds of miles away.

Wildfires

Wildfires, including grassland fires and forest fires, are an ongoing concern where there is dry, hot weather. During a wildfire, people throughout the surrounding area may suffer the effects of the smoke. Talk with your doctor about how to prepare for this smoke, especially if you or someone in the family fits into one of these categories: works outdoors; is under age 18 or over age 65; or has asthma, COPD or other lung diseases, chronic heart disease, or diabetes. Monitor your breathing and exposure to the smoke. If problems develop, call your physician immediately.

General recommendations

• Stay indoors: People living close to the fire-stricken areas should remain indoors and avoid breathing smoke, ashes and other pollution in the area.
• Don’t count on a dust mask: Ordinary dust masks, designed to filter out large particles, will not help. They still allow the more dangerous smaller particles to pass through. Special, more expensive dust masks with an “N-95” or “N-100” filter will filter out the damaging fine particles, but may not fit properly and are difficult for people with lung disease to use. These masks can make it more difficult for anyone to breathe and should only be used if you must go outside. Consult with your doctor before using a mask, especially if you have a lung disease.
• If you decide to keep a mask on hand, see the Respirator Fact Sheet provided by CDC’s National Institute for Occupational Safety and Health (https://www.cdc.gov/niosh/docs/2003-144/).
• Take precautions for kids: Extra precaution should be taken for children, who are more susceptible to smoke. Their lungs are still developing and they breathe in more air (and consequently more pollution) for their size than adults.
• Roll up your car windows: When driving your car in smoky areas, keep your windows and vents closed. Air conditioning should only be operated in the “recirculate” setting.
• Protect the air in your home: Stay inside as much as possible, with doors, windows and fireplace dampers shut and preferably with clean air circulating through air conditioners and air cleaners. Use air conditioners on the recirculation setting to keep from pulling outside air into the room. Air cleaning devices that have HEPA filters can provide added protection from the soot and smoke. Place damp towels under the doors and other places where the outside air may leak in.
• Prepare to evacuate if directed. Listen to your local or state officials and protect yourself and your family.
• Don’t exercise outside: If you live close to or in the surrounding area, don’t exercise outdoors, especially if you smell smoke or notice eye or throat irritation.

Figure 1. N-95 dust mask

Figure 2. N-100 dust mask

If you have lung disease, chronic heart disease or diabetes

• Check in with your doctor: People with asthma or other lung diseases, cardiovascular diseases or diabetes should check with their physician regarding any changes in medication that may be needed to cope with the smoky conditions.
• Keep an eye on symptoms: Higher levels of smoke in some areas can make breathing more difficult. If you are experiencing symptoms, please try to contact your physician. If you cannot, asthma patients can follow the asthma action plan developed with their physician. Use your peak flow meter if prescribed. Do not hesitate to take your medication, and avail yourself of the full spectrum of medications your doctor has prescribed to you.
• Ask about your oxygen use: People using oxygen should not adjust their levels of intake before consulting a physician. (Call your doctor BEFORE you take any action.)
• Know when to seek medical attention: If symptoms are not relieved by the usual medicines, seek medical attention. Symptoms to watch for: wheezing, shortness of breath, difficulty taking a full breath, chest heaviness, lightheadedness, and dizziness. If you have any concerns or questions please contact your physician.
• Watch for breathing issues after exposure: If you develop a persistent cough or difficult or painful breathing, call your physician. The first symptoms can appear as late as 24 to 48 hours after exposure. Smoke can remain in areas for many days after the fires have ended.

Clean Up

Residents and volunteers should use caution during clean-up because the process involves ashes and other sources of pollution.

• Avoid dust and soot: People with lung or heart problems should avoid clean-up activities and areas where dust or soot is present.
• Reduce dust and soot: Thoroughly wet dusty and sooty area prior to clean-up. This will help to reduce the amount of particles becoming airborne.
• Cover your face: Wear an appropriate dust mask during clean-up, a HEPA-filtered one or an N-95.
• Do not disturb: If exposure to asbestos or other hazardous materials is suspected, do not disturb the area. Dust masks do not protect against asbestos.

What is wildfire smoke and can it make me sick?

Wildfire smoke is a mix of gases and fine particles from burning vegetation, building materials, and other materials. Wildfire smoke can make anyone sick. Even someone who is healthy can get sick if there is enough smoke in the air. Breathing in smoke can have immediate health effects, including:

• Coughing
• Trouble breathing normally
• Stinging eyes
• A scratchy throat
• Runny nose
• Irritated sinuses
• Wheezing and shortness of breath
• Chest pain
• Headaches
• An asthma attack
• Tiredness
• Fast heartbeat

Older adults, pregnant women, children, and people with preexisting respiratory and heart conditions may be more likely to get sick if they breathe in wildfire smoke.

Who is at greatest risk from wildfire smoke?

