How Microbes Spoil Indoor Air Quality: Hidden Reasons and Threats

Unseen Indoor Air Quality

When we think of microbes, information about microbes residing in indoor environments where we spend more than 90% of our time is more important in today’s world. Indoor air quality can be 2 to 5 times more worse than outdoor levels, including not only chemical contaminants but also biological ones like bacteria, viruses, fungi, insects, mites, pollen, and pet dander leading to Indoor Air Pollution (IAP). These biological contaminants, or bioaerosols, contributing to an estimated 3.2 million deaths annually and leading to various health conditions such as Sick Building Syndrome (SBS), Building-Related Illnesses (BRIs), and Multiple Chemical Sensitivities.

Understanding the composition of the indoor microbiome and its effect on human health can help us create healthier living and work spaces. The indoor air quality can be influenced by factors such as building materials, humidity levels, temperature, ventilation, and human activities.

Sources of Microbial Contaminants in Indoor Air

The key sources include:

1. Humans: Human occupants significantly influence indoor microbial numbers and diversity through activities like talking, coughing, sneezing, cooking, and cleaning. Humans shed billions of skin cells daily, contributing to microbial concentrations in the air. Human movement from outside to inside can also increase dust and fungal levels.
2. Pets: Pets contribute to indoor microbial diversity through their skin, saliva, hair, fecal matter, and fleas. Households with pets like dogs and cats have been shown to have higher bacterial diversity and community richness.
3. Dust: House dust, comprising hair, fibers, bacteria, molds, and other particles, can resuspend into indoor air, increasing inhalation risks. Dust samples often contain skin-associated Gram-positive bacteria, and their microbial composition can be influenced by abiotic factors in the indoor environment.
4. Building Characteristics: Building design, maintenance, moisture buildup, and ventilation impact microbial buildup. Plumbing systems, toilet flushing, water-damaged areas, and HVAC (Heating, ventilating, and air conditioning) systems can all contribute to increased microbial counts. Inadequate ventilation and HVAC maintenance can exacerbate microbial proliferation.
5. Indoor Plants: While indoor plants can enhance air quality, they can also increase humidity and mold growth, contributing to higher levels of airborne fungi.

 

Wall Dampness

Pet Dander spoils air quality

Common Indoor Microbes and associated health risks

Bacteria:

1. Staphylococcus aureus: Commonly found on human skin and in the respiratory tract, this bacterium can cause skin infections, pneumonia, and food poisoning. Hospitals, in particular, are hotspots for opportunistic pathogens like MRSA (methicillin-resistant Staphylococcus aureus) and Clostridium difficile, which can cause severe healthcare-associated infections.
2. Pseudomonas aeruginosa: Found in moist environments like sinks and showers, it can lead to infections, especially in people with weakened immune systems.
3. Acinetobacter spp.: Frequently present in hospitals, these bacteria can cause severe infections such as pneumonia and bloodstream infections.

  

Fungi:

1. Aspergillus: A mold commonly found in indoor air and dust, it can cause respiratory issues, allergic reactions, and infections, particularly in immunocompromised individuals. Certain mycotoxins, like aflatoxin from Aspergillus flavus, are linked to cancer, particularly liver cancer. Stachybotrys chartarum, commonly known as black mold, is notorious for producing potent mycotoxins.
2. Penicillium: Another common mold found in damp or water-damaged buildings, it can cause allergic reactions and respiratory problems.
3. Candida: A yeast that resides on the skin and mucous membranes, it can lead to infections like thrush and candidiasis, especially in individuals with compromised immunity.

Spores of fungus can cause Mucous membrane irritation, allergic rhinitis, asthma, bronchitis, COPD or allergic alveolitis.

 

Mold and spores in ventilation

Mold in damp buildings, cause allergic reactions

Viruses:

1. Rhinovirus: The primary cause of the common cold, it spreads easily in indoor environments through respiratory droplets.
2. Influenza virus: Responsible for the flu, it can cause severe respiratory illness and spreads via airborne droplets and contaminated surfaces.
3. Norovirus: Known for causing gastroenteritis, it spreads through contaminated food, water, and surfaces, leading to outbreaks in places like schools and cruise ships.

Vulnerable populations, such as neonates, children, older adults, and individuals with comorbid conditions, are at higher risk of adverse health effects from indoor air pollution.

 

Factors Influencing Indoor Microbial Communities

Several factors influence the composition and behavior of indoor microbial communities:

1. Humidity and Moisture: High humidity and moisture levels promote the growth of mold and bacteria. Water-damaged buildings are particularly susceptible to microbial growth, which can lead to a proliferation of harmful microbes and allergens.
2. Ventilation: Poor ventilation can lead to the accumulation of indoor pollutants and microbes. Proper ventilation helps reduce the concentration of airborne microbes and improve indoor air quality.
3. Human Activity: Human occupants are major contributors to the indoor microbiome. Activities such as cooking, cleaning, and personal hygiene practices can introduce and disperse microbes throughout indoor spaces.
4. Building Materials: The choice of building materials can influence microbial growth. Materials like wood, carpet, and drywall can harbour moisture and provide substrates for microbial growth, whereas antimicrobial surfaces can inhibit microbial colonization.

Strategies for Managing Indoor Microbes

To minimize the negative impacts of indoor microbes and promote a healthy indoor environment, consider the following strategies:

1. Maintain Optimal Humidity Levels: Keep indoor humidity levels between 30% and 50% to prevent mold growth. Use dehumidifiers in damp areas and ensure proper ventilation in high-moisture areas like bathrooms and kitchens.
2. Enhance Ventilation: Improve airflow by using exhaust fans, opening windows, and maintaining HVAC systems. Consider using air purifiers with HEPA filters to reduce airborne microbes and allergens.
3. Regular Cleaning: Clean and disinfect surfaces regularly, especially high-touch areas like doorknobs, light switches, and countertops. Use cleaning products that are effective against a broad spectrum of microbes.
4. Use Antimicrobial Materials: Incorporate antimicrobial materials and coatings in building design and furnishings to inhibit microbial growth. However, be cautious of overuse, as this can contribute to the development of antimicrobial resistance.
5. Promote Beneficial Microbes: Encourage a healthy indoor microbiome by incorporating plants, which can host beneficial microbes and improve air quality. Avoid overly sterile environments, which can reduce microbial diversity and weaken immune defense.

Conclusion

Understanding the various indoor microbes and their impact on human health is crucial for creating healthier indoor environments. By recognizing the beneficial and harmful roles of these microorganisms, we can adopt strategies to manage indoor microbial communities effectively. This balance can lead to improved respiratory health, reduced infections, and a healthier immune system, ultimately enhancing our overall well-being. As research in this field continues to evolve, we can expect to uncover more ways to harness the power of microbes for healthier living spaces.