The U.S. Environmental Protection Agency (EPA) announced on December 1, 2011, that it granted a conditional registration for a pesticide product containing nanosilver as a new active ingredient. This is a momentous regulatory decision and very good news for supporters of nanopesticides.
HeiQ AGS-20 is a silver-based antimicrobial pesticide product intended to be incorporated into textiles or applied as a surface coating to suppress the growth of bacteria. Silver has been registered under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) for decades. The HeiQ silver is a nanoscale silver sintered onto amorphous silicon dioxide, and is the first such product to be registered by EPA.
Basis for Conditional Registration
Under FIFRA, EPA is required to assess the risks and calculate the benefits of a pesticide. Assuming the product doesn't pose unreasonable risks to human health and the environment, EPA is authorized to register the product subject to certain conditions of use. In its risk evaluation, EPA used very conservative assumptions — overestimating the dose of nanosilver — and maximum values for risk uncertainty factors.
For the purposes of risk from exposure to silver ions, EPA relied on the existing re-registration decision for silver and concluded that the human health or ecological risk from exposure to silver ions derived from HeiQ AGS-20 treated textiles isn't of concern.
The EPA notes that, although no intermediate- or long-term human or environmental toxicity studies are available for HeiQ AGS-20 or for the nanosilver that might break away, the scientific literature includes intermediate-term toxicity studies for analogous forms of nanosilver. EPA used these data to evaluate the risk from occupational and consumer exposure. Because the available exposure data are limited, EPA calculated the daily dose to workers assuming that all the silver in HeiQ AGS-20 was freely available as nanosilver.
For the daily dose to consumers, EPA made conservative assumptions that overestimated the daily dose of nanosilver that a person could potentially receive when working with HeiQ AGS-20 or wearing HeiQ AGS-20 treated textiles. Because the studies on which EPA relied don't evaluate toxicity over all life stages or evaluate all potential effects, EPA used a maximum 10-fold database uncertainty factor when evaluating the risk from exposure to the nanosilver that might break away from HeiQ AGS-20.
As a condition of registration, EPA is requiring HeiQ to conduct studies during the period of conditional registration. Tier I studies must be completed within four years. EPA intends to evaluate data as they are submitted to confirm the use of HeiQ AGS-20 won't cause unreasonable adverse effects to human health and the environment. Tier II data may be required if the results of Tier I studies suggest additional data are needed.
A Promising First Step
EPA says the use of HeiQ AGS-20 is in the public interest. This is great news for the nano community. EPA specifically states that AGS-20 may lead to less environmental loading of silver as compared to currently registered products with the same use patterns. In addition, EPA notes, HeiQ AGS-20 appears to offer prolonged ability to suppress the growth of odor-causing bacteria through the slow release of silver ions as compared to the rapid release of silver ions from registered products containing silver salts.
These are all positive statements and EPA is to be congratulated for registering a product of nanotechnology under FIFRA. While some may argue, with reason, that the risk assumptions are very conservative and the data development requirements are substantial, they are the price HeiQ pays for being first out of the gate with a nanopesticide product.
Another commercial burden HeiQ must bear is the time-limited nature of the registration. If after the end of the four-year period EPA's review of Tier I data yields a decision that yet more data are needed, or worse, EPA makes an adverse finding, continued registration could be all the more challenging and uncertain. This makes the significant investment in the product all the more impressive as under the terms of conditional registration, a long commercial life isn't certain. Despite these issues, the registration is promising news and a potentially game-changing development in the commercialization of nanopesticides.
EPA's Decision Document, which lists all the Tier I and Tier II data in Appendix A, is available at http://www.chemicalprocessing.com/epa-regulations.
LYNN BERGESON is Chemical Processing's Regulatory Editor. You can e-mail her at Lbergeson@putman.net.
Lynn is managing director of Bergeson & Campbell, P.C., a Washington, D.C.-based law firm that concentrates on chemical industry issues. The views expressed herein are solely those of the author.