• People who have heart or lung diseases, like heart disease, chest pain, lung disease, or asthma, are at higher risk from wildfire smoke.
• Older adults are more likely to be affected by smoke. This may be due to their increased risk of heart and lung diseases.
• Children are more likely to be affected by health threats from smoke. Children’s airways are still developing and they breathe more air per pound of body weight than adults. Also, children often spend more time outdoors engaged in activity and play.

Take steps to decrease your risk from wildfire smoke

• Check local air quality reports (https://www.airnow.gov/). Listen and watch for news or health warnings about smoke. Find out if your community provides reports about the U.S. Environmental Protection Agency’s Air Quality Index (AQI) or check the report on AirNow.gov (https://www.airnow.gov/). In addition, pay attention to public health messages about safety measures.
• Consult local visibility guides. Some communities have monitors that measure the amount of particles in the air. In the western United States, some states and communities have guidelines to help people determine if there are high levels of particulates in the air by how far they can see.
• Keep indoor air as clean as possible if you are advised to stay indoors. Keep windows and doors closed. Run an air conditioner, but keep the fresh-air intake closed and the filter clean to prevent outdoor smoke from getting inside. If you do not have an air conditioner and it is too warm to stay inside with the windows closed, seek shelter in a designated evacuation center or away from the affected area.
• Avoid activities that increase indoor pollution. Burning candles, fireplaces, or gas stoves can increase indoor pollution. Vacuuming stirs up particles already inside your home, contributing to indoor pollution. Smoking also puts even more pollution into the air.
• Prevent wildfires from starting. Prepare, build, maintain and extinguish campfires safely. Follow local regulations if you burn trash or debris. Check with your local fire department to be sure the weather is safe enough for burning.
• Follow the advice of your doctor or other healthcare provider about medicines and about your respiratory management plan if you have asthma or another lung disease. Consider evacuating if you are having trouble breathing. Call your doctor for advice if your symptoms worsen.
• Do not rely on dust masks for protection. Paper “comfort” or “dust” masks commonly found at hardware stores are designed to trap large particles, such as sawdust. These masks will not protect your lungs from the small particles found in wildfire smoke.
• Evacuate from the path of wildfires. Listen to the news to learn about current evacuation orders. Follow the instructions of local officials about when and where to evacuate. Take only essential items with you. Follow designated evacuation routes–others may be blocked–and plan for heavy traffic.
• Protect yourself cleaning up after a fire. Cleanup work can expose you to ash and other products of the fire that may irritate your eyes, nose, or skin and cause coughing and other health effects.

Indoor air pollution

Most people usually think of air pollution as being outdoors, but the air in your house or office could also be polluted. Sources of indoor pollution include:

• Mold and pollen
• Tobacco smoke
• Household products and pesticides
• Gases such as radon and carbon monoxide
• Materials used in the building such as asbestos, formaldehyde and lead

Sometimes a group of people have symptoms that seem to be linked to time spent in a certain building. There may be a specific cause, such as Legionnaire’s disease. Sometimes the cause of the illness cannot be found. This is known as sick building syndrome.

Usually indoor air quality problems only cause discomfort. Most people feel better as soon as they remove the source of the pollution. However, some pollutants can cause diseases that show up much later, such as respiratory diseases or cancer.

Making sure that your building is well-ventilated and getting rid of pollutants can improve the quality of your indoor air.

Health effects of secondhand smoke

Secondhand smoke is a serious health hazard causing more than 41,000 deaths per year. It can cause or make worse a wide range of damaging health effects in children and adults, including lung cancer, respiratory infections and asthma.

Key facts about secondhand smoke:

• Secondhand smoke causes approximately 7,330 deaths from lung cancer and 33,950 deaths from heart disease each year ⁷.
• Between 1964 and 2014, 2.5 million people died from exposure to secondhand smoke, according to a report from the U.S. Surgeon General. The report also concluded that secondhand smoke is a definitive cause of stroke ⁷.
• There is no risk-free level of exposure to secondhand smoke and even short-term exposure potentially can increase the risk of heart attacks ⁸.
• Secondhand smoke contains hundreds of chemicals known to be toxic or carcinogenic, including formaldehyde, benzene, vinyl chloride, arsenic ammonia and hydrogen cyanide ⁸.
• Secondhand smoke can cause heart attacks; even relatively brief exposure can trigger a heart attack, according to a report by the Institute of Medicine ⁹.

Secondhand smoke and children

• Secondhand smoke is especially harmful to young children. Secondhand smoke is responsible for between 150,000 and 300,000 lower respiratory tract infections in infants and children under 18 months of age, resulting in between 7,500 and 15,000 hospitalizations each year. It also causes 430 sudden infant death syndrome (SIDS) deaths in the U.S. annually ¹⁰.
• Secondhand smoke exposure may cause buildup of fluid in the middle ear, resulting in 790,000 doctor’s office visits per year, as well as more than 202,000 asthma flare-ups among children each year ¹⁰.
• More than 24 million, or about 37 percent of children in the U.S. have been exposed to secondhand smoke ¹¹.

How can dampness and mold impact health?

