SPRI Home About SPRI

Xylene - all isomers

SPRI Emission Reporting Threshold
1,000 Kg/yr Pollutant Emissions to Air
10.0 Kg/yr Pollutant Emissions to Water
10.0 Kg/yr Pollutant Emissions to Waste Water
200 Kg/yr Pollutant Emissions to Land
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?
Xylene is a member of the BTEX group of pollutants. BTEX is the term used to describe a group of chemicals related to benzene. This includes a variety of compounds: toluene (methyl benzene), ethyl benzene, xylenes and benzene itself. These compounds are usually colourless, sweet-smelling liquids which evaporate easily. They mix well with organic solvents, but do not dissolve well in water (and may float on the surface before evaporating into the air). BTEX compounds are part of the group of compounds known as volatile organic compounds (VOCs).
What is it used for?
BTEX are used in the manufacture of chemicals, rubber and plastics, in solvents, and in paints and lacquers.
Where does it come from?
The main sources of BTEX into the environment are the petroleum and chemical industries and other combustion processes. They are also released when natural materials are burned. Trace amounts are found in cigarette smoke.
How might it affect the environment?
The properties of BTEX compounds mean that most releases end up in the atmosphere, although some can be bound (relatively briefly) to soils and sediments. They react with other air pollution and are broken down, returned to the earth or involved in the formation of photochemical smog. Normal environmental concentrations of BTEX are unlikely to damage the environment, but higher concentrations resulting from a spillage are moderately toxic to aquatic life. Significant bio-accumulation and concentration through the food chain is unlikely. As VOCs, BTEX compounds are involved in the formation of ground level ozone which can damage crops and materials. BTEX is not however thought to have any environmental effects at a global level.
How might exposure to it affect human health?
Exposure to BTEX at normal environmental concentrations, and even to higher concentrations over a short period of time, is unlikely to damage health significantly. However long-term exposure to higher concentrations (usually only experienced in occupational settings) are toxic - damaging the liver, kidneys, central nervous system and eyes. Inhalation of ground level ozone (in the formation of which BTEX can be involved) can exacerbate respiratory conditions such as asthma.
What steps are being taken to limit the potential impacts?
Releases of the benzene part of BTEX are controlled in the UK (including Scotland) through the National Air Quality Strategy; regulations on pollution of surface waters (SI 1997/2560); and Pollution, Prevention and Control (PPC) regulations. European Directives controlling emissions of BTEX compounds include those concerned with pollution of aquatic environments (76/464); assessment and management of ambient air quality (96/62/EC); control of solvents (99/12/EC); the hazardous wastes directive; setting exposure limits for ethylbenzene in occupational settings (2000/39/EC); protection of health and safety at work (98/24/EC); and benzene is listed as a "priority substance" for the proposed Water Framework Directive. Internationally, the World Health Organisation (WHO ) has set safe limits for BTEX compounds. International releases of BTEX compounds are controlled through the OSPAR convention which protects the marine environment of the north-east Atlantic sea; the UNECE convention on long-range transboundary air pollution; and the Basel convention on transboundary movements and disposal of hazardous wastes.