Nanosilver Conditionally Registered as New Active Ingredient

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Courtesy of Bergeson & Campbell, P.C.

In August 2010, EPA announced that it was considering allowing the Swiss company HeiQ Materials Ag to enter the U.S. market with a new nanosilver pesticide and textile preservative, HeiQ AGS-20. On Dec. 1, 2011, the EPA issued a conditional registration for a pesticide product.

The Product
TAGS-20 is a nanosilver-silica composite where the nanosilver is sintered onto amorphous SiO2, with typical particle diameters of one micrometer (1,000 nanometers).

EPA’s risk assessment relied on the existing reregistration decision for silver and concluded that the human health or ecological risk from exposure to silver ions derived from AGS-20 treated textiles is not of concern. For purposes of risk from exposure to AGS-20, the manufacturer submitted results from short-term acute animal toxicity tests completed using high-level doses of AGS-20. No major issues were identified. According to EPA’s Decision Document, AGS-20 caused moderate to no irritation to the skin and eyes of test animals, but was not a skin sensitizer. Based on these results, EPA will require shipping containers filled with AGS-20 to use the DOT 'CAUTION' label.

EPA used conservative assumptions that overestimate the dose of nanosilver that could potentially be derived from AGS-20, along with maximum values for risk uncertainty factors. It determined that, for the period of conditional registration, there is a low probability of adverse risk to children and the environment. Thus, the agency concluded that use of AGS-20 will not cause unreasonable adverse effects on the environment during the period when newly required data is being developed. The agency notes that it does have a risk concern for occupational exposure when handling AGS-20 powder during mixing and loading operations.

As a condition of registration, EPA is requiring HeiQ to conduct many studies during the period of conditional registration. The required tests include route-specific toxicity studies for occupational exposure scenarios, as well as product characterization and stability tests to determine if nanosilver breaks away from AGS-20. EPA states that, if nanosilver is found to break away, then additional testing will be triggered to determine the effect that nanosilver has on humans and the environment. These studies must be completed within four years, since EPA chose to allow time for protocol reviews prior to initiation of the studies, completion of the studies and its review of the study results. The data requirements are set forth in Appendix A of the Decision Document. The studies listed in Table 1A are considered Tier I because their need is not based on the results of any other studies. Tier II studies may or may not be required based on the results of the Tier I studies.

EPA intends to evaluate the data to confirm that the use of AGS-20 will not cause unreasonable adverse effects to human health and the environment. If the manufacturer fails to take appropriate steps to initiate the required studies, or they fail to submit the protocols or data, EPA will issue a notice of intent to cancel the registration under FIFRA Section 6(e).

Discussion
EPA’s approval of the HeiQ nanopesticide product is a big deal. EPA’s determination that the use of AGS-20 is in the public interest is very promising. EPA states that it may lead to less environmental loading of silver as compared to currently registered products with the same use patterns. Importantly, EPA notes AGS-20 appears to offer prolonged ability to suppress the growth of odor causing bacteria through the slow release of silver ions, in comparison to the rapid release of silver ions from registered products containing silver salts. EPA’s Decision Document is available at www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2009-1012-0064 or use the tag with a smartphone.

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