1.1 What is silver? |
1.2 How might I be exposed to silver? |
1.3 How can silver enter and leave my
body? |
1.4 How can silver affect my health? |
1.5 What levels of exposure have resulted
in harmful health effects? |
1.6 Is there a medical test to determine
whether I have been exposed to silver? |
1.7 What recommendations has the federal
government made to protect human health? |
1.8 Where can I get more information? |
References |
|
|
|
December 1990 |
Public Health Statement |
for |
Silver |
|
|
|
This Public Health Statement is the
summary chapter from the Toxicological
Profile for silver. It is one in a series of Public Health
Statements about hazardous substances and their health effects.
A shorter version, the ToxFAQs™,
is also available. This information is important because this
substance may harm you. The effects of exposure to any hazardous
substance depend on the dose, the duration, how you are exposed,
personal traits and habits, and whether other chemicals are
present. For more information, call the ATSDR Information
Center at 1-888-422-8737.
|
|
|
This Statement was prepared to give you
information about silver and to emphasize the human health
effects that may result from exposure to it. The Environmental
Protection Agency (EPA) has identified 1,177 sites on it's
National Priorities List (NPL). Silver has been found at 27
of these sites However, we do not know how many of the 1,177
NPL sites have beer evaluated for silver. As EPA evaluates
more sites, the number of sites a which silver is found may
change. The information is important for you because silver
may cause harmful health effects and because these sites are
potential or actual sources of human exposure to silver.
When a chemical is released from a large
area, such as an industrial plant or from a container, such
as a drum or bottle, it enters the environment as a chemical
emission. This emission, which is also called a release, does
not always lead to exposure. You can be exposed to a chemical
only when you come into contact with the chemical. You may
be exposed to it in the environment by breathing, eating,
or drinking substances containing the chemical or from skin
contact with it.
If you are exposed to a hazardous substance
such as silver, several factors will determine whether harmful
health effects will occur and what the type and severity of
those health effects will be. These factors include the dose
(how much), the duration (how long), the route or pathway
by which you are exposed (breathing, eating, drinking, or
skin contact), the other chemicals to which you are exposed,
and your individual characteristics such as age sex, nutritional
status, family traits, life style, and state of health.
|
|
1.1
What is silver? |
Silver is one of the basic elements that
make up our planet. Silver is rare but occurs naturally in
the environment as a soft, "silver" colored metal Because
silver is an element, there are no man-made sources of silver
People make jewelry, silverware, electronic equipment, and
dental fillings with silver in its metallic form. It also
occurs in powdery white (silver nitrate and silver chloride)
or dark-gray to black compounds (silver sulfide and silver
oxide). Silver could be found at hazardous waste sites in
the form of these compounds mixed with soil and/or water.
Therefore, these silver compounds will be the main topic of
this profile. Throughout the profile, the various silver compounds
will at times be referred to simply as silver.
Photographers use silver compounds to
make photographs. Photographic materials are the major source
of the silver that is released into the environment. Another
source is mines that produce silver and other metals.
The natural wearing down of silver-bearing
rocks and soil by the wind and rain also releases large amounts
of silver into the environment.
Silver that is released into the environment
may be carried long distances in air and water. Rain washes
silver compounds out of many soils so that it eventually moves
into the groundwater. Silver is stable and remains in the
environment in one form or another until it is taken out again
by people. Because silver is an element, it does not break
down, but it can change its form by combining with other substances.
Over time it may change from the form first released, to metallic
silver, and then back to the same or other compounds. The
form it is found in depends on environmental conditions.
|
back to top |
|
1.2
How might I be exposed to silver? |
Most people are exposed daily to very
low levels of silver mainly in food and drinking water, and
less in air. The silver in these sources is at least partially
due to naturally occurring silver in water and soil. Skin
contact and breathing in air containing silver compounds also
occurs in the workplace. Other sources of exposure include
the use of silver in medicines, and in activities such as
jewelry-making, soldering, and photography. Exposure from
everyday use, such as wearing jewelry or eating with silver-coated
flatware, is not expected to result in silver being taken
into the body.
