What are common sources of indoor air pollution?

Indoor air pollution comes from a variety of sources, both inside and outside your home. Many common household items and activities release gases and particles that can accumulate in poorly ventilated spaces leading to health issues.

Here are some of the most common sources of indoor air pollution:

1. Combustion Sources:

• Tobacco Smoke (Secondhand Smoke): Contains thousands of chemicals, many of which are toxic and carcinogenic. One of the most dangerous indoor air pollutants.
• Fuel-Burning Appliances:
  • Gas Stoves, Ovens, Furnaces, Water Heaters, Fireplaces: These can release carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter, and other combustion byproducts if not properly vented or maintained. CO is especially dangerous as it’s odorless and colorless.
  • Wood Stoves and Fireplaces: Produce smoke, particulate matter, and other pollutants.
  • Kerosene and Gas Space Heaters: Can also release harmful gases and particles if unvented or improperly used.
  • Candles and Incense: Can release particulate matter and various chemicals when burned.

2. Building Materials & Furnishings:

• Volatile Organic Compounds (VOCs): Found in many products and materials, they “off-gas” into the air. Sources include:
  • Paints, Varnishes, Solvents: Especially strong-smelling ones.
  • Adhesives, Caulks, Sealants: Used in construction and DIY projects.
  • New Flooring: Carpets, vinyl, laminates.
  • Pressed Wood Products: Particleboard, plywood, medium-density fiberboard (MDF) often used in furniture, cabinetry, and subflooring. These can release formaldehyde, a known carcinogen.
  • Upholstery and Fabrics: Can off-gas chemicals.
• Asbestos: Formerly used in insulation, roofing, flooring, and other building materials (common in homes built before the 1980s). When disturbed or deteriorated, it releases microscopic fibers that can cause serious lung diseases.
• Lead: Found in old lead-based paint (especially pre-1978 homes). When paint chips or deteriorates, lead dust can become airborne.
• Deteriorating Materials: Any old, degrading building materials can release dust and particles.

3. Biological Contaminants:

• Mold and Mildew: Thrive in damp, humid environments (bathrooms, basements, leaky areas). They release spores into the air, causing allergic reactions, respiratory problems, and other health issues.
• Dust Mites: Microscopic organisms that live in dust, especially in bedding, carpets, and upholstered furniture. Their waste products are common allergens.
• Pet Dander: Tiny flecks of skin shed by pets with fur or feathers. A common allergen.
• Pollen: Enters from outdoors, especially through open windows or on clothing.
• Bacteria and Viruses: Can be airborne, especially in poorly ventilated spaces or when people are sick.
• Pests: Cockroaches, rodents, and their droppings can contribute allergens and irritants.

4. Household Products & Activities:

• Cleaning Supplies: Many conventional cleaners contain VOCs, ammonia, bleach, and other harsh chemicals that can irritate eyes, skin, and respiratory systems.
• Pesticides: Used for pest control, they can remain in the air and on surfaces long after application.
• Personal Care Products: Hairsprays, perfumes, deodorants, air fresheners often contain VOCs and other chemicals.
• Hobbies: Craft supplies, glues, solvents, paints, and other materials used in hobbies can release various pollutants.
• Cooking: Beyond fuel combustion, cooking itself (especially frying or high-heat cooking) can release particulate matter, grease vapors, and other compounds.

5. Outdoor Sources that Infiltrate Indoors:

• Radon: A naturally occurring radioactive gas that comes from the breakdown of uranium in soil and rocks. It can seep into homes through cracks in foundations, floors, and walls. It’s odorless and colorless but is a leading cause of lung cancer.
• Outdoor Air Pollution: Vehicle exhaust, industrial emissions, pollen, and other outdoor pollutants can enter homes through open windows, doors, cracks, and ventilation systems.
• Pesticides from outside the home: Can be tracked in on shoes or clothing.

6. HVAC Systems:

• Dirty Air Filters: Clogged filters can’t effectively trap particles, allowing them to recirculate.
• Ductwork: Uncleaned or leaky ducts can harbor dust, mold, and other contaminants, and distribute them throughout the home.
• Humidifiers: If not properly cleaned and maintained, humidifiers can become breeding grounds for mold and bacteria, releasing them into the air.
• Ozone Generators/Some Air Purifiers: Certain types of air purifiers (especially older ionizers or ozone generators) can intentionally or unintentionally produce ozone, which is a lung irritant.

7. Inadequate Ventilation:

• A major contributing factor to all indoor air pollution. Modern, energy-efficient homes are often built very tightly sealed, which can trap pollutants indoors if there isn’t sufficient mechanical ventilation or regular air exchange (e.g., opening windows).

Understanding these common sources can help you identify potential problems in your own home and take steps to improve your indoor air quality.