By Marie Clarke and Stephen R. Sides, American Coatings Association
The term “antimicrobials” has come to encompass a wide range of materials that control the growth of unwanted, deleterious microorganisms in the environment.
Purification of drinking water sources, cleaning contaminated surfaces in our homes and offices, sanitizing dishes and cookware used in food preparation, sterilizing surgical instruments, and treating serious wounds or simple cuts have all become part of the public trust, reinforcing the absolute need for effective antimicrobials to support public health, safety, and environmental protection.1
However, the benefits extend beyond these familiar and accepted uses and represent a growing reliance on antimicrobials in everyday products as part of broader public health protections. Microbe-resistant surfaces are desired in hospitals and day care facilities. Food processing, preparation, and storage facilities integrate antimicrobials in packaging to safeguard the food supply. In many of these facilities, paints and coatings are used to provide smooth, cleanable surfaces on building components and work surfaces (e.g., walls, ceilings, and fixtures such as tables, counters, and shelves). Increasingly, developers and facility managers are seeking paints and coatings that have antimicrobial properties as an additional safeguard.
Increased use of antimicrobials in construction products, however, has resulted in increased scrutiny of the inherent safety of the antimicrobials. The paint and coatings industry acknowledges the need to maintain proper safeguards when using antimicrobials, and cites a long history of effective collaboration with government to protect public health and the environment, and ensure effective policies for antimicrobial use that support continued availability.
Paint Industry Reliance on Antimicrobials
Microbial attack (i.e., mold and mildew) on painted surfaces is a wide-ranging and universal concern that has resulted in a global, coordinated strategy to combat it. The participants in this effort include the companies that make antimicrobials; paint manufacturers, who add antimicrobials to their products; users of paints containing antimicrobials, who have come to expect the efficacy of these products to protect the painted surface and maintain desired conditions; and the government agencies charged with protecting public health and the environment, who provide oversight and continued scrutiny of the safety and effectiveness of antimicrobial product use in paints and coatings.
Mold, mildew, and algae growth can lead to both an unpleasant appearance and physical degradation of paints and coatings and cause them to fail to protect the substrates on which they are applied. In addition to the aesthetic effects, microbial organisms increase porosity of the paint film, leading to loss of adhesion and intrusion of moisture, and further degradation of the surface risks deterioration of the very places where we live and work.
The impact of microbial growth is not limited to degradation of applied paint films, but also occurs during production and storage of paints and coatings. Increasingly, paint products have embraced waterborne technology, using formulations that are low in volatile organic compounds (VOCs) and other hazardous materials with lower emissions during application and drying.2 As with most waterborne products, paints require the use of “in-can” preservatives to protect them from spoilage. Without these antimicrobials, waterborne paints would fail in storage, first losing their viscosity, then progressing to malodor, before ultimately experiencing a complete product breakdown. In extreme cases, the microbial decomposition can generate gases that rupture the container.
The importance of antimicrobials use for in-can preservation and microbial attacks cannot be understated. Over the past 75 years, market growth and public acceptance of waterborne paints and coatings has only been possible with the use of antimicrobials. In the efforts to protect waterborne paints from microbial growth, manufacturers have enhanced plant hygiene and developed work practice controls that ensure product integrity throughout the supply chain. These efforts are part of a holistic approach to microbial control that ensures protection, but also optimizes the use of antimicrobials to a level that is necessary to do the job.
In selecting antimicrobials for paints, a number of critical performance factors must be considered, including:
- Are they considered safe from adverse impacts on human health and the environment?
- Do they achieve a broad spectrum of microbial control?
- Are they “fast acting” and “long lasting”?
- Do they adversely affect product performance (i.e., change the product’s color, affect ease of application, change solubility of the ingredients, etc.)?
- Are they easy to use (in formulation) and cost effective?
As a result of these and other considerations, developing paint formulations that require antimicrobials is a technical challenge. Similarly, reformulation of existing, successful products incorporating antimicrobials is not a “simple” matter, owing in large part to the need, first and foremost, for ensuring environmental and public health protections. Therefore, paint manufacturers across the globe work with government officials responsible for environmental health and product safety to establish consensus on safe, reliable antimicrobials for use in waterborne coatings.
Regulation of Antimicrobials in Paints and Coatings
Limited Number of Approved Antimicrobials Available
Fortunately, regulatory agencies around the world acknowledge the need for effective antimicrobials to use in formulating paints and coatings. A variety of legal constructs exist whereby manufacturers of antimicrobials provide detailed information on product safety and toxicology, efficacy in microbial control, and required formulation and use practices. This information is used by government scientists to determine if the proposed antimicrobial can be safely used as proposed. The review process is open to comment from interested parties, and additional expressed concerns are addressed. The rigor and thoroughness of these regulatory processes has resulted in a limited number of approved antimicrobials being deemed safe, and therefore available for use by industry.
