The air is clearing inside public buildings as an increasing number of government entities institute strict smoking bans.

California, Florida and Maine, as well as numerous cities throughout the nation, are leading the way. Norway has just joined Ireland in imposing an entire nationwide ban. Custody disputes in the United States now sometimes result in favor of non-smoking over smoking parents because of health concerns. And a bill to ban smoking in cars carrying small children is expected to be reintroduced soon in the California Assembly, after the first attempt failed to pass by only a small margin this year.

The moves are good news to Jesse Joad, a pediatric pulmonologist with UC Davis Children's Hospital. "There's no question that the trends are positive. Tight restrictions are going hand-in-hand with decreasing smoking rates. This is good news for both former smokers and the people around them."

Broad impacts

Joad spends a majority of her time at UC Davis Children's Hospital studying the effects of secondhand smoke exposure on developing children. In her clinic, she sees young patients with respiratory infections, asthma and hacking coughs, all of which are exacerbated by exposure to secondhand smoke.

Numerous epidemiological studies over the years have linked exposure to cigarette smoke during gestation and infancy with these problems, as well as sudden infant death syndrome (SIDS), babies born small for gestational age and numerous other health problems.

But epidemiological evidence "can only take you so far," said Joad. "Experimental research can prove a cause and effect relationship, and also deepen our understanding of the disease processes."

Joad and her colleagues have replicated conditions of secondhand smoke exposure on animal models. "We have found everything in animals that is apparent in humans," said Joad. "We see decreased fetal growth, poor lung maturation and altered airway reactivity."

Her team also observed that animals held their breath longer under certain circumstances, which potentially could contribute to SIDS.

Lifelong damage

Some outcomes were disturbing, she said. Rats exposed to tobacco smoke in utero and during early infancy had effects that did not reverse themselves later in life, even if exposure stopped during the childhood years. Permanent structural changes occurred in the lungs and even in nervous tissue, making the lungs more reactive to stimulation and more prone to cough.

"Exposing developing lungs to tobacco smoke is not the same as exposing adult lungs to smoke," said Joad. "There is a critical window during development in which cellular and physiological function is permanently altered."

Focus on teens

Joad believes it's critical to reach the teen population in smoking cessation efforts, both because of high rates during pregnancy and because most adult smokers became addicted during their teen years. "Most wish they had never started," she said.

National smoking trends show the rate of smoking during pregnancy has dropped in recent years. However, smoking rates of the youngest pregnant women are high compared to other pregnant women: In 2002, 16.7 percent of births to women aged 15 to 24 years were to smokers, compared to less than 10 percent of births to older women. Women with college degrees were the least likely to smoke during pregnancy, while nearly one in four pregnant women with nine to 11 years of education smoked.

Joad is optimistic about public health measures, such as the increasing prevalence of smoking bans in public places, and their success in bringing down smoking rates. "The focus on anti-smoking education, research and laws that is occurring worldwide would not have happened without the public advocacy this issue has generated," Joad said. "We should be very proud of these successes."