Substance profile
Selenium
Selenium is a reddish colored powder that may become black upon exposure to air.
01 · Identification
What Selenium is
Selenium is a reddish colored powder that may become black upon exposure to air. Its molecular formula is Se and its molecular weight is 78.97 g/mol. It boils at 685 °C, melts at 221 °C, is practically insoluble in water.
Under the GHS it carries the signal word Danger. It is classed as hazardous Air Pollutants (HAPs).
02 · Identifiers
Selenium identifiers and molecular data
Selenium CAS number and EC number
Selenium molecular formula and molecular weight
03 · GHS classification
Selenium hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Selenium pictograms and signal word
Selenium hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Acute toxicity - oral GHS chapter 3.1 | Category 3 | H301 | GHS06 |
| Acute toxicity - inhalation GHS chapter 3.1 | Category 3 | H331 | GHS06 |
| Specific target organ toxicity - repeated exposure GHS chapter 3.9 | Category 2 | H373 | GHS08 |
| Hazardous to the aquatic environment - chronic GHS chapter 4.1 | Category 4 | H413 | — |
Selenium hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H331 | Toxic if inhaled. |
| H301 | Toxic if swallowed. |
| H373 | May cause damage to organs <or state all organs affected, if known> through prolonged or repeated exposure <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H413 | May cause long lasting harmful effects to aquatic life. |
This page lists only the codes assigned to Selenium. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for Selenium
A Safety Data Sheet is written for a product, not for a substance: the supplier of the grade you actually buy issues it, so two suppliers of Selenium issue two different sheets. That is why there is no single authoritative SDS for a substance to download — what there is, is the job of collecting the sheets for the products you hold and keeping them current as suppliers revise them.
04 · Precautionary statements
Selenium precautionary statements
CLP Annex VI assigns 10 precautionary statements to Selenium. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Response
What to do once exposure, spillage or fire has already happened.
Disposal
What has to happen to the contents and the empty container.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
Selenium name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | селен |
| Spanish español | Selenio |
| Czech čeština | selen |
| Danish dansk | selen |
| German Deutsch | Selen |
| Estonian eesti | seleen |
| Greek ελληνικά | σελήνιο |
| English English | selenium |
| French français | sélénium |
| Croatian hrvatski | selen |
| Italian italiano | selenio |
| Latvian latviešu | selēns |
| Lithuanian lietuvių | selenas |
| Hungarian magyar | szelén |
| Maltese Malti | selenju |
| Dutch Nederlands | seleen |
| Polish polski | selen |
| Portuguese português | selénio |
| Romanian română | seleniu |
| Slovak slovenčina | selén |
| Slovenian slovenščina | selen |
| Finnish suomi | seleeni |
| Swedish svenska | selen |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
Selenium GHS label elements
Everything CLP Annex VI fixes for Selenium, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Selenium
- Toxic if inhaled.
- Toxic if swallowed.
- May cause damage to organs <or state all organs affected, if known> through prolonged or repeated exposure <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- May cause long lasting harmful effects to aquatic life.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Do not eat, drink or smoke when using this product.
- Use only outdoors or in a well-ventilated area.
- Avoid release to the environment.
- IF SWALLOWED:
- IF INHALED:
- Immediately call a POISON CENTER/doctor/…
- Get medical advice/attention if you feel unwell.
- Rinse mouth.
- Dispose of contents/container to …
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Selenium in the GHS label constructor →
07 · Health hazards
Selenium health hazards and exposure limits
Selenium hazard summary
Selenium is a naturally occurring mineral element that is distributed widely in nature in most rocks and soils. In its pure form, it exists as metallic gray to black hexagonal crystals, but in nature it is usually combined with sulfide or with silver, copper, lead, and nickel minerals. Most processed selenium is used in the electronics industry, but it is also used: as a nutritional supplement; in the glass industry; as a component of pigments in plastics, paints, enamels, inks, and rubber; in the preparation of pharmaceuticals; as a nutritional feed additive for poultry and livestock; in pesticide formulations; in rubber production; as an ingredient in antidandruff shampoos; and as a constituent of fungicides. Radioactive selenium is used in diagnostic medicine.
Source: Agency for Toxic Substances and Disease Registry (ATSDR)
Selenium carcinogenicity classification
Cancer Classification: Group D Not Classifiable as to Human Carcinogenicity
Source: Hazardous Substances Data Bank (HSDB)
CLASSIFICATION: D; not classifiable as to human carcinogenicity. BASIS FOR CLASSIFICATION: Based on inadequate human data and inadequate evidence of carcinogenicity in animals. The evidence for various selenium compounds in animal and mutagenicity studies is conflicting and difficult to interpret; however, evidence for selenium sulfide is sufficient for a B2 (probable human carcinogen) classification. HUMAN CARCINOGENICITY DATA: Inadequate. ANIMAL CARCINOGENICITY DATA: Inadequate.
Source: Hazardous Substances Data Bank (HSDB)
An IARC group and a CLP classification answer different questions. IARC judges whether the evidence for cancer in humans is strong enough; CLP Annex VI is the legally binding EU classification. A substance can carry one and not the other.
