Antimicrobial Additives:
advantages and guidelines
by R. Lee Pfaffle

itigating the presence of microorganisms on plastic parts has become a priority for consumers since the COVID-19 outbreak. In response to these concerns, a wide variety of plastic products are being treated with antimicrobial additives, such as:

  • Floor coverings, exercise equipment and cutting boards
  • Door or floor mats, bed rails and shopping carts
  • Food distribution carts and trays
  • Pallets and playground equipment
  • Storage containers, waste bins and luggage

These antimicrobial additives provide inherent microbe-fighting properties that control the spread of bacteria, fungi and algae on the surface of treated products. Antimicrobials prevent microorganisms from growing, producing energy and/or replicating when the microbe encounters the protected surface.

Types of additives
A treated article typically refers to any product that has been treated with an antimicrobial agent to protect it from microbe attack. Antimicrobial additives are added to the products during the manufacturing process. The most widely used types are inorganics, such as silver (Ag) and zinc (Zn) based systems, due to their high thermal stability. Loading levels vary depending on type and polymer, but typically fall between 0.5 – 5 percent. Better efficacy is achieved at higher loadings; however, the provider must strike a cost-benefit balance based on the application. Antimicrobials can be incorporated into most thermoplastics, such as polyethylene (PE), polypropylene (PP) and polystyrene (PS), thermoplastic elastomers (TPE), among others. Talk to your supplier if you have questions about adding antimicrobials to a material.
poultry feed cups
These poultry feed cups were treated with INTERACT AMX PPC from Primex Color, Compounding and Additives.
rails on hospital bed
The rails on this hospital bed were treated with INTERACT AMX PEC from Primex Color, Compounding and Additives.
A word about public health claims
Treated products often make implied or explicit public health claims designed to protect the public against harmful microorganisms. However, the Environmental Protection Agency (EPA) stipulates that only end-use products registered with the EPA can make public health claims. A public health claim is defined as any claim or suggestion that the product will have a positive effect on the health of a human or animal. These may include, but are not limited to statements such as:

  • Antibacterial, bactericidal, germicidal
  • Kills pathogenic bacteria
  • Effective against E. coli and Staphylococcus
  • Reduces the risk of food-borne illness from bacteria
  • Provides a germ/bacteria-resistant surface
  • Surface kills common gram positive and negative bacteria
  • Surface minimizes the growth of both gram positive and negative bacteria
  • Reduces risk of cross-contamination from bacteria
  • Improves indoor air quality through the reduction of microorganisms
  • Controls allergy-causing microorganisms
handle of a shopping cart
The handle on this shopping cart was treated with INTERACT AMX NYC from Primex Color, Compounding and Additives.
Treated article exemptions are granted by the EPA for any non-public health use of an antimicrobial that is intended to protect only the treated plastic from unsightly discoloration, unpleasant odors and polymer degradation. It is important to note that the treated articles exemption only applies to product protection and is not intended for public health purposes. Products that qualify for a treated article exemption must adhere to strict statement protocols. Approved statements include the following examples:

  • Contains an antimicrobial to control odors.
  • Contains an antimicrobial to resist bacterial odors.
  • Contains an antimicrobial that acts to mitigate odors.
  • Contains an antimicrobial to prevent microorganisms from degrading the product.
  • Contains an antimicrobial that inhibits the growth of bacterial odors.
  • Contains an antimicrobial that resists microbial odor development.
  • Contains an antimicrobial that retards the growth and action of bacterial odors.
  • Contains an antimicrobial that guards against degradation from microorganisms.
  • This article has been treated with a fungistatic agent to protect the product from fungal growth.
  • Contains a fungistatic to extend product life by controlling deterioration caused by mildew.
  • This article contains a preservative to prevent discoloration by algae.
  • Contains a fungistatic to make it resistant to mildew stains.

The EPA requires that all manufacturers making any efficacy claims associated with controlling microorganisms, such as E. coli, S. aureus, Salmonella sp. or Streptococcus sp., must first register their product with the EPA. Prior to EPA certification, each manufacturer must submit test data in support of the public health claim as well as fitness for use criteria. Once approved, the product may only claim efficacy for said product in the specified application. Any deviation either by performance or application requires recertification.

R. Lee Pfaffle is the product manager for Primex Color, Compounding & Additives. For more information, contact Primex Color, Compounding & Additives at 193 Commerce Place, Jasper, TN 37347 USA; phone (800) 234-6159, www.primexcolor.com.