15. Building an Early Life Exposome by Integrating Multiple Birth Cohorts: HELIX

The exposome has conceptually been described to comprise three overlapping domains: (1) a general external environment including factors such as the urban environment, climate factors, social capital, stress; (2) a specific external environment including specific contaminants, diet, physical activity, tobacco, and (3) an internal environment including internal biological factors such as metabolism, gut microflora, inflammation, and oxidative stress. Here, we aim to illustrate how these three domains and their interrelations may be studied in an epidemiological study design, using the HELIX (Human Early Life Exposome) project as an example. HELIX takes pregnancy and childhood periods (“early life”) as a starting point. In six existing birth cohort studies in Europe, HELIX estimated prenatal and postnatal exposures. Exposure models for the outdoor exposome (air pollutants, noise, meteorological factors, and natural and built environment characteristics) were developed for a total of 30,000 mother–child pairs. Exposure biomarkers (for persistent organic pollutants, metals, phthalate metabolites, phenolic compounds and organophosphate pesticides) and omics markers (metabolites, proteins, mRNA, miRNA, DNA methylation) were measured in a subset of 1200 children. Nested repeat-sampling panel studies (N = 150) collected data on variability in personal exposure to air pollution and built environment measures, in biomarkers for nonpersistent chemicals (phthalates and phenolic compounds) and in all omics techniques. Outcome examinations were carried out using common protocols in the six cohorts. We will discuss some first results of the HELIX project, including a description of the correlation structure of multiple exposure data.