Niklas Hlubek

Population-Scale Evidence on Socioeconomic Disparities in Air Pollution Exposure and Health

Samenvatting

Air pollution is a leading environmental contributor to the burden of non-communicable disease in Europe. Exposure to air pollution is not evenly distributed, and environmental health inequalities can arise through two mechanisms: differential exposure, where some socioeconomic groups live in more polluted environments, and differential vulnerability, where some groups experience greater harm at similar exposure levels. Although socioeconomic disparities in exposure have been documented across Europe, few studies have examined whether and how they translate into health inequalities. This thesis investigates socioeconomic inequalities in air pollution exposure and their associations with health in the Netherlands, using nationwide, longitudinal registry data. Chapters 2 and 3 describe trends in residential exposure to particulate matter (PM2.5, PM10) and nitrogen dioxide (NO2) from 2014 to 2019 in more than 12 million adults by linking annual average concentrations at the home address to registry data. Using household-level indicators, Chapter 2 shows that individuals in the lowest socioeconomic groups disproportionately lived in highly urbanised and more polluted areas. Using neighbourhood-level indicators, Chapter 3 shows that exposure patterns differed by urbanicity: in rural to moderately urbanised areas, residents of higher socioeconomic neighbourhoods were consistently more exposed, whereas in highly urbanised areas, residents of lower socioeconomic neighbourhoods were more exposed. Concentrations fell in all groups, with generally stronger relative reductions in lower socioeconomic groups. Chapter 4 examines whether changes in the urban exposome following residential relocation are associated with changes in adolescent lung function. In two European birth cohorts, BAMSE (Sweden) and PIAMA (the Netherlands), exposure clusters were identified for three domains: traffic-related air pollution, built-up surface, and area-level socioeconomic disadvantage. In a difference-in-differences framework among adolescents who moved at least once between ages 8 and 16, relocation to areas with more built-up surface was associated with reduced lung function in BAMSE. Chapter 5 examines effect modification by socioeconomic position in the association between long-term air pollution exposure and incident ischemic stroke among 11.9 million adults. Exposure to all pollutants was associated with increased stroke risk. Associations varied by socioeconomic position and urbanicity: in rural to moderately urbanised areas, lower socioeconomic groups showed stronger associations, while differences were minimal in highly urbanised areas. Chapter 6 investigates associations between air pollution and natural-cause, cardiovascular, respiratory and lung cancer mortality among 9.9 million adults aged 30 years and older, and quantifies socioeconomic differences on both the relative and the absolute scale. Higher exposure was associated with increased mortality for all pollutants and outcomes. Relative risk differences across socioeconomic indicators were inconsistent, but absolute differences showed a steep and consistent gradient: lower socioeconomic groups carried a substantially greater excess mortality burden, driven largely by their higher baseline mortality rates. Chapter 7 concludes that environmental health inequalities stem not only from differential exposure but importantly from differential vulnerability. It discusses the methodological considerations of using nationwide administrative data, underlines the importance of reporting both relative and absolute measures to capture health inequalities fully, and shows how linked registry, socioeconomic and environmental data can generate policy-relevant evidence across geographic scales.