Dr. Martha S. Tingen, co-director of Georgia Health Sciences University's Child Health Discovery Institute and interim program leader of the Georgia Health Sciences University Cancer Center, said the breakdown of nicotine in the saliva proves the children were exposed to secondhand smoke.
"It's bad news," Tingen said in a statement. "Smoking is one of the major causes of low-birth weight infants, it increases the incidence of Sudden Infant Death Syndrome by 10 times, increases breathing problems, asthma-related hospital admissions, ear and upper-respiratory infections -- yet all these kids are living in a smoking environment."
The study of 428 fourth graders and 453 parents in seven rural and seven urban Georgia schools also showed that the urban children were more likely to be smokers -- 14.9 percent versus 6.6 percent. Additionally urban children have the most exposure to smokers: 79.6 percent versus 75.3 percent, the study found.
Tingen and colleagues found children in the rural areas were more likely to be white and living with both parents; children in urban settings tended to be poorer, lived with one parent, received healthcare at community health clinics and had a parent who smoked.
The findings were presented to the 15th World Conference on Tobacco or Health in Singapore.
2014: The Year in Music [PHOTOS]