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Hydrogen fluoride

Anhydrous hyrofluoric acid

SPRI Emission Reporting Threshold
1.00 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?
Under normal conditions, Hydrogen fluoride will be a colourless gas, which has a sharp, pungent smell. It is highly toxic and irritating, but non-flammable. Hydrogen fluoride is however usually found as a strong solution in water, whereby it is Hydrofluoric acid. Hydrofluoric acid is an extremely strong acid. It will severely corrode metals, glass, minerals and many organic (carbon-containing) substances - and will release highly flammable hydrogen in the process.
What is it used for?
Hydrogen fluoride is used industrially to produce a variety of chemicals. It is also used to clean and etch glass, during the manufacture of semi-conductors, in the production of uranium nuclear fuels, as a catalyst in oil refineries, as part of electro-plating and other metal treatment processes, in the production and cleaning of ceramics and porcelain, to make dental fixtures and to remove rust. In the past, Hydrogen fluoride was used to manufacture Chlorofluorocarbons (CFCs) which were widely used as refrigerants and propellants until concerns about their impact on the global environment prompted bans on their use.
Where does it come from?
The main releases of Hydrogen fluoride occur from high temperature industrial processes. In the UK, the most significant releases will occur from coal-fired power stations. Hydrogen fluoride may also be released when products containing fluorine compounds (such as plastics and rubbers, fire extinguishing agents, aerosol propellants and other chemicals) are burned. Hydrogen fluoride is also released naturally from volcanic eruptions, but the amounts emitted are small in comparison to man-made sources.
How might it affect the environment?
Hydrogen fluoride gas is highly corrosive and will damage metal structures and buildings or monuments made of limestone. If high levels of Hydrogen fluoride gas dissolve in a water body, aquatic organisms will be harmed and even killed. Hydrogen fluoride gas can attach itself to particles in the air, which are then deposited on soils or plants. If significant amounts are ingested by wildlife and cattle, they can suffer from an overdose of Fluoride known as "Fluorosis". These effects are only likely as a result of an accidental spill of much larger amounts of Hydrogen fluoride than are typically released to the environment. The very high solubility of Hydrogen fluoride gas means that releases to the atmosphere are quickly washed out by rain and moisture in the air. Some soils and lakes may be sensitive to this acid rain if amounts of it falling are above certain amounts defined as "critical loads". This makes Hydrogen fluoride pollution a global as well as local environmental problem.
How might exposure to it affect human health?
Hydrogen fluoride can enter the body either by inhalation of air containing hydrogen fluoride or by dermal contact with hydrofluoric acid (dissolved form of hydrogen fluoride). Dermal contact with hydrofluoric acid occurs mainly in the occupational setting. Inhalation of air containing hydrogen fluoride can cause irritation of the eyes, nose and throat. Exposure to high levels may cause muscle spasms and can damage the lungs and heart and in extreme cases can result in death. Dermal contact with hydrofluoric acid can cause severe skin burns. The skin may initially be red and painful while severe burns and internal tissue damage can develop over time following exposure. Absorption of large quantities of hydrofluoric acid through the skin can affect the heart and lungs and in extreme cases may result in death. The International Agency for Research on Cancer has not designated hydrogen fluoride in terms of its carcinogenicity. However, exposure to hydrogen fluoride 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 Hydrogen fluoride are regulated through the UK Pollution, Prevention and Control (PPC) Regulations. It is also regulated through the European Directive concerned with emissions from waste incinerators (96/61/EC), that concerned with the treatment of hazardous wastes (91/689/EEC) and that regulating pollution of aquatic environments (76/464/EEC). Internationally, substances contributing to acid rain are controlled through the UN/ECE Convention on Long-Range Transboundary Air Pollution.