ESTIMATION OF SO2 EFFECT THRESHOLDS FOR HEATHLAND SPECIES

1. An ecotoxicological risk analysis was applied to data on the effects of SO2 on a heathland ecosystem to study the merits of this analysis for use in setting safety standards for air pollution. 2. Fourteen species native to heathland vegetation were exposed to a range of SO2 concentrations up to 520-mu-g m-3 in controlled fumigation chambers. 3. The effect of fumigation on visual injury and several growth parameters was determined after 6 weeks. 4. Species dominating heathlands in The Netherlands were hardly affected by the fumigations, while the bryophytes and species from the Violion caninae alliance were much more sensitive to SO2. 5. The threat of elevated SO2 concentrations to heathland vegetation from injury was estimated by incorporating SO2 effect threshold levels for these species into an ecotoxicological risk analysis. 6. Based on this analysis and within the limitations of the available data set, the air quality standard would have to be lowered to that equivalent to a 42-day mean of 8-mu-g m-3 to protect 95% of the species native to heathland vegetation in The Netherlands from injury.