e-Digest Statistics about: Air Quality
Emissions and Concentrations of Benzene
Benzene emissions fell by 74 per cent between 1990 and 2006, and by 53 per cent between 1999 and 2000 alone. The reduction since 1999 is largely due to a sharp reduction in the benzene content of petrol, as well as the ongoing effect of the penetration of catalytic converters in the vehicle fleet. Emissions of 1,3-butadiene fell by 79 per between 1990 and 2006 largely as a result of a fall of 87 per cent in emissions from road transport.
Benzene is a known human carcinogen and 1,3-butadiene is a suspected human carcinogen. Tables 18 and 19 show trends in estimated benzene and 1,3-butadiene emissions by emission source. The main source of benzene in the atmosphere is the combustion and distribution of petrol and the main source of 1,3-butadiene is motor vehicle exhausts where 1,3-butadiene is formed from the cracking of higher olefines. Also, benzene is emitted in a number of industrial processes and 1,3-butadiene is used in the production of synthetic rubber for tyres, both of which may contribute to local exposure.
Table 20 shows concentrations of benzene and 1,3-butadiene and exceedances against Air Quality Strategy criteria at the five automatic monitoring sites in 2006. Site numbers were reduced from 13 in 2000 to 4 in 2001 to allow for an expansion in the number of sites monitoring benzene to a total of 41 in 2004 (using a combination of automatic and non-automatic monitoring methods). Concentrations of benzene and 1,3-butadiene at the 36 non-automatic sites are given in Table 30. This rapid expansion of benzene monitoring was to ensure the UK complies with the second EU Daughter Directive on carbon monoxide and benzene. The objectives that the maximum running annual means for benzene should not exceed 16.25 µg/m³ and for 1,3-butadiene should not exceed 2.25 µg/m³ by the end of 2003 were met at all sites in 2006, automatic and non-automatic. Figures 13 and Figure 14 show trends in exceedances at urban sites of the objective levels for the annual means of benzene and maximum running annual mean of 1,3-butadiene respectively.
Air Quality Strategy for England, Scotland, Wales and Northern Ireland, sets objectives for benzene [27], to be met by the end of 2010. In Scotland and Northern Ireland, the objective is that the running annual mean should not exceed 3.25 µg/m³, and in England and Wales that the annual mean should not exceed 5 µg/m³.
Table 21 gives annual mean and maximum hourly concentrations for eight selected hydrocarbon compounds - ethane, ethene, ethylbenzene, ethyne, (m+p)-xylene, o-xylene, propene and toluene. These have been selected as representing a large fraction of the total hydrocarbon mass measured at UK sites. In addition, they illustrate different source types. The concentrations data show a range of values between sites, reflecting different source intensities for each site. Concentrations are also influenced by the prevailing weather conditions during the sampling period. Data on further hydrocarbon compounds are available from the Archive.
Further Information:
- Data Tables:
- 18 Estimated emissions of benzene by UNECE source category: 1990-2006 XLS
- 19 Estimated emissions of 1,3-butadiene by UNECE source category: 1990-2006 XLS
- 20 Concentrations of benzene and 1,3-butadiene and exceedances against the Air Quality Strategy criteria at national monitoring network sites: 2006 XLS
- 21 Concentrations of selected hydrocarbons from the Urban Hydrocarbon Network: 2006 XLS
- 30 Annual average concentrations of benzene and 1,3-butadiene against the Air Quality Strategy criteria at national non-automatic monitoring network sites: 2002-2006 XLS
- Chart 13 Benzene running annual mean: Comparison with health objectives for 2003: 1995-2006 XLS
- Chart 14 1,3 butadiene running mean, compared with health objective for 2003: 1995-2006 XLS
- Chart 26 Benzene emissions by source: 1990-2006 XLS
- References, further reading and links to other resources:
- [16] National Environmental Technology Centre, (1997). Acid Deposition Monitoring in the UK, 1986 to 1996. AEA Technology.
- [27] Department for Environment, Food and Rural Affairs (2003), The Air Quality Strategy for England, Scotland, Wales and Northern Ireland: Addendum
- Internet Links:
- UK National Atmospheric Emissions Inventory (NAEI)
- National Air Quality Information Archive
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Page last modified:13 March 2008
Page published: 13 March 2008