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Indoor Air

Indoor Air

The quality of the air we breathe affects our health. Polluted air can worsen allergies and asthma and can contribute to infections like bronchitis. Long-term exposure to certain pollutants can increase the risk of heart disease, chronic obstructive pulmonary disease (COPD), and, in serious cases, early death.

Factors such as how much of a pollutant a person contacts (the dose), how long they are in contact with it (the duration) and a person’s sensitivity (e.g. overall health, genetics, age) help determine whether contact with any pollutant could affect health.

Many people encounter only low doses of pollutants in daily life, which are not expected to cause health problems. Higher doses or repeated exposures can increase health risks.

Although outdoor air pollution often receives the most attention, indoor air quality is important to consider. Indoor air can sometimes be more polluted than outdoor air because pollutants may build up in enclosed spaces. Things like mold, fuel burning appliances, building materials and furniture or wood products that release volatile organic compounds (VOCs) can reduce indoor air quality.

Indoor air can also be affected directly by outdoor air quality, especially when polluted outdoor air enters the home through open windows and doors. Knowing potential sources of air pollution inside your home — and knowing current outdoor air quality — can help you make decisions about when to let outdoor air inside.

Dust visible in the air, lit by an open window

Stay informed about outdoor air quality in Michigan at Michigan.gov/MiAir.

A residential street on a hazy day, with a climate change icon in the corner of the image

Climate Change and Indoor Air

A warming climate may worsen air quality both inside and outside our homes.

One way this may impact Michigan is that there may be a longer and more active wildfire season that increases the risk of being exposed to harmful particulate matter from wildfire smoke.

Using air filters can often help improve indoor air quality. Using carbon monoxide detectors, smoke alarms, and radon detectors can alert you to some of the most dangerous indoor air hazards.

If you want to learn more about chemicals that might be in indoor air, the resources below can help. Many of these resources also include steps you can take to lower your exposure to these possible hazards.

Not all chemicals that may be found in a home are listed here. If you are interested in understanding health effects associated with a chemical that is not listed here, call your healthcare provider or our Environmental Health Hotline at 800-648-6942, Monday through Friday between 8 a.m. and 5 p.m. If you believe you are in immediate danger, call 911 or contact Poison Control at 800-222-1222.

Common acronyms on these pages include:

  • ATSDR – Agency for Toxic Substances and Disease Registry.
  • CDC – Centers for Disease Control and Prevention.
  • EGLE – Michigan Department of Environment, Great Lakes, and Energy.
  • EPA – United States Environmental Protection Agency.
  • FDA – Food and Drug Administration.
  • LEO – Michigan Department of Labor and Economic Opportunity.
  • MDHHS – Michigan Department of Health and Human Services.

Indoor Air: Potential Hazards

  • Asbestos

    How it may enter indoor air: Asbestos is the name for a group of six naturally occurring minerals. When materials that contain asbestos are damaged or disturbed, tiny asbestos fibers can be released into the air. These fibers are too small to see without special equipment. Breathing in asbestos fibers is a health risk.

    To learn more, review the resources below.

  • Combustion Gases

    How they may enter indoor air: Fuel‑burning appliances—such as some furnaces, stoves, water heaters and fireplaces—can release combustion gases (like carbon monoxide and nitrogen dioxide) into indoor air.

    Learn about combustion gases at EPA’s website, Sources of Combustion Products, and at the links below:

    • Carbon monoxide (CO) is a gas that forms whenever carbon-based fuel is burned, including natural gas, kerosene, gasoline, propane, charcoal, oil and wood. You cannot see, taste or smell CO but it can be deadly when you breathe it in. Your furnace, stove, water heater, fireplace or generator could give off CO into your home if they are not working right or if they are not properly maintained.
    • Learn more at MDHHS’s webpage, Carbon Monoxide.
    • You can find data about CO Poisoning in Michigan on MiTracking’s webpage, Carbon Monoxide Poisoning.
    • Nitrogen Dioxide (NO2) is a harsh-smelling gas that is also formed when fuels are burned. Homes that use gas-burning appliances are more likely to have NO2 levels that are higher than the outdoor air. Learn more at EPA’s webpage, Nitrogen Dioxide’s Impact on Indoor Air Quality.

