PERSPECTIVE ON POLLUTION : Smog Award Goes to . . . Weekends! : Rather than trying to change human behavior, maybe we should try harder to build a better, cleaner car.

While Southern California’s 1992 smog season had the least number of alerts on record, a curious variation emerged:

Weekends have become the new smog headaches. Friday, once considered the smoggiest day, has been replaced by Saturday.

When heavy-smog episodes are called, school districts cancel strenuous outdoor physical activity in the affected areas. The at-risk population, which includes the very old and the very young, are advised to remain indoors. No such program is widely administered by park districts and sports leagues on smoggy weekends.

During the past year, of the 36 air monitoring stations recording ozone levels in the four-county South Coast Air Quality Management District, 24 registered their highest level of the year on a Saturday. Five more recorded it on a Sunday. The highest reading of the year, 0.30 parts of ozone per million parts of air, occurred on a Saturday (April 25) in Glendora.

For years, Friday prevailed as the worst smog day. Seeking an early jump on the weekend, residents further burdened the congested freeways by driving alone, adding tons of contaminants to an atmosphere already afflicted with residual pollution from the previous day. Consequently, from April through October, Friday smog levels soared. Out of 81 alerts called from the beginning of air monitoring in 1955 to 1971, 23 occurred on Friday. Thursday had 15, with about a dozen each for the other weekdays. Only five alerts were called on Saturday, and none on Sunday.

The absence of the early-morning traffic jams on the weekends brought a dramatic break to the established scenario, allowing the area to be swept clean by even the meekest of summertime winds. In a big sense, the weekends were always considered to be a breath of fresh air for Los Angeles.

Ironically, increased car-pooling and the switch to a four-day work week may be factors that have aided the weekend, elevated ozone values. Deprived of their private cars during the week, many people shift their chores to the weekend. An extra day off, generally a Friday or a Monday, adds to the new, interminable driving habit. It also increases the number of cold-starts, the initial starting of a vehicle or restarting it after an hour’s rest. During a cold-start and the first two to three minutes of the car’s operation, more reactive hydrocarbons are discharged into the air than during any other of the car’s driving cycles.

Ozone, or Los Angeles-type smog, is a colorless, highly reactive gas with a sharp odor that is formed by a complicated series of reactions in the air. When the two key precursors, hydrocarbons and oxides of nitrogen, are discharged by motor vehicles and industry, Southern California’s strong sun triggers the smog-forming reaction.

High smog values are common when there is a low, strong temperature inversion, light winds, weak pressure gradients and maximum sunshine. Interestingly, meteorological conditions last year did not depart from the norm and had little, if anything, to do with the weekday / weekend differences.

Industrial and manufacturing sources, with little or no activity on Saturdays and Sundays, do not appear to contribute significantly to weekend ozone. And, although there are fewer motor vehicle emissions on the weekends, they appear to be of the correct ratio and discharged at the right time and place to alone cause excessive violations of the federal health-based standard.

Recently announced enhancements to the smog-check program may provide for more complete tests and even catch failed catalytic converters, but they cannot correct the cold-start dilemma--and will continue to provide unrealistic inventory data, since cars will be tested when they are warm. The auto manufacturers have turned their attention to preheated or quickly heated catalytic converters, but that also will not deal with the current problem, the cars on the road today.

The changing smog motif suggests many things. First of all, with more people in the open air during weekends, the statistics that cover population exposure to smog may be entirely wrong. Weekend smog affects more people and for longer periods of time.

Today, the SCAQMD seeks quick implementation of a market-incentives program, with complex rules and intricate pollution-trading. Still, the shifting nuances from the greatest of all smog-makers--the car--is not fully understood. Despite the efforts to create a clean industrial and manufacturing community, at a very high cost, the atmosphere is so impacted with motor-vehicle emissions it will hardly show a difference.

And yet, the weekend smog problem can be defined, and the definition suggests the cure. One answer may lie in the development of a quickly heated, retrofit catalytic converter. This will minimize pollution from the cold-start cycle.

The timing is almost perfect for this to happen. The SCAQMD board meets today and Friday. For months, the business and industrial community has accused the district of over-regulation and moving jobs, not smog, out of the basin. Real control efforts aimed at the car’s tailpipe are long overdue.