Nanotechnology Lawyer & Attorney : Porter Wright Morris & Arthur : Nanotechnology Law Report - Germanium nanobead image provided by UT-Battelle, which manages Oak Ridge National Laboratory for the Department of Energy

Silver (CASRN 7440-22-4) is a naturally occurring metal. It is usually found in extremely low concentrations in natural waters. “Humans are exposed to small amounts of silver from dietary sources.” “Silver levels of less than 0.000001 mg silver per cubic meter of air (mg/m³), 0.2-2.0 parts silver per billion parts water (ppb) in surface waters, such as lakes and rivers, and 0.20-0.30 parts silver per million (ppm) in soils are found from naturally occurring sources.” A 50 year old person has “an average retention of 0.23-0.48 g silver.”

Silver production in 1999 was estimated at 15.5 million kilograms world-wide, with Mexico and the US leading the list of producers. It is estimated that approximately 2.5 million kgs of silver in various forms is lost to the environment in the US every year, and that 29% of that amount is released to water and 68% to land. The most prevalent release routes are purportedly from smelting operations, photographic processing supplies, manufacturing of electrical components and wires, coal combustion, electroplating operations, and cloud seeding. NIOSH estimates that 70,000 people are exposed to silver in the workplace each year and inhalation is the most important route of exposure.

People and Animals. Silver has exhibited no known toxic effects to humans. According to the EPA, human health effects from breathing, eating, and/or drinking silver are "unknown." However, if you eat, drink, or breathe enough of it, your skin may turn a blue-gray color. This permanent cosmetic condition called “argyria” is not harmful to health. It results from silver depositing in the dermis layer of skin.   Breathing high levels of silver dust may cause breathing and respiratory problems, throat irritation, or stomach pain – as with other types of particulate matter.  Silver is not a known human carcinogen, but has been shown to cause cancer when inserted in lab animals under certain conditions. There are few, if any, toxicity animal studies based on oral or respiratory silver intake. “Tests in animals show that silver compounds are likely to be life-threatening for humans only when large amounts (that is, grams) are swallowed and that skin contact with silver compounds is very unlikely to be lifethreatening.”  Some occupational studies intimate that exposure to silver may cause kidney problems, although more research is needed on this issue. 

Silver Ions.  Monovalent silver ions are very rare in the natural environment. “The acute toxicity of silver to aquatic species varies drastically by the chemical form and correlates with the availability of free ionic silver.” “For freshwater fish, the acute toxicity of silver is caused solely by silver ion interacting with the gills . . .” “On the basis of available toxicity test results, it is unlikely that bioavailable free silver ions would ever be at sufficiently high concentrations to cause toxicity in marine environments.” “About 95% of the total silver [lost to water in the environment] is removed in publicly owned treatment works from inputs containing municipal sewage and commercial photprocessing effluents, and effluents contain less than 0.07 ug ionic silver/litre.”

Drinking Water. The federal government has issued guidelines concerning the maximum level of silver allowed in drinking water (Maximum Contaminant Level – MCL): long term exposure is limited to 0.1 mg/L (previously 0.05mg/L), and short term exposure (1-10 days) is limited to 1.142 mg/L. The silver MCL was first promulgated by the United States Public Health Service in 1962 before the Environmental Protection Agency was ever formed. Silver was included on the original list on the basis of epidemiological data and the fact that it was used as an antimicrobial. The epidemiological data was based on exposures to medicinal silver and exposures through mining and metalworking. In 1989 EPA proposed changing the MCL for silver from 0.05 mg/L to 0.09 mg/L because the only potential human health concern was from argyria. “The proposal was finalized, using an CML of 0.1 mg/L, on January 30, 1991.”

Surface Water.  Silver in surface water tends to settle down into the sediment. “Silver can remain attached to oceanic sediments for about 100 years under conditions of high pH, high salinity, and high sediment concentrations of iron, manganese oxide, and organics.” Silver levels in pristine surface water in unpolluted areas are approximately 0.01 μg /L and approximately 0.01 - 0.1 μg/L in urban and industrialized areas. The federal government regulates silver in surface water through the Federal Water Pollution Control Act (aka/ Clean Water Act) -- 33 U.S.C. § 1251. “The silver criteria contains values to protect human health from ingestion of contaminated aquatic organisms and maximum acceptable concentrations to protect organisms that live in freshwater and salt water from toxic effects. The human health part of the silver criteria was drawn directly from the drinking water MCL. Criteria for the protection of aquatic life, on the other hand, were derived using a newly developed set of guidelines that called for extensive laboratory test data. The values are given as total recoverable silver.”  The freshwater criteria maximum concentration (CMC) for silver is (3.2) 100mg/L, and the saltwater CMC is (1.9).

Air. Silver is not considered an air pollutant harmful to public health or environment under the National Ambient Air Quality Standards mandated by the Clean Air Act. Purportedly “[t]reatment of air emissions containing silver is not a concern as atmospheric emissions rarely approach the federal threshold limit value for occupational exposure of 0.01 mg/m³.”

Workplace. Workplace exposures to silver present unknown/unquantified health risks to humans. Most occupational exposures to silver are purportedly through photographic processing chemicals (dermal) or inhalation of silver dust particles from the ambient air. OSHA has set the maximum air quality standard for silver at 0.01 mg/m3 based on an 8 hour workday and 40 hour workweek.

