Background and purpose: A description of passive smoking during the first year of life might assist planning preventive efforts.
Methods: Changes in the ecology of passive smoking were investigated in a sample of infants in central North Carolina followed from birth to one year of age.
Results: The prevalence of tobacco smoke absorption, indicated by excretion of cotinine, increased from 53 percent to 77 percent (95% CI of difference: 14, 35) during the first year of life. Most infants (92 percent) excreting cotinine at three weeks of age were also excreting it at one year. Moreover, 61 percent of infants not excreting cotinine at age three weeks were excreting it at one year. This increase reflected an increased exposure to household and, particularly, nonhousehold sources of smoke; the proportion of infants exposed to nonhousehold smokers increased from 14 percent to 36 percent.
Conclusions: These findings suggest that prevention of the onset of passive smoking should begin very early.