Green space, air pollution, traffic noise and children’s health: The PIAMA birth cohort study

In daily life, people are exposed to multiple environmental risks (such as air pollution and noise) and environmental amenities with potentially positive health effects (such as green space). Exposures to green space, air pollution and traffic noise are generally spatially correlated since road traffic is a major source of both air pollution and noise. Additionally, higher levels of green space are associated with lower levels of air pollution and traffic noise, because of the absence of air pollution and noise sources in green areas. It is therefore important to distinguish the effects of green space, air pollution and traffic noise exposure in studies of long-term exposure and children’s health. This thesis evaluated associations of green space, ambient air pollution and traffic noise with overweight, cardiometabolic health, saliva cortisol and mental wellbeing in children and adolescents in the Dutch PIAMA birth cohort study. Residential exposure to green space in a buffer of 3000m was associated with a larger diurnal decrease in saliva cortisol concentrations, indicating lower chronic stress levels, in children aged 12 years and a better mental wellbeing throughout adolescence. These findings add to the growing body of research that suggests beneficial effects of green space on mental health. Additionally, we found associations of ambient nitrogen dioxide concentrations, but not with green space or traffic noise, with overweight throughout childhood. Higher exposure to ambient air pollution was related to a worse mental wellbeing in adolescents, but these associations weakened after adjustment for green space. These findings demonstrate the importance of investigating the health effects of multiple environmental exposures in one study.