Mold exists everywhere; there are no indoor spaces without mold ¹². However, without sufficient moisture, mold cannot grow If mold is growing, too much moisture is present.

Dampness may show up in visible moisture, like leaks, or as high humidity. Dampness in homes or buildings creates the environment for mold spores to grow. Dampness can cause harm even when mold is not present. Excessive moisture also promotes the growth of dust mites, cockroaches, bacteria and viruses, which can impact health ¹³.

Exposure to mold can trigger allergic reactions and asthma symptoms in people who are allergic to mold. However, even without mold, dampness indoors causes asthma attacks and other upper and lower respiratory problems. Anyone—with or without allergies—may experience irritation of the eyes, skin, nose, throat and lungs when exposed to airborne mold particles ¹².

Dampness and mold have been linked to:

• Worsening of asthma
• Coughing
• Wheezing
• Nasal congestion
• Sore throat
• Sneezing
• Rhinitis ¹³

An uncommon disease known as hypersensitivity pneumonitis has been associated with exposure to indoor mold in people who have weakened immune systems ¹⁴. Hypersensitivity pneumonitis disease creates flu-like symptoms that may recur.

Where does the moisture come from?

Water from many sources within a home or building causes moisture problems or mold. Some sources are impossible to stop, so all indoor spaces need to be well-ventilated. Problems arise when materials remain wet, especially long enough for mold to grow. If you discover a water problem, fix it quickly.

Moisture may build indoors in many different ways. These include:

• Flooding or leaks that allow rainwater indoors.
• Poorly connected plumbing and leaky pipes.
• Continually damp carpet (may occur if carpet is installed on poorly ventilated floor).
• Inadequate exhaust of bathrooms and kitchens.
• Outdoor humidity.
• Condensation or moisture build-up in humidifiers, dehumidifiers, air conditioners and drip pans under refrigerator cooling coils.1,3,5

How can dampness and mold be prevented?

The best way to control dampness and mold indoors is to control the sources of moisture. That means preventing the problem from developing as well as fixing new problems quickly. Common problem areas include air-conditioning units; basements, attics and crawl spaces; bathrooms; humidifiers and dehumidifiers; and refrigerator drip pans.

Here are some key steps ¹².:

• Keep indoor humidity levels below 50 percent.
• Fix all leaks.
• Increase air movement and ventilation.
• Run exhaust fans in the bathroom and kitchen to reduce moisture.
• Keep appliance drip pans clean.
• Regularly and thoroughly clean places where molds are likely to grow.

Watch out for these signs to identify a dampness problem:

• Musty odor;
• Moisture on hard surfaces; and
• Water stains that signify water leaks or condensation ¹².

How can dampness and mold problems be fixed?

• Identify and eliminate the water problem. The most critical step is to identify and eliminate the source of the water that is creating a damp environment. You may need technical assistance from a plumber or contractor to determine what needs to be fixed or changed.
• Determine the extent of the problem. EPA recommends calling for professional help to clean any mold growth that covers more than 10 square feet ¹². If you are unable to determine the extent of the problem, contact a professional, who can help you protect your family.
• Remove, clean or discard affected materials. To get rid of mold, wash it off materials that can be effectively cleaned, such as hard surfaces. Use detergent and warm water. Dry the surface completely. If the materials cannot be cleaned or are too damaged to reuse, discard them. Porous materials, like ceiling tiles, likely cannot be cleaned thoroughly and must be discarded ¹².
• Protect occupants and workers during the cleanup process. At minimum, wear an N-95 mask (available at hardware stores), disposable gloves and goggles. Workplace cleanup requires that the N-95 mask be professionally fitted ¹².

If water build up was caused by sewage, floods or other contaminated water, call a professional.

What are the health effects of carbon monoxide?

Carbon monoxide (CO) is an odorless, colorless, and tasteless but dangerous gas. Carbon monoxide is produced when fuels are burned such as gasoline, natural gas, oil, kerosene, wood or charcoal. Breathing carbon monoxide reduces the blood’s ability to carry oxygen. Carbon monoxide (CO) can reach dangerous levels indoors or outdoors.

Sources of carbon monoxide include:

• Gas appliances (furnaces, ranges, ovens, water heaters, clothes dryers, etc.)
• Fireplaces, wood stoves
• Coal or oil furnaces
• Space heaters or oil or kerosene heaters
• Charcoal grills, camp stoves
• Gas-powered lawn mowers and power tools
• Automobile exhaust fumes

Once inhaled, carbon monoxide attaches to the hemoglobin in the red blood cells. Hemoglobin normally carries oxygen throughout the body. When carbon monoxide attaches, it blocks the oxygen the body must have, creating a wide range of health problems.

Breathing low levels of carbon monoxide can cause:

• Headache
• Nausea
• Dizziness
• Weakness
• Confusion
• Disorientation ¹⁵

Many of these symptoms are similar to the flu, food poisoning or other illnesses. So you may not suspect carbon monoxide poisoning. If symptoms persist, and especially if they get better after you leave the building, carbon monoxide may be the cause.

