&EPA
      United States
      Environmental Protection
      Agency
         Technical Fact Sheet -
                                   Tungsten
                                       January 2014
                                                        TECHNICAL FACT SHEET- TUNGSTEN
  At a Glance

  *  Hard, steel-gray to 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), Occupational Safety
     and Health Administration
     (OSHA) and the American
     Conference of Governmental
     lndustrialHygienists(ACGIH).

    Treatment methods for tungsten
     in environmental media are
     currently under development.
     Methods under investigation
     include electrokinetic soil
     remediation and
     phytoremediation.
Introduction
This fact sheet, developed by the U. S. Environmental Protection Agency
(EPA) Federal Facilities Restoration and Reuse Office (FFRRO), provides a
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. This
fact sheet provides basic information on tungsten to site managers and other
field personnel who may address tungsten contamination at cleanup sites.
Tungsten was originally considered a stable metal in soil that does not
dissolve easily in water. However, tungsten-contaminated environmental
media are now a growing concern to the 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 from soil into
underlying aquifers (ATSDR2005). 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.
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, but typically not as a pure metal (ATSDR 2005; NIOSH 2010).
   There are more than 20 known tungsten-bearing minerals. Wolframite
   ([FeMn]WO4) and Scheelite (CaWO4) are two common minerals that
   contain tungsten and that are mined commercially (ATSDR 2005;
   Koutsospyros and others 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; NIEHS 2003; NIOSH
   2010).
   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; Gbaruko and Igwe 2007; Koutsospyros
   and others 2006).
 Disclaimer: The U.S. EPA prepared this fact sheet from publically-available sources;
 additional information can be obtained from the source documents. This fact sheet is not
 intended to be used as a primary source of information and is not intended, nor can it be
 relied upon, to create any rights enforceable by any party in litigation with the United
 States. Mention of trade names or commercial products does not constitute
 endorsement or recommendation for use.
United States
Environmental Protection Agency
           Office of Solid Waste and
           Emergency Response (5106P)
                  1
EPA 505-F-14-004
    January 2014

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  Technical Fact Sheet - Tungsten
What is tungsten (continued)?
    Tungsten in the form of finely divided powder is
    highly flammable and may ignite spontaneously on
    contact with air. Powdered tungsten may also
    cause fire or explosion on contact with oxidants
    (HSDB 2009a; NIOSH 2010).
    Tungsten ore is used primarily to produce
    tungsten carbide and tungsten alloys, which are
    used in many general welding and metal-cutting
    applications, for operations within the aerospace
    industry and in sporting good products such as
    golf clubs. Tungsten metal is also used to produce
    lamp filaments, X-ray tubes, dyes and  paints for
    fabrics (Koutsospyros and others 2006; NIEHS
    2003).
    Tungsten/nylon "green" bullets were introduced as
    a replacement to lead bullets and other
    ammunition in the United States and other
    countries. DoD began using tungsten as a
    replacement for lead in bullets in 1999 for training.
    In early 2003, the production of  tungsten/nylon
bullets was discontinued based on flight instability
issues (ATSDR 2005; USAGE 2007).
Recent reports of tungsten contamination in
groundwater and soil at military sites have raised
concerns about tungsten's stability in the
environment and resulted in the suspension of
tungsten/nylon bullets in some military
applications. For example, the use of
tungsten/nylon bullets at the Massachusetts
Military Reservation was suspended in February
2006 based on concerns about tungsten's mobility
in the environment (Kennedy and others 2012;
USAGE 2007).
Under the U.S. Army's Green Ammunition
program, at least 85 million rounds of
tungsten/nylon bullets were produced. Currently,
the Army Environmental Center evaluating the fate
and transport properties of tungsten at training
ranges (USAGE 2007).
                  Exhibit 1: Physical and Chemical Properties of Elemental Tungsten
                         (ATSDR 2005; HSDB 2009a; NIEHS 2003; NIOSH 2010)
Property
Chemical Abstracts Service (CAS) Number
Physical Description (physical state at room temperature)
Molecular weight (g/mol)
Water solubility
Boiling point (C at 760 mm Hg)
Melting point (C)
Vapor pressure at 2,327C (mm Hg)
Specific gravity/Density at 20/4 C

7440-33-7
Hard, steel-gray to tin-white solid
183.85
Insoluble
5,900
3,410
1.97x10"'
18.7 to 19.3
     Abbreviations: g/mol - grams per mole; C - degrees Celsius; mm Hg - millimeters of mercury.

