4.5 Comparison with international benchmarks
In general, no ambient air quality standards have been set for PAHs. However, proposals and guidelines have been developed for the PAH, benzo(a)pyrene (BaP), in Europe. The UK has proposed an annual average goal of 0.25 ng/m3 for BaP from 2010. The European Commission is also considering a proposal for a BaP goal of between 0.5 and 1.0 ng/m3 to be implemented in 2005.
The UK goal was based on research which indicated:
- the relative proportion of BaP in total PAH for each sample does not vary greatly
- BaP is currently estimated to be the most toxic of the common PAH compounds and, even though found in modest concentrations, is the largest contributor to overall toxicity.
BaP is therefore used as a surrogate measure for total PAH and the numerical value of the goal reflects this.
Sampling in this study was primarily in winter rather than throughout the year, which makes direct comparison with the available international goals difficult because they are expressed as annual average concentrations.
To facilitate comparison with the proposed international standards for benzo(a)pyrene, Tables 9 and 10 report the BaP results from the study.
Table 9: Total BaPs (24-hour averages: ng/m3) winter and summer-Sydney, Newcastle and Wollongong sites (average of each group) and all other sites (except Orange)
| Nowra | Sydney (average of all sites) | Wollongong (average of all sites) | Newcastle (average of all sites) | Tumut | Cooma | Armidale | Lithgow | |
| WINTER | ||||||||
| Average | 0.07 | 0.46 | 0.16 | 0.30 | 1.12 | 1.12 | 1.30 | 4.21 |
| Max. | 0.07 | 2.25 | 1.21 | 1.92 | 3.06 | 3.02 | 3.77 | 8.99 |
| Samples | 6 | 52 | 59 | 31 | 14 | 13 | 5 | 14 |
| SUMMER | ||||||||
| Average | - | 0.03 | 0.03 | 0.06 | 0.09 | 0.03 | 0.02 | 0.03 |
| Max. | - | 0.07 | 0.07 | 0.40 | 0.27 | 0.04 | 0.02 | 0.07 |
| Samples | Nil | 14 | 8 | 11 | 4 | 4 | 2 | 4 |
The seven Orange samples (collected over a shorter period than the other sites and over winter) found an average BaP result of 1.45 ng/m3 and a maximum of 4.34 ng/m3.
Table 10: Total BaPs (24-hour averages: ng/m3) winter and summer- Sydney sites
| Richmond | Lindfield | Rozelle | Blacktown | Sydney CBD | Earlwood | |
| WINTER | ||||||
| Average | 0.14 | 0.39 | 0.38 | 0.43 | 0.77 | 0.76 |
| Max. | 0.32 | 1.67 | 1.35 | 1.92 | 1.68 | 2.25 |
| Samples | 8 | 12 | 8 | 10 | 4 | 10 |
| SUMMER | ||||||
| Average | 0.02 | - | 0.05 | 0.04 | - | 0.02 |
| Max. | 0.02 | - | 0.07 | 0.07 | - | 0.02 |
| Samples | 4 | Nil | 4 | 4 | Nil | 2 |
Figure 7 presents the BaP winter and summer averages for an average of the Sydney, Newcastle and Wollongong sites plus all other sites, except Orange. Figure 8 shows the BaP winter and summer averages for each of the Sydney sites.
Figure 7: Seasonal variations in BaP-Sydney, Newcastle and Wollongong sites (average of each group) and all other sites (except Orange)
It is worth noting that the emissions at the Armidale, Cooma, Lithgow and Tumut sites comprised a relatively higher proportion of BaP compared with the city sites. This is consistent with the use of solid fuel heaters in these areas, although BaP is not exclusively produced by these appliances.
Figure 8: Seasonal variations in BaP-Sydney sites