&EPA
United States
Environmental Protection
Agency
Technical Fact Sheet-
Tungsten
May 2012
TECHNICAL FACT SHEET-TUNGSTEN
At a Glance
* Hard, steel-gray to tin-white
solid.
* Highest melting point among
metals and is a good conductor
of electricity.
* Typically used in welding, oil-
drilling, electrical, and
aerospace industries.
* Low solubility in water and high
sorption (soil/water distribution)
coefficients at low to neutral pH
levels.
* Questions are being raised
about tungsten's environmental
stability.
* Exposure may cause eye and
skin irritation, cough, nausea,
diffuse interstitial pulmonary
fibrosis, and changes in blood.
* No federal drinking water
standard established.
* Exposure limits set by the
National Institute for
Occupational Safety and Health
(NIOSH) and the American
Conference of Governmental
Industrial Hygienists (ACGIH).
* Treatment methods for tungsten
in environmental media currently
under development. Methods
under investigation involve ice-
electrodes, electrokinetic soil
remediation, and chemical
recovery/soil washing.
Introduction
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
did not dissolve easily in water. However, it is now a growing concern to
EPA and the U. S. 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 and transport 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 cleanup sites.
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
(ATSDR 2005; NIOSH 2007).
Wolframite ([FeMn]WO4) and Scheelite (CaWO4) are two common
minerals that contain tungsten (Koutsospyros et al. 2006).
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 a powdered or solid form (ATSDR 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; Koutsospyros et al. 2006;
Massachusetts DEP 2006).
Tungsten powder is highly flammable and may ignite instantly on
contact with air. Tungsten also may cause fire or explosion on contact
with oxidants (ATSDR 2005; NIOSH 2007).
DoD has used tungsten as a replacement for lead in bullets and other
ammunition since 1999 (Massachusetts National Guard 2006).
United States
Environmental Protection Agency
Solid Waste and
Emergency Response (5106P)
1
EPA 505-F-11-005
May 2012
-------
Technical Fact Sheet - Tungsten
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;
Koutsospyros et al 2006).
Under the U. S. Army's Green Bullet program, nearly
88 million tungsten bullets were produced; 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
(Inside EPA 2007).
Exhibit 1: Physical and Chemical Properties of Tungsten
(HSDB 2009; NIEHS 2003; NIOSH 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 - grams per mole; g/L - grams per liter; °C - degrees Celsius; mm Hg - millimeters of mercury.
What are the environmental impacts of tungsten?
»> Tungsten is a common contaminant at industrial
sites that use the metal and at DoD sites involved
in the manufacture, storage, and use of tungsten-
based ammunition. It is also found in detectable
amounts in municipal solid waste and landfill ,«.
leachate because of its use in common household
products such as light bulbs (Koutsospyros et al.
2006).
»> 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 A
be deposited through rain or other forms of
precipitation (ATSDR 2005; MA DEP 2006).
»> Tungsten is considered a "lithophilic" element,
based on its strong soil binding capacity and its
insolubility in water. Sorption coefficients increase
at lower pH values, indicating lower mobility of
tungsten (Koutsospyros et al. 2006).
»> Increased acidification and oxygen depletion of
soils from dissolution of tungsten powder have
What are the health effects of tungsten?
been shown to trigger changes in the soil microbial
community, causing an increase in fungal biomass
and a decrease in the bacterial component (Strigul
et al. 2005).
Studies indicate that an elevated pH 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 ground water
table (ATSDR 2005; ASTSWMO 2008).
Tungsten has been detected at six National
Priorities List (NPL) sites (ATSDR 2005).
In 2006, the assumed stability of tungsten in the
environment was questioned when tungsten was
detected in ground water and above baseline
levels in soil at a small arms range at
Massachusetts Military Reservation (MMR) where
tungsten nylon bullets were being used. The use of
these bullets was then suspended (ATSDR 2005;
EPA 201 Ob; Massachusetts National Guard 2006).
Toxicological information on tungsten and its
compounds is limited (Koutsospyros et al. 2006).
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).
-------
Technical Fact Sheet - Tungsten
What are the health effects of tungsten? (continued)
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 2007).
Tungsten was included as part of EPA's 2008
Integrated Risk Information System (IRIS) agenda.
Toxicity is currently being assessed (EPA 201 Oa).
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 (NIEHS 2003).
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).
Are there any 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 Council of
Government 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; ASTSWMO 2008).
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).
Massachusetts has established action levels of 1 to
2 parts per million (ppm) in soil and 15 ppm in
groundwater (ASTSWMO 2008).
What detection and site characterization methods are
available for tungsten?
