4 PM10 Projections for alternative emissions scenarios
The PM₁₀ projections presented in the APEG report represent our current best estimates of the likely impact of current national and international policy measures on PM₁₀ concentrations in the UK. PM₁₀ projections for a range of alternative scenarios are presented in this section and the receptor modelling results are clearly relatively insensitive, even to extreme reductions in either primary or secondary particle concentrations. At least to some extent, this is due to high concentrations of 'other' particles within the receptor modelling (section 2.4). Projections for comparison with the NAQS objective are listed in Tables 4.1 to 4.8. The scenarios that we have examined include emissions reductions additional to those assumed in the business as usual scenario. The reductions listed below are all relative to business as usual. The non-traffic primary combustion PM₁₀ contribution and the 'other' particle contribution are held at 1996/1995 levels in all scenarios:

Table	Primary particles	Secondary particles
Table 4.1	50% less traffic emissions	business as usual
Table 4.2	100% less traffic emission	business as usual
Table 4.3	business as usual	50% less secondary
Table 4.4	50% less traffic emissions	50% less secondary
Table 4.5	100% less traffic emission	50% less secondary
Table 4.6	business as usual	100% less secondary
Table 4.7	50% less traffic emissions	100% less secondary
Table 4.8	100% less traffic emission	100% less secondary

It should be noted that no specific policy measures have been identified which could achieve the reductions implied by these alternative scenarios.