United States
Environmental Protection
Agency
Office of Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-93-005
June 1993
R.E.D. FACTS
Pesticide
Reregistration
All pesticides sold or used in the United States must be registered by
EPA, based on scientific studies showing that they can be used without
posing unreasonable risks to people or the environment. Because of
advances in scientific knowledge, the law requires that pesticides which
were first registered years ago be reregistered to ensure that they meet
today's more stringent standards.
In evaluating pesticides for reregistration, EPA obtains and reviews a
complete set of studies from pesticide producers, describing the human
health and environmental effects of each pesticide. The Agency imposes
any regulatory controls that are needed to effectively manage each
pesticide's risks. EPA then reregisters pesticides that can be used without
posing undue hazards to human health or the environment.
When a pesticide is eligible for reregistration, EPA announces this and
explains why in a Reregistration Eligibility Document, or RED. This fact
sheet summarizes the information in the RED for silver.
Use Profile
Silver, a naturally-occurring element, is registered for use in water filters to
inhibit the growth of bacteria within the filter unit of water filter systems
designed to remove objectionable taste, odors, and color from municipally
treated tap water; these bacteriostatic water filters account for over 90% of
its pesticidal use. Silver also is used to control several types of algae in
swimming pool water systems; this algicide use accounts for only about 3%
of silver's use as a pesticide.
Silver manufacturing use products are granular formulations, the
bacteriostatic water filters are impregnated with silver, and the swimming
pool algicides are formulated as soluble liquid concentrates.
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Silver also has many other non-pesticidal, industrial uses including use in photo
processing, mirror production, dental alloys, coinage, tableware and jewelry
production, solder, electroplating, the manufacture of inks and dyes, the
processing of food and beverages, and the etching of ivory. Silver salts and
nitrate also are used as therapeutic agents in treating warts, burns, and eye
infections.
Regulatory Silver was first registered as a pesticide in the United States in 1954, for use
History *n disinfectants, sanitizers and fungicides. Currently, about 80 pesticide
products are registered which contain silver as an active ingredient.
Many regulations pertaining to silver have been promulgated through the
years, particularly by EPA's Office of Water (OW). The most recent of
these was a secondary maximum contaminant level (SMCL) issued in 1991,
based on silver's ability to cause argyria, an undesirable cosmetic condition.
OW classified silver as a Group D carcinogen (one that is not classifiable as
to carcinogenicity in humans) in 1988. EPA established an oral Reference
Dose (RfD), or daily intake limit, of 0.005 mg/kg/day for silver in 1991.
The Office of Pesticide Programs (OPP) issued a Data Call-In (DCI) for
silver in 1992, requiring additional product chemistry and toxicity data.
The silver RED reflects EPA's reassessment of all data submitted in
response to the DCI.
Human Health Toxicity
AsS6SSm6nt Most usually-required toxicity and exposure studies have been waived for
silver since adequate published information is available.
Human Toxicology
Silver can be absorbed from the lungs and the gastrointestinal tract. When
an excessive amount of silver is absorbed, tissues become impregnated with
silver sulfite, which forms a complex in elastic fibers. Large amounts of
this complex under the skin will give it bluish, grey-blue, or in extreme
cases a black color. This condition is called argyria. Although it is not a
toxic effect, argyria is undesirable and usually permanent.
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Excessive exposure to silver also can cause lung and kidney lesions;
exposure to dusts can cause breathing problems, lung and throat infections
and abdominal pain; and skin contact can cause mild allergic reactions such
as rashes, swelling, and inflammation.
Animal Toxicology
The acute toxicity of silver is relatively low by the oral route (it has been
placed in Toxicity Category III for this effect). Silver also is of low acute
dermal toxicity (Toxicity Category III), is not an eye or skin irritant
(Toxicity Category IV), and is not a skin sensitizer.
Silver is not known to have human carcinogenic potential, and does not
appear to be a mutagen. Although long term ingestion of silver may cause
argyria in humans and animals, this effect is cosmetic only and is not
harmful to health.
Dietary Exposure
Silver is not registered for application to food or feed crops nor for use on
processed commodities. Silver is a natural element and trace amounts are
normally present in the human diet. Minimal dietary exposure may result
from the use of silver in human drinking water systems. EPA does not
anticipate that dietary exposure to these low levels of silver will be
associated with any significant degree of risk.
