The Exposome: Understanding the Effect of the Environment on Our Health

Since the 1980s, research on the origin of diseases has focused on the genetic component. If you search in Pubmed for “causes of diseases” you will find 764,469 publications relating it to “genetics” whereas only 74,055 for “exposures”. Research on origin of diseases had such a strong focus on the genetic part that we forgot that disease cases would be prevented if particular exposures were eliminated.

Nearly half of global mortality can be attributed to known exposures

Nearly half of global mortality can be attributed to known exposures such as airborne particles, salt intake, alcohol, active and passive tobacco smoking. This means that the imbalance of research towards genetics, motivated by the technologic ability, relied solely on self reported exposures. This obscured important causal factors of today’s chronic diseases. “By not dedicating a higher level of thought and effort to the role of the environment in health and disease, we are doing a disservice to biology.” as Gary Miller from Emory University, Atlanta, US, declared at the first exposome course this month./p>

Every exposure to which an individual is subjected from conception to death

The “exposome” is finally created, defined as every exposure to which an individual is subjected from conception to death. It starts with unprecedented collaboration across various disciplines such as exposure assessment, toxicology, analytical chemistry, geographical information technologies and environmental epidemiology. This field benefits from the incredible advances in computational power and analytical platforms to measure the exposome.

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.

Can provide very effective tools for disease prevention

The Exposome has a huge potential because environmental factors are highly modifiable. For example, air pollution exposure can be reduced through environmental interventions at the community level, such as urban and transport planning, and have been shown to be promising and more cost effective than interventions at the individual level. Even more important better understanding of environmental hazards in early life (pregnancy and childhood periods) can provide very effective tools for disease prevention, given that interventions at that time can reshape biological programming and shift the body’s developmental track to the normal function. However, the environment is a complex interlinked system and has so far only be measured on a one-by-one, very scattered, basis. So with the exposome we hope to get closer to the complexities of multiple exposures.

The HELIX project has built an early life exposome based

To understand the level of impact of multiple environmental hazards, the HELIX project has built an early life exposome based at ISGlobal. Children and mothers from Spain, Norway, Greece, Lithuania, England and France have now completed an extensive study as part of the €8.6M European HELIX research project. We are receiving our first results after 3 years of research, and have created exposure measures for outdoor exposures for a total of 28,000 mother-child pairs in Europe. Experts used data from satellite remote sensing, national resources, existing cohorts etc… to compare exposure over pregnancy to air pollutants, noise, meteorological factors, natural (e.g. access to parks) and built environment in cities.

We find that pregnant women with higher education are less likely to be exposed to air pollution, noise and also have greater access to green spaces (within 100 meters of their home). Social capital was related to healthy urban environments within some European cities, which may impact on the development of their children.

The majority of children had detectable levels of harmful pesticides

We were also surprised, when investigating exposure to pollutants in a subset of 1,200 children, that the majority of children had detectable levels of harmful pesticides in their blood and urines. We confirmed that some persistent pesticides such as DDT, which was totally banned from agricultural use in 1991 but is still present in the food chain due to its low degradation rate, are still detected in population bio-samples. Modern pesticides, used for pest control at home or in agriculture activities, such as organophosphates are believed to be less persistent, but we could still detect them in 46% of children samples regardless of the European country of origin.

We are investigating how dietary patterns, such as consumption of organic foods or other lifestyle behaviors, might influence exposure loads at the individual levels. It was reassuring to find that urinary cotinine, a marker of passive tobacco smoking, was detected in only 19% of the children. Different exposure patterns were identified across the countries. For instance, the Spanish children from Sabadell, had higher levels of mercury, a heavy metal found in high concentration in seafood, than in other countries of Europe.

The HELIX project benefited from a great collaboration across 13 partners from eight European countries, including two SME’s and six birth cohort studies. As well as a strength of this project it raised some difficulties to have comparable information on children living in such different environments. The genetic code seems like a piece of cake in comparison, only 'written' in four letters in a linear sequence for every human being.

Researchers in ISGlobal are still harmonizing information collected from the six countries, sometimes trying to find common indicator of what seems incomparable. For example what is “comfortable living” or a “high level of education” in families living in Norway or Greece just after the economical crisis in 2009. We also have to ensure that country-specific sensitivity to personal data privacy is respected. Norway for example has the strictest standards due to its small population and the potential to link health data very easily with individuals.