The adverse effects of passive environmental tobacco smoke have been well documented in children and adults. In infants and children, these adverse effects include increased frequency of lower respiratory tract illnesses, asthma, otitis media, hospitalization and sudden infant death syndrome. The studies investigating passive tobacco smoke exposure have concentrated on maternal smoking but have not looked at other sources of smoke exposure. Estimates of passive smoke exposure in infants and children tend to be under-reported for various reasons. One method of measuring levels of passive tobacco smoke is to use biomarkers in blood, saliva or urine. Ownby and associates used questionnaires and biomarkers to study exposure to passive smoke in infants and children.

A cohort of infants was followed prospectively from birth to two years of age. They were enrolled in the study if they were determined to be at high risk for allergic diseases based on cord blood IgE. A study nurse made monthly visits to the participating families and collected information about the infant's exposure to tobacco smoke, including that from parents and guardians, persons providing day care in or outside the home, persons visiting the home and persons visited away from home. In addition, an attempt was made every two months to collect urine samples to measure cotinine-creatinine ratios (CCRs), a biomarker for tobacco smoke exposure.

A significant correlation was seen between the frequency of smoking by all persons who spent time around the infants and the infants' average CCRs. Analysis of the data showed that higher averages of CCRs were associated with smoking by parents and day care workers, persons visited away from home and persons other than parents living in the home.

The authors conclude that smoking by persons other than parents significantly contributes to infants' exposure to passive tobacco smoke. Efforts should be made by health care providers to identify infants at risk for exposure to tobacco smoke by sources other than parents. Efforts should also be made to assist parents in reducing the amount of passive tobacco smoke exposure their infants receive from these sources. These efforts may reduce the adverse health effects that can result from passive exposure to tobacco smoke.