What are the environmental impacts of tungsten?
    Tungsten is a common contaminant at mining
    sites, 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 filaments in
    incandescent light bulbs (Koutsospyros and others
    2006).
    Tungsten particles may be present in the
    environment as a result of mining, weathering of
    rocks, burning of coal and municipal solid waste,
    land application of fertilizers or industrial
    applications that involve tungsten (ATSDR 2005).
    In the ambient atmosphere, tungsten compounds
    exist in the particulate phase because of their low
    vapor pressures. These particles may settle on
    soil, water or other surfaces and can be deposited
through rain or other forms of precipitation (ATSDR
2005; NIEHS 2003).
Tungsten is considered a "lithophilic" element
(preferring terrestrial over atmospheric or aquatic
environments) based on its low vapor pressure and
atmospheric interference factor. Tungsten
compounds are expected to exist as ions or
insoluble solids in the environment; therefore,
volatilization from soil surfaces is  not considered
an important fate and transport process
(Koutsospyros and others 2006; NIEHS 2003).
The sorption coefficients for tungsten increase as
pH decreases, indicating low to moderate mobility
of tungsten in soil under low to neutral
environmental conditions. Sorption coefficients for
the tungstate ion range from  100 to 50,000 at
about pH 5, 10 to 6,000 at about pH 6.5 and 5 to
90 at pH 8 to 9 (Meijer and others 1998).

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  Technical Fact Sheet - Tungsten
What are the environmental impacts of tungsten? (continued)
    Studies indicate that an elevated pH in soil 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; ASTSWMO 2011).
    Increased acidification and oxygen depletion of
    soils from dissolution of tungsten powder have
    been shown to trigger changes in the soil microbial
    community, causing an increase in fungal biomass
    and a decrease in the bacterial component
    (Dermatas and others 2004; Strigul and others
    2005).  In water, tungsten compounds are
    expected to adsorb to suspended solids and
    sediment based on their sorption coefficients
    (HSDB 2009b).
    In 2006, the assumed stability of tungsten in the
    environment was  questioned when tungsten was
    detected in groundwater and in soil above
    baseline levels at a small arms range at the
    Massachusetts Military Reservation, where
    tungsten/nylon bullets were being used. The use
   of these bullets was then suspended in
   Massachusetts per a Governor's Office Cease and
   Desist Order (ASTSWMO 2011; EPA Region 1
   2013; USAGE 2007).
   Studies suggest that the tungsten powder used in
   the Army's tungsten/nylon bullets forms oxide
   coatings on the bullets that are soluble in water
   (Dermatas and others 2004; USAGE 2007).
   Tungsten has been shown to accumulate in plants
   in substantial amounts. The extent of
   accumulation appears to be related to the
   tungsten content in soil and varies widely,
   depending on the plant genotype (Koutsospyros
   and others 2006).
   Results from an aged soil bioassay indicated that
   sodium tungstate-spiked soil impaired cabbage
   growth (Kennedy and others 2012).
   As of 2005, tungsten had been identified at more
   than six sites on the EPA National Priorities List
   (NPL) (HazDat 2005).
What are the routes of exposure and the health effects of tungsten?
   Toxicological information on tungsten and its
   compounds is limited (Koutsospyros and others
   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).
   Occupational exposure to tungsten is known to
   affect the eyes, skin, respiratory system and
   blood. Tungsten may cause irritation to eyes and
   skin; diffuse interstitial pulmonary fibrosis; loss of
   appetite; nausea; cough; and changes in the blood
   (Gbaruko and Igwe 2007; NIOSH 2010).
   Studies on female 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).
   Studies on rats also found that tungsten primarily
   accumulated in bones and in the spleen after oral
   exposure (NIEHS 2003).
   Tungsten has not been classified for carcinogenic
   effects by the Department of Health and Human
   Services, the International Agency for Research
   on Cancer or the EPA.
   The EPA's Toxic Substances Control Act (TSCA)
   Interagency Testing Committee has included
   tungsten compounds in the Priority Testing List,
   which is a list of chemicals regulated by TSCA for
   which there are suspicions of toxicity or exposure
   and for which there are few, if any, ecological
   effects, environmental fate or health effects testing
   data (EPA 2006).
Are there any federal  and state guidelines and health standards for
tungsten?
   A federal drinking water standard has not been
   established for tungsten. In addition, the EPA has
   not derived a chronic inhalation reference
   concentration (RfC) or a chronic oral reference
   dose (RfD) for tungsten or tungsten compounds
   (EPA 2013).
 The American Council of Governmental Industrial
   Hygienists (ACGIH) has established a threshold
   limit value of 5 milligrams per cubic meter (mg/m3)
   as the time-weighted average (TWA) over an 8-
   hour work exposure and 10 mg/m3 as the 15-
   minute short-term exposure limit (STEL) for
   airborne exposure to tungsten metal and for
   insoluble tungsten compounds (ACGIH 2008).

