5.4 Comparison with international benchmarks
There are few international goals for heavy metals against which the levels found in the study can be compared. The World Health Organization's Air Quality Guidelines for Europe (2nd Edition, 1996) and the European Commission's draft standards for certain heavy metals are all based on annual averages, i.e. the average of all 24-hour samples collected over one year. Given the different sampling used in this study, only general inferences are possible.
Table 11 compares the study data with those international goals available. For beryllium, an assessment based on available US EPA risk factors was used rather than a goal.
None of the metals sampled exceeded international goals where they existed and many were well below those goals.
The mean 24-hour results shown in Table 11 are likely to be high readings for these heavy metals. This is because the data collected for the study was sampled during winter when regional concentrations of air-borne heavy metals are thought to be elevated. As a consequence, annual average concentrations calculated from data across the whole year are likely to be lower than these readings and below current (annual average) international goals.
Table 11: Heavy metals-Study results and internationally recognised goals
| Metal | Mean of samples (24-hour: ng/m3) | Range of samples (24-hour: ng/m3) | Ambient air goals (annual average: ng/m3) | Source |
| Antimony | 1.2 | 0.04-4.6 | None available | |
| Arsenic | 0.6 | 0.1-2.5 | 1-20 | EC1 |
| Beryllium | ND | ND | 0.4 | US EPA |
| Cadmium | 0.18 | 0.03-1.0 | 0.5-15 | EC1 |
| Cobalt | 0.19 | 0.10-0.39 | None available | |
| Copper | 8.2 | 2.4-28 | None available | |
| Lead | 29.9 | 3.4-99 | 500 | NEPM2 & WHO3 |
| Manganese | 18.0 | 4.4-119 | 150 | WHO3 |
| Nickel | 3.6 | 1-20 | 3-50 | EC1 |
| Selenium | 0.2 | 0.10-0.65 | None available | |
| Vanadium | 2.6 | 0.16-49 | 1000 (daily average) | WHO3 |
| Zinc | 32.6 | 11-71 | None available | |
ND: not detected
1 European Commission goals are proposals only and a range of values is under discussion.
2 NEPM: This is the Australian goal for lead set in the National Environment Protection (Ambient Air Quality) Measure.
3 WHO: World Health Organization goals are based on guidelines for the risk of health impacts.
Page last updated: 26 February 2011
