The Metro Index: Air Apparent

Year the term smog was coined: 1905

Worst hour for smog in summer: 2 p.m.

Best time of day in L.A. Basin for air: 6 a.m.

Number of August days exceeding federal ozone limit in past decade: 274

Number of January or December days over limit: 0

Last Stage 3 ozone episode in basin: 1974

Last Stage 2 ozone episode: 1988

Total smog episode days in 1978: 139

Smog episodes last year: 13

Days with smog episodes in Pasadena in 1978: 93

Pasadena smog episodes in 1995: 1

Days with health advisories in basin last year: 59

Tons of carbon monoxide emitted daily: 6,200

Tons emitted in San Francisco area: 3,200

Tons emitted in San Diego: 1,400

Square miles covered by South Coast Air Quality Management District: 12,000

Population of the basin in 1950: 4.8 million

Population of the basin in 1990: 13 million