Public Health Statement for Tungsten
Spanish: Tungsteno
CAS#: 7440-33-7
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This Public Health Statement is the
summary chapter from the Toxicological Profile for Tungsten. It is one in a series of Public Health Statements about hazardous substances and their health effects. A shorter version, the ToxFAQsTM
, 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 1-800-232-4636.
This public health statement tells you about tungsten and the effects of exposure to it.
The Environmental Protection Agency (EPA) identifies the most serious hazardous waste sites in the nation. These sites are then placed on the National Priorities List (NPL) and are targeted for long-term federal clean-up activities. Tungsten has been found in at least 6 of the 1,662 current or former NPL sites. Although the total number of NPL sites evaluated for this substance is not known, the possibility exists that the number of sites at which tungsten is found may increase in the future as more sites are evaluated. This information is important because these sites may be sources of exposure and exposure to this substance may harm you.
When a substance is released either from a large area, such as an industrial plant, or from a container, such as a drum or bottle, it enters the environment. Such a release does not always lead to exposure. You can be exposed to a substance only when you come in contact with it. You may be exposed by breathing, eating, or drinking the substance, or by skin contact.
If you are exposed to tungsten, many factors will determine whether you will be harmed. These factors include the dose (how much), the duration (how long), and how you come in contact with it. You must also consider any other chemicals you are exposed to and your age, sex, diet, family traits, lifestyle, and state of health.
What is tungsten?
Tungsten is a naturally occurring element that, in most environments, is a solid. In nature, it occurs in rocks and soil as minerals, but never as the pure metal. Two kinds of tungsten-bearing mineral rocks, called wolframite and scheelite, are mined commercially. The mineral ore is processed to recover the tungsten and turn it into either chemical compounds or metal. Elemental tungsten, like elemental copper or gold, is a metal. Its color can range from tin white (for the pure metal) to steel gray (for metal that has impurities in it). Tungsten can be used as a pure metal or mixed with other metals to make alloys. Tungsten alloys tend to be strong and flexible, resist wear, and conduct electricity well. Tungsten and its alloys are used as light bulb filaments, as the part of x-ray tubes where x-rays are formed, as a catalyst to speed up chemical reactions, as a component of steel in high-speed tools, in turbine blades, in phonographic needles, as welding electrodes, as gyroscope wheels, as counterbalance and fishing weights, in darts, and in golf club components. They can be used in bullets (as a replacement for lead) and in armor penetrators (as a substitute for depleted uranium). Chemical compounds of tungsten are used for many purposes. Cemented tungsten carbide, a hard substance used to make grinding wheels and cutting or forming tools, is the most common tungsten compound. Other tungsten compounds are used in ceramic pigments, as fire retardant coatings for fabrics, and as fade-resistant dyes for fabrics.
What happens to tungsten when it enters the environment?
Tungsten occurs naturally in the environment,
in minerals, but not as the pure metal. As an element, tungsten
can be neither created nor destroyed chemically, although
tungsten can change forms in the environment.
Tungsten is released into air as fine
dust-like particles by weathering. Emissions from hard metal
industries also increase tungsten levels in air. The amount
of tungsten that has been measured in the ambient air is,
in general, less than 10 billionths of a gram per cubic meter
(or parts per billion [ppb]). Very small dust particles of
tungsten in the air fall out onto surface water, plant surfaces,
and soil either by themselves or when rain or snow falls.
These tungsten particles eventually recycle back in the soil
or in the bottoms of lakes, rivers, and ponds, where they
stay and mix with tungsten that is already there.
Tungsten in water originates mainly from
dissolution of tungsten from rocks and soil that water runs
over and through. Tungsten has not been detected in the vast
majority of surface water and groundwaters of the United States.
Some exceptions include areas near mines and natural deposits,
and also in Churchill County (City of Fallon), in Nevada,
where tungsten has been detected in municipal water and groundwater.
Only a very small fraction of tungsten in water originates
from the settling of dust out of the air. Most tungsten products
of human-origin that enter waterways originate from industry
discharges of waste water. Tungsten in water may be in either
soluble or insoluble forms. Insoluble tungsten in water can
settle to the bottom where it enters sediment. Some insoluble
tungsten compounds, however, can remain suspended in ocean
water for many years, requiring as long as 1,000 years to
settle to the bottom.
