Early exposure to tobacco toxicants poses a significant threat during the first years of life, with the potential to profoundly affect children’s development and result in long-term health consequences. Despite this evidence, the European region as defined by the World Health Organisation (WHO) still has a high prevalence of tobacco smoking, leading to extensive exposure of children to tobacco smoke toxicants both at home and in public places. The implementation of smoke-free policies in public and in workplaces over the last few decades has led to a reduction of TSE and has resulted in the voluntary adoption of smoking bans in many homes. Nevertheless, children are not only exposed to tobacco smoke at home, but also in outdoor spaces such as school entrances, sports events, terraces of bars and restaurants, and private cars.

The multidisciplinary researchers of the ECHOES project aimed to investigate the extent of children’s TSE in Spain and explore potential social inequalities underlying this exposure. The project involved the participation of 390 children, aged 4 to 11 years old, living in the Tarragona region of Northeastern Spain. The cohort was gender-balanced and representative of Spanish socioeconomic status, including household income and parents’ educational attainment. The study objectives were addressed by collecting caregiver-reported survey data on socioeconomic factors, children’s daily habits, and reports of children’s exposure to tobacco smoke, combined with the analysis of exposure markers in a subsample of the children’s urine. This comprehensive approach allowed the authors to determine unequivocally the extent of children’s exposure to tobacco smoke and further evaluate parents’ awareness of their children’s exposure. 
 

Children’s TSE remains a pressing social and health concern in Spain. Alarmingly, nearly one in three children (31%) were reported to live with a smoking adult, exposing them to tobacco toxicants in their homes. Furthermore, two out of every five caregivers who smoke admitted to smoking inside the home in the presence of their children (12% of all participants). This indicates that awareness among smoking parents regarding the dangers of early exposure to tobacco smoke toxicants remains disturbingly low.

Further, the percentage of children reportedly exposed to TSE outside their homes was higher among those living with smokers (more than one in three children living with smoking parents were also reported to be exposed outside), and the reported exposure was lower for children who lived with non-smokers (approximately one child in ten was reported to be exposed outside). However, overall reported TSE exposure, which includes both inside and outside the home, affected 39% of the participating children. Given the risks associated with early-life TSE exposure, this percentage cannot be overlooked.

Participating children’s reported exposure to tobacco smoke (TSE) was linked with their parents’ socioeconomic status. The study revealed a negative association between TSE and three socioeconomic factors: residing with both parents, parents’ educational attainment, and household income. Consequently, children residing with both parents were less likely to be exposed to tobacco smoke (28% compared to 44% of those living with only one parent). There was a similar pattern with educational attainment, as children living with parents holding a university degree were reported to be less exposed to TSE. Specifically, 56% of participants with parents with a lower educational level (incomplete primary education, complete primary education, or lower secondary education) were exposed to tobacco smoke, in contrast to 34% for those with parents having a medium educational level (higher secondary education) and 25% for those with university degrees. A similar trend emerged for household income, where higher children’s TSE was reported in the lower income groups (32% and 41% for the € 1,000-2,000 and the € 2,000 income groups, respectively) while the lowest rates were reported in higher income groups (26% and 23% for the € 3,000-4,000 and the >€ 4,000 income groups, respectively).

These results suggest the presence of social inequalities in children’s access to clean air, indicating that households with socioeconomic stability are more likely to shield children from exposure to toxicants in tobacco smoke.

TSE extends beyond the direct inhalation of smoke during cigarette burning, as tobacco toxicants and particles can adhere to surfaces such as house dust, curtains, furniture, and parents’ clothing, where they can persist for months. This novel and frequently overlooked pathway of exposure to tobacco toxicants, known as third-hand smoke, is prevalent in both outdoor and indoor environments and has a particularly significant impact on children under 5 years old.

To assess the extent of TSE in early life, the authors examined the presence of urinary exposure biomarkers of tobacco smoke in the 4-year-old participants (n = 149). Remarkably, tobacco exposure biomarkers were detected in 90% of the 4-year-olds’ urine samples. These findings significantly contrast with the children’s TSE as reported by their parents, as only 35% of these children were reported to live with smokers. Moreover, 30% of the children who were reported as unexposed at home (according to parent questionnaires) exhibited a higher relative concentration of tobacco exposure biomarkers than the average for children living with smokers. This indicates that substantial TSE is occurring outside their homes. These results underscore both the substantial underestimation of early-life exposure to tobacco toxicants and the ubiquitous presence of tobacco smoke toxicants in the environment.

To investigate potential social inequities in children’s early-life TSE, the authors examined the association between TSE urinary biomarkers in 4-year-old participants and various sociodemographic parameters. The study revealed a negative correlation with parental educational attainment. Consequently, low and medium levels of parental education were associated with higher concentrations of urinary TSE biomarkers. This pattern persisted when analysing the educational levels of fathers and mothers separately. Children with parents with a high level of education (holding university degrees) exhibited lower TSE exposure, with approximately 40% and 60% lower concentrations associated with the mother’s and the father’s education, respectively. 

This research emphasises the widespread exposure of children to tobacco smoke and highlights the need to enhance parents’ awareness of the extent of their children’s exposure. Scepticism among parents, especially those who smoke, was found to be higher, resulting in one out of three children being exposed to tobacco smoke outside their homes. The study also highlights social inequities in early-life TSE, with lower parental educational attainment being associated with higher urinary biomarkers of tobacco smoke in children. These findings indicate the necessity for new directions in smoke-free policies to prevent and reduce tobacco use, stressing the importance of raising the general awareness of the ubiquity of tobacco smoke toxicants, particularly among smokers.

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