Socioeconomic patterning in changes in child exposure to secondhand smoke after implementation of smoke-free legislation in Wales.

INTRODUCTION: Secondhand smoke (SHS) exposure is higher among children from lower socioeconomic status (SES) households. Legislation banning smoking in public places has been linked with reduced SHS exposure in children. However, socioeconomic patterning in responses to legislation has been little explored. METHODS: A total of 3,083 children aged 10-11 years, within 75 Welsh primary schools, completed questionnaires either before legislation or 1 year later. Saliva samples were provided by 2,787 of these children for cotinine assay. Regression analyses assessed socioeconomic differences in SHS exposure, and associations of legislation with exposure among children from low, medium, and high SES households. Changes in parental smoking in the home, car-based exposure, and perceived norms were assessed. RESULTS: SHS exposure was highest among children from lower SES households. The likelihood of providing a sample containing an undetectable level of cotinine increased significantly after legislation among children from high [relative risk ratio (RRR) = 1.44, 95% CI = 1.04-2.00] and medium SES households (RRR = 1.66, 95% CI = 1.20-2.30), while exposure among children from lower SES households remained unchanged. Parental smoking in the home, car-based SHS exposure, and perceived smoking prevalence were highest among children from low SES households. Parental smoking in the home and children's estimates of adult smoking prevalence declined only among children from higher SES households. CONCLUSIONS: Post-legislation reductions in SHS exposure were limited to children from higher SES households. Children from lower SES households continue to have high levels of exposure, particularly in homes and cars, and to perceive that smoking is the norm among adults.