Air quality

Review and Assessment of 1,3-butadiene

Information about air quality in solihull

4 Review and Assessment of 1,3-butadiene

4.1 The Government has adopted a running annual mean

of 2.25µg/m³ (1ppb) as an air quality standard for 1,3 butadiene, with an objective of meeting that standard by the end of 2003. Given an averaging period of one year, the focus of the review and assessment should be on non-occupational exposures at near ground level locations, including:-

• Background locations,
• Roadside locations, such as on pavements or close to the facades of buildings,
• Other locations where people may be regularly exposed, such as schools or hospitals.

4.2 1,3-butadiene is a volatile organic compound

consisting of four carbon and six hydrogen atoms. At normal ambient temperatures it is a gas, and trace amounts are detectable in the atmosphere.

Almost all the 1,3-butadiene found in the atmosphere, near ground level in the United Kingdom, is likely to have resulted from human activity.

4.3 The main sources of 1,3-butadiene for non-occupational exposures are emissions from petrol-engined vehicle exhausts and a small number of industrial processes. Whilst 1,3-butadiene is not present in petrol, it is produced from the partial combustion of the fuel and is therefore a component of the emissions from vehicle exhausts.

Specific sources of 1,3-butadiene in Solihull are:-

• Emissions from motor vehicle exhausts.

Solihull has no industrial sources of 1,3-butadiene but the West Midlands Atmospheric Inventory identified railways as a minor source of 1,3-butadiene emissions (Figure 4.1):.

Sources of Butadiene in the West Midlands

Figure 4.1

This shows that approximately 96% of the 1,3 butadiene is emitted from road transport related activity.

4.4 In the West Midlands, emissions of 1,3 butadiene are only derived from the combustion of fuel in motor vehicles and, apparently, railway engines.

4.5 National policies to control vehicle emissions have already reduced the tailpipe emissions of 1,3-butadiene from motor vehicles. Our calculations, based on changing emissions factors, show that the emissions are expected to fall by 60% between 1996 and 2005 and the Government advice is that emissions from road traffic is not expected to cause any breach of the air quality objective, by 2003.

4.6 1,3 butadiene Levels in the West Midlands

1,3 butadiene is only measured at one location in the West Midlands; the Birmingham East automatic hydrocarbon monitoring station. This station is owned and operated by the Government, as part of the national Hydrocarbon Monitoring Network (HMN). Figure 3.2 shows how the concentrations of 1,3 butadiene at this station have changed through the 1990s and how they are expected to change through the first five years of the new century.

Trends in West Midlands Air Quality 1,3-butadiene: Annual Average Values

Figure 4.2

4.7 Future Trends in 1,3 butadiene Levels

Government considers that the levels of 1,3 butadiene arising from road traffic and from petrol stations are unlikely to present a significant risk of breaching the standard in 2003.

Measurements of the levels of 1,3 butadiene in the atmosphere at the hydrocarbon monitoring station support that opinion.

Since Solihull has no other sources of benzene, there is little risk of the 1,3 butadiene objective being breached.