Benzene (C6H6) is a complex compound of carbon and
hydrogen which is liquid at room temperature but evaporates to emit
small amounts into the atmosphere.
It is gradually broken down in the atmosphere but this will take
several days.
Benzene found at ground level is almost certainly a result of human
activity.
Approximately 66% of Benzene in the atmosphere is as a result of
petrol vehicle emissions (only one per cent as a result of
diesel vehicles).
Evaporation from petrol stations accounts for about five per
cent while industry is responsible for approximately seven per
cent.
Benzene studies on laboratory animals have shown that the chemical
can damage the genetic make up of tissue cells.
Those exposed to high levels of Benzene have a greater risk of
developing certain types of leukaemia, and there is evidence that
exposure to Benzene can also increase the likelihood of contracting
liver, lung, and stomach cancer.
In North Somerset Benzene concentrations have been measured at 31
sites.
The measurements were taken using specific diffusion tubes,
which are open ended tubes with pollution absorbing gel at one
end.