4.6 Conclusions
Most of the NSW data was collected in winter, which showed the highest PAH readings compared with the lower concentrations in autumn and spring and the very low concentrations of summer. An annual average measure at each site (the standard favoured overseas) is therefore expected to be between a quarter and a half of the winter concentration found in the study.
The suggested overseas goals for annual average concentrations of BaP range from 0.25 ng/m3 (UK proposed by 2010) to a 2 ng/m3 standard for a `limit' value in Croatia. In between, the European Commission is considering setting a standard between 0.5 and 1.0 ng/m3 for 2005, with indications that it is likely to be towards the higher end of that spectrum.
Assuming, as suggested above, that an annual average reading would be one-quarter to one-half of the current winter average at each of the NSW sites, all of them except Lithgow would meet a standard of 1 ng/m3. Most would probably meet a standard of 0.5 ng/m3; and the Sydney CBD, Earlwood and some Great Dividing Range sites would fail only the toughest standard of 0.25 ng/m3.
On existing knowledge, it is likely that emissions in the Sydney CBD are primarily from motor vehicles with some contribution from woodsmoke. The Earlwood site is located at the bottom of a valley where temperature inversions are likely to trap air, carrying emissions from both vehicles and woodheaters, especially in winter. Both of these sites, while estimated to have BaP levels in the vicinity of the more stringent international goals, will benefit in the short to medium term from improvements in vehicle emissions and programs to reduce smoke from woodheaters.
The general conclusion on some regional NSW centres, Lithgow in particular, is that concentrations of PAHs are elevated and ongoing action is required to reduce those emissions.
The EPA will continue to review progress in international standards to determine whether additional action needs to be taken.
Page last updated: 26 February 2011
