Smoking a cigarette in a car makes the air inside 10 to 30 times more toxic than the air outdoors on one of Southern California's most polluted days.
On Thursday, state officials put on a live demonstration of that health hazard to promote a new law that bans smoking in cars carrying minors.
Neil Klepeis, a Stanford University environmental health scientist, attached sensors to the dashboard of a 1999 Toyota Corolla parked on the lot of the Hollywood United Methodist Church. He attached additional sensors to a child safety seat in the back.
The sensors measured particulate pollution -- toxic, airborne pollutants found in cigarette smoke as well as in fumes from wood-burning stoves, diesel engines and other forms of combustion. The particles, about 30 times narrower than human hair, can lodge deep in the lungs and cause long-term health problems.
Such fine particles are particularly dangerous to children -- whose lungs are still developing -- and the elderly, said Dr. Mark Horton, director of the California Department of Public Health.
"Pound for pound, children breathe more air in than adults," he said. "Fine particulate matter is damaging to their lungs and can affect them forever."
Fine particles can cause or irritate asthma, bronchitis, pneumonia and ear infections, Horton said.
The demonstration showed how rapidly the particles build up in a small, enclosed space.
A volunteer smoker lit up in the driver's seat of the Corolla. Within 20 seconds, computer monitors showed particle levels in the front seat bounding beyond "unhealthy" and "very unhealthy" to "hazardous," the level that, if recorded outdoors, would draw a warning from the Environmental Protection Agency for residents to stay inside and not to exert themselves. Then, in less than a minute, the computer registered 30 times that hazardous level of particles.
The air in the back seat reached levels 10 times the "hazardous" level. When the smoker extinguished the cigarette and rolled down the window, the unhealthy levels lingered.
"You're creating a very large exposure for that child," said Klepeis, who last year published a study on secondhand smoke pollution in cars. "Smoke gets trapped in the back seat and can stay at high levels for a half-hour and at moderate levels for an hour or two."
In a repeat demonstration with the driver's side window open about 8 inches, the air still reached hazardous levels within a minute.
The new state law carries a fine of up to $100. Police officers cannot pull motorists over for smoking, but they can cite smokers if that offense is discovered in conjunction with another violation such as speeding.
"I'd be happy if we don't have to issue one citation," said state Sen. Jenny Oropeza (D-Long Beach), who sponsored the "Smoke-free Cars with Minors" law. "The objective of this new law is education. The objective is to get people to stop smoking in the car with kids."
California, which has been a leader in banning smoking in the workplace, restaurants and bars, follows Arkansas, Louisiana, Puerto Rico and Bangor, Maine, in banning smoking in cars with children. California's law is the most comprehensive because it covers passengers up to age 18, said Kimberly Belshe, secretary of the California Health and Human Services Agency.
In 2006 about 13% of California adults were smokers, down from 23% in 1988, in part because such laws have changed social norms, Belshe said.
Anthony Marquez, the volunteer smoker in the demonstration, approves of the new law and hopes it will prod him to quit smoking. He's tried quitting twice, he said.
On latimes.com To view a video of the demonstration, visit latimes.com/smoking.