Breathing higher levels of carbon monoxide causes flu-like symptoms such as headaches, dizziness and weakness in healthy people.

Breathing high levels of carbon monoxide also can cause:

• Sleepiness
• Nausea
• Anxiety or depression
• Vomiting
• Confusion
• Impaired vision
• Impaired coordination
• Disorientation ¹⁶

Breathing carbon monoxide at low levels regularly may cause permanent mental or physical problems. At very high levels, it causes loss of consciousness and death ¹⁶.

Approximately 430 people die each year from carbon monoxide exposure related to fuel-burning, residential appliances. Thousands more became ill or sought medical attention.3 carbon monoxide poisoning is estimated to cause more than 50,000 emergency room visits in the United States each year ¹⁶.

In addition, outdoor air can have too much carbon monoxide, especially near roads where tailpipe emissions can build up ¹⁷. Carbon monoxide can also react with other gases to form ozone pollution.

How can you protect yourself from carbon monoxide?

After an emergency or power outage, be sure to remember these steps so you don’t risk your family’s health. Too many people are poisoned by carbon monoxide after bad weather emergencies, like snowstorms and hurricanes. You may need to seek shelter elsewhere until the electricity is back.

• Make sure all appliances work and are fully vented.
  • Make sure appliances are installed and working according to manufacturers’ instructions and local building codes.
  • Never use unvented appliances — make sure all appliances are fully vented to the outdoors.
  • Have the heating system, chimney and flue inspected and cleaned by a qualified technician every year.
  • Make sure your furnace has an adequate intake of outside air.
• Use appliances and stoves appropriately.
  • Do not use ovens and gas ranges to heat your home.
  • Do not burn charcoal, kerosene lanterns or portable camp stoves inside a home, cabin, recreational vehicle or camper.
• Keep carbon monoxide out of your home.
  • Do not operate gasoline-powered engines in confined areas such as garages or basements.
  • Never leave your car or mower running in a closed garage.
  • If you must use a portable generator in an emergency, keep it as far away from your home as possible and away from windows or doors.
  • Never let anyone smoke inside your home. Cigarettes, pipes and cigars also produce carbon monoxide.
• Install a carbon monoxide detector with an audible alarm near sleeping areas, on indoor walls shared with a garage, and near combustion equipment in your home.
• Don’t exercise along a busy street or highway.

After an emergency or power outage, be sure to remember these steps so you don’t risk your family’s health. Too many people are poisoned by carbon monoxide after bad weather emergencies, like snowstorms and hurricanes. You may need to seek shelter elsewhere until the electricity is back.

Why should I buy a carbon monoxide detector?

• Every home should have a working carbon monoxide detector; it may save your life.

Carbon monoxide detectors should:

• Meet Underwriters Laboratories, Inc. (UL) standards;
• Have a long-term warranty; and
• Be easily self-tested and reset to ensure proper functioning.

For maximum effectiveness while you sleep, carbon monoxide detectors should be placed as close to sleeping areas as possible.

What should I do if the carbon monoxide detector goes off?

• Make sure it is your carbon monoxide detector and not your smoke detector.
• Check to see if any member of the household is experiencing symptoms of carbon monoxide poisoning.
• If they are, get them out of the house immediately and seek medical attention. Tell the doctor that you suspect carbon monoxide poisoning.
• If no one is feeling symptoms, ventilate the home with fresh air and turn off all potential sources of carbon monoxide. That includes your oil or gas furnace, gas water heater, gas range and oven, gas dryer, gas or kerosene space heater, and any vehicle or small engine.
• Have a qualified technician inspect your fuel-burning appliances and chimneys. They can make sure everything is operating correctly and nothing is blocking fumes from being vented outside.

What are the health effects of radon?

Radon is a naturally occurring colorless, tasteless and odorless gas that can have a big impact on indoor air quality and your health. You can’t see or smell it, and radon can build up inside homes, buildings and schools to dangerous levels. Exposure to high levels of radon can cause lung cancer. Exposure to radon is the second leading cause of lung cancer in the United States, after smoking. Radon-related lung cancers are responsible for an estimated 21,000 deaths annually in the United States ¹⁸. Exposure to radon causes no immediate symptoms, but the long-term threat of lung cancer is significant to everyone. People who have never smoked make up approximately 2,900 of the estimated 21,000 radon-related lung cancer deaths each year.

Radon forms naturally. Uranium in soil or rock breaks down to form radium, which then turns into radon gas. Once formed, radon enters a home through cracks in walls, basement floors, foundations and other openings. As radon decays, it releases radioactive byproducts that are inhaled into your lungs and bombard your lung cells with dangerous, cancer-causing radiation ¹⁹. Smoking and radon exposure can separately increase your risk of lung cancer. But if you smoke, know that exposure to both greatly enhances your risk of lung cance.. Because radon comes from rock and soil, it can be found anywhere. Exposure to limited concentrations, like those found outdoors, is impossible to avoid. However, when radon gets trapped indoors, it may exist in dangerous concentrations.

