Emerging Contaminant - Tungsten
April 2008
FACT SHEET
At a Glance
Introduction
Hard, steel-gray to tin-white solid.
Highest melting point among metals.
Highly flammable and may cause fire
or explosion when exposed to
oxidants.
Low solubility in water and high
sorption (soil/water distribution)
coefficients at low to neutral pH levels.
Typically used in welding, oil-drilling,
electrical, and aerospace industries.
Currently used in "Green Bullets" as
an environmentally friendly alternative
to conventional lead-based
ammunition.
Exposure may cause eye and skin
irritation, cough, nausea, diffuse
Interstitial pulmonary fibrosis, and
changes in blood.
Has not been classified for
carcinogenic effects.
Exposure limits set by the National
Institute for Occupational Safety and
Health (NIOSH) and the American
Conference of Governmental Industrial
Hygienists(ACGIH).
No federal drinking water standard has
been established.
Treatment methods for tungsten in
environmental media are currently
under development. Methods under
investigation involve ice-electrodes,
chemical recovery/soil washing, and
phytoremediation.
An "emerging contaminant" is a chemical or material that is
characterized by a perceived, potential, or real threat to human health or
the environment or a lack of published health standards. A contaminant
may also be "emerging" because a new source or a new pathway to
humans has been discovered or a new detection method or treatment
technology has been developed (DoD 2007). This fact sheet, developed
by the U.S. Environmental Protection Agency (EPA) Federal Facilities
Restoration and Reuse Office (FFRRO), provides a brief summary for
tungsten, including: physical and chemical properties; environmental
and health impacts; existing federal and state guidelines; detection and
treatment methods; and additional sources of information.
Tungsten was originally considered a metal that remains stable in soil
and does not dissolve easily in water. However, it is now a growing
concern to the EPA and Department of Defense (DoD) because recent
research indicates that tungsten may not be as stable as was indicated
in earlier studies. Furthermore, varying soil properties such as pH may
cause tungsten to dissolve and leach into the underlying aquifer (ATSDR
2005). Currently, little information is available about the fate of tungsten
in the environment and its effects on human health. Research about
tungsten is ongoing and includes health effects and risks, degradation
processes, and an inventory of its use in the defense industry as a
substitute for lead-based munitions. This fact sheet provides basic
information on tungsten to site managers and other field personnel who
may be faced with tungsten contamination at a cleanup site.
What is tungsten?
* Tungsten (also known as Wolfram and represented by the letter W
in the periodic table) is a naturally occurring element that exists in
the form of minerals or other compounds but typically not as a pure
metal (NIOSH 2005; ATSDR 2005).
* Wolframite ([FeMn]WO4), and Scheelite (CaWO4) are two common
minerals that contain tungsten (Werner and others 1998).
* Based on its purity, the color of tungsten may range from white for
the pure metal to steel-gray for the metal with impurities. It is
commercially available in powdered or solid form (ATSDR 2005;
NIOSH 2005; NIOSH 2007).
* The melting point of tungsten is the highest among metals and it
resists corrosion. It is a good conductor of electricity and acts as a
catalyst in chemical reactions (ATSDR 2005; Massachusetts DEP
2006; Werner and others 1998).
United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5106P)
1
EPA 505-F-07-005
April 2008
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What is tungsten (continued)?
Tungsten ore is used primarily to produce
tungsten carbide and tungsten alloys, which are
used in many general welding and metal-cutting
applications, in making drilling equipment for oil
wells, and in operations within the aerospace
industry. Tungsten metal is also used to
produce lamp filaments, X-ray tubes, dyes, and
paints for fabrics (ATSDR 2005; Werner and
others 1998).
The DoD has used tungsten as a replacement
for lead in bullets and other ammunition since
1999 (Massachusetts National Guard 2006).
What are the environmental impacts of tungsten?
Tungsten is a common contaminant at industrial
sites that use tungsten and at DoD sites
involved in the manufacture, storage, and use of
tungsten-based ammunition (DoD 2007).
Tungsten particles may be present in air as a
result of mining, weathering of rocks, or
industrial applications that involve tungsten.
These particles may settle on soil, water, or
other surfaces and can be deposited through
rain or other forms of precipitation (ATSDR
2005; Massachusetts DEP 2006).
