Acid rain can damage lakes and aquatic life and affect the human respiratory system.
The auction gives power plants, brokers, and private citizens anywhere in the world the chance to buy and sell SO2 allowances. Electric utilities account for 70 percent of nationwide SO2 emissions. CBOT received 159 bids for the spot auction, of which 41 were successful. The total number of year 1997 allowances sold was 150,000. There were 44 bids for the six-year advance auction, of which six were successful.