Less frequently, radon may enter buildings from water used in bathroom showers and faucets. Concerns have also been raised about the radon released indoors from building materials, such as granite countertops or tiles. However, these sources have rarely proven to be a problem by themselves ²⁰.

Concerns have also recently emerged about radon in natural gas extracted by hydraulic fracturing, or fracking ¹⁹. Follow-up research has found that the natural gas coming into homes in the Northeast did not generally contain enough radon to pose a serious additional risk ²¹.

Who should be worried about radon?

Every home should be tested for radon. Radon has been found at elevated levels in homes in every state and the only way to know is to test. Your home can have elevated levels of radon while your neighbor’s home does not. Testing is the only way to determine if you have a problem. Radon testing is easy and inexpensive and it could save your life. Thousands of lung cancer deaths could be avoided each year if home and building owners acted to test and fix.

How can radon be detected?

The only way to detect a buildup of radon in your home is to test the air. Various forms of do-it-yourself test kits are simple to use and inexpensive.

Short-term tests typically take two to seven days. During this time, place the kit in a location where it will not be disturbed, in the lowest level regularly used in your home. Follow the test directions and other official guidance to prevent problems that can affect the testing. Once the testing period is complete, seal the test kit and send it to a laboratory for analysis. Most test kits include the cost of lab analysis and an addressed envelope for submission. In a matter of weeks, you will be notified of the radon level in your home.

Long-term tests tend to be more accurate as they collect more data. They take at least three months and measure long-term averages. If you don’t want to wait for a long-term test, short-term tests can indicate if your home has a problem and requires follow-up testing.

If you prefer, hire a certified radon-testing professional. The best way to find a certified professional is to contact your state radon program. EPA has an interactive map with contact information for state radon agencies (https://www.epa.gov/radon/find-information-about-local-radon-zones-and-state-contact-information).

Radon gas is measured in picocuries per liter (pCi/L) of air. The EPA recommends taking action to reduce radon if the result is 4.0 pCi/L or greater and to consider similar actions when the radon level is between 2 and 4.0 pCi/L. The ultimate goal is to get your radon level to the lowest level possible.

How can I protect against radon?

There are several ways to protect you and your family from the dangers of radon gas.

If you have an existing home with elevated levels of radon, you can fix the problem by having a radon mitigation system installed. A radon mitigation system consists of a vent pipe, fan and the proper sealing of cracks. This system collects radon gas from underneath the foundation and vents it to the outside of your home. If you need to have a radon mitigation system installed, it is best to contact a certified radon mitigation professional to do the installation. A list of certified professionals can usually be obtained by contacting your state radon program.

If you are building a new home, ask your contractor to install radon-resistant features. These features include gravel and plastic sheeting below the foundation, along with proper sealing of cracks and the installation of a vent pipe. Once the radon-resistant features have been installed and the home is completely built, make sure to perform a radon test, as the levels could still be elevated. If the radon levels are still elevated, a radon fan should be added to the system to lower the radon level.

Detailed information about radon reduction in your home or building can be found in EPA’s Consumer’s Guide to Radon Reduction (https://www.epa.gov/radon).

What is pet dander allergy?

Pet dander is composed of tiny, even microscopic, flecks of skin shed by cats, dogs, rodents, birds and other animals with fur or feathers. These bits of skin can cause reactions in people who are specifically allergic to these triggers.

Additional allergy triggers or allergens come from sources other than the animal’s skin. Proteins found in saliva, urine and feces from cats, dogs and other pets can cause allergic reactions in some people. The most common allergies are caused by the Fel d I protein from cats and the Can f I and Can f II proteins from dogs. Dried saliva containing allergens may flake off from an animal’s fur and become airborne, where it is inhaled by the allergic person. Dust from dried feces can be suspended in the same way ²².

Which animals pose the biggest problems?

Cats are kept as pets in 27 percent of homes in the United States and dogs are found in 32 percent. However, roughly twice as many people report allergies to cats when compared to dogs. Research also indicates that male cats produce less Fel d I allergen than female cats, although the reason is not clear ²².

Animals with fur may be more likely to carry allergens from other sources, like dust, but the fur itself is generally not a trigger. For that reason, short-haired or hairless animals contribute dander and allergens to indoor air pollution just as effectively as long-haired animals do. There is no such thing as a non-allergenic dog or cat ²².

How do pet allergens occur?

Pet allergens are very light weight and small. They remain suspended in the air for a long time, much longer than allergens from cockroaches or dust mites. Because of their microscopic size and jagged shape, pet allergens easily stick to furniture, bedding, fabrics and many items carried into and out of the home. Animal dander is easily spread through the home and out to public places like schools and hospitals ²². They can be found even in homes and buildings without pets ²².

How do pet allergens affect health?

