Second-hand smoke exposure in 4-year-old children in Spain: Sources, associated factors and urinary cotinine

Introduction Second-hand smoke exposure (SHS) in children remains as a major pollution problem, with important consequences for children's health. This study aimed to identify the sources of exposure to SHS among 4-year-old children, comparing self-reports to a urinary biomarker of exposure, and characterize the most important variables related to SHS exposure in this population. Methods 4-year-old children's exposure to SHS was assessed by a parental-reported questionnaire and by urinary cotinine (UC) measurements in 1757 participants from 4 different areas of the Spanish INMA (INfancia y Medio Ambiente – Environment and Childhood) Project. The questionnaire about SHS included information about smoking habits at home by household members, and about exposure to SHS in other places including other homes, bars, restaurants or transportation. The association between quantified UC levels (>4 ng/ml) and sociodemographic variables and the different sources of SHS exposure was examined using logistic regression. Results Based on parental reports, 21.6% of the children were exposed to SHS at home and 47.1% elsewhere; making a total 55.9% of the children exposed to SHS. In addition, 28.2% of the children whose parents reported being not regularly exposed to SHS had quantified UC values. Children from younger mothers (<34 vs. ≥39.4 y) had a higher odds of exposure to SHS [OR (95% CI): 2.28 (1.70–3.05) per year], as well as from families with a lower educational level [OR secondary: 2.12 (1.69–2.65); primary or less: 2.91 (2.19–3.88)]. The odds of quantifiable UC in children dropped after the smoking ban in public places [OR=0.59 (0.42–0.83)]. Regarding the sources of SHS exposure we observed that quantifiable UC odds was increased in children whose parents smoked at home in their presence [OR mother occasionally: 13.39 (7.03–25.50); mother often: 18.48 (8.40–40.66); father occasionally: 10.98 (6.52–18.49); father often: 11.50 (5.96–22.20)] or in children attending other confined places, mainly other houses where people smoked [OR: 2.23 (1.78–2.80)]. Conclusions Children's SHS exposure is nowadays an unresolved major public health problem in Spain. After the ban of smoking in public places health care professionals should put more emphasis to the parents on the importance of controlling the exposure of their children in private spaces.INMA project is funded by grants by the Carlos III Instituto de Salud (Red INMA G03/176 and CB06/02/0041) and Fundación Roger Torné. The studies in the specific regions were funded by the Spanish Ministry of Health (FIS-FEDER 03/1615, 04/1436, 04/1509, 04/1112, 04/1931, 05/1079, 05/1052, 06/0867, 06/1213, 07/0314, 08/1151, 09/02647, 04/2018, 09/02311, 11/02591, 11/02038, 13/02032, 13/02429, 14/0891, 14/1687, and MS13/00054), the Generalitat de Catalunya (CIRIT 1999SGR00241), the Diputación Foral de Gipuzkoa (DFG06/004), the Department of Health of the Basque Government (2005111093), the Regional Government of Andalucía (SAS 07/183), and support of Obra Social Cajastur/Fundación Liberbank, University of Oviedo and the Conselleria de Sanitat Generalitat Valenciana. http://www.proyectoinma.org/instituciones-participantes/en_entidades-colaboradoras/. The authors are grateful to all fieldworkers for their assistance in administering the questionnaires. A full listing of the INMA project researchers can be found at http://www.proyectoinma.org/presentacioninma/listado-investigadores/en_listado-investigadores.htm