Effective Ongoing Oversight
Once an antimicrobial is approved for use, additional ongoing scrutiny takes place by regulators and product manufacturers, both of whom have obligations to report any significant adverse incidents involving regulated materials in commerce. Any new finding of an adverse impact may result in a re-evaluation of product safety and a change in authorized use.
Critical Concerns Acknowledged: Water Solubility, Exposure on Application and Drying, Surface Migration, End-of-Life Management—Responsible Industry Action
Among a number of active considerations in affirming “safe use” of antimicrobials in coatings are the inherent water solubility of the antimicrobial and the potential for “leaching” from the surface (or “surface migration”), both of which are mitigated by industry research affirming the encapsulation of antimicrobial in the paint film itself. Industry studies also show that exposure during application is controlled both by the prescribed method of application (i.e., spray, roller, or brush), the natural or mechanical ventilation in the spaces, and the use of personal proactive equipment by the applicator (i.e., respirators for spray application). Recent industry research on indoor air quality has demonstrated that paint-related exposures decrease to non-detectible levels over a short period of time, again informing on safe use. Finally, end-of-life management practices for leftover paint increasingly are finding reuse, recycling, and waste-energy management outlets that can be accomplished without concerns for additional antimicrobial exposure or release into the environment.3
These important product safety considerations and ongoing industry research, when coupled with active support for government agency evaluations and oversight, continue to demonstrate a responsible industry whose use of antimicrobials is legitimate, rational, and warrants continued reliance.
Other Industry Uses of Antimicrobials
Additional specialized uses of antimicrobials in certain paints and coatings are critical to protection of the substrates on which they are applied. Wood preservative materials are used to suspend the growth of microorganisms and other lifeforms that are associated with the destruction of wood and wood structures. Marine and offshore protective coatings are used to reduce the growth of marine microorganisms and associated biofilms that degrade vessels and steel structures, and slow their propulsion through the water. Both uses are highly regulated and face increased and stringent regulatory controls whereby end users, paint manufacturers, and the producers of the antimicrobials (i.e., active ingredients) work closely with government agencies to ensure safe use.
Ongoing Industry Stewardship
It is also important to acknowledge that the paint and coatings industry is focused on its customers, and open to concerns or expectations that arise. Facing pressure from purchasers and the wider green building community, the American Coatings Association has engaged with interested members to address concerns over the safe use of antimicrobials in paint products. Most recently, ACA and other allied trades responded to a white paper published by Perkins+Will and the Healthy Building Network entitled, “Healthy Environments: Understanding Antimicrobial Ingredients in Building Materials.” In the paper, the architectural firm placed building products marketed as “antimicrobial” on its precautionary list and urged its clients to avoid them whenever possible. ACA joined the American Chemistry Council, Consumer Specialty Products Association, and Silver Task Force of North America in writing to Perkins+Will, urging them to retract or revise the document. The trade group letter makes clear that antimicrobials are strictly regulated by the U.S. EPA. and there is no scientific evidence to support the white paper’s claim that they pose a threat to public and environmental health.
The white paper follows a similar bulletin issued by Kaiser Permanente, which banned the specification of fabric, furniture, and finishes containing any concentration of 13 listed antimicrobial substances. In the bulletin, Kaiser Permanente stated that products treated with antimicrobials tend to cost more, and there is no direct correlation between their use and patient infection rates.
ACA and the allied trade groups continue work to respond to continued questions by stakeholders contemplating similar policies. The coordinated science-based response seeks to demonstrate the safe use and effectiveness of antimicrobial substances in paints and coatings.
1 “Benefits of Antimicrobial Pesticides in Public Health and Industrial Uses,” American Chemistry Council, March 2010. Available for download at: https://www.americanchemistry.com/ProductsTechnology/Biocides/Benefits-of-Antimicrobial-Pesticides-April-2010.pdf.1 “Benefits of Antimicrobial Pesticides in Public Health and Industrial Uses,” American Chemistry Council, March 2010. Available for download at: https://www.americanchemistry.com/ProductsTechnology/Biocides/Benefits-of-Antimicrobial-Pesticides-April-2010.pdf
2 The Costs and Benefits of the Reduction of Volatile Organic Compounds from Paints. Prepared by European Directorate General for the Environment, Air and Noise Unit, 2 May 2002.
3 Gartner, S. Burkhardt, “Reduction of environmental risks from the use of biocides,” Environmental Research of the (German) Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety Project No. (FKZ) 3711 63 410 Report No. (UBA-FB) 002023/E, March 2014.
CoatingsTech | Vol. 14, No. 5, May 2017