What are Antimicrobials?

Antimicrobials are chemicals added to a wide array of products with the goal of killing microbes and slowing the spread of infections. This includes paints and coatings, furniture, fabrics, ceiling tiles, flooring materials like carpet, fixtures and hardware. Sounds good, right? Well, unfortunately, these chemicals can often cause more harm than good. Like many of the other chemicals of concern that have been discussed in this series, many antimicrobials are toxic, persistent, “forever chemicals” that bioaccumulate in ecosystems and bodies. Overuse of these chemicals is having long-term consequences like disruption of soil and water nutrient cycles and the proliferation of antibiotic-resistant bacteria.

Antimicrobials target microorganisms including bacteria, viruses, protozoans and fungi to increase a building product’s life span, reduce stain and odor-causing microbes in finishes and prevent microbe accumulation on surfaces of products like bathroom fixtures, fabrics, furniture, etc. While there may sometimes be a hygiene benefit to antimicrobials, that is almost certainly not worth the resulting damage to human and ecosystem health

Different types of Antimicrobials

1. Halogenated Organic Compounds contain chlorine, fluorine, or bromine, which make them persistent and bio accumulative. Examples include Triclosan & Triclocarban found in treated plastics, coatings, and adhesives; and chlorinated phenols like Pentachlorophenol (PCP) used as a wood preservative.

2. Heavy Metal-Based Antimicrobials include copper-based compounds like copper naphthenate or copper azole, used in wood treatments, zinc-based like Pyrithione & Zinc Borate used in paints & coatings; and silver nanoparticles (AgNPs) found in antimicrobial coatings and textiles.

3. Formaldehyde-Releasing Biocides which gradually release formaldehyde, a known carcinogen, to kill microorganisms. Examples include DMDM Hydantoin, Imidazolidinyl Urea, & Bronopol used in adhesives, paints, and coatings.

4. Isothiazolinones like Methylisothiazolinone (MIT) & Methylchloroisothiazolinone (CMIT) are used as preservatives in coatings, paints, and adhesives.

5. Pesticidal Antimicrobials (Highly Toxic Fungicides & Insecticides), antimicrobials that also function as pesticides like Tributyltin (TBT) & Other Organotin Compounds used in antifungal coatings and plastics and Iodopropynyl Butylcarbamate (IPBC) found in wood treatments and paints.

Why are we concerned about Antimicrobials?

Human Health

Human health is impacted in the following ways by leaching, off-gassing, and burning of HFRs from different products.

1. Antibiotic Resistance: Some antimicrobial agents contribute to the development of antibiotic-resistant bacteria, making infections harder to treat. Overuse of antimicrobials in non-medical settings accelerates this issue.

2. Toxicity & Chemical Exposure: Certain antimicrobial chemicals, such as triclosan and triclocarban, can be toxic to humans and animals.

3. Long term effects: Long-term exposure may lead to skin irritation, hormone disruption, reproductive issues, immune system suppression, or even carcinogenic effects.

4. Respiratory Conditions: Volatile organic compounds (VOCs) released by antimicrobial coatings can contribute to poor indoor air quality. This can exacerbate respiratory conditions like asthma or cause headaches and dizziness.

5. False Sense of Security: Marketing claims about "antimicrobial protection" can create a false sense of security, leading people to rely on treated materials instead of effective hygiene practices

Social Health & Equity

Risk is increased risk for underserved populations due unequal access to safe alternatives, proximity to production and disposal facilities, and lack of education.

1. Disproportionate Exposure in Marginalized Communities: Antimicrobial-treated materials may be more commonly used in low-cost housing, public schools, and healthcare settings, increasing exposure to potentially harmful chemicals.

2. Indoor Air Quality & Health Disparities: Some antimicrobial building materials release volatile organic compounds (VOCs). Children, the elderly, and individuals with pre-existing health conditions are more vulnerable to these exposures.

3. Increased Healthcare Costs & Burden on Public Health Systems: Low-income populations face barriers to healthcare access, meaning they are less likely to receive timely treatment for health conditions related to antimicrobial exposure, which may be chronic.