  • Formaldehyde

    How it may enter indoor air: Some building materials, consumer products treated with formaldehyde resins, household products or fuel-burning appliances may release formaldehyde into the air. At room temperature, formaldehyde is a colorless, flammable gas that has a distinct, pungent smell.

    Learn more from the ATSDR factsheet, Formaldehyde ToxFAQs, or EPA’s webpage, What Should I Know About Formaldehyde and Indoor Air Quality?

  • Metals

    How they may enter indoor air: Metals are not expected to be at high levels in indoor air. If metals are found in indoor air, there is often a specific source – like from nearby industrial activities (e.g., nearby industrial smokestack) or from an indoor event (e.g., broken mercury thermometer) or other activity (e.g. burning materials or smoking).

    If you have a mercury spill in your home follow the instructions on the webpage, Mercury Spills in Homes right away.

    Below are brief descriptions of how each of these metals may enter the home along with links to resources that explain how these metals can be released into the air and ways you can limit your exposure to them.

    • Aluminum – This metal is common in soil and the environment and small amounts can settle in household dust. It may be present in the environment, including outdoor air, at higher levels near certain industrial activities. To learn more about aluminum, review these Frequently Asked Questions About Aluminum (Spanish, Arabic).
    • Cadmium - Smoking and vaping can release cadmium into indoor air, and people are exposed to it by breathing in smoke or vape aerosols. Other, less common, sources of cadmium in indoor air include burning products that contain cadmium. To learn more about cadmium, review these Frequently Asked Questions About Cadmium (Spanish, Arabic).
    • Chromium - Several different types of chromium are present in the environment. Combustion processes and metal industries can be sources of chromium released into the outdoor air, which can impact indoor air if it is released near homes. Smoking and vaping can also release chromium into the air and people are exposed to it by breathing in smoke or vape aerosols. To learn more, review these Frequently Asked Questions About Chromium (Spanish, Arabic).
    • Cobalt – This naturally occurring metal can be found in rocks and soil and small amounts may settle in household dust. Smoking and vaping can also release cobalt into the air and people are exposed to it by breathing in smoke or vape aerosols. To learn more, review these Frequently Asked Questions About Cobalt (Spanish, Arabic).
    • Lead – Lead occurs naturally in the environmental but is often found at high levels due to human activity. There is no safe level of lead, and this is true for lead in air. Breathing in lead-containing dust is harmful, especially for pregnant women, children and fetuses. Lead can be found in home dust or indoor air when:
      • Lead-based paint is scraped, dry sanded, heated or burned.
      • Windows and doors that have been painted with lead-based paint rub against their trim.
      • Lead-contaminated soil is brought indoors.
      • Lead from a job or hobby is brought home on clothes, shoes or hands.
      Learn more about lead in dust and paint chips at the MDHHS webpage on lead paint and dust. Industrial processes and non-jet aircraft can release lead into the air (lead from non-jet aircraft is being phased out). Learn more about lead air pollution at the EPA’s webpage, Lead (Pb) Air Pollution.
      To learn more, review these Frequently Asked Questions About Lead (Spanish, Arabic).
    • Manganese - Smoking and vaping can release manganese into the air and people are exposed to it by breathing in smoke and vape aerosols. Mining operations and automobile exhaust also contribute to the amount of manganese in the outdoor air, which may impact indoor air. To learn more, review these Frequently Asked Questions About Manganese (Spanish, Arabic).
    • Mercury - Elemental Mercury (or “quicksilver”) is toxic to humans and animals. Around the home, older thermometers, fluorescent light bulbs, some thermostats, antique barometers, clock pendulums and other items may contain elemental mercury. If these items break, mercury can spill out. Spilled mercury can give off an odorless and invisible vapor that people may breathe in. This vapor can be harmful to everyone but is especially a threat to children and fetuses. To learn more, visit the MDHHS webpage about mercury.
      • If you have a mercury spill in your home, follow the instructions on this page right away: Mercury Spills in Homes.
      • Exposure to another form of mercury called methylmercury is also a health concern. However, methylmercury is usually found in food and water sources, not in the air. (see the home hazards page on food for more information).
    • Thallium - Thallium is a naturally occurring element found in rocks, soil and plants and it is possible for it to settle in household dust. Industrial activities such as metal smelting, coal burning and making certain types of electronics add thallium to the environment where it can make its way indoors. Smoking and vaping can also release thallium into the air and people are exposed to it by breathing in smoke and vape aerosols. To learn more, review these Frequently Asked Questions About Thallium (Spanish, Arabic).

