Open Access Research article

A longitudinal study of environmental tobacco smoke exposure in children: Parental self reports versus age dependent biomarkers

Carme Puig12, Oscar Garcia-Algar12*, Toni Monleon3, Roberta Pacifici4, Piergiorgio Zuccaro4, Jordi Sunyer5, Cecilia Figueroa12, Simona Pichini4 and Oriol Vall12

Author Affiliations

1 Environmental and Pediatric Research Unit (URIE), Pediatric Department, Hospital del Mar, Barcelona, Spain

2 Department of Pediatrics, Obstetrics and Gynecology, and Preventive Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain

3 Department of Statistics, Universitat de Barcelona, Barcelona, Spain

4 Department of Therapeutic Research and Medicines Evaluation, Istituto Superiore di Sanità, Rome, Italy

5 Center for Research in Environmental Epidemiology (CREAL), Institut Municipal d'Investigació Mèdica (IMIM), Barcelona, Spain

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BMC Public Health 2008, 8:47  doi:10.1186/1471-2458-8-47

Published: 6 February 2008



Awareness of the negative effects of smoking on children's health prompted a decrease in the self-reporting of parental tobacco use in periodic surveys from most industrialized countries. Our aim is to assess changes between ETS exposure at the end of pregnancy and at 4 years of age determined by the parents' self-report and measurement of cotinine in age related biological matrices.


The prospective birth cohort included 487 infants from Barcelona city (Spain). Mothers were asked about maternal and household smoking habit. Cord serum and children's urinary cotinine were analyzed in duplicate using a double antibody radioimmunoassay.


At 4 years of age, the median urinary cotinine level in children increased 1.4 or 3.5 times when father or mother smoked, respectively. Cotinine levels in children's urine statistically differentiated children from smoking mothers (Geometric Mean (GM) 19.7 ng/ml; 95% CI 16.83–23.01) and exposed homes (GM 7.1 ng/ml; 95% CI 5.61–8.99) compared with non-exposed homes (GM 4.5 ng/ml; 95% CI 3.71–5.48). Maternal self-reported ETS exposure in homes declined in the four year span between the two time periods from 42.2% to 31.0% (p < 0.01). Nevertheless, most of the children considered non-exposed by their mothers had detectable levels of cotinine above 1 ng/mL in their urine.


We concluded that cotinine levels determined in cord blood and urine, respectively, were useful for categorizing the children exposed to smoking and showed that a certain increase in ETS exposure during the 4-year follow-up period occurred.