Health Effects of Benzene

Monitoring results 1995 - 1997

Health Effects.

Benzene is a genotoxin, so named because it damages the genetic material in cells. It is also a known carcinogen, that is it is implicated in the development of certain cancers. Studies have shown that workers exposed to high levels of benzene over a long period of time have an increased risk of developing leukaemia. As such there is no safe level of exposure. However, according to EPAQS levels that currently exist outdoors are such that the risk to people is very small. Benzene is present in tobacco smoke and a smoker's exposure to benzene is much greater than a non smoker would be exposed to in ambient air.

Sources.

Benzene is an aromatic hydrocarbon occurring as a colourless clear liquid at room temperature that readily evaporates into the atmosphere. Human activity accounts for practically all of the benzene detected in ambient air. The main source being from the use and storage of petrol. In Hammersmith and Fulham in excess of 80% of the detected benzene is from the use of petrol. Other sources include smoking and the combustion of oil and other fuels.

Standard

EPAQS has set a standard of 5 parts per billion (ppb) as a running average mean. However a target of 1ppb has been recommended in the longer term.

Monitoring Results

Table 6, shows the recorded levels of Benzene in the borough since 1995. The levels are measured using diffusion tubes. The sites are listed in Table 3 above. Results in Table 3 show no exceedences of Benzene concentrations in 1996 or 1997 compared to the standards set in the NAQS.

Compliance with standard

The results from the diffusion tube survey over the last three years has seen a fall of recorded levels to below that of the standard set for the year 2005. Control measures such as the introduction of vapour recovery at all major petrol stations from December 1998 will see a further fall in levels. 

Nationally, emissions of benzene are predicted to fall by 50% by 2005, from 1995 levels (NAQS Table II.3.1) and it is the Government's prediction that concentrations will be below the standard in 2005. The NAQS (page 90, paragraph 23 and 25) state "it is clear that current policies, if rigorously enforced, should eliminate exceedences of the standard by 2005......Policies already in hand should, furthermore, reduce dramatically the exceedence of the longer term target level of 1 ppb recommended by EPAQS." The objective of 5ppb is almost certainly to be met and as such, no further assessment is likely. If, however the standard of 1 ppb is adopted then further assessment may be required at certain locations within the borough.

Table 6 Benzene Concentrations 1995 - 1997.

Back to Stage One Pollution main page