Selenium occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 0.2 [mg/m3], as Se (compds.) | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 0.2 mg/m³ | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 0.2 mg/m3 [*Note: The PEL also applies to other selenium compounds (as Se) except Selenium hexafluoride.] | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 0.2 mg/m³ | Occupational Safety and Health Administration (OSHA) |
| REL | TWA 0.2 mg/m3 [*Note: The REL also applies to other selenium compounds (as Se) except Selenium hexafluoride.] | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 1 mg Se/m3 (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 1.0 [mg/m3], as Se | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 1 mg/cu m (as Se) | Hazardous Substances Data Bank (HSDB) |
These are United States values. The European Union sets its own indicative and binding limits, and the figure that applies at a given workplace is the one in the local regulation — not the one shown here.
08 · Physical and chemical properties
Selenium properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
Selenium boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 685 °C (1265 °F) | HSDB | |
| 685 °C (1265 °F) | at 760 mmHg | CAMEO |
Selenium melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 220.8 °C (429.4 °F) | gray selenium | HSDB |
| 200 °C (392 °F) | NIOSH |
Selenium density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 4.39 g/cm³ | alpha form | HSDB |
| 4.28 g/cm³ | NIOSH |
Selenium solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Soluble in aq potassium cyanide soln, potassium sulfite soln, dilute aqueous caustic alkali soln | HSDB | |
| Insoluble in water and alcohol | HSDB | ||
| Soluble in concentrated nitric acid. | HSDB |
Selenium vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 0 mmHg | approx | NIOSH |
| 0.0007501 mmHg | at 20 °C | ICSC |
Selenium lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | Combustible Solid | NIOSH |
Selenium critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 1493 °C (2719.1 °F) | HSDB |
Selenium corrosivity
| Property | Value | Conditions | Source |
|---|---|---|---|
| Corrosivity | Strongly corrosive, especially at high temperature. | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Selenium fire and explosion behaviour
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
Fire and explosion
During attempted conversion of recovered selenium metal to the dioxide by heating in oxygen, a vigorous explosion occurred. This was attributed to selenium-catalysed oxidation traces of organic impurities in the selenium. Oxidation of recovered selenium with nitric acid is rendered vigorous by presence of organic impurities, but is a safe procedure.
Source: HSDB
10 · Handling and storage
Selenium storage and handling
Selenium safe storage
Separated from strong oxidants, strong acids and food and feedstuffs. Dry. Store in an area without drain or sewer access. Provision to contain effluent from fire extinguishing.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Selenium storage conditions
Usually stored at room temperature. Precautions must be taken to avoid contact with water or prolonged exposure to air and other materials with which it may react. Storage area construction must be such that rain water will not leak in or ground water will not enter. Used drums should be stored in this same dry area to avoid contamination /SRP: of the area/ and to minimize any hazard due to the residues.
Source: Hazardous Substances Data Bank (HSDB)
Selenium incompatible materials
Selenium + Silver bromate: The reaction is violently explosive.
Source: Hazardous Substances Data Bank (HSDB)
Selenium reactivity
SELENIUM, silicon, or sulfur ignites in fluorine gas at ordinary temperatures [Mellor 2:11-13 1946-47]. A mixture of barium carbide and selenium heated to 150 °C becomes incandescence [Mellor 5:862 1946-47]. Calcium carbide and selenium vapor react with incandescence [Mellor 5:862 1946-47]. A moist mixture of selenium and chlorates, except the alkali chlorates, becomes incandescent. Selenium reacts violently with chromium trioxide [Mellor 11:233 1946-47]. Reaction of selenium and silver bromate (also potassium bromate) is violently explosive [Mellor 2, Supp1:763 1956]. Freshly reduced selenium reacts vigorously with nitric acid. Trace amounts of organic matter probably influenced the reaction [J. Chem. Soc. 1938 p.391]. The reaction between zinc and selenium or tellurium is accompanied by incandescence [Mellor 4:476-480 1946-47].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Selenium in the storage compatibility matrix →
11 · Questions
Selenium — frequently asked questions
What is the CAS number of Selenium?
The CAS number of Selenium is 7782-49-2. Its EC number is 231-957-4.
What is the chemical formula of Selenium?
The molecular formula of Selenium is Se and its molecular weight is 78.97 g/mol.
What does a Selenium label have to show?
Under CLP Annex VI the label for Selenium carries the pictograms Skull and crossbones and Health hazard and the signal word is Danger.
Is Selenium flammable?
CLP Annex VI assigns Selenium no flammability hazard class. That is not a statement that it cannot burn: the harmonised list only records the hazards that were assessed for it.
Is Selenium a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Selenium. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health. IARC places it in Group 3: not classifiable as to its carcinogenicity to humans.
What is the exposure limit for Selenium?
The US occupational exposure limit reported for Selenium is 0.2 [mg/m3], as Se (compds.) (Haz-Map, Information on Hazardous Chemicals and Occupational Diseases). Limits differ by country: the EU sets its own indicative and binding values, and the figure that applies at a given workplace is the one in the local regulation.
What is the boiling point of Selenium?
The boiling point reported for Selenium is 685 °C (1265 °F) (HSDB).
What is the melting point of Selenium?
The melting point reported for Selenium is 220.8 °C (429.4 °F), gray selenium (HSDB).
How should Selenium be stored?
Usually stored at room temperature. Precautions must be taken to avoid contact with water or prolonged exposure to air and other materials with which it may react. Storage area construction must be such that rain water will not leak in or ground water will not enter. Used drums should be stored in this same dry area to avoid contamination /SRP: of the area/ and to minimize any hazard due to the residues. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Selenium
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