Damages from the criteria-pollutant-forming emissions were calculated, as described above, for each of 406 plants that generated electricity from coal in 2005.23 Table 2-7 and Figure 2-5 present the distribution of monetized damages across plants. (In Table 2-7 all plants are weighted equally, hence the mean figures are arithmetic means of damages across all plants.) As Table 2-7 makes clear, most damages come from SO2 (85%), followed by NOx (7%), PM2.5 (6%) and PM10 (2%). This reflects the size of SO2 and NOx emissions from coal-fired power plants and the damages associated with fine particles formed from SO2 and NOx.24 Directly emitted PM2.5 has very high damages per ton (see Table 2-8), but very little PM2.5 is emitted directly by power plants; most is formed from chemical transformations in the atmosphere.

Table 2-8 shows how the damages per ton of pollutant vary across plants, again weighting all plants equally. Variation in damages per ton reflects differences in the size of the populations (human and other) exposed to pollution from each plant, as well as differences in effective stack heights across plants. The assumption implicit in our calculations—that the damage per ton of pollutant emitted is independent of the number of tons emitted at the plant—is consistent with the epidemiological literature and with the calculation of air-pollution damages by EPA and other agencies.25

Damages from the criteria-pollutant-forming emissions in 2005 averaged $156 million per plant, but the range of damages across plants was wide—the 5th and 95th percentiles of the distribution are $8.7 and $575 million dollars, respectively (2007 USD). As Figure 2-5 shows, the distribution is highly skewed. After ranking all the plants according to their damages, we found that the most damaging 10% of plants produced 43% of aggregate air-pollution damages from all plants, and the least damaging 50% of the plants produce less than 12% of aggregate damages.26 Where are the plants with the highest damages located? The map in Figure 2-6 shows the size of damages created by each of the 406 plants, by plant location. Plants with large damages are concentrated to the east of the Mississippi, along the Ohio River Valley, in the Middle Atlantic and the South.

Some of the variation in damages across plants occurs because plants that generate more electricity tend to produce greater aggregate damages;

23

Each of our plants is classified as SIC 4911. Together they accounted for 94.6% of electricity generated from coal and sold to the grid (EIA 2009d, Table 1.1).

24

Approximately 99% of the damages associated with SO2 come from secondary particle formation, that is, the transformation of SO2 into PM10 and PM2.5.

25

The concentration-response functions in the air pollution literature are approximately linear in ambient concentrations. The unit values assigned to health and other endpoints are likewise assumed to remain constant over the relevant ranges of the endpoints.

26

Each set of plants—the most damaging 10% and the least damaging 50%—account for approximately one quarter of electricity generated by the 406 plants.



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