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Hexachlorobenzene

"bunt cure"

SPRI Emission Reporting Threshold
1.00 Kg/yr Pollutant Emissions to Air
0.01 Kg/yr Pollutant Emissions to Water
0.01 Kg/yr Pollutant Emissions to Waste Water
1.00 Kg/yr Pollutant Emissions to Land
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 hexachlorobenzene (HCB) is white crystals with an unpleasant smell which can evaporate fairly easily. It hardly dissolves at all in water, but readily dissolves in organic (carbon-containing) solvents, fats and oils. HCB is part of the group of compounds known as the volatile organic compounds (VOCs).
What is it used for?
Although now banned in the UK and the rest of Europe, HCB is used widely as a fungicide on seeds (especially protecting against the fungal disease "bunt" which affects cereal crops). It is also used in the manufacture of widely-used chlorinated organic solvents.
Where does it come from?
HCB is released into the atmosphere from the combustion of coal, waste incineration and from certain metal processes. Releases also occur from its manufacture and use as a fungicide and because it contaminates some pesticides. Small amounts of HCB may also be released naturally from fires and volcanoes.
How might it affect the environment?
HCB is classified as "dangerous" to the environment. This is mainly because of its ability to persist and accumulate in fish, marine mammals and certain plants. HCB is classified as a persistent organic pollutant (POP). Exposure to high doses can damage the reproductive system and cause birth defects in animals. As a VOC, it can also be involved in reactions with other air pollutants to produce potentially damaging ground level ozone. The ease with which HCB evaporates combined with its persistence and tendency to bioaccumulate mean that it can be transported long distances to remote (potentially very sensitive) regions. For example, HCB has been detected in air, water and in organisms in the arctic region.
How might exposure to it affect human health?
Exposure to HCB can occur through inhalation of polluted air or through eating contaminated food. At sufficient levels, HCB is toxic to humans - possibly causing liver damage, damage to the immune system, affecting the reproductive system and inducing birth defects. The levels required to have these effects are rare. Exposure to very high levels following an accidental release or in occupational settings could cause a syndrome known as "porphyria", the symptoms of which include blistering of the skin, sensitivity to light, susceptibility to skin infection and possibly osteoporosis. Inhalation of ground level ozone (in the formation of which HCB is slightly involved) can exacerbate respiratory conditions such as asthma.
What steps are being taken to limit the potential impacts?
In the UK (including Scotland), HCB is a "red list substance", highlighting that it is of particular concern to the environment and health. UK releases of HCB are controlled through regulations on emissions of dangerous substances to surface waters (SI 1997/2560); the pollution prevention and control regulations; the food and environmental protection act (FEPA 1985); and regulations on the use of pesticides (COPR 1986). Its use as a pesticide has been banned in the UK since 1975 and in all of the Europe since 1998. A number of European Directives are concerned with emissions of HCB: controls on the marketing and use of certain substances (76/769) and of certain plant protection products (79/117); risk assessments of certain chemicals (793/93); and emissions to water (76/464, COMM(2000)47 & 99/61); and it is listed as a "priorty hazardous substance" for the proposed Water Framework Directive. Internationally, the use of HCB as a pesticide is expected to be banned; HCB is scheduled for inclusion in the UNEP persistent organic pollutants (POPs) convention; and it is listed as a priority substance under the OSPAR and Helsinki conventions which protect the marine environments of the north-east Atlantic and Baltic sea respectively.