Objective: To test the efficacy of behavioural counselling for smoking mothers in reducing young children's exposure to environmental tobacco smoke.
Design: Randomised double blind controlled trial.
Setting: Low income homes in San Diego county, California.
Participants: 108 ethnically diverse mothers who exposed their children (aged <4 years) to tobacco smoke in the home.
Intervention: Mothers were given seven counselling sessions over three months.
Main outcome measures: Children's reported exposure to environmental tobacco smoke from mothers in the home and from all sources; children's cotinine concentrations in urine.
Results: Mothers' reports of children's exposure to their smoke in the home declined in the counselled group from 27.30 cigarettes/week at baseline, to 4.47 at three months, to 3.66 at 12 months and in the controls from 24.56, to 12.08, to 8.38. The differences between the groups by time were significant (P=0.002). Reported exposure to smoke from all sources showed similar declines, with significant differences between groups by time (P=0.008). At 12 months, the reported exposure in the counselled group was 41.2% that of controls for mothers' smoke (95% confidence interval 34.2% to 48.3%) and was 45.7% (38.4% to 53.0%) that of controls for all sources of smoke. Children's mean urine cotinine concentrations decreased slightly in the counselled group from 10.93 ng/ml at baseline to 10.47 ng/ml at 12 months but increased in the controls from 9.43 ng/ml to 17.47 ng/ml (differences between groups by time P=0.008). At 12 months the cotinine concentration in the counselled group was 55.6% (48.2% to 63.0%) that of controls.
Conclusions: Counselling was effective in reducing children's exposure to environmental tobacco smoke. Similar counselling in medical and social services might protect millions of children from environmental tobacco smoke in their homes.