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
parts soil (ppm) in soils are found from naturally occurring
sources. Silver compounds are also found in groundwater and
at hazardous waste sites throughout the United States. Drinking
water supplies in the United States have been found to contain
silver levels of up to 80 ppb. Surveys show that one-tenth
to one third of samples taken from drinking water supplies
(both groundwater and surface water) contain silver at levels
greater than 30 ppb.
|
back to top |
|
1.3
How can silver enter and leave my body? |
Silver may enter your body through the
mouth, throat, or digestive tract after eating food or drinking
water that contains silver, or through your lungs after breathing
air containing silver. It can also enter your body through
your skin when you put your hands into solutions containing
silver compounds, such as those used in photography, or when
you come in contact with silver-containing powders. Silver
is also known to enter the body when medicines containing
it are taken or applied to the skin or gums. Generally, much
less silver will enter the body through the skin than through
the lungs or stomach.
Because many silver compounds dissolve
in water and do not evaporate, the most common way that silver
may enter the body of a person near a hazardous waste site
is by drinking water that contains silver or eating food grown
near the site in soil that contains silver. Silver can also
enter the body when soil that has silver in it is eaten. Most
of the silver that is eaten or breathed in leaves the body
in the feces within about a week. Very little passes through
the urine. It is not known how much of the silver that enters
the body through the skin leaves the body. Some of the silver
that is eaten, inhaled, or passes through the skin may build
up in many places in the body.
|
back to top |
|
1.4
How can silver affect my health? |
Since at least the early part of this
century, doctors have known that silver compounds can cause
some areas of the skin and other body tissues to turn gray
or blue-gray. Doctors call this condition "argyria." Argyria
occurs in people who eat or breathe in silver compounds over
a long period (several months to many years). A single exposure
to a silver compound may also cause silver to be deposited
in the skin and in other parts of the body; however, this
is not known to be harmful. It is likely that many exposures
to silver are necessary to develop argyria. Once you have
argyria, it is permanent. However, the condition is thought
to be only a "cosmetic" problem. Most doctors and scientists
believe that the discoloration of the skin seen in argyria
is the most serious health effect of silver.
Exposure to dust containing relatively
high levels of silver compounds such as silver nitrate or
silver oxide may cause breathing problems, lung and throat
irritation and stomach pain. These effects have been seen
in workers in chemical manufacturing facilities that make
silver nitrate and silver oxide. One man developed severe
breathing problems shortly after working with molten silver.
Skin contact with silver compounds has been found to cause
mild allergic reactions, such as rash, swelling, and inflammation,
in some people.
Studies of the health effects of silver
in animals commonly use silver nitrate. Doctors and scientists
assume that effects seen using silver nitrate in animals will
be very similar to effects in humans caused by any silver
compound. While this is likely to be true, it is still possible
that some silver compounds will be more harmful, or toxic,
than silver nitrate.
One animal study suggests that long-term
exposure (125 days) to moderately high levels of silver nitrate
in drinking water may have a slight effect on the brain because
exposed animals were less active than animals drinking water
without silver. Another study found that some of the animals
that drank water containing moderately high levels of silver
for most of their lives (9 months or longer) had hearts that
were larger than normal. It is not yet known whether these
effects would occur in humans. There have been suggestions
in some occupational studies in humans that silver can cause
kidney problems; however, more people exposed to silver need
to be studied to find out if silver causes these effects.
No studies of cancer or birth defects
in animals from eating, drinking, or breathing in silver compounds
were found. Therefore, it is not known if these effects would
occur in humans. One study of animals who drank silver compounds
mixed with water for most of their lives found no effect on
fertility. Another study found that reproductive tissues were
damaged in animals after they received injections of silver
nitrate. However, the tissue recovered even while the animals
received more injections of silver nitrate. 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 life-threatening.