Some people are allergic to pets or have asthma that is triggered by pet allergens. For these individuals, breathing animal allergens can make respiratory symptoms worse and lead to a decline in the ability of the lungs to function. The concentrations of an allergen required to cause a reaction vary greatly by individual ²².

People with allergies may experience upper and lower respiratory tract symptoms including congestion, sneezing, runny nose, chest tightness and wheezing. Other symptoms are itching, watery eyes, and eczema or rashes ²².

How do you control pet allergens?

For homes with sensitive individuals, the best way to protect indoor air quality is to remove the animal from the home. However, pet allergens may stay in the home for months after the pet is gone because the allergens remain in house dust. Allergy and asthma symptoms may take weeks or even months to improve ²².

If the pet stays in the home, keep it out of the bedroom of anyone who has asthma or allergies. Do not allow the pet on furniture, especially upholstery, and keep the pet away from carpets. Clean the home often and do not allow dust to accumulate.

What can lead do to your health?

Lead is a toxic metal that was once regularly used in the manufacturing of common household products and gasoline. There is no safe level of exposure to lead ²³. Lead is a naturally occurring element and, unlike many pollutants, it does not go away over time.

The most common source of lead air pollution indoors is old paint found in homes built before 1978 ²⁴. If left untouched and in good condition, lead-based paint may not pose a significant hazard to health. However, if it is chipped or deteriorating, paint can create dust, chips and suspended particles that can be inhaled. Activities like remodeling, dry scraping, and demolition also disturb and re-suspend paint particles.

Contaminated soil and dust tracked indoors from outside are also large contributors to indoor lead pollution ²⁵. Levels of lead in soil are higher near sources such as lead smelters, mines, old agricultural fields and heavily trafficked roadways and runways ²⁶. Lead dust from workplace exposures also may be brought home and contribute to indoor air pollution ²⁵. People who work with or around lead must take care to avoid carrying lead particles home on their clothing or equipment.

Exposure to lead can harm nearly every system in your body. Lead can even kill. Lead accumulates in your bones, liver, and kidneys and can get into your blood. The effects of lead poisoning may continue after the source of exposure has been eliminated ²⁵.

The nervous system is the main target of lead’s effects on the bodies of both adults and children. Children are most vulnerable to lead pollution because their nervous systems are developing and can be harmed for life.

Lead can:

• Harm cognitive functions;
• Cause behavioral problems; and
• Decrease IQ ²³.

The acute effects of lead poisoning include:

• Seizures
• Paralysis
• Anemia
• Abdominal pain
• Constipation
• Vomiting
• Decreased appetite
• Death ²³

Chronic, ongoing exposure to high levels of lead may also cause:

• Severe damage to the brain and kidneys
• Reproductive system damage
• Increased blood pressure
• Anemia ²³

When taken up and stored in bone, lead can disrupt skeletal development and affect calcium absorption. Lead accumulated in the skeleton may be released during pregnancy and breast feeding and can be passed from a mother to her vulnerable, developing child ²⁶.

The EPA has determined that lead is a probable cancer-causing agent, or carcinogen, in humans ²⁵.

Who is at risk lead toxicity?

Young children living in houses or apartment buildings built before 1978 (especially those located in inner cities or built before 1950) are at greatest risk from exposure to lead. Young children are likely to play on the floor where lead-laden dust may settle. They also are more likely to put their hands or lead-contaminated objects into their mouths. Children and babies are also most vulnerable to the harmful health effects of lead because their nervous systems are still developing ²³.

Also at risk are people who work in industries that use lead, such as lead smelting and refining industries, brass/bronze foundries, rubber products and plastics industries, soldering, steel welding and cutting operations, battery manufacturing plants and lead compound manufacturing. Construction and demolition workers, painters and people who work at municipal waste incinerators, pottery and ceramics industries, radiator repair shops and other industries that use lead solder also may be exposed ²³.

People living at a disadvantaged socioeconomic status also are more likely to suffer the health effects of lead exposure ²⁷. Lower income residences tend to be older and in worse condition than higher income housing. Chipping and deteriorating paint is a major source of lead indoors.

How can lead exposure in the home be avoided?

If you suspect that there is lead-based paint in your home, take steps to protect your family.

• First, leave lead paint intact if possible. If you are concerned about the presence of lead paint, paint over it rather than try to remove it. Or hire a professional to remove it. If the paint is flaking, damp-mop floors to remove contaminated dust and wipe window ledges with a warm, damp rag and phosphate-containing dishwashing detergent.
• If you plan on renovating, be sure to take precautions. Pregnant women and children should leave the building until the work is completed ²⁴.
  • Hire someone who has specialized training to remove lead paint.
  • Keep areas being remodeled separate from living areas.
  • Don’t let children near the remodeling site.
  • Keep your home dust-free and, if possible, leave lead-based paint untouched if it is in good condition ²⁴

Don’t bring lead into the home. People who work with lead should follow the standards set by the Occupational Health and Safety Administration, such as wearing proper protective gear. Do not bring dirty clothing or equipment that might have been exposed to lead particles into your home.

