Saliva continine levels of babies and mothers living with smoking fathers under different housing types in Hong Kong: a cross-sectional study

Abstract

BACKGROUND: After the Smoking Ordinance enacted in HK since 1/2007, shifting of smoking from outdoor to home was found, home becomes a major source of secondhand smoke (SHS) exposure of nonsmokers. OBJECTIVES: It aimed to assess the SHS exposure of babies and mothers living with smoking fathers of two housing types by using a biomarker. METHODS: Trios of smoking father, non-smoking mother and a baby under 18-months were recruited from Maternal and Child Health Centres (MCHCs) from 6/2008 to 10/2009. Consented couples completed the baseline survey including demographic data, fathers’ household smoking behaviors and mothers’ actions in protecting babies from household SHS exposure. Saliva samples from baby and mother were collected and then sent to the National University of Singapore for cotinine analyses. Log-transformations were used for the saliva cotinine due to skewed data. There were 2 housing types (public/private) and father was asked if they smoked at home (yes/no). MANOVA was used to compare the babies’ and mothers’ cotinine levels when fathers smoked at home under the 2 housing types. RESULTS: 1,158 trios were consented. 1,142 mothers’ and 1,058 babies’ samples were assayed. The mean age of the fathers and mothers was 35.5(±7.0) and 31.2(±4.9). The mean mothers’ cotinine level was 12.15ng/ml (±61.20) while babies’ was 2.38ng/ml (±6.01). 606 and 501 trios were living in public and private housing. Fathers’ smoked at home led to higher mothers’ and babies’ saliva cotininary (mean log of mothers’ cotininary: 0.14±0.62 vs. 0.05±0.55, p=0.06; babies: 0.16±0.38 vs. 0.07±0.34, p=0.003). Housing types influenced babies’ cotinine level (public: 0.17±0.37; private: 0.10±0.36, p=0.01). MANOVA showed that fathers smoked at home (Λ=0.99, p=0.01) and housing types (Λ=0.99, p=0.01) were positively related to the saliva cotinine levels. CONCLUSIONS: Father smoked at home and the housing types have greater impact on babies’ saliva cotininary, showing that they were highly exposed at home and in public housing environment. HK government should promote smoke-free homes and to provide more smoking cessation services to minimize the household SHS exposure to babies