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  Technical Fact Sheet - Tungsten
Are there any federal and state guidelines and health standards for
tungsten? (continued)
   Tungsten and related compounds were included
   as part of EPA's 2012 Integrated Risk Information
   System (IRIS) agenda. The current projected start
   date for conducting the literature search for the
   chemical is fiscal year 2014 (EPA 2012).
   The National Institute for Occupational Safety and
   Health (NIOSH) has established a recommended
   exposure limit of 5 mg/m3 as the time-weighted
   average (TWA) over a 10-hour work exposure and
   10 mg/m as the 15-minute short-term exposure
   limit (STEL) for airborne exposure to tungsten and
   insoluble tungsten compounds (NIOSH 2010).
The Occupational Safety and Health
Administration (OSHA) recommends a permissible
exposure limit of 5 mg/m3 for insoluble compounds
of tungsten and a PEL of 1 mg/m3 limit for soluble
compounds in the construction and shipyard
industries as a TWA over an 8-hour work
exposure. OSHA also established a PEL of 10
mg/m3 as the 15-minute STEL for airborne
exposure to insoluble compounds of tungsten and
3 mg/m3 as the 15-minute STEL for airborne
exposure to soluble tungsten compounds (OSHA
2013).
What detection and site characterization methods are available for
tungsten?
   Tungsten is commonly deposited in the
   environment as discrete particles with strongly
   heterogeneous spatial distributions. Unless
   precautions are taken, this distribution causes
   highly variable soil data that can lead to confusing
   or contradictory conclusions about the location
   and degree of contamination. Proper sample
   collection (using an incremental field sampling
   approach), sample processing (which includes
   grinding) and incremental subsampling are
   required to obtain reliable soil data (EPA 2003).
   NIOSH Method 7074 uses flame atomic
   absorption to detect tungsten in air. It has a
   detection limit of 0.125 mg/m3 for insoluble forms
   of tungsten and 0.05  mg/m3 for soluble forms of
   tungsten (NIOSH 1994).
   Other NIOSH methods for the detection of
   tungsten in air are Methods 7300 and 7301,
   involving inductively coupled argon plasma-atomic
   emission spectroscopy. The working range for
   these methods is 0.005 to 2.0 mg/m3 for each
   element in a 500-liter sample. Special sample
   treatment may be required for some tungsten
   compounds (NIOSH 2003a, b).
OSHA Method ID-213 is also used for the
detection of tungsten in air. The method uses
inductively coupled plasma (ICP)-atomic emission
spectroscopy (AES) and has a quantitative
detection limit of 0.34 mg/m3 (OSHA 2013).
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
analytes under EPA SW-846 Methods 6010, ICP-
AES, and 6020, ICP-MS; however, these methods
may be modified for the detection of tungsten in
soil and water (ASTSWMO 2011; EPA 2007b, c).
Tungsten is also not currently included on the list
of recoverable metals using SW-846 Method
3051 A, a microwave-assisted acid digestion
method. Therefore, the digestion method is being
modified to enhance tungsten recovery from soils
(EPA 2007a;  Griggs and others 2009).
Trace concentrations of tungsten in water and air
can also be estimated by instrumental neutron
activation analysis (Gbaruko and Igwe 2007;
NIEHS2003).
What technologies are being used to treat tungsten?
   Treatment technologies to address tungsten
   contamination in environmental media are
   currently under development.
   Preliminary studies indicate that phytoremediation
   may be a potential treatment method for tungsten
   contaminated sites based on the reported
   accumulation of tungsten in plant tissue (Strigul
   and others 2005; Tuna and others 2012).
Electrokinetic soil remediation is an emerging in
situ technology for removal of tungsten from low-
permeability soils in the presence of heavy metals
such as copper and lead. A direct current is
applied to contaminated soils using electrodes
inserted into the ground (Braida and others 2007).