Regulation of silver hazardous waste. Resource Conservation and Recovery Act (RCRA) is designed to (in part) prevent leaching of hazardous concentrations of particular toxic constituents into groundwater, and looks back to Primary Drinking Water Standards. Any waste that contains 100 times the amount of the relevant constituent is considered a hazardous waste. The “100 times” level was designed to compensate for the dilution of materials as they pass through soil when headed for ground water. Note, howeverm that the ACRA standard does not track the 1997 amendment to the drinking water standard. Since the original drinking water standard for silver was is 0.05mg/L, the maximum allowable limit is 5.0 mg/L for RCRA purposes. Wastes containing silver at this level or above are labeled as “hazardous wastes” under RCRA and are subject to further regulation under that Act. “Under CERCLA, silver-bearing hazardous wastes are designated as hazardous substances with a reportable quantity (RQ) equal to 1 pound (.454 kg).” Any release that exceeds the RQ in a 24-hour period must be reported to the National Response Center.

Select Bibliography:

“Toxicological Profile for Silver,” Agency for Toxic Substances and Disease Registry, U.S. Public Health Service (December 1990).

P.D. Howe, et al., “Concise International Chemical Assessment Document 44: Silver and Silver Compounds: Environmental Aspects,” World Health Organization (2002).

US EPA Integrated Risk Management System (IRIS), Silver (CASRN 7440-22-4), http://www.epa.gov?IRIS/subst/0099.htm.

 “25 Years of the Safe Drinking Water Act: History and Trends.”

Many states also regulate silver. Some state standards are more restrictive than EPA standards. See, e.g., “The Regulation of Silver in Photographic Processing Facilities,” Kodak Environmental Services, J-124 (1996).

T. Purcell, et al., “Historical Impacts of Environmental Regulation of Silver,” Environmental Toxicology and Chemistry, Vol. 18, No.1, pp. 3-8, 1999.

Aquatic life testing guidelines can be found at Fed. Reg. 45:79341 – U.S. EPA. 1980. “Guidelines for determination of ambient water quality for the protection of aquatic organisms and their uses.”

65 C.F.R. 31682

“The Regulation of Silver in Photographic Processing Facilities,” Kodak Environmental Services, J-124 (1996).

US EPA, Solid Waste and Emergency Response (5305W), RCRA Photo Processing, EPA530-K-99-002, January 1999.

IOGEAR was selling two wireless mouses (mice?) and a wireless mouse/keyboard combination claiming that the nano-coatings killed germs and pathogens.  While the nano-coating remains unspecified (although the quote below indicates its nanosilver), the violation was pursuant to the Federal, Insecticide, Fungicide, and Rodenticide Act (FIFRA).  EPA's representative, Katherine Taylor, associate director of the Communities and Ecosystems Division at EPA’s Region 9 was quoted a saying, “We’re seeing far too many unregistered products that assert unsubstantiated antimicrobial properties...Whether the claim involves use of an existing material such as silver, or new nano technology, the EPA takes these unverified public health claims very seriously. Consumers should always follow common-sense hygiene practices, like washing hands frequently and thoroughly.”

It was really only a matter of time until the fines began.  We've seen many examples, check out yesterday's post for the easy links, of products claiming antibacterial and microbial claims go unregistered, and it appears that it finally wore down EPA's patience.  FIFRA is pretty clear that in order to make "pest killing" claims, the product must be registered so that EPA may be satisfied that the product does not pose an unreasonable risk to consumers.  Now that nanotechnology is getting more of the spotlight, I suspect we'll begin to see more enforcement actions like this to ensure consumer products are complying with applicable legal requirements.

This morning, Mr. Feder tells the story of an interesting little device called The Handler.  In short, its a key-chain hook that is coated with nanosilver in order to stay microbe free while allowing one to handle germ covered surfaces, like handles in public restrooms.  Its fun to flip them open and closed, and I even have one (albeit for demonstration purposes only).  The Handler's manufacturers have run into the same problem as Samsung--marketing a product as anti-microbial runs afoul of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) without prior registration.  These aren't the only products making such claims (for a specific example see the earlier post on the Seal Shield keyboard and mouse).

Correctly, Mr. Feder refocuses our prior discussion on what happens to these products while the EPA determines how best to regulate them.  In this case, The Handler's production has been suspended while the owners figure out what is required of them.  In other cases, the anti-microbial claims were dropped altogether--case in point, no where on the Seal Shield box is an anti-microbial claim.  Its implied, I believe, by the use of the phrase "infection control" and quotes from physicians using the words "disinfected" or "harmful bacteria," but nowhere does it make claims that it will kill the microbes or bacteria.  And Samsung?  Mr. Feder tells us that they were allowed to continue sales of the Silvercare machine while it developed the necessary registration paperwork.

It is unclear when The Handler will again be available for purchase in the United States, but this will not be the last product impacted by such uncertainty.  Is this cause for alarm or a rush to regulation?  No, but it shows the need to continually evaluate the science and data available in order to properly mitigate risks as they are presented.  One, ok two, final questions are again raised in my mind: are existing laws and regulations suitable to address the unique realities of nanotechnology?  While existing laws seem to be serving as a suitable "stop-gap" during this period of uncertainty, how long will those measure be sufficient in order to properly treat these new products and uses without unnecessarily endangering the public or unnecessarily stifling the development of such a promising technology?

The ability to put these materials into the dishwasher may reignite the debate over silver ions being released into wastewater.  If you remember, there was a rather large discussion over the use of Samsung's Silvercare washing machine that released silver ions into the rinse cycle.  One of the concerns was that we are not sure what will happen to environmental systems when silver ions are released into the wastewater system.  While US EPA elected to regulate the washing machine under the labeling provisions of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the concerns over environmental impacts were not discussed in a wide forum.  These new products may restart that debate over releasing nanomaterials freely into the environment (not to mention the potential FIFRA ramifications given the antibacterial claims).

However, as with all things nano these days, I would be remiss if I didn't mention the benefits these products pose.  Seal Shield is proposing using these products in the medical field where bacterial infection is a concern and the ability to wash and sterilize items is important.  Consequently, we're back to the debate over finding the middle ground.