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Selenium

SPRI Emission Reporting Threshold
100 Kg/yr Pollutant Emissions to Air
Disclaimer
This sheet is a generic summary, designed to give the reader a basic level of background information about the substance in question. Great care has been taken to represent as effectively and correctly as possible the broad range of (not necessarily consistent) information which is available from a variety of sources. The reader must accept therefore that this sheet has no legal status and cannot be relied upon in any legal proceedings. SEPA disclaims any responsibility or liability whatsoever for errors and omissions in this sheet.
What is it?
Pure Selenium occurs in a number of different physical forms, all of which have no smell. The most stable type has a hexagonal crystalline structure and is a dull grey coloured solid at room temperature. Selenium with a lattice-type crystalline structure is a deep red glassy solid. Selenium also occurs in amorphous forms, which have no definite or repetitive crystalline structure. Amorphous Selenium can be either a red coloured powder or a black jelly-like substance. Selenium has a boiling point of over 900 degrees celsius. Elemental Selenium is not soluble in water or organic (carbon-containing) solvents. Many different types of compounds of Selenium also exist, with a variety of properties.
What is it used for?
Selenium is used to make a variety of commercial products. The main uses are in the manufacture of glassware, in the production of photographic and electronics equipment, in pigments and dyes, as additives for metal processing and as trace nutrients added to animal feed.
Where does it come from?
The most significant releases of Selenium are likely to occur from industry manufacturing or using it. Selenium may also be released when coal or oil containing it is burned. Small amounts of Selenium compounds may also be released naturally from rocks, soils and water bodies containing them.
How might it affect the environment?
The various forms and compounds of Selenium behave very differently in the environment. Soluble forms are very mobile and may seep into groundwaters, whereas other forms may be relatively static and persist in soils. Selenium can be accumulated by aquatic organisms living in contaminated waters. It can also accumulate to high levels in plants grown in soils rich in Selenium (either because of natural releases or through man-made pollution). Wildlife consuming these plants may be harmed if levels are high, although trace amounts are actually required as essential nutrients. It is not considered likely that Selenium pollution has any effects on the global environment.
How might exposure to it affect human health?
Selenium can enter the body either by inhalation of air containing selenium, ingestion of water or food containing selenium or by dermal contact with selenium and its compounds. Inhalation of air containing selenium mainly occurs in an occupational setting. Exposure to high levels of selenium may lead to dizziness, fatigue, irritation of the digestive tract and in extreme cases may lead to collection of fluid in the lungs and bronchitis. Ingestion of elevated levels of selenium over long periods of time may lead to effects such as brittle hair, deformed nails, tooth decay, irritation of the digestive tract, fatigue, depression and loss of feeling in the arms and legs. Ingestion of extremely high levels of selenium compounds can be fatal. Dermal contact with selenium compounds mainly occurs in the occupational setting and can cause rashes, swelling, redness and pain. Contact with the eyes can cause irritation and burning. The International Agency for Research on Cancer has designated selenium and its compounds as being not classifiable as to their carcinogenicity to humans. However, exposure to selenium and its compounds at normal background levels is unlikely to have any adverse effect on human health.
What steps are being taken to limit the potential impacts?
Releases of Selenium are controlled through the UK Pollution, Prevention and Control (PPC) Regulations. European Directives regulating releases of Selenium include the Hazardous Waste Directive, which protects groundwaters (91/689/EEC); and that concerned with combating air pollution from industrial plants (84/360/EEC). At an international level, Selenium is included in the Basel Convention concerning the transboundary movement and disposal of hazardous wastes and is listed as a priority substance under the Helsinki Convention which aims to protect the marine environment of the Baltic Sea.