(HealthDay News) -- Poor children are exposed to more secondhand smoke than their wealthier counterparts, a new study has found.
A big reason for this is that "poor kids are far more likely to live with multiple adult smokers than are non-poor kids," said study author Dr. Michael Weitzman, a professor of pediatrics at New York University.
Children exposed to secondhand smoke are more likely to develop respiratory infections, earaches and severe asthma. In addition, studies have linked exposure to secondhand smoke to hyperactivity disorder and behavioral problems.
"This paper demonstrates the complex network of who exposes children in their homes," Weitzman said. "Secondhand smoke is the most ubiquitous and pernicious child environmental health exposure in the U.S."
For the study, which is in the April issue of Pediatrics, the researchers collected data on families who participated in the Medical Expenditure Panel Survey conducted from 2000 to 2004.
They found that slightly more than a third of the children lived in homes with at least one adult smoker. But about 49 percent of children from lower-income households lived with someone who smoked, compared with 21 percent of kids from wealthier families, and poorer children were more apt to live with more than one smoker as well.
Among the approximately 5 million children who did not live with their parents, about 53 percent lived with a grandparent who smoked, and 46 percent lived with another relative who smoked, whereas 33 percent of children who lived with their parents co-existed with an adult smoker.
Considering just children who lived with someone who smoked, the smoker was the child's mother 59 percent of the time, and 57 percent of the children lived in homes where two people smoked. In contrast, 17 percent of the children whose mother did not smoke lived with other adult smokers, the researchers noted.
"The best thing you can do as a smoker in a household of kids is to stop smoking," said Danny McGoldrick, research director at the Campaign for Tobacco-Free Kids. "We know that kids who have parents who smoke are much more likely to become smokers themselves."
"Once again, it's the most vulnerable in our society who pay the price for tobacco use," he said.
But beyond direct exposure to smoke from their living situations, young people also appear to be influenced, when deciding whether to smoke, by the movies they watch.
Another study in the same issue of Pediatrics found that seeing movie characters smoking has an effect on teenagers.
"This is the first study to demonstrate that movie smoking exposure has a long-term impact on smoking behavior," said lead author Madeline Dalton, director of the Hood Center for Children and Families at Dartmouth Medical School.
Dalton's research team asked 1,791 teens about their movie-watching and smoking habits, first when they were 14 or 15, and then again when they were 18.
Compared with those who watched the fewest movies with characters who smoked, teens who saw the most smoking in movies were twice as likely to become established smokers as young adults, Dalton said.
"Importantly, movie smoking exposure was a stronger predictor of who went on to become an established smoker than having friends or parents who smoke," she said.
Eliminating exposure to smoking in movies when kids are young could reduce by a third the number of young adults who become addicted smokers, Dalton said. And that could be a key factor in preventing long-term adverse health consequences related to smoking, she said.
"Children's exposure to movie smoking can be eliminated through a combination of policy changes and parental behavior," Dalton said. "Parents should be aware that what children watch at a young age influences their behavior later in life. The movie industry should act responsibly and take steps to ensure that children are not exposed to smoking in movies."
McGoldrick also thinks that smoking in movies needs to be curbed.
"This study adds to the evidence that kids exposed to smoking in movies are more likely not only to experiment with smoking, but become established smokers later in life," he said.
The Campaign for Tobacco-Free Kids calls for movies that show smoking to be rated R. The group also would like filmmakers to certify that they received no money from tobacco companies or others to use a particular brand of cigarettes in the film.
"In addition, movies with smoking in them should have anti-smoking ads before the movie," McGoldrick said.
The U.S. Centers for Disease Control and Prevention has more on secondhand smoke.
SOURCES: Michael Weitzman, M.D., professor, pediatrics, New York University, New York City; Madeline Dalton, Ph.D., director, Hood Center for Children and Families, Dartmouth Medical School, Lebanon, N.H.; Danny McGoldrick, research director, Campaign for Tobacco-Free Kids, Washington, D.C.; April 2009 Pediatrics