Ecosystem Health

Risks to natural habitats, food, and water sources include:

1. Water Contamination & Aquatic Toxicity: Antimicrobials can leach into water systems through rainwater runoff, wastewater, or improper disposal. Many antimicrobial compounds, such as triclosan and silver nanoparticles, are not easily removed in wastewater treatment plants and can accumulate in rivers, lakes, and oceans.

2. Disruption of Beneficial Microbial Communities: Natural microbial ecosystems in soil and water are essential for nutrient cycling, decomposition, and ecosystem stability. Antimicrobial compounds can kill beneficial bacteria and fungi, leading to imbalances that may allow harmful microbes to thrive.

3. Bioaccumulation, Persistence & Toxicity in the Environment: Certain antimicrobial chemicals persist in the environment and accumulate in the tissues of plants and animals leading to hormonal disruption, reproductive issues, and immune system suppression and affecting biodiversity. Many antimicrobials, such as triclosan, triclocarban, and quaternary ammonium compounds (QACs), do not break down easily and can remain in the environment for years. Their persistence increases the likelihood of widespread ecological disruption over time.

Climate Health

Risks that accelerate or amplify the impacts of the Climate Crisis include:

1. Greenhouse Gas (GHG) Emissions from Production & Disposal: Manufacturing antimicrobial-treated materials (e.g., plastics, coatings, textiles) requires energy-intensive processes, often reliant on fossil fuels. Disposal of these materials in landfills or incinerators releases greenhouse gases and toxic byproducts, contributing to climate change.

2. Damage to Carbon Sinks: Pollutants like triclosan and silver nanoparticles are toxic to phytoplankton and algae, which are essential for absorbing CO₂ and producing oxygen. They also alter soil microbiomes, killing beneficial bacteria and fungi that store carbon in the soil. Degradation of healthy soils weakens their ability to capture and store CO₂. This contributes to desertification, reduced plant growth, and loss of biodiversity, all of which exacerbate climate instability.

3. Waste Management Challenges & Microplastic Pollution: Many antimicrobial-treated building materials (e.g., paints, sealants, flooring) contain synthetic chemicals that persist in waste streams. When these materials break down, they release microplastics and toxic residues. Microplastics have been found to alter oceanic carbon cycles, reducing the ocean’s ability to regulate climate.

Circular Economy

Many antimicrobial treatments contain persistent and toxic chemicals, making it difficult to safely recycle treated materials. Contaminated materials may require specialized recycling processes, increasing costs and carbon impact. Some antimicrobial coatings interfere with the bonding and processing of recycled content, reducing the quality and performance of new materials.

There are significant challenges in material recovery & reuse. Some antimicrobial additives degrade over time, leading to material deterioration, discoloration, or reduced mechanical strength. This makes materials less suitable for reuse in second-life applications. Antimicrobial additives are often not visibly distinguishable, making it difficult to sort and recover safe materials from demolition waste.

How can architects mitigate the impacts of antimicrobials in building materials?

Understand common applications in construction

1. Flooring & Surfaces

Vinyl & Laminate Flooring – Often treated with antimicrobial additives to prevent mold, mildew, and bacterial growth.

Countertops & Solid Surfaces – Materials like quartz, Corian, and laminate may contain antimicrobial agents to resist bacterial contamination.

2. Paints & Coatings

Antimicrobial Paints – Used in hospitals, schools, and commercial buildings to prevent mold, mildew, and bacterial growth.

Wall Coatings & Sealants – Applied in humid environments like bathrooms and kitchens to resist fungal growth.

3. HVAC Systems & Air Filters

Air Duct Coatings – Antimicrobial coatings help prevent mold and bacteria buildup inside HVAC ducts.

Air Filters & Purifiers – Some high-efficiency filters include antimicrobial treatments to reduce bacterial contamination.

4. Insulation Materials

Fiberglass & Foam Insulation – Some insulation products contain antimicrobial treatments to prevent mold growth in damp environments.

