Antimicrobials in paints - adding cost and risk for no known benefit
Julie Silas - June 10, 2010
Antimicrobial use in building materials, including paints and coatings, has grown rapidly in recent years and is coming under increasing scrutiny as concerns about health impacts and effectiveness rise.
There is a wide range of antimicrobial use in paints and coatings. Most manufacturers, with some exceptions (e.g. epoxy-based paints and coatings), use "in-can preservatives" to prevent mold and fungal growth in the can and keep the paint from spoiling. They claim that because latex is made from starch, it is a good food source for bacteria. Other manufacturers add what they call "biocides" or mildewcides to exterior coatings to prevent algae and mold growth. Additionally, some manufacturers add antimicrobials to their products explicitly to claim antimicrobial protection on the surface of the coating once it has cured, even for interior applications.
Aggressively marketed for enhanced infection control, antimicrobials are used in paint to inhibit mold (as well as in other interior finish products, including carpet, privacy curtains and upholstery fabric, wallcovering, wall protection, and door hardware/handles). In some products, metals, such as silver, are impregnated into the product to provide the antimicrobial properties. In others, products such as Microban are used as antimicrobials, made from the chemical Triclosan, a chemical of concern because of its acute toxicity.
Research indicates that environmental concerns exist from the manufacturing processes associated with antimicrobials (e.g. metals may be released into our water, soil, and air -- the same metals that ironically may contribute to antibiotic resistance). Silver, in particular, has been linked with bacterial resistance. Antimicrobials can also lead to what is known as "cross-resistance," whereby through an intricate process, bacteria become resistant to the antimicrobial itself, as well as to a whole host of other antibiotics.
At the same time, serious questions are being raised as to whether added antimicrobials even serve a measurably useful function in interior finishes. The efficacy of antimicrobials has been called into question by several independent studies. The Centers for Disease Control and Prevention (CDC) concluded a 2003 comprehensive study of infection control practice with the statement that "No evidence is available to suggest that use of these [antimicrobial] products will make consumers and patients healthier or prevent disease. No data support the use of these items as part of a sound infection-control strategy." Kaiser Permanente similarly concluded in a December 2006 position statement that "[w]e do not recommend environmental surface finishes or fabrics that contain antimicrobials for the purpose of greater infection control and the subsequent prevention of hospital acquired infections." KP states that there is "no evidence that environmental surface finishes or fabrics containing antimicrobials assist in preventing infections." Rather, the organization recommends strict hand hygiene and environmental surface cleaning and disinfection.
Meanwhile, more and more products are being introduced with added antimicrobials. Just this week, the Pharos Team received an e-mail announcing a new product from Jamestown Coating Technologies, SurfaGuard.™ The e-mail claims that SurfaGuard™ antimicrobial paints and coatings are designed to "provide an extra defensive shield against bacteria, molds, and fungi. The new product... incorporates silver ions via a new nanotechnology, SmartSilver™ that are proven to work against microbes."
In light of the fact that the growing market for such added antimicrobials seems to be at odds with the science, Pharos would like to remind our subscribers that when they get claims from manufacturers about added antimicrobials in products, that the experts at the CDC have said, "No evidence is available to suggest that use of these [antimicrobial] products will make consumers and patients healthier or prevent disease. No data support the use of these items as part of a sound infection-control strategy." The whole added antimicrobial discussion reminds me of my parental role every time my kids come to me after seeing an advertisement for the newest pair of jeans or the most up-to-date PlayStation game - just because the advertiser says you need something, that doesn't mean you really do!
 Only a very few acrylic paint manufacturers do not add some type of preservative in the can. In the past, mercury was added to paint, which acted both as an in-can preservative and as an antimicrobial additive. For some time in the 1990's, formaldehyde replaced mercury and was used to provide these protections. In the 21st century, chemical compounds such as benzisothiazolin-3-one (BIT) or methylisothiazolin (MIT) are used as in-can preservatives. Further study beyond the scope of this blog is needed to learn more about these different applications and the chemical compounds associated with them. When manufacturers disclose in-can biocides, we have included them in the product evaluation.
 "Antimicrobial Chemicals in Buildings: Hygiene or Harm" Environmental Building News, Volume 16, Number 8. August 2007 p 13.
 Centers for Guidelines for Environmental Infection Control in Health-Care Facilities Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC)
 Kaiser Permanente, "Evaluation of Antimicrobial Property Claims in Finishes and Fabrics," December 1, 2006. (http://www.healthybuilding.net/healthcare/KP_Antimicrobial_Position_Paper.pdf)
 CDC. Op. cit.