Very young children living in poverty in rural areas of the U.S. seemed to have a higher risk for second- and third-hand smoke exposure than previously recognized, researchers said.
The analysis of data from a long-term study of rural poverty found that 15% of children (ages 6 months to 4 years)- had levels of the nicotine byproduct cotinine that were comparable to those reported in adult smokers, reported Lisa Gatzke-Kopp, PhD, of Pennsylvania State University (Penn State) in University Park, and colleagues.
Well over half (63%) had detectable levels of cotinine, suggesting widespread exposure to second-hand and third-hand cigarette smoke, they wrote in Nicotine & Tobacco Research.
Gatzke-Kopp told MedPage Today that the study is among the first to quantify specific levels of nicotine exposure in very young children, adding that it was definitely a surprise to find very young children with levels of exposure similar to those seen in adult smokers.
“We spent a lot of time looking through the literature to see if others had shown this,” she said, noting that most previous studies did not quantify exposure levels to the extent their study did, or researchers dismissed such high exposures as unrealistic.
“We really have not had a good understanding of this magnitude of exposure, and the impact of this level of exposure on children’s brain development,” she said.
The researchers noted that exposure to second-hand cigarette smoke has been shown to increase young children’s risk for asthma, respiratory and ear infections, and sudden infant death syndrome. Early nicotine exposure may also be a significant source of lead exposure, and it may also increase the long-term risk for cardiovascular, metabolic, and other diseases.
Exposure to environmental smoke includes both second-hand smoke directly emitted from burning cigarettes, and third-hand smoke, which involves the residue from cigarette smoke that settles in clothing, hair, furniture, walls, floors, and other surfaces.
“Third-hand routes of exposure may be especially relevant for infants and toddlers, as young children spend significant amounts of time in close physical proximity to parents, whose hair and clothing could carry nicotine residue, and often spend a significant amount of time on the floor where nicotine residue in carpeted surfaces may be persistent,” the researchers wrote.
They analyzed data from the Family Life Project, which is an ongoing study of the impact of growing up in rural areas being conducted by researchers from the University of North Carolina and Penn State. Gatzke-Kopp noted that the majority of children in the study were from low-income homes.
Saliva samples were taken from 1,218 children living in rural North Carolina and Pennsylvania at ages 6 months, 1 -month, 2 years, and 4 years.
The children were classified into three groups based on their cotinine levels. The analysis revealed that 15% of the children were in the high exposure group, with exposures of ≥12 ng/mL across time points, including 12% of children age 6 months, 12% of children age 15 months, 10% of those age 24 months, and 5% of those age 48 months.
Also, roughly 64% of children in the three younger age groups had moderate exposures between 0.45 to 12 ng/mL of cotinine.
Low exposures across time points (<0.45 ng/mL cotinine) were seen in 24% of kids ages 6 and 15 months, in 26% of kids age 24 months, and 41% of those age 48 months.
“Although our results indicated a high level of stability within the exposure classes, exposure was lower at the 48-month assessment. It is possible that this finding is commensurate with developmental changes occurring by age 4 years, when children are less likely to place objects in their mouth and may be more compliant with hand-washing practices than younger children; or it may reflect older children spending more time outside of the home, such as in pre-school settings,” the researchers wrote.
Gatzke-Kopp noted that attending daycare was associated with lower levels of exposure, and greater exposures were associated with lower parental income, less education, and more residential instability.
“Our modeling found that kids with the highest very early exposures continued to have high exposures throughout the study,” she said.
The researchers were not able to assess the impact of second- and third-hand nicotine exposures from electronic cigarette smoke.
“E-cigarette smoke doesn’t smell like tobacco smoke, so people may think there is no risk,” Gatzke-Kopp said. “But many e-cigarettes have a lot of nicotine and the residue is settling on surfaces just like cigarette smoke.”
The study was funded by the NIH, the National Institute of Child Health and Human Development, and the National Institute on Drug Abuse.
Gatzke-Kopp disclosed no relevant relationships with industry. Two co-authors disclosed relevant relationships with Salimetrics and Salivabio.