Occupational and Residential Exposure
Occupational exposure can be expected for individuals handling silver
algaecide solutions or silver-impregnated filter materials. When the soluble
liquid concentrates used for water treatment in swimming pools are applied
through a pool skimmer basket, splashes to the eye or on the skin may
occur. People handling silver-impregnated filters may be exposed to minute
quantities of silver-containing charcoal. Thus, the potential exists among
mixers, loaders and applicators for eye, inhalation and dermal exposure to
concentrated solutions or dusts.
Residential exposure to very low levels of silver may be expected through
consumption of drinking water filtered through bacteriostatic filters, and by
swimming in treated pools.
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Human Risk Assessment
Applicator Exposure
Residential consumption of water filtered through filtering systems
containing silver is not expected to result in build-up of silver in the body to
an argyria-comparable level. The use of silver as a water treatment for
pools is minor, and of little concern from a toxicity perspective. Thus, the
residential uses of silver are not expected to constitute an unreasonable risk
or hazard.
Occupational exposure to silver may occur; however, this exposure
generally would be of such a low level, and silver is of sufficiently low
toxicity, that it is not expected to present unreasonable risks or hazards.
Environmental
Assessment
Environmental Fate
Because a large data base is available for silver, most environmental fate
testing was waived. However, registrants must clarify the nature of the
concentrate used in swimming pools, due to concern about the potential
formation of water soluble or colloidal species that swimmers may ingest.
Products containing silver are not to be applied in marine/estuarine
environments or oil fields. Discharge of effluent into lakes, streams and
ponds or public water is subject to NPDES license restrictions. Water
treated with silver as a pesticide cannot be discharged into sewage systems
without notifying the sewage plant authority.
Ecological Effects
The available acute toxicity data indicate that silver is highly toxic to fish,
aquatic invertebrates and estuarine organisms. Avian toxicity data were
required in the 1992 Data Call-in and these studies are underway. The risk
to birds will be assessed after the data are submitted and reviewed.
However, exposure to birds should be low from the pesticidal uses of silver.
Ecological Effects Risk Assessment
Silver exposure from products used for swimming pool and human drinking
water systems will be discharged to municipal water systems, and treated in
municipal water treatment plants and is regulated under NPDES permits.
The Agency does not expect unreasonable adverse effects to the
environment from these uses.
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Additional Data EPA is requiring a new confidential statement of formula (CSF) detailing
RedUJr0d the nature of the soluble liquid concentrate. EPA also is requiring product-
specific data and revised labeling for reregistration of pesticide products
containing silver.
Product Labeling
Changes Required
The labels of all registered pesticide products containing silver must comply
with EPA's current pesticide labeling requirements. EPA has determined
that the current end-use label precautions are still appropriate and are
required for product reregistration. It is the Agency's position that these
precautions must continue to include a statement indicating that:
a.
This pesticide [silver] is toxic to fish and aquatic
invertebrates.
"Do not discharge effluent containing this product into lakes,
streams, ponds, estuaries, oceans or other waters unless in
accordance with the requirements of a National Pollutant
Discharge Elimination System (NPDES) permit and the
permitting authority has been notified in writing prior to
discharge. Do not discharge effluent containing this product to
sewer systems without previously notifying the local sewage
treatment plant authority. For guidance, contact your State
Water Board or Regional Office of E.P.A."
That the drinking water filters are for use on cold water only.
Regulatory
Conclusion
The use of currently registered pesticide products containing silver in
accordance with approved labeling will not pose unreasonable risks or
adverse effects to humans or the environment. Therefore, all uses of
products containing silver registered as of June 23, 1993 are eligible for
reregistration.
These silver products will be reregistered once the required confirmatory,
product-specific data and revised labeling are received and accepted by
EPA.
For More EPA is requesting public comments on the Reregistration Eligibility
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Information Document (RED) for silver during a 60-day time period, as announced in a
Notice of Availability published in the Federal Register. To obtain a copy
of the RED or to submit written comments, please contact the Pesticide
Docket, Public Response and Program Resources Branch, Field Operations
Division (7506C), Office of Pesticide Programs (OPP), US EPA,
Washington, DC 20460, telephone 703-305-5805.
Following the comment period, the silver RED will be available from
the National Technical Information Service (NTIS), 5285 Port Royal Road,
Springfield, VA 22161, telephone 703-487-4650.
For more information about silver or about EPA's pesticide
reregistration program, please contact the Special Review and Reregistration
Division (7508W), OPP, US EPA, Washington, DC 20460, telephone 703-
308-8000. For information about reregistration of individual products
containing silver, please contact Joanne I. Miller, Product Manager,
Registration Division (7505C), OPP, US EPA, Washington, DC 20460,
telephone 703-305-7830.
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