Acoustic Panels – Used in ceilings and walls to prevent microbial buildup in sound-absorbing materials.

5. Textiles & Wall Coverings

Carpets & Rugs – Some carpets are treated with antimicrobial agents to reduce mold and bacteria in high-moisture areas.

Wallpaper & Fabric Wall Coverings – Often infused with antimicrobial coatings to prevent microbial growth.

6. Bathroom & Plumbing Fixtures

Toilets, Sinks & Faucets – Some are coated with antimicrobial finishes to reduce bacterial buildup.

Shower Curtains & Mats – Frequently treated to resist mold and mildew in damp environments.

7. Wood & Composite Materials

Pressure-Treated Wood – Often contains antimicrobial agents to prevent rot and fungal growth.

Composite Decking & Siding – Some include antimicrobial additives to resist mold, algae, and mildew.

8. Adhesives & Sealants

Caulks & Grouts – Many antimicrobial versions are available to prevent mold in bathrooms, kitchens, and outdoor applications.

Construction Adhesives – Some contain antimicrobial additives to maintain material integrity in high-moisture environments.

9. Smart & High-Touch Surfaces

Door Handles, Railings & Touchscreens – Frequently treated with antimicrobial coatings in public spaces to reduce bacterial transfer.

Elevator Buttons & Keypads – Some incorporate silver-based antimicrobial technology to minimize pathogen spread.

Specify alternatives to Antimicrobials

1. Physical & Passive Antimicrobial Strategies: These solutions reduce microbial growth through material properties rather than chemical additives.

• Moisture Control & Proper Ventilation: Prevents mold and bacterial growth by reducing humidity. Includes vapor barriers, dehumidifiers, and proper HVAC design.
• Non-Porous & Easy-to-Clean Surfaces: Materials like stainless steel, glazed ceramic, and glass naturally resist microbial adhesion. Ideal for high-touch areas like countertops and wall panels.
• High-pH Materials (e.g., Lime-Based Plasters & Cement): Naturally antimicrobial due to their alkalinity. Used in walls and flooring for mold prevention.

2. Natural & Non-Toxic Antimicrobial Additives: Certain natural compounds offer antimicrobial properties without the health risks of synthetic biocides.

• Essential Oils (e.g., Tea Tree, Eucalyptus, Citrus, Thyme): Used in eco-friendly paints and coatings. Antifungal, antibacterial, and biodegradable.
• Chitosan (Derived from Shellfish Exoskeletons): Used in biopolymer coatings for antimicrobial effects. Safe and biodegradable.
• Tannin-Based Wood Treatments: Naturally occurring in some woods (e.g., oak, walnut). Acts as a natural preservative.
• Clay and Mineral-Based Paints/Plasters: Highly alkaline and moisture-regulating, preventing mold growth. Used as an alternative to synthetic antimicrobial paints.

3. Advanced Eco-Friendly Technologies: Innovative materials can provide antimicrobial properties without harmful chemicals.

• Photocatalytic Coatings (e.g., Titanium Dioxide - TiO₂): Breaks down microbes when exposed to light. Used in self-cleaning glass, tiles, and paints.
• Bio-Based Polymers & Resins: Made from plant-based sources that resist microbial colonization. Used in flooring, insulation, and composite materials.
• Copper and Brass Surfaces (Natural Antimicrobial Metals): Naturally kills bacteria and viruses. Used in door handles, railings, and countertops.
• Hydrophobic & Superhydrophobic Coatings: Repel water and prevent microbial adhesion. Used in concrete, textiles, and painted surfaces.

4. Alternative Construction Practices to Reduce Microbial Growth: Instead of relying on antimicrobials, improving construction methods can prevent microbial issues.

• Proper Drainage & Waterproofing: Prevents water intrusion and mold growth in walls and foundations.
• Breathable, Vapor-Permeable Materials: Reduces trapped moisture that promotes mold growth. Includes materials like lime plaster, hempcrete, and natural fiber insulation.

Using Naturally Mold-Resistant Wood: Certain wood types (e.g., cedar, teak, bamboo) have built-in antimicrobial properties.