Tungsten occurs naturally in soil as
a mineral, or component of soil. It occurs in amounts that
vary over a wide range from less than 1 to as high as 83 thousandths
of a gram per kilogram of soil. Another way to say this is
that the tungsten concentration ranges from 1 to 83 parts
per million (ppm) in soil by weight. Disposal of coal ash,
incinerator ash, and industrial wastes may increase the amount
of tungsten in soil. A portion of tungsten in soil does not
dissolve in water, but remains bound and is not likely to
move deeper into the ground and enter groundwater. The remaining
soluble portion may move deeper into the ground and enter
groundwater if the pH is greater than 7. In the environment,
chemical reactions can change the water-soluble tungsten compounds
into insoluble forms. In some cases, water-insoluble tungsten
compounds can change to soluble forms. In general, exposure
to water-soluble tungsten compounds in the environment will
pose a greater threat to human health than water-insoluble
forms.
How might I be exposed to tungsten?
You can be exposed to low levels of tungsten
by breathing air, drinking water, or eating food that contains
tungsten. The average ambient concentration of tungsten in
air has been reported to be less than 10 nanograms in a cubic
meter of air (1 nanogram is 1 billionth of a gram). Cities
have higher levels of tungsten in the air because tungsten
is released from industry. Tungsten has been detected in municipal
water from Fallon, Nevada. However, the amounts of tungsten
in drinking water are generally not known. This is probably
because the tungsten levels are lower than the laboratory
methods are able to detect without concentrating samples,
or the laboratory does not measure for tungsten. The amounts
in foods are generally not known, possibly for the same reasons.
Tungsten in plants was either taken up by the plant or was
attached to the plant as a component of the soil. The concentration
of tungsten in onions collected from Denmark is 17 micrograms
in a kilogram of fresh vegetables. Although very limited data
are available, exposure to tungsten from air, drinking water,
and food is expected to be insignificant.
In certain workplaces, you can be exposed
to levels of tungsten in air that are higher than background
levels, which are very small or none. Exposures are mostly
in the form of tungsten metal or tungsten carbide. Occupational
exposure to tungsten occurs primarily at places where individuals
use hard metals containing tungsten or are engaged in the
machining of these metals. This includes the grinding (pointing)
of tungsten metal welding electrodes prior to use. Occupational
exposure to tungsten carbide occurs during the machining of
tungsten carbide tools in the manufacturing process. The total
number of individuals occupationally exposed to tungsten or
its compounds has been estimated to be about 47,000.
Tungsten metal and metal alloys occur
in consumer products such as electronics, light bulb filaments,
cemented tungsten carbide grinding wheels, carbide tipped
tools, and "green" bullets. No other consumer products
or products used in crafts, hobbies, or cottage industries
were identified that contain significant amounts of tungsten.
It is unlikely that tungsten present in consumer products
poses a hazard. However, appropriate dust masks are recommended
for amateur craftsmen engaging in activities that may potentially
produce tungsten carbide dust (e.g., metal grinding).
How can tungsten enter and leave my body?
Tungsten can enter your body from the
food you eat or the water you drink, from the air you breathe,
or from contact with the skin. When you eat, drink, breathe,
or touch things containing tungsten compounds that can easily
be dissolved in water, tungsten enters your blood and is carried
to all parts of your body. Most of the tungsten that enters
your blood is rapidly released from your body in the urine.
When you eat or drink things containing tungsten, much of
the tungsten passes through your digestive system and is released
from your body in the feces. When you breathe air that contains
tungsten, some of the tungsten moves quickly to your bloodstream
from the lungs, and some of the tungsten is cleared from your
lungs in mucus that is either swallowed or spit out. When
you swallow tungsten that was first in your lungs, it passes
through your digestive system as if you had eaten it. Some
enters your blood from your digestive system and some passes
out with the feces. A small portion of the tungsten that enters
your blood may spend some time in bone, fingernails, or hair.
Some of this tungsten is slowly eliminated from your body
through the urine and feces.
How can tungsten affect my health?
Scientists use many tests to protect
the public from harmful effects of toxic chemicals and to
find ways for treating persons who have been harmed.
One way to learn whether a chemical will
harm people is to determine how the body absorbs, uses, and
releases the chemical. For some chemicals, animal testing
may be necessary. Animal testing may also help identify health
effects such as cancer or birth defects. Without laboratory
animals, scientists would lose a basic method for getting
information needed to make wise decisions that protect public
health. Scientists have the responsibility to treat research
animals with care and compassion. Scientists must comply with
strict animal care guidelines because laws today protect the
welfare of research animals.
You are not likely to experience any
health effects that would be related to exposure to tungsten
or tungsten compounds. Tungsten compounds have caused breathing
problems and changed behavior in some animals given very large
amounts of tungsten compounds, but you are not likely to be
exposed to amounts of tungsten in the air you breathe or the
food or water you take into your body that would be large
enough to cause similar effects. If you are a worker who has
inhaled tungsten heavy metal dust, your exposure would help
determine if health effects similar to those seen in animals
might occur.
How can tungsten affect children?
