NATION'S SMOG RACE GETS DOWN AND DIRTY L.A., HOUSTON RUN TAILPIPE TO TAILPIPE.

Byline: Harrison Sheppard Staff Writer

With only a few weeks left in the race for the dubious achievement of being America's Smoggiest City, Los Angeles is only one pollutant-clogged day behind Houston, officials said Wednesday.

And the race could turn into a dead-heat today.

Wednesday was close to being declared a high-ozone day in Los Angeles, because a monitoring station in the San Bernardino Mountains reported high readings late in the afternoon. But South Coast Air Quality Management District officials said they wouldn't know the full results until today.

It's not, of course, a race that either city wants to win. Los Angeles held the title for decades until last year. Thanks to tighter air quality controls in California and especially hot weather in Texas, Houston, to its chagrin, overtook the City of Angels for the first time in 1999.

As of Wednesday afternoon, Houston had 38 high-ozone days this smog season; Los Angeles, 37.

``I wish you all the luck,'' joked Kathy Barton, a spokeswoman for the Houston Health Department.

The smog title has become something of an issue in the presidential campaign, where Republican George W. Bush has been running on his record as Texas governor against Vice President Al Gore, a staunch environmentalist. It also has become the source of a lighthearted war of words between the two cities as they ran tailpipe to tailpipe all summer.

The smog season in Los Angeles winds up by early October, while it lasts a few additional weeks in Houston.

No matter how the race ends up, however, Houston is likely to have the single smoggiest day this year, environmental officials said. The Texas gulf city had a day with 225 parts per billion concentration of ozone, compared with Los Angeles' peak this season of 180 ppb.

An unhealthy smog day is declared when the levels at a monitoring station average at least 130 ppb for an hour.

Thanks to tight emissions controls, Los Angeles has already made enormous improvements since the late 1970s, when it had 208 high-ozone days.

``We've made steady progress at cleaning the air and that has shown in the numbers,'' said AQMD spokesman Sam Atwood. ``There have been blips up and down each year due to the weather, but on average we've had steady decline of the number of unhealthy air quality days each year.''

Last summer, Los Angeles also had zero days of Stage One smog alerts, a more serious problem where the level of ozone reaches 200 ppb, and is unlikely to have any this year, Atwood said.

In the late 1970s, L.A. typically had more than 120 Stage One smog alerts in a year, he said.

Houston, however, is determined to not keep the crown for too long.

The state of Texas is holding hearings this week on a controversial plan to improve air quality in the greater Houston region by, among other restrictions, lowering highway speeds, limiting times for using power lawn mowers and limiting the amount of time large trucks can idle. The plan is expected to generate strong opposition from business owners and other users of heavy equipment.

Smog levels are affected not only by the amount of emissions from vehicles and factories, but also by weather conditions. Hot, sunny days with few breezes foster the chemical reactions that increase smog in the air - part of the reason that Houston, which has had an unusual number of high temperature days this summer is still ahead of Los Angeles.

Barton noted that Houston also has a high number of industrial sites around the city, especially in the petroleum industry, as well as hot, windless weather at the end of summer.

``We crank out a bunch of (volatile organic compounds),'' Barton said. ``When you're cranking out VOCs, you're going to pay the price.''

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Chart: SMOG-A-THON