Tungsten

by Posted on

Tungsten, also known as wolfram, is a chemical element with symbol W and atomic number 74. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][1] Based on its purity, the colour of tungsten may range from white for the pure metal to steel-grey for the metal with impurities. It is commercially available in a powdered or solid form. 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. 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. [2]

.

Uses [3]

 

Tungsten is used in filaments in incandescent light bulbs, it is also used in electric contacts and arc-welding electrodes. Tungsten is used in alloys, such as steel, to which it imparts great strength. Cement carbide is the most important use for tungsten: its main component is tungsten carbide (WC). It has the strength to our cast iron and it makes excellent cutting tools for the machining of steel. X-ray tubes for medical use have a tungsten emitter coil and the screen used to view X-rays rely on calcium and magnesium tungstate phosphors to convert X-rays into blue visible light. Tungsten is also used in microchip technology and liquid crystals displays.

 

In the Environment [4]

 

  • Tungsten is an element that exists naturally in the environment.
  • It is an element that cannot be formed or destroyed.
  • Tungsten in water comes mainly from water dissolving tungsten from rocks and soil that it runs over or through.
  • Tungsten in air comes from the weathering of rocks, from the mining of tungsten ore, or from emissions from industries making tungsten metal or hard metal products.
  • Tungsten particles in air can settle out onto soil, water, or plant surfaces, or they can be brought down in rain or snow.
  • Water and air are not normally tested for tungsten.
  • If coal ash, incinerator ash, or industrial waste contains high levels of tungsten, it can increase the levels in soil with which it is mixed.
  • Most tungsten in soil binds with the soil and will not reach groundwater.
  • As soil conditions change, tungsten may dissolve out of soil and rocks in one location and bind back to soil and rocks in another location.

 

Sources & Routes of Exposure [5]

 

Sources of Exposure

 

General Populations

 

  • The general population may be exposed to tungsten in ambient air and food.

 

Occupational Populations

 

  • Occupational exposure to tungsten and its compounds occurs during the production of tungsten metal from the ore and preparation of tungsten carbide powders.
  • Exposure to cemented tungsten carbide can occur during the manufacturing and grinding of cemented tungsten carbide hard metal parts.
  • Workers can also be exposed to dusts and mists of tungsten and its compounds or cemented tungsten carbide during crushing, mixing, ball milling, loading and unloading, and grinding operations.

 

Routes of Exposure

 

  • Inhalation (breathing) – A route of typically low exposure for the general population. Predominant route of exposure for tungsten and hard metal workers.
  • Oral (mouth) – A route of typically low exposure to tungsten is via ingestion of food and water.
  • Dermal – Minor route of exposure.

 

Health Effects [3]

 

Tungsten has been shown to act by antagonising the action of the essential trace element, molybdenum. Long industrial experience has indicated no pneumoconiosis to develop among workers exposed solely to W or its insoluble compounds (at air concentrations of the order of 5 mg/m3).

 

Acute Health Effects

 

  • Irritating to the skin and eyes on contact.
  • Inhalation will cause irritation to the lungs and mucus membrane.
  • Irritation to the eyes will cause watering and redness.
  • Reddening, scaling, and itching are characteristics of skin inflammation.

 

Chronic Health Effects

 

  • Tungsten has no known chronic effects.
  • Repeated or prolong exposure to this compound is not known to aggravate medical conditions.

 

Safety [6]

 

First Aid Measures

 

  • Eye Contact: Check for and remove any contact lenses. Do not use an eye ointment. Seek medical attention.
  • Skin Contact: If the chemical got onto the clothed portion of the body, remove the contaminated clothes as quickly as possible, protecting your own hands and body. Place the victim under a deluge shower. If the chemical got on the victim’s exposed skin, such as the hands- gently and thoroughly wash the contaminated skin with running water and non-abrasive soap. Be particularly careful to clean folds, crevices, creases and groin. If irritation persists, seek medical attention. Wash contaminated clothing before reusing.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek medical attention.
  • Inhalation: Allow the victim to rest in a well ventilated area. Seek immediate medical attention.
  • Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. WARNING: It may be hazardous to the person providing aid to give mouth-to-mouth resuscitation when the inhaled material is toxic, infectious or corrosive. Seek immediate medical attention.
  • Ingestion: Do not induce vomiting. Loosen tight clothing such as a collar, tie, belt or waistband. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek immediate medical attention.

 

Fire & Explosion Information

 

  • Tungsten may be combustible at high temperature.
  • Small fires should be extinguished using dry chemical powder
  • Large fires should be extinguished using water spray, fog or foam. Do not use water jet.
  • Tungsten in powder form, may be capable of creating a dust explosion.

Exposure Controls and Personal Protection

 

Engineering Controls

 

  • Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits.
  • If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.

 

Personal Protective Equipment

 

The following personal protective equipment is recommended when handling tungsten:

  • Splash goggles;
  • Synthetic apron;
  • Dust respirator (be sure to use an approved/certified respirator or equivalent);
  • Gloves.

 

Personal Protection in Case of a Large Spill:

 

  • Splash goggles;
  • Full suit;
  • Dust respirator;
  • Boots;
  • Gloves;
  • A self-contained breathing apparatus should be used to avoid inhalation of the product. Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

 

Regulation

United States [7]

 

OSHA: The Occupational Safety & Health Administration has set the following Permissible Exposure Limit (PEL):

  • Construction Industry: 5 mg/m3 TWA

 

ACGIH: The American Conference of Governmental Industrial Hygienists (has set a Threshold Limit Value (TLV)for tungsten of 5 mg/m3 TWA; 10 mg/m3 STEL

 

NIOSH: The National Institute for Occupational Safety and Health has set a Recommended Exposure Limit (REL) for tungsten of 5 mg/m3 TWA; 10 mg/m3 STEL

 

Australia [8]

 

Safe Work Australia: Safe Work Australia has established a Time Weighted Average Concentration (TWA) for tungsten of 5 mg/m3 for a 40-hour work week and a 15-min short term exposure limit of 10 mg/m3.

 

References

 

  1. https://en.wikipedia.org/wiki/Tungsten
  2. http://www.epa.gov/sites/production/files/2014-03/documents/ffrrofactsheet_contaminant_tungsten_january2014_final.pdf
  3. http://www.lenntech.com/periodic/elements/w.htm
  4. http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=805&tid=157
  5. http://www.atsdr.cdc.gov/toxguides/toxguide-186.pdf
  6. http://www.sciencelab.com/msds.php?msdsId=9925358
  7. https://www.osha.gov/dts/chemicalsampling/data/CH_274500.html
  8. http://www.safeworkaustralia.gov.au/sites/SWA/about/Publications/Documents/772/Workplace-exposure-standards-airborne-contaminants.pdf

[/fusion_builder_column][/fusion_builder_row][/fusion_builder_container]