Tungsten powder is highly flammable and may
ignite instantly on contact with air (ATSDR 2005;
NJDEP 2000). Tungsten also may cause fire or
explosion on contact with oxidants (NIOSH
2007).
Tungsten has been detected at six National
Priorities List (NPL) sites (ATSDR 2005).
Earlier research on tungsten indicated that it is
stable in soil because of its soil binding capacity
and its insolubility in water. At lower pH values,
sorption coefficients increase, indicating lower
mobility of tungsten. Recent studies indicate
that an elevated pH level in soil at a site may
increase the solubility of tungsten by decreasing
its sorption coefficient, which may cause it to
leach more readily into the groundwater table.
(ATSDR 2005; NIEHS 2003; TOXNET 2007;
Warminsky and Larson 2004).
In 1997, EPA Region 1 issued administrative
orders to suspend the use of lead bullets at the
Massachusetts Military Reservation (MMR).
Small arms training at MMR continued
uninterrupted using tungsten nylon bullets.
However, the stability of tungsten in the
environment became questionable when
tungsten was detected in the groundwater and
above baseline levels in soil at a
small arms range at MMR in 2006, resulting in
the suspension of the use of the tungsten nylon
bullets at MMR (EPA 2007; ATSDR 2005;
Massachusetts National Guard 2006).
Under the U.S. Army's Green Bullet program,
nearly 88 million bullets were produced, of which
33 million remain unfired and available for use at
training ranges across the country. Currently,
the Army Environmental Center is looking at
training ranges to evaluate the presence of
various chemicals and other potential
contaminants, including tungsten (Defense
Environmental Alert 2007).
Exhibit 1: Physical and Chemical Properties of Tungsten
(NIOSH 2005; NIEHS 2003; TOXNET 2007)
Property
CAS Number
Physical Description (Physical state at room temperature)
Molecular weight (g/mol)
Water solubility (g/L at 25°C)
Boiling point (°C)
Melting point (°C)
Vapor pressure at 25°C (mm Hg)
Specific gravity
7440-33-7
Hard, steel-gray to tin-white solid
183.9
Insoluble at pH less than 6.5
5,927
3,410
0
19.3
Notes: g/mol - gram per mole; g/L - grams per liter; °C - degrees Celsius; mm Hg - millimeters of mercury.
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What are the health effects of tungsten?
Occupational exposure is considered the most
common scenario for human exposure to
tungsten and its compounds. Inhalation,
ingestion, and dermal and eye contact are the
possible exposure pathways (ATSDR 2005;
NIOSH 2007).
Occupational inhalation exposure to tungsten is
known to affect the eyes, skin, respiratory
system, and blood (ATSDR 2005). Tungsten
may cause irritation to eyes, skin and throat;
diffuse interstitial pulmonary fibrosis; loss of
appetite; nausea; cough; and changes in the
blood (NIOSH 2005).
Tungsten has not been classified for
carcinogenic effects by the Department of
Health and Human Services (DHHS), the
International Agency for Research on Cancer
(IARC), or EPA (ATSDR 2005).
Studies on rats have shown that oral exposure
to tungsten caused post-implantation deaths and
developmental abnormalities in the
musculoskeletal system. Exposure of pregnant
rats to sodium tungstate resulted in fetal death
(NIEHS2003).
Are there any existing federal and state guidelines and health standards for
tungsten?
A federal drinking water standard has not been
established for tungsten.
The National Institute for Occupational Safety
and Health (NIOSH) and the American
Conference of Industrial Hygienists (ACGIH)
have established a recommended exposure limit
(REL) of 5 milligrams per cubic meter (mg/m3)
as the time-weighted average (TWA) over a 10-
hour work exposure and 10 mg/m3 as the 15-
minute, short-term exposure limit (STEL) for
airborne exposure to tungsten (ATSDR 2005;
NIOSH 2007; NJDEP 2000).
The Occupational Safety and Health
Administration (OSHA) recommends an
exposure limit of 5 mg/m3 to insoluble
compounds of tungsten and a 1 mg/m3 limit of
exposure to soluble compounds in construction
and shipyard industries (ATSDR 2005).
What detection and site characterization methods are available for tungsten?
NIOSH Method 7074 - flame atomic absorption
spectroscopy with a detection limit of 0.1 mg/m3
for insoluble forms of tungsten and 0.05 mg/m3
for soluble forms of tungsten in air (NIOSH
2005; TOXNET 2007).
