In a bid to get antimicrobial nanosilver used in clothing, baby blankets and other textiles off the market, the Natural Resources Defense Council on Thursday filed suit against the Environmental Protection Agency.

The group says that nanosilver has been inadequately tested and could have potentially dangerous effects on health and the environment. The EPA in December conditionally approved the use of nanosilver made by HeiQ Materials as a textile preservative for the next four years, but is requiring additional safety data.

The suit, filed in the U.S. Court of Appeals for the 9th Circuit, asks the court to set aside the EPA’s order. The Federal Insecticide, Fungicide, and Rodenticide Act allows certain challenges to agency orders to be brought at the circuit court level.

“EPA gave this company a four-year free pass to sell an inadequately tested product,” said Mae Wu, program attorney in NRDC’s health program, in a news release. “EPA’s approval of nanosilver is just the most recent example in a long line of decisions that treats humans and our environment as guinea pigs.”

The NRDC argues that while silver (which is highly toxic) has been used in pesticides for years, nanosilver is different because of its incredibly tiny size, which allows it to penetrate organs and tissues in the body that larger forms of silver cannot reach, like the brain, lung and testes. The group wants more tests before nanosilver-treated products can be sold.

The NRDC noted that while HeiQ came to EPA to have its product registered, other nanosilver manufacturers have not. “The unregulated and untested use of nanosilver in such products as food storage containers and hair dryers continues to grow, despite potential dangerous health effects,” wrote NRDC senior scientists Jennifer Sass in a blog.

HeiQ in documents filed with the EPA claimed its product presents “no unreasonable adverse harm to humans and the environment,” wrote counsel James Votaw, then a partner at Wilmer Cutler Pickering Hale and Dorr and now counsel to Manatt, Phelps & Phillips. The product has low toxicity, and the particles are embedded within a solid silica matrix “so there is essentially no release of free particles of silver.”

Exposure to any silver ions that might be released when fabric is washed, he continued, is “similar to, or less than, those from currently registered products” using silver. “The product does not generate any unique concerns different than for other sources of silver ions.”

In comments filed with the EPA, BASF Corp., which makes several pesticides containing silver, wondered why EPA considered nanosilver to be something new. “Silver has been an active ingredient in pesticide products since the 1970s,” wrote Marie Paquette, senior product regulations specialist. “It is unclear as to why the agency would list silver as a new active ingredient.”

The Dow Chemical Co. echoed the question. “Silver is not a new active ingredient, and it is unclear why EPA has chosen to identify this submission as containing a new active,” wrote Abigail Trueblook, senior regulatory specialist.

To NRDC and other groups that filed comments opposing EPA approval, it’s not so simple.

“There are differences between biological and environmental behavior between conventional silver and some intentionally produced nanosilver particles, at least in laboratory studies,” wrote JoAnne Shatkin, managing director of CLF Ventures, Inc., an affiliate of the Conservation Law Foundation. “These differences warrant further investigation.” The group also asked the EPA to require labeling of all fabrics containing nanosilver.

The California Department of Pesticide Regulation also urged caution. “The data gaps regarding products containing nanosilver are significant,” wrote Marylou Verder-Carlos, assistant director of the Pesticide Programs Division. “It is our position that the U.S. EPA should wait for the additional data to be developed before proceeding with the conditional registration.”

Jenna Greene can be contacted at jgreene@alm.com.