Silver does have helpful uses. For example,
silver nitrate was used for many years as drops in newborns'
eyes to prevent blindness caused by gonorrhea, and it is also
used in salves for burn victims. Some water treatment methods
(including water filters) also use a form of silver to kill
bacteria.
|
back to top |
|
1.5
What levels of exposure have resulted in harmful health effects? |
Reports of cases of argyria suggest that
gram amounts of a silver compound taken in medication in small
doses over several months may cause argyria in some humans.
People who work in factories that manufacture silver compounds
can also breathe in the compounds. In the past, some of these
workers have become argyric. However, the level of silver
in the air and the length of exposure that caused argyria
in these workers is not known. It is also not known what level
of silver causes breathing problems, lung and throat irritation,
or stomach pain in people. Studies in rats show that drinking
water containing very large amounts of silver (2,589 parts
of silver per million parts of water, or about 2.6 grams per
liter) is likely to be life-threatening.
There is very little information about
health effects following skin contact with silver compounds.
Argyria that covers the entire body is not seen following
skin contact with silver compounds, although the skin may
change color where it touches the silver. However, many people
who have used skin creams containing silver compounds such
as silver nitrate and silver sulphadiazine have not reported
health problems from the silver in the medicine. In one animal
study, a strong solution of silver nitrate (81 milligrams
silver nitrate per liter of water) applied to the skin of
guinea pigs for 28 days did not cause the animals to die;
however, it did cause the guinea pigs to stop gaining weight
normally. It is not known if this would happen to people if
they were exposed the same way.
|
back to top |
|
1.6
Is there a medical test to determine whether I have been exposed
to silver? |
There are reliable and accurate ways
of measuring silver in the body. Silver can be measured in
the blood, urine, feces, and body tissues of exposed individuals.
Because urine and blood samples are easy to get, these fluids
are most often used to find out if a person has been exposed
to silver in the last week or so. Silver builds up in the
body, and the best way to learn if past exposure has occurred
is to look for silver in samples of skin. Tests for silver
are not commonly done at a doctor's office because they require
special equipment. Although doctors can find out if a person
has been exposed to silver by having blood or skin samples
examined, they cannot tell whether any health effects will
occur.
|
back to top |
|
1.7
What recommendations has the federal government made to protect
human health? |
The EPA recommends that the concentration
of silver in drinking water not exceed 0.10 milligrams per
liter of water (0.10 mg/L) because of the skin discoloration
that may occur.
The EPA requires that spills or accidental
releases of 1,000 pounds or more of silver be reported to
the EPA.
The Occupational Safety and Health Administration
(OSHA) limits silver in workplace air to 0.01 milligrams per
cubic meter (0.01 mg/m³) for an 8-hour workday,
40-hour workweek. The National Institute of Occupational Safety
an Health (NIOSH) also recommends that workplace air contain
no more than 0.01 mg/m³ silver.
The American Conference of Government
Industrial Hygienists (ACGIH) recommends that workplace air
contain no more than 0.1 mg/m³ silver metal and
0.01 mg/m³ soluble silver compounds.
The federal recommendations have been
updated as of July 1999.
|
back to top |
|
1.8 Where can I get more information? |
If you have any more questions or concerns, please contact
your community or state health or environmental quality department or:
Agency for Toxic Substances and Disease Registry
Division of Toxicology
1600 Clifton Road NE, Mailstop F-32
Atlanta, GA 30333
Information line and technical assistance:
Phone: 888-422-8737
FAX: (770)-488-4178
ATSDR can also tell you the location of occupational and environmental health
clinics. These clinics specialize in recognizing, evaluating, and treating illnesses
resulting from exposure to hazardous substances.
To order toxicological profiles, contact:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Phone: 800-553-6847 or 703-605-6000
|
back to top |
|
References |
Agency for Toxic Substances and Disease
Registry (ATSDR). 1990. Toxicological
profile for silver. Atlanta, GA: U.S. Department of Health
and Human Services, Public Health Service.
|
back to top |
|
|
|