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Recent Antimicrobial Registration Provides for Intermediate Master Batches

On May 15, 2015, EPA’s Office of Pesticide Programs (OPP) (Antimicrobials Division) conditionally approved Nanosilva LLC’s registration of “NSPW-L30SS” as a materials preservative with an explicit clearance allowing the manufacture of intermediate master batches.  EPA Reg. No. 84610-2.  NSPW-L30SS is an antimicrobial additive containing 1.00% nanoscale silver that can be incorporated into synthetic textile and non-food use indoor and outdoor materials (e.g., household items, electronics, sports gear, hospital equipment, bathroom fixtures, etc.) to suppress the growth of bacterial, fungus, mold, and mildew.  The registration is conditional and includes tiered testing requirements related to the nano aspect of the particles being registered.  One aspect of the registration may have broad significance for all registrants of products used to make treated articles and, particularly, for formulators of master-batch intermediates.

NSPW-L30SS’s label and accompanying technical bulletin contain limitations common to antimicrobials intended for use as a materials preservative, i.e., the requirement that no public health claims may be made and that no health benefit arises to users.  Unlike most materials preservative registrations, however, the label explicitly provides “for use in the protection of polymeric intermediates and subsequent treatment of polymer and polymer-based products.”  The registration includes a technical bulletin with a long list of products that may be preserved.  The listed product categories are very broad and contain no limitations regarding materials of construction.  There is a maximum silver content for consumer finished products of 0.003% or 30 ppm and such products may not be manufactured directly from NSPW-L30SS.  The registered product must be integrated into end use products by first manufacturing a treated intermediate based on a linear low-density polyethylene (LLDPE) or polyethylene terephthalate polymer matrix with a maximum concentration of 2% NSPW-L30SS.  Furthermore, this intermediate blend must be produced in a closed system.  The concentration limitation imposed on the intermediate treated article serves to limit downstream exposure so there is no need for closed systems or other exposure controls by those that integrate the treated intermediate into consumer finished articles.

To summarize the above in terms that emphasize the potential relevance of this approach to master-batch formulators, EPA has essentially defined permissable use conditions for an unregistered NSPW-L30SS “master-batch” product.  As a treated article, the intermediate formulation could contain custom additive packages for specific end use applications.  These “master-batch” formulations are exempt from registration as pesticides (as long as claims are properly limited to product protection) and the following conditions are met:

  1. The maximum concentration of NSPW-L30SS allowed in the master batch is 2%;
  2. The master batch matrix must be either linear low-density polyethylene (LLDPE) or polyethylene terephthalate based polymers; and 
  3. The weight of the master batch applied to finished products does not exceed 15%. 
While nano-silver products routinely attract special attention from EPA, the registration approach used here to explicitly define and impose limitations on a treated intermediate is one that could easily be added to the registrations of products for which there is a large demand for master-batch formulations at use concentrations above the treated article use level for which the product is currently registered.  Indeed, we understand that EPA AD is currently reviewing, and has approved, several label amendments adding intermediate treated articles to the label. This promises to be a more efficient approach than seeking registrations for multiple master batch formulations.  

Keller and Heckman LLP is available to assist registrants of nanomaterials and intermediate treated articles.  To find more information on this particular nanomaterial registration, please visit and searching for docket “EPA-HQ-OPP-2012-0594.”  In addition, Keller and Heckman LLP’s Pesticides Practice Group is available to counsel clients on a wide-range of FIFRA registration and compliance issues and can be reached at 202-434-4100.