What type of substance is it?
Xylenes are both naturally occuring chemicals and are manufactured by man. They are colourless, sweet-smelling flammable liquids. Xylenes can be toxic to wildlife and they are also volatile organic compounds (VOCs) that can contribute to harmful ground-level ozone formation.
How is it released?
Xylenes are released to the environment through their manufacture and use as solvents, in paint, petrol spillages and evaporation. They also occur naturally in petroleum and coal tar and are formed in small amounts during forest fires.
Detailed information
Scientific name:
1,2-dimethyl-benzene (ortho-xylene); 1,3-dimethyl-benzene (meta-xylene); 1,4-dimethyl-benzene (para-xylene)
Other names:
1,2-dimethly-benzene, o-methyltoluene, 1,2-xylene, o-xylol, ortho-xylene, 1,3-dimethly-benzene, m-methyltoluene, 1,3-xylene, m-xylol, 1,4-dimethly-benzene, p-methyltoluene, 1,4-xylene, p-xylol,
CAS Number:
1330-20-7 (mixed isomers); 108-38-3 (m-xylene); 95-47-6 (o-xylene); 106-42-3 (p-xylene)
Before 1940 virtually all of the aromatic solvents, including xylene, were produced from coal. Thereafter production of xylene from petroleum refining started. It occurs naturally in petroleum and coal tar and is formed during forest fires. It is readily volatile and flammable. It is also classed as a VOC (Volatile Organic Compound) and is one of the 50 most significant VOCs (in terms of mass emission) released into the UK environment. VOCs contribute to the formation of ozone in the lower atmosphere
Over 90% of mixed xylene isomers is used for blending into petrol. The remainder is used in a variety of solvent applications, as well as to produce the individual isomers of xylene. Xylene based solvents are widely used in the paint and printing ink industries, for polyester fibre, film and fabricated items and perfumes, pesticide formulations, pharmaceuticals and adhesives. It is also used for household products such as aerosol paints and lacquers Xylene is also used as a cleaning agent, and as a thinner for paints and varnishes. Individual isomers of xylene are used in the manufacture of certain plastics.
Xylene is an aromatic hydrocarbon that exists in 3 isomeric (structural) forms. It is a colourless liquid at room temperature with a strong odour. It can be produced naturally and is highly flammable.
Where is it released?
Xylene can enter the environment when it is made, packaged, shipped or used. Most xylene that is accidentally released evaporates into the air, although some could be released into soil, rivers and lakes. The major sources of release are during its use as a solvent and its release from motor vehicle exhausts. A small proportion is also likely to enter water and soil due to oil/petrol spillages. It has been found in waste sites and landfills from discarded solvent, paint or varnish. Motor boats could be a significant source of xylenes in surface water. Migration of petroleum products from leaking underground storage tanks could pose a groundwater contamination problem. Xylene occurs naturally in petroleum and coal tar and is formed in small amounts during forest fires.
Local environmental effects
The xylene isomers are harmful to aquatic organisms. The acute toxicity to birds is low. Overall risk to aquatic environment is low, except near localised industrial discharges or spillages. Only very small amounts are taken up by plants, fish and birds. In the air, xylenes are broken down by sunlight, contributing to the formation of ozone in the lower atmosphere. In soil and water o-xylene and p-xylene are readily biodegraded under a wide range of aerobic and anaerobic conditions, but m-xylene is more persistent under similar conditions.
Global environmental effects
No significant global impacts are considered likely.
Possible health concerns
Excessive exposure to xylene isomers may affect the brain, digestive system, ear, eye, heart, kidney, liver, lung, skin, nose, reproductive system, throat and the unborn child. The Environment Agency aims to ensure that environmental exposures are too low to harm human health.
Legislation
Why was this substance selected for the Pollution Inventory?
For air releases included in : Environment Agency categorisation as a hazardous Volatile Organic Compound (VOC). For water releases included in : European Pollutant Emission Register (EPER) reporting requirements; UK Surface Waters (Dangerous Substances) (Classification) Regulations reporting requirements.
Standard risk phrases for the pure substance
The standard risk phrases provided here are generally those used by suppliers of chemicals to describe substances - for example on packaging materials. The most important source of these phrases are the CHIP Regulations - Chemicals (Hazard Information and Packaging for Supply) - provided by the Health and Safety Executive. Some substances do not have CHIP risk phrases and in these circumstances we have used other risk phrases, the sources of which are indicated.
CHIP Phrase(s) : Xn: Harmful; Xi: Irritant; R10: Flammable; R20/21: Harmful by inhalation and in contact with skin; R38: Irritating to skin
Controlling legislation and international agreements
The UK legislation controlling releases of xylenes are the Surface Water Regulations and the Pollution Prevention and Control Regulations. The UK is also committed to reduce VOC emissions under its Air Quality Strategy. Xylene releases also regulated under EC Directive 76/464: Pollution of the aquatic environment by dangerous substances (plus daughter directives). It is also regulated under (EC) Regulation 793/93 - evaluation and control of risks of existing substances (second list of priority substances) and by the Solvents Directive. Internationally xylene is covered under the OSPAR and Helsinki Conventions as a candidate substance for evaluation. As a VOC the main international legislation are the UN/ECE Convention on Long-Range Transboundary Air Pollution and Basel Conventions. Directive 99/13/EC on solvents (VOC emissions) will also apply.
These factsheets have been compiled to provide users with information on the Pollution Inventory substances and represent our best efforts to summarise a large number of disparate and sometimes conflicting data sources. We emphasise that this information describes potential hazards rather than actual effects and that the Environment Agency seeks to regulate releases to minimise emissions and hence any risk of detrimental effects occurring.
