EPA Announces Conditional Registration For Antimicrobial Containing Nanosilver

By Patrick Ambrosio

The Environmental Protection Agency announced Dec. 1 that it is conditionally registering an antimicrobial pesticide product containing nanosilver as a new active ingredient.

EPA issued a conditional registration for the product, HeiQ AGS-20, because HeiQ has had insufficient time to generate and submit newly required data, according to the decision document. EPA also determined that use of AGS-20 is in the public interest and will not cause unreasonable adverse effects on the environment while new data are being developed.

AGS-20 is a nanosilver-silica composite that is incorporated in textiles to suppress the growth of bacteria.

“HeiQ AGS-20 is an innovative and efficient technology that enables effective antimicrobial protection for textiles—from shirts, uniforms and sheets to tents and tarps—because it uses less silver than other comparable products,” Carlo Centonze, chief executive officer of HeiQ Materials, said in a Dec. 1 news release. “EPA has approved HeiQ AGS-20 in part because it could lead to less silver released in the environment while providing longer protection against the growth of odor and stain causing bacteria.”

EPA first proposed a conditional registration in 2010 to address what it described as a competitive disadvantage for HeiQ because other companies already had products containing nanoscale silver on the market. EPA said that it approved at least four similar antimicrobial pesticides without knowledge that the products contained nanosilver as an active ingredient (34 CRR 831, 8/23/10).

EPA Reviewed Toxicity Tests, Occupational Risks

EPA said that it reviewed short-term acute animal-toxicity tests that showed no mortalities or abnormalities in test animals following high-level doses of AGS-20. However, the tests showed exposure resulted in moderate to no irritation to the skin and eyes of test animals. Shipping containers filled with AGS-20 will be required to carry a label stating “CAUTION,” EPA said.

EPA also addressed a risk concern for occupational exposure during the mixing and loading of AGS-20 powder. The conditional registration will require the product's label to require workers to wear personal protective equipment and use engineering controls when handling AGS-20 powder to address occupational exposure risks.

EPA assessed occupational risks by assuming that all of the silver contained in AGS-20 was freely available as nanosilver due to a limited amount of available exposure data.

EPA said that it used conservative assumptions that overestimate potential nanosilver exposure to determine a low probability of adverse risk to children and the environment during the period of conditional registration. This included assuming that the entire population of the United States would each purchase one T-shirt treated with AGS-20 and that all of the silver contained in the shirts would be released as nanosilver.

Additional Studies Required

EPA is requiring HeiQ to conduct “a number of studies during the period of conditional registration,” according to the decision paper.

The requirements include route-specific toxicity tests for a variety of occupational exposure scenarios, as well as product characterization and stability tests that will show if nanosilver breaks away from AGS-20. EPA said that if the tests show that nanosilver breaks away from the pesticide or textiles treated with the pesticide, additional testing will be required to show the impact of that nanosilver on humans and the environment.

EPA is requiring that all testing be completed within four years. EPA will evaluate all data to confirm the continued use of AGS-20 will not cause “unreasonable adverse effects to human health and the environment,” the statutory requirements for registration under the Federal Insecticide, Fungicide and Rodenticide Act.

Environmental Group Questions Legality

Jennifer Sass, senior analyst at the National Resources Defense Council, told BNA Dec. 1 that EPA should have required concrete data on nanosilver risks before issuing a conditional registration.

“The law says that you have to have data before you register a pesticide,” Sass said. “I am very curious how they [EPA] justify it in a defensible way.”

Sass said that nanosilver is more toxic and more reactive than regular silver and should be “tested as a different material” before being registered as an active ingredient. She said that EPA should have addressed the competitive disadvantage for HeiQ by going after the companies that had products on the market containing unregistered nanosilver, rather than approving a conditional registration.

Sass said that NRDC will be “looking closely” at EPA's decision and will consider “all options, including legal options,” to challenge the conditional registration.

EPA released a document responding to public comments, including a comment submitted by Sass, on the conditional registration of AGS-20. In that document, EPA said that the slower rate of silver release of nanosilver particles would mean that less AGS-20 would be used, resulting in a reduced amount of nanosilver and lower environmental exposure.

EPA's decision document on the conditional registration of HeiQ AGS-20 is available at http://op.bna.com/env.nsf/r?Open=mdas-8p6mbw .

EPA's response to comments received on the proposed conditional registration is available at http://op.bna.com/env.nsf/r?Open=mdas-8p6me4 .