What are the health effects of formaldehyde in indoor air?

Formaldehyde is a colorless and flammable gas with a distinct odor detectable at very low concentrations. Formaldehyde is a volatile organic compound that causes cancer and other harmful health effects ²⁸. Formaldehyde is a naturally occurring chemical; your body even produce small amounts of formaldehyde. However, at high concentrations, formaldehyde vapors are dangerous.

Formaldehyde causes cancer ²⁸. Evidence shows formaldehyde can cause a rare cancer of the nasopharynx, which is the upper part of the throat behind the nose.

Formaldehyde irritates the nose, eyes, and throat. These irritations can happen at low levels of formaldehyde, especially in people who are especially sensitive to the odors ²⁸. Other short-term effects include headache, runny nose, nausea and difficulty breathing ²⁹. Exposure may cause wheezing, asthma attacks and other respiratory symptoms ³⁰.

Individuals vary in how they respond to formaldehyde. Some people have a natural allergic sensitivity to airborne formaldehyde and others may develop an allergy as a result of skin contact with liquid formaldehyde ²⁹. Researchers have found that some individuals with asthma are more vulnerable to the effects of inhaled formaldehyde ³¹.

What are the sources of formaldehyde indoors?

Many industries use formaldehyde. It is used to produce wood, paper, plywood, glues and adhesives, permanent press fabrics, some paints and coatings, and certain insulation materials. It is also found in many consumer products, including cosmetics, dish soaps, medicines, leather treatments and fabric softeners ³⁰.

Formaldehyde is present both indoors and outdoors. However, formaldehyde levels are usually much higher indoors. Because formaldehyde is volatile, which means it evaporates easily, it is released into the air from many products inside the home. High humidity and high temperatures speed up the release of formaldehyde.

Smoking indoors produces high concentrations of formaldehyde. Burning wood products, fuel, paper and other products is also an important source of formaldehyde.

How can you reduce exposure to formaldehyde indoors?

There are a few simple ways to protect yourself from formaldehyde indoors.

• Chose low-formaldehyde products when building or remodeling. Furniture and pressed-wood board made with laminated surfaces release less formaldehyde and other volatile organic compounds. If possible, use non-toxic alternatives to formaldehyde-containing products like glue and adhesives.
• Ventilate indoor spaces. Open windows or use exhaust fans to blow indoor air out and bring fresh air in. Make sure any combustion appliance has a separate exhaust to the outdoors. Remember to ventilate indoor spaces when using cleaners, cosmetic products like nail polish remover or most paints.
• Air out new furniture and pressed-wood products. Many consumer products that emit formaldehyde, such as plywood and particle board, release the highest concentrations when they are new. Air them out before installing them or bringing them indoors.
• Don’t allow smoking indoors. Not smoking and prohibiting smoking indoors can reduce exposure to formaldehyde. Secondhand smoke contains many chemicals in addition to formaldehyde that can harm health.
• Wash permanent press clothing before wearing. Formaldehyde is used in the production of special fabrics.

How does asbestos impact health?

Asbestos refers to a group of naturally occurring, fibrous minerals. Asbestos was once widely used in building supplies and other consumer products. Research shows asbestos fibers can cause major breathing problems and cancer (e.g., mesothelioma) ³². Old and brittle asbestos products can release tiny, even microscopic, fibers. These fibers can remain suspended in the air and enter your lungs when you inhale. Airborne asbestos fibers have no odor or taste. Because of the health risks, the federal government has banned the use of asbestos in certain products, but it can still be used in others ³³.

Asbestos can cause cancer. Inhaling asbestos fibers increases the risk of developing lung cancer and mesothelioma, a deadly cancer of the thin lining surrounding the lungs and other organs ³². The risk depends on how much you inhale, how long ago you were exposed and whether you smoke. Smoking cigarettes, in addition to inhaling asbestos, increases your chances of developing lung cancer ³⁴.

When you inhale asbestos, the tiny fibers enter your air passages. Your body’s natural defenses remove most of these particles. The majority will be carried away or coughed up in a layer of mucus that protects your lungs. However, some fibers may bypass those defenses and lodge deep within your lungs. Those fibers can remain in place for a very long time and may never be removed. Most of the harmful impacts of asbestos will not be seen immediately. They often develop years after exposure occurs ³².

Exposure to high concentrations of airborne asbestos over long periods can create non-cancerous problems in the lungs and chest. Such exposure also can scar tissue in the lungs, in a condition called asbestosis ³⁴. The scar tissue does not behave like normal, healthy lung tissue and makes breathing difficult. Asbestosis is a very serious and life-threatening disease. Fortunately, most people who are only exposed to moderate levels of asbestos are not likely to develop these more serious diseases ³².

What are the sources of asbestos?

Deteriorating, damaged or disturbed products—such as insulation, fireproofing, acoustical materials and floor tiles—may be sources of airborne asbestos indoors.1 When asbestos-containing materials are disturbed, tiny fibers break off and are suspended in the air. These fibers may remain airborne for long periods of time before settling in dust.