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  Technical Fact Sheet - Tungsten
What technologies are being used to treat tungsten? (continued)
    Studies have reported the efficient removal (98 to
    99 percent) of tungsten from industrial wastewater
    by precipitation, coagulation and flocculation
    processes using ferric chloride under acidic
    conditions (pH  below 6) (Plattes and others 2007).
A recent study demonstrated the efficient recovery
of tungsten (over 90 percent) in aqueous solutions
using a water-soluble polymer (polyquaternium-6)
for complexing anion forms of tungsten prior to
ultrafiltration (Zeng and others 2012).
Where can I find more information about tungsten?
   Agency for Toxic Substances and Disease
   Registry (ATSDR). 2005. "lexicological Profile for
   Tungsten."
   www.atsdr.cdc.gov/toxprofiles/tp186.pdf
   American Conference of Governmental Industrial
   Hygienists (ACGIH). 2008. Tungsten. "Threshold
   Limit Values for Chemical Substances and
   Physical Agents and Biological Exposure Indices."
   Cincinnati, Ohio.
   Association of State and Territorial Solid Waste
   Management Officials (ASTSWMO). 2011.
   "Tungsten Issues Paper." www.astswmo.org/
   Files/Policies and  Publications/Federal Facilities/
   2011-02 FINAL Tungsten  Issues 2-O.pdf
   Braida, W., Christodoulatos, C., Ogundipe, A.,
   Dermatas, D., and G. O'Connor. 2007.
   "Electrokinetic Treatment of Firing Ranges
   Containing Tungsten-Contaminated Soils." Journal
   of Hazardous Materials. Volume 149. Pages 562
   to 567.
   Dermatas, D., Braida, W., Christodoulatos, C.,
   Strigul, N., Panikov, N.,  Los, M., and S. Larson.
   2004. "Solubility, Sorption, and Soil Respiration
   Effects of Tungsten and Tungsten Alloys."
   Environmental Forensic. Volume 5. Pages 5 to 13.
   Gbaruko, B.C. and J.C.  Igwe. 2007. "Tungsten:
   Occurrence, Chemistry, Environmental and Health
   Exposure Issues." Global Journal of
   Environmental Research. Volume 1 (1). Pages 27
   to 32.
   Griggs C., Larson, S., Nestler, C., 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).
   2009a. Elemental Tungsten, http://toxnet.nlm.nih.
   gov/cgi-bin/sis/htmlgen?HSDB
   HSDB. 2009b. Tungsten Compounds.
   http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?
   HSDB
HazDat. 2005. HazDat Database: ATSDR's
Hazardous Substance Release and Health Effects
Database. Atlanta, GA.
Kennedy, A.J., Johnson, D.R., Seiter, J.M,
Lindsay, J.H., Boyd, R.E., Bednar, A.J., and P.G.
Allison. 2012. "Tungsten Toxicity,
Bioaccumulation, and Compartmentalization into
Organisms Representing Two Trophic Levels."
Environmental Science and Technology. Volume
46 (17). Pages 9646 to 9652.
Koutsospyros, A., Braida, W., Christodoulatos, C.,
Dermatas, D., and N. Strigul. 2006. "A Review of
Tungsten: From Environmental Obscurity to
Scrutiny." Journal of Hazardous Materials. Volume
136. Pages 1 to 19.
Meijer, A., Wroblicky, G., Thuring, S., and  M.W.
Marcell. 1998. "Environmental Effects of Tungsten
and Tantalum Alloys." Elgin Air Force Base,
Florida: Air Force Research Laboratory. AFRL-
MN-EG-TR-2000-7017.
National Institute of Environmental Health
Sciences (NIEHS). 2003. "Tungsten and Selected
Tungsten Compounds - Review  of Toxicological
Literature." http://ntp.niehs.nih.gov/ntp/htdocs/
Chem  Background/ExSumPdf/tungsten 508.pdf
National Institute for Occupational Safety and
Health (NIOSH). 1994. "Tungsten (Soluble and
Insoluble) - Method 7074." NIOSH Manual of
Analytical Methods (NMAM), Fourth Edition.
www.cdc.gov/niosh/docs/2003-154/pdfs/7074.pdf
NIOSH. 2003a. "Elements by ICP (Nitric/Perchloric
Acid Ashing)  - Method 7300." NIOSH Manual of
Analytical Methods (NMAM), Fourth Edition.
www.cdc.gov/niosh/docs/2003-154/pdfs/7300.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/pdfs/7301 .pdf
NIOSH. 2010. NIOSH Pocket Guide to Chemical
Hazards: Tungsten.
www.cdc.gov/niosh/npg/npgd0645.html

