• Uncertainties in emission projections are significant. A comparison of atmospheric measurements with inventory calculations shows differences per group of substances (CFCs, HCFCs, HFCs and PFCs) in the order of 10?25 % .

• A substance that is organic and will rapidly biodegrade.

• The presence of toxic substances in groundwater or surface water contaminated by leachate from a badly engineered and operated landfill does not necessarily imply exposure of the resident population, as drinking water in the region may be sourced elsewhere.