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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