Indoor Air Quality, What You’re Really Breathing at Home

Our homes are often assumed to be sanctuaries of safety, a refuge from outdoor pollution and environmental stressors. However, scientific research shows that indoor air can contain a complex mixture of pollutants, sometimes at concentrations higher than those found outdoors¹.

Because most people spend the majority of their time indoors, indoor air quality plays a significant role in long term health and wellbeing².

Why Indoor Air Quality Matters

People in industrialised countries spend approximately 90% of their time indoors, making indoor air the primary source of daily exposure to airborne pollutants².

Indoor environments can contain:

• Fine particulate matter (PM2.5 and PM10)

• Volatile organic compounds (VOCs)

• Nitrogen dioxide (NO₂)

• Biological pollutants such as mold spores and allergens¹

Multiple studies associate prolonged exposure to these pollutants with respiratory symptoms, aggravated asthma, cardiovascular stress and reduced overall air quality related wellbeing³.

Common Indoor Air Pollutants and Their Sources

Particulate Matter

Fine particulate matter consists of microscopic particles that can penetrate deep into the lungs. Indoors, PM is generated by cooking, candles, smoking, fireplaces and infiltration from outdoor air⁴. Exposure to PM2.5 has been linked to respiratory inflammation and cardiovascular effects³.

Volatile Organic Compounds

VOCs are chemicals that easily evaporate at room temperature. Common indoor sources include: paints and varnishes, cleaning products, synthetic furnishings, adhesives and sealants and personal care products⁵

Formaldehyde, benzene and toluene are among the most frequently detected VOCs in residential environments. Short term exposure can cause irritation and headaches, while long term exposure may affect liver and kidney function⁵.

Nitrogen Dioxide

Gas stoves and unvented combustion appliances are a major indoor source of nitrogen dioxide. Elevated indoor NO₂ levels are associated with increased respiratory symptoms, especially in children⁶.

Biological Contaminants

Mold, dust mites, pet dander and pollen contribute to indoor air pollution. High humidity and inadequate ventilation increase biological contaminant growth, particularly in bedrooms and bathrooms⁷.

Indoor vs Outdoor Air Quality

Contrary to common belief, indoor pollutant concentrations can equal or exceed outdoor levels. Poor ventilation, combined with continuous indoor emission sources, allows pollutants to accumulate over time¹.

Several reviews confirm that indoor concentrations of VOCs and particulate matter often remain elevated even when outdoor air quality is relatively good³.

The Role of Ventilation

Ventilation is one of the most consistently effective strategies for improving indoor air quality. Increasing air exchange dilutes indoor pollutants and reduces overall exposure⁸.

Studies show that both natural ventilation and mechanical systems significantly lower concentrations of VOCs and particulate matter when properly used⁸.

Health Effects of Poor Indoor Air Quality

Scientific literature links poor indoor air quality to: respiratory irritation and asthma exacerbation³, increased allergy symptoms⁷, reduced lung function with chronic exposure³ and cardiovascular strain associated with fine particles⁴. 

The evidence is strongest for particulate matter and VOC exposure, especially in poorly ventilated indoor spaces.

Evidence Based Steps to Improve Indoor Air Quality

• Increase ventilation regularly, especially after cooking or cleaning

• Reduce emission sources such as fragranced products and solvent based cleaners

• Use HEPA filtration where ventilation is limited⁹

• Control humidity to prevent mold growth⁷

These strategies consistently appear in international indoor air quality guidelines.

Conclusion

Indoor air quality is a daily exposure issue, not an abstract environmental concern. Pollutants originating from household activities and materials shape the air we breathe for most of our lives¹².

Improving ventilation, reducing indoor emission sources and applying targeted filtration are evidence based steps that meaningfully reduce exposure. Clean air is one of the most fundamental elements of a healthy home.

Scientific References

1. World Health Organization. WHO Guidelines for Indoor Air Quality: Selected Pollutants https://www.who.int/publications/i/item/9789289002134

2. Klepeis NE et al. The National Human Activity Pattern Survey. Environmental Health Perspectives https://pubmed.ncbi.nlm.nih.gov/11477521/

3. Jones AP. Indoor air quality and health. Atmospheric Environment
   https://www.sciencedirect.com/science/article/pii/S135223100200072X

4. U.S. Environmental Protection Agency. Particulate Matter and Indoor Air Quality
   https://www.epa.gov/pm-pollution

5. U.S. Environmental Protection Agency. Volatile Organic Compounds’ Impact on Indoor Air Quality https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality

6. Lin W et al. Indoor nitrogen dioxide and respiratory symptoms. Environmental Health Perspectives https://pubmed.ncbi.nlm.nih.gov/22221928/

7. Institute of Medicine. Damp Indoor Spaces and Health  https://www.ncbi.nlm.nih.gov/books/NBK215643/

8. Wargocki P et al. Ventilation and health in non industrial indoor environments. Indoor Air https://pubmed.ncbi.nlm.nih.gov/12216467/

9. Fisk WJ et al. Benefits of particle filtration in buildings. Indoor Air https://pubmed.ncbi.nlm.nih.gov/23397961/