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  Technical Fact Sheet - Tungsten
Where can  I find more information about tungsten? (continued)
    Occupational Safety and Health Administration
    (OSHA). 2013. "Tungsten and Cobalt in
    Workplace Atmospheres (ICP Analysis)."
    www.osha.gov/dts/sltc/methods/inorganic/id213/id
    213.html
    Plattes, M., Bertrand, A., Schmitt, B., Sinner, J.,
    Verstraeten, F., and J. Welfring. 2007. "Removal
    of Tungsten Oxyanions from Industrial Wastewater
    by Precipitation, Coagulation  and Flocculation
    Processes." Journal of Hazardous Materials.
    Volume 148 (3). Pages 613 to 615.
    Strigul, N., Koutsospyros, A.,  Arienti, P.,
    Christodoulatos, C., Dermatas, D., and W. Braida.
    2005. "Effects of Tungsten on Environmental
    Systems." Chemosphere. Volume 61. Pages 248
    to 258.
    Tuna, G.S., Braida, W., Ogundipe, A., and D.
    Strickland. 2012. "Assessing Tungsten Transport
    in the Vadose Zone:  From Dissolution Studies to
    Soil Columns." Chemosphere. Volume 86 (12).
    Pages 1001 to 1007.
    U.S. Army Corps of Engineers (USAGE). 2007.
    "Fate and Transport of Tungsten at Camp
    Edwards Small Arms Ranges." ERDC TR-07-5.
    www.crrel.usace.army.mil/librarv/technicalreports/
    TR-07-5.pdf
    U. S. Environmental Protection Agency (EPA).
    2003. "Guidance for Obtaining Representative
    Laboratory Analytical Subsamples from Particulate
    Laboratory Samples." EPA/600/R-03/027.
    EPA. 2006. "Fifty-Eighth Report of the TSCA
    Interagency Testing Committee to the
Administrator of the Environmental Protection
Agency; Receipt of Report and Request for
Comments; Notice." Federal Register. Volume 71
(132). Page 39187.
EPA. 2007a. "Method 3051 A. Microwave Assisted
Acid Digestion of Sediments, Sludges, Soils, and
Oils." SW-846 On-line, www.epa.gov/osw/
hazard/testmethods/sw846/pdfs/3051a.pdf
EPA. 2007b. "Method 601OC. Inductively Coupled
Plasma-Atomic Emission Spectrometry." SW-846
On-line, www.epa.gov/osw/hazard/testmethods/
sw846/pdfs/6010c.pdf
EPA. 2007c. "Method 6020A: Inductively Coupled
Plasma-Mass Spectrometry." SW-846 On-line.
www.epa.gov/osw/hazard/testmethods/sw846/pdfs
/6020a.pdf
EPA. 2012. Integrated Risk Information System
(IRIS); Announcement of 2012 Program. Federal
Register. Volume 77 (88). Pages 26751 to 26755.
www.gpo.gov/fdsys/pkg/FR-2012-05-07/html/
2012-10935.htm
EPA. 2013. Drinking Water Contaminants.
water.epa.gov/drink/contaminants/index. cfm#List
EPA. Region 1. 2013. Massachusetts Military
Reservation, www.epa.gov/region01/mmr/.
Zeng, J., Sun,  X., Zheng, L, He, Q. and S. Li.
2012. "Recovery of Tungsten (VI) from Aqueous
Solutions by Complexation-Ultrafiltration Process
with the Help of Polyquaternium." Chinese Journal
of Chemical Engineering. Volume 20 (5). Pages
831 to 836.
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 email at cooke.maryt@epa.gov.

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