According to the Environmental Protection Agency, there is some good news in that air pollution has been slowly declining in the United States. For example, carbon monoxide emissions have gone down from 178 million tons (161.5 metric tons) in 1980 to 81 million tons (73.5 million metric tons) in 2007. Volatile organic compounds (VOCs) and sulfur dioxide have both been cut in half (from 30 to 15 million tons [27.2 to 13.6 metric tons] for VOCs and 26 down to 13 million tons [23.6 to 11.8 metric tons] for SO2) over the same time period, and nitrogen oxides have been lowered from 27 to 17 million tons (24.5 to 15.4 metric tons). Overall, from 1980 to 2007, air pollutant rates have dropped from 267 million tons (242 metric tons) produced annually to 129 million tons (117 metric tons). This is still a lot of pollution, without question, but it is significant progress, especially considering that the U.S. population has risen from about 226 million people in 1980 to 300 million in 2007.