This section discusses potential health
effects in humans from exposures during the period from conception
to maturity at 18 years of age.
Children could be affected in the same
ways as adults. In adult animals, very large amounts of tungsten
compounds have been shown to cause breathing problems and
changes in behavior. However, it is not likely that children
would be exposed to amounts of tungsten in the air they breathe
or the food or water they consume that would be large enough
to cause effects similar to those that were seen in the animals.
Animal studies have shown that tungsten in the blood of a
pregnant mother can enter the blood of a fetus in the womb.
Studies in dairy cows have shown that tungsten may also enter
the milk. There is no information to suggest that the effects
seen in animals could not occur in humans. We do not know
whether unborn babies, babies, and children might differ from
adults in their susceptibility to health effects from exposure
to tungsten or tungsten compounds.
How can families reduce the risk of exposure to tungsten?
If your doctor finds that you have been
exposed to substantial amounts of tungsten, ask whether your
children might also have been exposed. Your doctor might need
to ask your state health department to investigate.
Children living near waste sites containing
tungsten are likely to be exposed to higher environmental
levels of tungsten through breathing contaminated air, drinking
contaminated water, touching soil, and eating contaminated
soil. Children sometimes eat dirt, which should be discouraged.
Parents should supervise to see that children wash their hands
frequently and before eating. Parents should consult their
family physicians about whether (and how) hand-to-mouth behaviors
in their children might be discouraged. If your community's
drinking water has been reported to contain elevated levels
of tungsten, you should take advantage of alternative water
sources such as bottled water for drinking. Some children
may be exposed to tungsten by contact with a family member
who works in a facility using tungsten or who works with tungsten
carbide grinding wheels. If you work at a facility that uses
tungsten or have tungsten dust on your clothes, change your
clothes and clean your hair and skin before leaving your job
or work site and returning home. Do not bring objects home
such as work tools that may be contaminated with tungsten.
Is there a medical test to determine whether I have been exposed
to tungsten?
Medical tests exist that can determine
whether your body fluids contain high levels of tungsten.
Samples of blood or feces can be collected in a doctor's office
and sent to a laboratory that can measure tungsten levels.
It is easier for most laboratories to measure tungsten in
blood than in feces. The presence of high levels of tungsten
in the feces can mean recent high tungsten exposure. High
levels of tungsten in the blood can mean high tungsten consumption
and/or high exposure. High tungsten levels in blood or feces
reflect the level of exposure to tungsten. Measuring tungsten
levels in urine and saliva also may provide information about
tungsten exposure. Tests to measure tungsten in hair may provide
information on long-term tungsten exposure.
What recommendations has the federal government made to protect human health?
The federal government develops regulations
and recommendations to protect public health. Regulations
can be enforced by law. The EPA, the Occupational Safety and
Health Administration (OSHA), and the Food and Drug Administration
(FDA) are some federal agencies that develop regulations for
toxic substances. Recommendations provide valuable guidelines
to protect public health, but cannot be enforced by law. The
Agency for Toxic Substances and Disease Registry (ATSDR) and
the National Institute for Occupational Safety and Health
(NIOSH) are two federal organizations that develop recommendations
for toxic substances.
Regulations and recommendations can be
expressed as "not-to-exceed" levels, that is, levels
of a toxic substance in air, water, soil, or food that do
not exceed a critical value that is usually based on levels
that affect animals; they are then adjusted to levels that
will help protect humans. Sometimes these not-to-exceed levels
differ among federal organizations because they used different
exposure times (an 8-hour workday or a 24-hour day), different
animal studies, or other factors.
Recommendations and regulations are also
updated periodically as more information becomes available.
For the most current information, check with the federal agency
or organization that provides it. Some regulations and recommendations
for tungsten include the following:
There are few guidelines for tungsten
and tungsten compounds. For tungsten and insoluble tungsten
compounds, NIOSH has established a recommended exposure limit (REL; 10-hour time weighted average) of 5 mg/m3 and a short-term exposure limit (STEL; 15-minute time weighted average) of 10 mg/m3. OSHA has established permissible exposure limits (PELs; 8-hour time weighted average) for tungsten of 5 mg/m3 (insoluble compounds) and 1 mg/m3 (soluble compounds) for construction and shipyard industries.
References
Agency for Toxic Substances and Disease Registry (ATSDR).
2005. Toxicological profile for Tungsten.
Atlanta, GA: U.S. Department of Health and Human Services,
Public Health Service.
Where can I get more information?
If you have questions or concerns, please contact your community or state health or environmental quality department or:
For more information, contact:
Agency for Toxic Substances and Disease Registry
Division of Toxicology and Human Health Sciences
4770 Buford Highway
Chamblee, GA 30341-3717
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO
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.