In a variation to this base case, costs are also calculated where the health effects of PM10 are estimated without a threshold. This variation provides a sensitivity analysis that shows how specifying a threshold affects total cost estimates. As acknowledged by Kunzli et al. (1999), the approach of using one pollutant as an indicator of the air pollution mix and only estimating the impact of PM10 above a baseline will probably underestimate the impact of air pollution. In Sydney, ozone is a pollutant of particular concern, and epidemiological studies suggest that there are ozone health impacts additional to those.
