sponses of individual facilities to be aggregated to the entire industrial sector. Long-term simulations with these models could allow a first assessment of how changes in NSR rules might affect technology adoption and emission trends. However, such a model would have to be subjected to thorough sensitivity analysis to see how much the conclusions change with different input assumptions and scenarios—for example, concerning the rate of innovation, the stringency of regional or national caps on pollutant emissions, surrenders of emissions allowances under NSR settlements, and the cost of alternative electricity-generation and pollution control technologies. Furthermore, models with the capacity for representing alternative technologies in a long-term simulation are not available for other sectors, and the time and resources available to the committee are not sufficient to support the construction of sector models for this purpose. For these other sectors, therefore, any generalization from the estimates of facility-level responses to estimates of industrial-sector responses will have to be undertaken more informally.

For the most part, the multisector models are even less able to represent the types of changes we are assessing than the sector models. Modifying the available models so that they can reflect these changes is substantially beyond the committee’s capacity or resources. Therefore, any intersector impacts will also have to be assessed informally, and any estimates of their direction or magnitude are likely to be highly uncertain.

The most appropriate way of assessing the impacts on health and other outcomes of any emission changes estimated on the basis of the above assessments will depend substantially on the amount and quality of information resulting from these assessments. In many cases, the human health impacts, for instance, are likely to depend on which specific facilities change their emissions in response to the rule changes, who is exposed to the emissions from these facilities, and the ambient air quality in the vicinity of these facilities before the alterations occur. It is unlikely that we will be able, at least in most cases, to make estimations with such specificity. Where we cannot, attempting to undertake sophisticated modeling of human health impacts would have little validity, and we probably will be able to do little more than indicate the likely direction and possibly the rough magnitude of these impacts, if any.

As discussed in Chapter 6, it will be necessary to consider a range of possible scenarios for the economic and environmental assumptions that are applied to estimate and compare outcomes from the revised NSR rules with outcomes from the NSR rules before to the revisions.



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