What are the most common indoor air pollutants?

According to the EPA, there are 13 common indoor air pollutant sources. They fall into one of four categories: VOCs, biological pollutants, combustion byproducts, and legacy pollutants. These pollutants can affect the health and comfort of building occupants. Some health effects may show up shortly after a single exposure, or years later after prolonged exposure.

The most common indoor air pollutants include:

  1. Asbestos
  2. Biological Pollutants
  3. Carbon Monoxide
  4. Cookstoves and Heaters
  5. Formaldehyde
  6. Lead (Pb)
  7. Nitrogen Dioxide (NO2)
  8. Pesticides
  9. Radon (Rn)
  10. Indoor Particulate Matter
  11. Secondhand Smoke/Environmental Tobacco Smoke
  12. Volatile Organic Compounds (VOCs)
  13. Wood Smoke

1. Asbestos

Asbestos is a mineral fiber. It occurs naturally in rock and soil. Because of its strength and heat resistance, it has been utilized in a variety of construction materials, including insulation, roofing shingles, and as a fire retardant. It has also been used in friction products on cars. Asbestos exposure can increase one’s risk of developing lung disease, mesothelioma, or asbestosis. As a result of these health effects, there are existing bans on the import, manufacture, and distribution of asbestos-related materials.

2. Biological Pollutants

Biological pollutants are contaminants produced by living things. As a result, they are often found in areas with excessive food or moisture. Biological pollutants can include bacteria, viruses, pet dander/saliva, dust, mites, and pollen. In buildings, these pollutants are commonly found near excessive moisture, like in humidifiers or an unvented bathroom, as excessive moisture can be a breeding ground for mold, mildew, and bacteria.

3. Carbon Monoxide

Carbon monoxide (CO) is an odorless gas that is released when fossil fuels are burned. The greatest outdoor contributors of CO are vehicles, while kerosene lamps and gas heaters are the leading sources of CO indoors.

Carbon monoxide can be extremely harmful to humans when inhaled in large amounts, as it affects the oxygen-carrying capacity of the blood. This means it reduces the amount of oxygen that the body can transport in the bloodstream to critical organs. Carbon monoxide poisoning can cause dizziness, unconsciousness, and even death. CO is a threat mostly to tightly enclosed indoor environments with poor ventilation, as high levels of CO are unlikely to occur outdoors.

4. Cookstoves and Heaters

Burning solid fuels such as wood or charcoal to cook or heat a building can contribute to poor indoor air quality. While not necessarily common in the US, these cooking/heating methods are still used by billions of households worldwide. The smoke and fumes produced by these cooking and heating methods combined with poor ventilation can lead to substantial health and lung issues.

5. Formaldehyde

Formaldehyde is present in many building materials and household products. It is commonly used in resins on wood products, insulation materials, glues, paints, cosmetic preservatives, and pesticides. It is a chemical compound that is also a combustion byproduct, which means it can be emitted from fuel-burning appliances. Long term and high exposure to formaldehyde could cause cancer. Shorter-term exposure is known to cause skin, eye, nose, and throat irritation.

6. Lead (Pb)

Lead emissions find their way into the air from a variety of sources. The most common source is from metal processing and the burning of leaded fuel. Once inhaled, lead can accumulate throughout the body, causing many adverse effects. In adults, high levels of lead can cause health issues with the nervous, cardiovascular, and reproductive systems. For children, it can lead to learning or behavioral issues.

7.  Nitrogen Dioxide (NO2)

Nitrogen Dioxide (NO2) is part of the highly reactive family of nitrogen oxide gases. It is emitted from burning fuel, often from cars, trucks, and power plants. When combined in high levels with water in the atmosphere, it can form acid rain.

NO2 can be extremely harmful to those with preexisting respiratory diseases, particularly asthma, as it can cause coughing, wheezing, and difficulty breathing. Exposure over time can lead to an increased susceptibility to respiratory infections.

8. Pesticides

Pesticides are used to control insects, pests, microbes, termites, and rodents. As a result, they are inherently toxic. Pesticides are common household products such as insecticides and disinfectants. Exposure to pesticides can have a variety of short-term and long-term effects, including skin, eye, nose, and throat irritation, increased risk of cancer, and damage to the central nervous system.

9. Radon (Rn)

Radon is a naturally occurring radioactive gas. It has no taste, color, or smell, making it very difficult to detect without specific radon testing. Because it occurs naturally in trace amounts, it is generally not a major health issue outdoors. However, most radon exposure occurs indoors as radon gas becomes trapped inside after entering through cracks and holes in a building’s envelope.

Long-term radon exposure can increase one’s risk of developing lung cancer. Radon is the second leading cause of lung cancer in the US. Testing can identify levels of radon indoors. If levels are high, they can usually be corrected by improving ventilation or increasing the rate of air change throughout the building.

10. Indoor Particulate Matter

Particulate matter, or particle pollution, is the mixture of solid particles in the air. While some particulate matter is large enough to be seen by the human eye (dust, dirt, sand, and smoke) other particles are so small, they can only be seen with the aid of a microscope. Particulate matter can be emitted directly from a source, such as a construction site or beach, but oftentimes is the result of a complex chemical reaction from pollutants emitted from burning fuels.

Prolonged exposure to particulate matter can lead to a variety of health issues, including heart attacks, irregular heartbeats, aggravated asthma, and increased respiratory symptoms. Those with preexisting respiratory diseases, such as asthma, are at a greater risk for experiencing adverse effects from particulate matter. To determine the level of exposure to this pollutant, the Air Quality Index (AQI) is a good indicator of pollution levels in the air.

11. Secondhand Smoke/Environmental Tobacco Smoke

Secondhand smoke, also known as environmental tobacco smoke (ETS) is a mixture of the smoke released by the burning of tobacco products, such as cigarettes and cigars. Exposure to secondhand smoke is often referred to as passive smoking. It is classified by the EPA as a Group A carcinogen and contains more than 7,000 substances. Secondhand smoke can cause heart disease, stroke, lung cancer, asthma attacks, and other lung conditions.

12. Volatile Organic Compounds (VOCs)

Volatile organic compounds (VOCs) are gases emitted from certain solids or liquids. They can be a result of many common household products including paints, wood preservatives, aerosol sprays, cleansers and disinfectants, moth repellants, air fresheners, stored fuels, dry-cleaned clothing, and pesticides. VOCs include a variety of chemicals that can have short term and long term effects. Health effects may include eye, nose, and throat irritation, headaches, and damage to the liver, kidney, and central nervous system.

13. Wood Smoke

Smoke is a complex mixture of gases and fine microscopic particles (particulate matter) produced when wood and other organic matter burn. The biggest health threat from wood smoke comes from the particulate matter in the smoke, discussed above. Many still use wood stoves for warmth and cooking. While they provide the necessary benefits of food and warmth, they can release harmful smoke if not ventilated properly. Changing out old wood stoves with newer, cleaner technology can help reduce health risks from wood smoke.

Button that links to an article with actionable steps for improving indoor air quality