* Benzene is a clear, colourless, volatile liquid derived from petroleum, with a characteristic sweet "aromatic" smell.

* Breathing very high levels can result in death, while high levels can cause drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion and unconsciousness. Eating or drinking foods containing high levels of benzene can cause vomiting, dizziness, sleepiness, convulsions, rapid heart rate and death.

* It should only be handled with protective clothing, including a chemical hood, goggles and gloves. First aid measures including flushing eyes and skin with copious water and removing contaminated clothing.

* Benzene has been found to cause cancer in laboratory animals and it is classed as a human carcinogen by the US government.

* It is a basic chemical used as a building block in the petrochemical industry to produce a wide range of everyday products such as paints, dyes, packaging, adhesives and compact discs. Benzene is used in small quantities in gasoline to improve the octane rating but its presence is being minimised.