Table 42.-Air quality trends in major urban areas, 1980-1991.

PMSA

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 number of PSI days greater than 100

Source: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, National Air Quality and Emissions Trends Report, 1990, EPA-450/4-91-023, (Research Triangle Park, NC: EPA, October 1992).

Notes: PMSA-Primary Metropolitan Statistical Area. PSI-Pollutant Standards Index. The PSI index integrates information from many pollutants across an entire monitoring network into a single number which represents the worst daily air quality experienced in the urban area. Only carbon monoxide and ozone monitoring sites with adequate historical data are included in the PSI trend analysis above, except for Pittsburgh, where sulfur dioxide contributed a significant number of days in the PSI high range. PSI index ranges and health effect descriptor words are as follows: 0 to 50 (good); 51 to 100 (moderate); 101 to 199 (unhealthful; 200 to 299 (very unhealthful); and 300 and above (hazardous). The table above shows the number of days when the PSI was greater than 100 (=unhealthy or worse days).

Related Tables: 37, 40, 43.

Table 43.-Persons living in counties with air quality levels above
National Ambient Air Quality Standards, 1984-1991.

Source: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, National Air Quality and Emissions Trends Report, 1991, and earlier reports in this series, EPA-450-R-92-001, (Research Triangle Park, NC: EPA, October 1992).

Notes: Particulates for 1984-1986 refer to total suspended particulates. After 1986, particulates refer to PM-10 (particulates less than 10 micrometers in diameter). Related Tables: 37, 40, 42.

Source: Karl, T.R., C.N. Williams & F.T. Quinlan. United States historical climatology (HCN) serial temperature and precipitation data, NDP-019/R1, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, (Oak Ridge, TN: DOE, 1990).

Note: Calendar year mean (January-December). Seasonal year mean, calculated from four seasons in the following sequence: Winter (December-February); Spring (March-May); Summer (June-August); and Fall (September-November). For seasonal means, see Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Trends '91: A Compendium of Data on Global Change, p. 573, (Oak Ridge, TN: DOE, 1991).

Related Tables: 27, 28, 38.

Land, Agriculture, and Forestry

Million Acres

Figure 19.-Land use in the United States, 1900-1987.

300

250

200

150

100

50

0

Transportation
National defense

Source: See Table 46.

Parks/Wilderness
Urban areas

Wildlife areas
Farmsteads