NIOSH Method 7074 - flame atomic absorption
spectroscopy has a detection limit of 0. 1 mg/m3 for
insoluble forms of tungsten and 0. 05 mg/m for
soluble forms of tungsten in air (HSDB 2009; NIOSH
2007).
Other NIOSH methods known to be used for
tungsten are Methods 7300 and 7301, involving
inductively coupled argon plasma, atomic emission
spectroscopy, each with a detection limit of 0. 005
mg/m3 (NIOSH 2003a, b). Special sample treatment
may be required for some tungsten compounds.
ID213 - inductively coupled plasma atomic emission
spectroscopy (ICP-AES) has a detection limit of 0.
34 mg/m3 for tungsten in air (NIOSH 2007; 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).
Tungsten is not currently included on the list of
recoverable metals using SW-846 Method 3051.
However, the digestion method has modified to
enhance tungsten recovery from soils (Griggs et al.
2009).
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 (Lehr 2004; 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 (Lehr 2004).
Electrokinetic soil remediation is an emerging in situ
technology for removal of tungsten from low-
permeability soils in the presence of copper and
lead. A direct current is applied to contaminated
soils using electrodes inserted into the ground
(Braida et al. 2007).
-------
Technical Fact Sheet - Tungsten
Where can I find more information about tungsten?
»> Agency for Toxic Substances and Disease Registry •
(ATSDR). 2005. Toxicological Profile for Tungsten.
www.atsdr.cdc.gov/toxprofiles/tp186.pdf
»> Association of State and Territorial Solid Waste
Management Officials (ASTSWMO). 2008. Tungsten
Issues Paper. www.astswmo.org/Files/
Policies and Publications/Federal Facilities/TUNG
STEM FINAL 120208.pdf
»> Braida, W., C. Christodoulatos, A. Ogundipe, D.
Dermatas, and G. O'Connor. 2007. Electrokinetic
treatment of firing ranges containing tungsten-
contaminated soils. Journal of Hazardous Materials.
Volume 149. Pages 562 to 567.
»> Griggs C., S. Larson, C. Nestler, and M. Thompson.
2009. Coupling of oxygen and pH requirements for
effective microwave-assisted digestion of soils for
tungsten analysis. Land Contamination &
Reclamation. Volume 17. Pages 121 to 128.
»> Hazardous Substances Data Bank (HSDB):
Tungsten Compounds. 2009.
http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen7HSDB
»> Inside EPA. 2007. Defense Environment Alert -
Emerging Contaminants: Army risk study on
tungsten could be first step toward regulation.
January 23, 2007.
»> Koutsospyros, A., W. Braida, C. Christodoulatos, D.
Dermatas, and N. Strigul. 2006. A review of
tungsten: From environmental obscurity to scrutiny.
Journal of Hazardous Materials. Volume 136. Pages
1 to 19.
•:« Lehr, Jay H. 2004. Wiley's Remediation
Technologies Handbook: Major Contaminant
Chemicals and Chemical Groups (ISBN 0-471-
45599-7). Pages 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.
Contact Information
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). 2003a. Elements by ICP (Nitric/Perchloric
Acid Ashing) - Method 7300. NIOSH Manual of
Analytical Methods (NMAM), Fourth edition.
www.cdc.gov/niosh/pdfs/97-162-f.pdf
NIOSH. 2003b. Elements by ICP (Aqua Regia
Ashing) - Method 7301. NIOSH Manual of Analytical
Methods (NMAM), Fourth Edition.
www.cdc.gov/niosh/docs/2003-154/chaps.html
NIOSH. 2007. NIOSH Pocket Guide to Chemical
Hazards: Tungsten, www.cdc.gov/niosh/docs/2005-
149/pdfs/2005-149.pdf
Occupational Safety and Health Administration
(OSHA). 2007. Tungsten and Cobalt in Workplace
Atmospheres (ICP Analysis).
Strigul, N., A. Koutsospyros, P. Arienti, C.
Christodoulatos, D. Dermatas, and W. Braida. 2005.
Effects of tungsten on environmental systems.
Chemosphere. Volume 61. Pages 248 to 258.
U. S. Environmental Protection Agency (EPA).
201 Oa. IRIS Agenda and Literature Searches.
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm7deid
=187215
EPA. 201 Ob. Region 1. Massachusetts Military
Reservation, www.epa.gov/region01/mmr/.
Warminsky, Michael F. and Dr. Steven Larson.
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/trainin
granges.htm.
If you have any questions or comments on this fact sheet, please contact: Mary Cooke, FFRRO, by phone at
(703) 603-8712 or by email at cooke.maryt@epa.gov.
------- |