3.3 Results
Over 1000 samples were collected at the five primary measurement sites. The three Sydney sites were sampled continuously from early 1996 to August 2001, while sampling at the Newcastle and Wollongong sites ran from mid-1997 to mid-2001.
Each sample was analysed for the full range of TO-14 compounds with 1,3-butadiene also measured from mid-1998, following validation of the test method for this compound.
Twelve of the 41 targeted compounds were not detected in any of the samples collected (see Table 3).
Table 3: Organic compounds not detected
| 1,1,2,2-tetrachloroethane | 1,4-dichlorobenzene |
| 1,1,2-trichloroethane | cis-1,3-dichloropropene |
| 1,1-dichloroethene | Chlorobenzene |
| 1,2-dibromoethane | Chloroethane |
| 1,2-dichlorobenzene | Freon® 114 |
| 1,2-dichloropropane | trans-1,3-dichloropropene |
Of the 29 compounds detected, 10 were rarely encountered, being found in fewer than 1% of the samples taken (see Table 4).
Table 4: Organic compounds in fewer than 1% of samples
| 1,2-dichloroethane | Vinyl chloride |
| 1,3-dichlorobenzene | 1,2,4-trichlorobenzene |
| Chloroform | 1,1-dichloroethane |
| 3-chloropropene | Bromomethane |
| Hexachloro-1,3-butadiene | cis-1,2-dichloroethene |
Of the remaining 19 compounds which were detected in more than 1% of samples, most were present at very low levels. Figure 2 shows the source of these organic compounds at the five primary sites of the study.
Figure 2: Likely sources of major organic compounds detected at the five primary sites
Table 5: Organic compounds detected at the five primary sites classified by likely source
| Source | Organic compound |
| Motor vehicles | Toluene Benzene Xylenes (para and meta) Xylenes (ortho) 1,2,4-trimethylbenzene Ethylbenzene 1,3-butadiene 4-ethyltoluene 1,3,5-trimethylbenzene Styrene |
| Ozone-depleting substances | Freon® (11, 12 and 113) Carbon tetrachloride 1,1,1-trichloroethane |
| Industrial | Dichloromethane Trichloroethylene Tetrachloroethylene |
| Natural, domestic and industrial | Chloromethane |
Figure 2 highlights that the majority of these pollutants are generated by motor vehicles. Industry is the primary source of only three of the compounds detected. One compound (chloromethane) is generated from industrial and domestic sources as well as naturally.
While ozone-depleting substances, including chlorofluorocarbons, are the next largest group of organics (after substances sourced from motor vehicles), they are no longer in production or use. The EPA found that the concentrations of these substances were not significantly higher than those at remote sites at Cape Grim (Tasmania) and Alaska.
The highest annual average levels for the 19 organic compounds were found consistently in the Sydney CBD. St Marys, Newcastle CBD and Wollongong CBD had good air quality with respect to organic air toxics. Rozelle had satisfactory average concentrations, although it demonstrated a more pronounced effect from motor vehicle sources.
Page last updated: 26 February 2011
