Understanding the Exposome

The Exposome concept

The exposome concept, initially described by Wild in 2005 and 2012, refers to the totality of exposures an individual is subjected to from conception throughout lifetime. This can range from maternal smoking during pregnancy, certain food intake in childhood, noise at school, or parental education, to social characteristics in the neighbourhood or surrounding green spaces.

The exposome concept was introduced as a complement to the so-called medical genome initiative. This initiative seeks to improve our understanding of disease by decoding the human genetic information, consisting of sequences of the DNA of a person, the human genome. The exposome approach strives to map every exposure an individual is subjected to from conception to death, providing a DNA-like detailed level of exposure information.

The exposome concept differentiates between the external exposome, encompassing the wide range of external, for example physical and social, exposures individuals encounter over the life course, and the internal exposome. The internal exposome refers to ‘markers’ that can be found for example in saliva or blood samples that reflect the body’s response to external exposures, as well as indicators of an individual’s sensitivity or of early-effect markers.

These markers can, for example, be changes in protein levels or substances detectable in the blood. Whether exposures cause an internal effect is dependent on the sensitivity of the individual and the accumulation of different exposures over time.

Applying the exposome approach, the Equal-Life project studied multiple exposures across the life course in children and adolescents (0-21 years) in relation to mental health and cognition. These exposures include physical and social environments at different phases of a child’s development at different places where they spend time. For example, during the prenatal phase, exposures take place in the uterus or at a later age at home, the neighbourhood or school.

The exposome approach provides a comprehensive framework to study the long-term effects of the multiple exposures children are exposed to, including causes and mechanisms driving inequalities in health. Important here is also how single exposures (e.g. pollutants, social relations) add up or interact and how this affects mental health and cognitive development. The relationship between exposure and outcome is often not direct but can depend on other factors known as mediators. In Figure 3 a simplified version of the Equal-Life framework is presented, symbolising he balance between the exposome on the left and the outcomes on the right through the mediators