Available science does not provide us with ‘safe’ levels for a number of air pollutants. The working group, convened by the National Society for Clean Air and Environmental Protection (NSCA) considered the question of how future strategies for reducing concentrations of the various air pollutants for which standards exist might be developed, recognising the difficulty in attaining some of the existing standards.
A first important outcome was that the group considered that there were alternative strategies that could be used. The first was a gap closure approach, in which the gap between existing and natural levels would gradually be reduced.
The second, developed largely by EMRC, was to provide a mechanism for combining the risk posed by each legislated air pollutant into an overall risk index. The objective of future legislation based around such an approach would be to reduce this combined risk in the most cost-effective manner, with less focus on which pollutants of the mixture to which we are all exposed would be dealt with. This added flexibility could improve the cost-effectiveness of future legislation. Balanced against this are the problems of uncertainty in developing such an index. NSCA are currently consulting on the paper, which is available from the NSCA web site (see ‘Air Quality Limit Values – Is There a Better Way?’).