Other NIOSH methods known to be used for
tungsten are Methods 7300 and 7301.
Information about detection limits for these
methods is not available in the references cited
(NIOSH 2005; TOXNET 2007).
OSHA ID213 - inductively coupled plasma
atomic emission spectroscopy (ICP-AES) with a
detection limit of 0.34 mg/m for tungsten in air
(NIOSH 2005; OSHA 2007).
Tungsten in soil and water can be measured
using the ICP-AES, ICP-mass spectrometry
(ICP-MS), and ultraviolet/visible spectroscopy
(UV/VIS) methods (ATSDR 2005).
What technologies are being used to treat tungsten?
Treatment technologies to address tungsten
contamination in environmental media are
currently under development. According to
preliminary studies conducted by various
research groups, potential treatment methods
involve chemical recovery/soil washing and
phytoremediation (Lehr2004; Warminsky and
Larson 2004).
"Ice electrode" is an innovative technology being
evaluated for liquid media. This technology is
based on the conventional electroplating
technique and uses an electrode coated with a
thin layer of ice. Tungsten ions adhere to the
ice-coated electrode and can be removed by
melting the ice (Lehr2004).
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Where can I find more information about tungsten?
Agency for Toxic Substances and Disease
Registry (ATSDR). 2005. Toxicological Profile
for Tungsten.
http://www.atsdr.cdc.gov/toxprofiles/tp186.pdf
Hazardous Substances Data Bank: Tungsten
Compounds, http://toxnet.nlm.nih.gov/cgi-
bin/sis/search/r?dbs+hsdb:@term+@na+tungste
n+compounds.
Inside EPA. 2007. Defense Environment Alert
- Emerging Contaminants: Army risk study on
tungsten could be first step toward regulation.
January 23, 2007.
Lehr, Jay H. 2004. Wiley's Remediation
Technologies Handbook: Major Contaminant
Chemicals and Chemical Groups (ISBN 0-471-
45599-7), pp. 282, 567, & 568.
Massachusetts Department of Environmental
Protection (DEP). 2006. Fact Sheet: Tungsten
and Tungsten Compounds.
Massachusetts National Guard. 2006.
Massachusetts National Guard Temporarily
Suspends Use of Tungsten-Nylon Ammunition
at Camp Edwards, Massachusetts - News
Release. .
National Institute for Occupational Safety and
Health (NIOSH). 2005. NIOSH Pocket Guide to
Chemical Hazards: Tungsten.
National Institute of Environmental Health
Sciences (NIEHS). 2003. Tungsten and
Selected Tungsten Compounds - review of
Toxicological Literature.
National Institute for Occupational Safety and
Health (NIOSH). 2007.
www.cdc.gov/niosh/ipcsneng/neng1404.html.
New Jersey Department of Health and Senior
Services. 2000. Hazardous Substance Fact
Sheet: Tungsten.
http://ni.gov/health/eoh/rtkweb/documents/fs/195
9.pdf
Occupational Safety and Health Administration
(OSHA). 2007. Tungsten and Cobalt in
Workplace Atmospheres (ICP Analysis).
U.S. Department of Defense. 2007. Emerging
Contaminants.
www.denix.osd.mil/denix/Public/Library/MERIT/
merit.html.
U.S. Environmental Protection Agency Region 1.
2007. Massachusetts Military Reservation.
www.epa.gov/region01/mmr/.
Warminsky, Michael F. (AMEC Earth and
Environmental, Inc., Somerset, NJ) and Dr.
Steven Larson (U.S. Army Engineer Research
and Development Center, Vicksburg, MS).
Recovery and Recycling of Tungsten and Lead
from Small Arms Firing Range Soils. 2004.
Presented at the Annual Conference on Soil,
Sediment, and Water- University of
Massachusetts Fall Conference (October 19-
21).
www.umasssoils.com/abstracts2004/Tuesday/tr
ainingranges.htm.
Werner, Antony B.T., W. David Sinclair, and
Earle B. Amey (USGS). 1998. International
Strategic Mineral Issues Summary Report—
Tungsten; USGS Circular 930-O.
http://pubs.usgs.gov/pdf/circular/c930-o.pdf
Contact Information
If you have any questions or comments on this fact sheet, please contact: Mary Cooke, FFRRO, by phone at
(703) 603-8712 or by e-mail at cooke.maryt@epa.gov.
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