Researchers from the University of Cincinnati and San Diego State University have shown that the amount of nicotine on children’s hands is related to their health. Hospitalized children with high levels of nicotine on their hands were more likely to be diagnosed with an infectious disease, or a pulmonary or bacterial disease.

By Leta Dickinson

September 2, 2021

Thirdhand smoke: This often-invisible chemical residue left behind by tobacco products is elusive and challenging for researchers to study. It persists in indoor environments despite vigorous cleaning yet is difficult to pinpoint and even harder to measure accurately. Many thirdhand smoke studies have measured cotinine in the urine of nonsmokers, a chemical that results from the body’s breakdown of nicotine, to estimate thirdhand smoke exposure. However, cotinine is produced from any tobacco smoke exposure and does not distinguish between second and thirdhand smoke, leaving researchers with an incomplete picture of a person’s exposure.

Researchers from the University of Cincinnati and San Diego State University have identified nicotin residue on the hands of young children as a promising way to better understand thirdhand smoke exposure.

The researchers identified 276 children who were admitted to the Cincinnati Children’s Hospital Medical Center with symptoms that could potentially be caused by tobacco smoke exposure and who lived with at least one parent who smoked cigarettes. Symptoms linked to tobacco smoke exposure include coughing, difficulty breathing, congestion, or ear pain. Urine samples were taken to measure cotinine, while hand wipes were collected to measure nicotine. When the children were discharged from the hospital, the researchers noted the conditions the children had, and examined the data to see if there were any patterns in hand nicotine or urine cotinine levels and the discharge diagnosis.

“We know that kids who have high cotinine levels are more likely to have certain respiratory and infectious diseases,” says Dr. Mahabee-Gittens, lead researcher of the study. “We didn’t yet know the association between children who have high hand nicotine levels and illnesses. We expected to see the same associations between cotinine and illnesses as between hand nicotine and illnesses, but we didn’t find that though. We found that cotinine actually was not associated with any of the clinical discharge diagnoses, but that hand nicotine was associated with several of the diagnoses.”

Specifically, Dr. Mahabee-Gittens and the other researchers found that children with higher levels of hand nicotine were more likely to have had an infectious disease, pulmonary, or bacterial diagnosis. Hand nicotine levels may be a better marker of exposure to tobacco smoke pollutants in a child’s environment than cotinine in the urine, because hand nicotine is not a result of internal body processes and other variability. Hand nicotine may be especially telling with younger children who interact closely with surfaces where tobacco smoke residue is deposited (sucking on objects, placing their hands in their mouth).

Despite the promising nature of hand nicotine as a measure of tobacco smoke exposure, Dr. Mahabee-Gittens explains that every method has its limitations. Self-report surveys are the easiest way to get exposure information, but they depend on the accuracy of the information offered by those surveyed. Urine cotinine and hand nicotine are both easy to collect, but accurate analysis of these samples is expensive. There are less expensive methods of analysis, but these methods are less sensitive to lower levels of exposure, such as those seen from thirdhand smoke. With the current knowledge that researchers have, using multiple methods to measure tobacco smoke exposure may be the best way to capture the most accurate information.

Dr. Mahabee-Gittens emphasizes why measuring tobacco smoke exposure and pinpointing the sources are crucial to children’s health: “Secondhand smoke exposure may not be causing these illnesses along—thirdhand smoke exposure may be causing these illnesses as well. Thirdhand smoke exposure is an important pathway of exposure to tobacco smoke pollutants in children. And that’s something that really has not been recognized before, and that we really need to do something about.”

Click here to read the research study.