When Bangor became one of the first cities in the country to ban smoking in cars carrying children, supporters touted the benefits to public health, while opponents argued the ordinance “moralized” against smokers.

The 2007 ordinance set the stage for a statewide smoke-free vehicle law, which new research indicates then paved the way for more Mainers to voluntarily ban smoking in their cars and homes.

Before the statewide law passed in 2008, just shy of 75 percent of Maine adults reported instituting a smoke-free car rule, according to the new study by University of New England researcher Rebecca Murphy-Hoefer. After the law, that number increased to 78.8 percent. Those few percentage points translate to more than 33,000 Mainers.

Since more people could be expected to ban smoking in their cars in the wake of the law, Murphy-Hoefer also examined smoking bans in Mainers’ homes, which are “completely unregulated,” she said. “It’s an excellent indicator of social norms.”

About 80 percent of Maine adults banned smoking in their homes before the law, compared to 83.1 percent after, a rise of about 25,000 Mainers, according to the study published in the health journal “Preventing Chronic Disease.”

The study is the first in the country to examine the prevalence of smoke-free vehicle and home rules both before and after the passage of statewide law, Murphy-Hoefer said. But other research has shown a relationship between smoke-free policies and changing attitudes toward the acceptability of tobacco use and exposure to secondhand smoke, she said.

“It’s not a surprise, that’s what we hoped, but it looks as though the people of Maine have really embraced this law and have learned from the education that surrounded the law,” said Murphy-Hoefer, an evaluator for the Partnership for a Tobacco-Free Maine.

The statewide law is just one factor contributing to shifting attitudes around tobacco in Maine, she said. Maine’s also a leader in implementing clean indoor air laws and policies, she noted, citing the work of the Breathe Easy Coalition, which promotes voluntary smoke-free laws in multi-unit housing facilities.

The rise in smoke-free car and home rules indicates Mainers are taking steps to protect not only children but also nonsmokers from the harmful effects of tobacco, Murphy-Hoefer said.

“When you see these changing social norms, you see better public health, and that’s what we’re seeing in Maine,” she said.

The study’s publication coincides with last week’s release of the 2014 U.S. Surgeon General’s report, which added to the list of health problems associated with tobacco use on the 50th anniversary of the first Surgeon General’s report that linked smoking to lung cancer, heart disease and other deadly illnesses. Smoking can cause liver and colorectal cancer, erectile dysfunction and arthritis, among other illnesses, while exposure to secondhand smoke is associated with strokes, the new report found.

While smoking among American adults has plunged over the years, more than half of children ages three to 19 are exposed to secondhand smoke, according to the report.

Murphy-Hoefer’s survey found that more than 16 percent of respondents still allowed smoking in their vehicles when children weren’t present. That’s worrying, she said, because residue from tobacco smoke lingers on car surfaces, which children can pick up on their hands and transfer to their mouths.

Research indicates the pollutants persist even after cleaning, she said, which could pose a problem even for nonsmokers if they buy a used car previously owned by a smoker.

“You not only have the pollution from cigarette smoke, but you also have that combined with the pollution from other vehicles,” she said. “It creates carcinogens in the vehicle, and they don’t go away, they stick.”

While five other states have smoke-free car laws, only Maine had the foresight to survey adults about smoke-free car and home rules before such legislation took effect, Murphy-Hoefer said.

Her findings are based on the Behavioral Risk Factor Surveillance System, the world’s largest telephone health survey, run by the U.S. Centers for Disease Control and Prevention. The study included data for 13,461 Maine adults.

The research also examined income and education levels, finding that Mainers who earned less than $20,000 a year and those with less than a high-school education were less likely to institute smoke-free car rules, both before and after the law passed. That population tends to have higher rates of smoking.

Murphy-Hoefer said she hopes her research helps to further anti-smoking efforts in Maine and other states. Smokers can institute smoke-free home and vehicle rules to protect others, as well as limit their own opportunities to light up during the day, she said.

“Most smokers want to quit, hopefully this is also helping people who just need one more reason to quit smoking,” she said.