5 Projections for Individual Monitoring Site Locations

Projections of the maximum running annual mean for benzene and 1,3-butadiene have been made for 12 of the sites on the UK Hydrocarbon Monitoring Network. For the purposes of this report, all 12 sites have been considered to be urban background, with the exception of Harwell (a rural site).

Several hypothetical scenarios have been considered (see below), and the estimated concentrations for 2005 are given in Figures 5.1 and 5.2. The two hypothetical scenarios given in Figures 5.1 and 5.2 are in addition to the business as usual scenario.

Scenario a	Business as usual (as used with all other projections in this report)
Scenario h	Reduction in emissions from traffic:	30% In Inner/Central London
		30% In Outer London
		30% In all other Locations
Scenario i	Reduction in emissions from cars:	30% In Inner/Central London
		30% In Outer London
		30% In all other Locations

The ratios of concentration between the sites remain relatively constant, even though the absolute concentrations decrease substantially. In each of the scenarios, all of the sites comply with the target value for benzene of 1ppb (see Section 6).

The method used to generate these projections does not incur the uncertainties associated with the mapping methods. Consequently, the projections for each site may be compared with the 1.0 ppb value, rather than the 0.7 ppb threshold (chosen to account for the uncertainties in the mapping methodology and the difference between maximum annual running means and fixed annual means).