  • Mold

    How it may enter indoor air: Mold is a living organism that grows from tiny spores found almost everywhere. When these spores land on something damp, mold can quickly grow and may become visible or smelly. For some people, mold exposure can cause irritation in the throat, nose and lungs. For those with conditions like asthma or other breathing problems, mold can make existing symptoms much worse.

    To learn more, visit the MDHHS webpage, All About Mold, or review the following resources:

    An increase in heavy rainfall events increases the risk of flooding. Mold can quickly develop in flooded homes. To learn how to clean up after a flood, review Staying Safe After a Flood.

  • Particulate Matter

    How it may enter indoor air: Particulate matter (PM) is a mix of solid and liquid particles that are suspended in air, they can easily flow inside from outdoor air through open windows, doors or ventilation systems. When these tiny particles are inhaled, they can damage lungs and trigger breathing problems. PM comes from a wide variety of sources, including, but not limited to:

    • Burning fuel or organic matter (like food or wood).
    • Cooking.
    • Candles and incense.
    • Combustion fuels.
    • Dust.
    • All smoke including cigarettes, campfires, indoor fireplaces and wildfires.

    Learn more at the EPA’s webpage, Sources of Indoor Particulate Matter. The MDHHS MiTracking Data Portal has data on PM2.5 that is specific to Michigan, including the annual PM2.5 level and number of days above the regulatory standard.  

    You can protect your health by using indoor air filters, especially on days when there is an air quality alert due to ozone or wildfire smoke. Learn more at the MDHHS's webpage, Your Health and Wildfire Smoke.

  • Radon

    How it may enter indoor air: Radon is a common and naturally occurring gas that has no odor, is invisible and is radioactive. It can enter your home through cracks in the foundation, floor or walls. Radon is the first leading cause of lung cancer for non-smokers and the second leading cause of lung cancer in the United States.

    Testing for radon is the only way to know if you are exposed to it. Radon can be easily tested in indoor air with continuous home radon monitors. MDHHS recommends everyone test their home for radon and take steps to reduce elevated radon levels. If you have high levels of radon in your home, a contractor can use several methods to lower radon levels. To learn more about radon and how to find out if radon levels in your home are too high, visit EGLE’s webpage, Michigan Indoor Radon Program.

  • VOCs: Volatile Organic Compounds

    How they may enter indoor air: VOCs are a large group of chemicals that easily evaporate into the air. VOCs may enter indoor air from many sources including:

    • Consumer products you bring into your home. The EPA’s webpage, VOCs Impact on Indoor Air Quality, provides additional information so you can make informed decisions about the products you bring into your home.
    • Drinking water. If VOCs are in your drinking water, they may also be released into the air during everyday water use like:
      • Showering or bathing.
      • Running faucets.
      • Washing dishes or laundry.
      • Learn more about VOCs in drinking water at the MDHHS webpage on drinking water contamination.
    • Vapor intrusion is when a VOC has been spilled, spreads through the ground and rises through cracks in a home’s foundation. Learn more about vapor intrusion in this short video called What is Vapor Intrusion? and on the EGLE webpage, Vapor Intrusion.

     Learn more about common VOCs from the following chemical-specific factsheets:

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