air-pollution standards. Resolution of these uncertainties would also allow construction of environmental accounts. The panel's review of work in this area indicates that the preparation of estimates of the economic impacts of air pollution is feasible today, but there are enormous uncertainties at virtually every stage of the effort. While BEA or those preparing environmental accounts would not necessarily be involved in preparing dose-response estimates, the accountants will need to work closely with public-health, agricultural, forestry, and ecological experts to use the best information available.

In addition to understanding the dose-response relationship, national accounting requires regular, statistically valid monitoring of the relevant populations and the doses they are receiving. A basic limitation of much of the data currently collected is that ambient concentration levels in areas where individuals, crops, forests, or other relevant entities actually reside are poorly measured. Most measurements occur at sites of convenience rather than sites of relevance. Air pollution monitors are often placed with other monitoring devices where airplanes congregate rather than where people live.

A full account of economic-environmental interactions also requires tracking the fate and transport relationship, or the connection between the emission of a particular pollutant or pollutant precursor at one time and geographic point and the level, time, and location of the pollutant at the point where it affects an economic asset or activity. These relationships are generally highly complex and variable. For air pollutants, wind direction and speed, temperature, cloudiness, and precipitation all affect how a pollutant is dispersed or concentrates. Precursor pollutants sometimes do not create damage themselves, but react chemically in the atmosphere to create other agents that are damaging. Acid precipitation and tropospheric ozone are examples. The formation of these pollutants depends on the presence of other agents that may limit, speed, or slow the process. Monitoring of emissions, concentrations, exposures, and consequences would provide the physical foundation for a complete set of environmental accounts, and is also a critical part of environmental management.

The goals of environmental accounting will dictate the assignment of priorities for improved data. Extensive data on the fate and transport of emissions and concentrations of pollutants are a lower priority if the goal is scorekeeping; even dose-response relationships may be secondary to more direct measurement of consumption flows or changes in important capital and environmental assets and human health status. If one is interested primarily in measuring the sustainability of economic activity, understanding the health status of human and natural systems is more important than understanding why conditions have changed. On the other

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