People working with or around asbestos (miners, asbestos abatement workers, custodial and maintenance workers, and insulation workers) face greater risk of exposure. If proper safety precautions—masks and coverings—are not used, workers may carry asbestos fibers to their homes and families ³⁴.

How can you protect yourself from asbestos?

If you know or suspect there is asbestos in your home or workplace, leave the material alone if possible. Exposure to asbestos-containing materials is minimal as long as they are in good condition and not disturbed. Fibers are unlikely to become airborne unless materials are cut, ripped or sanded. If you need to remodel, remove or clean up asbestos, be sure to hire trained professionals ³².

If a material is damaged and you suspect it may contain asbestos, limit access to the area. Do not try to take samples yourself to see if it is asbestos. That sampling can do more damage than leaving the material alone. Consult a trained professional. Sealing or covering the exposed material often can be a better option than removal ³².

10 Tips to Protect Yourself from Unhealthy Air

The American Lung Association encourages everyone to get involved in the fight for cleaner, healthier air. Here are some simple, effective tips for protecting you and your family from the dangers of air pollution:

1. Check daily air pollution forecasts in your area. Other sources include local radio and TV weather reports, newspapers and online at airnow.gov.
2. Avoid exercising outdoors when pollution levels are high. When the air is bad, walk indoors in a shopping mall or gym or use an exercise machine. Limit the amount of time your child spends playing outdoors if the air quality is unhealthy.
3. Always avoid exercising near high-traffic areas. Even when air quality forecasts are green, the vehicles on busy highways can create high pollution levels up to one-third mile away.
4. Use less energy in your home. Generating electricity and other sources of energy creates air pollution. By reducing energy use, you can help improve air quality, curb greenhouse gas emissions, encourage energy independence and save money! Check out the U.S. Environmental Protection Agency’s easy tips for conserving energy at home.
5. Encourage your child’s school to reduce exposure to school bus emissions. To keep exhaust levels down, schools should not allow school buses to idle outside of their buildings. Many school systems are using the U.S. EPA’s Clean School Bus Campaign to clean up these dirty emissions.
6. Walk, bike or carpool. Combine trips. Use buses, subways, light rail systems, commuter trains or other alternatives to driving your car.
7. Don’t burn wood or trash. Burning firewood and trash are among the major sources of particle pollution (soot) in many parts of the country.
8. Use hand-powered or electric lawn care equipment rather than gasoline-powered. Old two-stroke engines like lawnmowers and leaf or snow blowers often have no pollution control devices. They can pollute the air even more than cars, though engines sold since 2011 are cleaner.
9. Don’t allow anyone to smoke indoors and support measures to make all public places tobacco-free.
10. Get involved. Start by checking out Fighting for Air which has more information about what you can do.

Bottom line: Help yourself and everyone else breathe easier. Support national, state and local efforts to clean up sources of pollution. Your life and the life of someone you love may depend on it.

How to reduce air pollution

There are actions every you can take to reduce air pollution and keep the air cleaner, and precautionary measures you can take to protect your health.

These guides will help you determine ways to protect your family’s health when ozone or particle pollution levels reach the unhealthy range, and ways you can help reduce air pollution.

Transportation Tips

• Choose a cleaner commute — car pool, use public transportation, bike or walk when possible.
• Combine errands to reduce “cold starts” of your car and avoid extended idling.
• Be sure your tires are properly inflated.
• Keep car, boat and other engines properly tuned, and avoid engines that smoke.
• Follow gasoline refueling instructions for efficient vapor recovery. Be careful not to spill fuel and always tighten your gas cap securely.

Household Tips

• Use environmentally safe paints and cleaning products whenever possible.
• Some products that you use at your home or office are made with smog-forming chemicals that can evaporate into the air when you use them. Follow manufacturers’ recommendations for use and properly seal cleaners, paints, and other chemicals to prevent evaporation into the air.
• Conserve electricity. Consider setting your thermostat a little higher in the summer and lower in winter. Participate in local energy conservation programs.
• Look for the ENERGY STAR label when buying home or office equipment.
• Consider using gas logs instead of wood. If you use a wood-burning stove or fireplace insert, make sure it meets EPA design specifications. Burn only dry, seasoned wood.

Days when ozone is expected to be high:

• Conserve electricity and set your air conditioner at a higher temperature.
• Choose a cleaner commute—share a ride to work or use public transportation. Bicycle or walk to errands when possible.
• Refuel cars and trucks after dusk.
• Combine errands and reduce trips.
• Limit engine idling.
• Use household, workshop,and garden chemicals in ways that keep evaporation to a minimum, or try to delay using them when poor air quality is forecast.
• Pesticides

Days when particle pollution is expected to be high:

• Reduce or eliminate fireplace and wood stove use.
• Avoid using gas-powered lawn and garden equipment.
• Avoid burning leaves, trash and other materials.

Lawn/Garden Tips

• Mulch or compost leaves and yard waste.

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