Exposome

Exposome (pronounced eks-poh-sohm)

(1) A concept describing (1) the environmental exposures an individual encounters throughout life and (2) how these factors impact an individual's biology and health.

(2) The collection of environmental factors (stress, diet, climate, health-care etc) to which an individual is exposed and which can have an effect on health outcomes.

2005: The construct was expos(e) +‎ -ome, the word coined by cancer epidemiologist Dr Christopher Wild, then director of the International Agency for Research on Cancer (IARC).  Expose (in the sense of “to lay open to danger, attack, harm etc”; “to lay open to something specified”) dates from the mid-fifteenth century and was from the late Middle English exposen, from the Middle French exposer (to lay open, set forth), from the Latin expōnō (set forth), with contamination from poser (to lay, place). The –ome suffix was an alteration of -oma, from the Ancient Greek -ωμα (-ōma).  It was only partially cognate to -some (body), from σῶμα (soma) (body), in that both share the case ending -μα (-ma), but the ω was unrelated.  The sense was of “a mass of something” and use is familiar in forms such as genome (in genetics the complete genetic information (DNA (deoxyribonucleic acid) or RNA (ribonucleic acid)) and phenome (the whole set of phenotypic entities in a cell, tissue, organ, organisms, and species). Exposome is a noun and exposomic is an adjective; the noun plural is exposomes.

The study and assessment of external and internal factors (chemical, physical, biological, social, climatic etc) factors that may influence human health is not new and evidence of interest in the topic(s) exist in the literature of physicians and philosophers (there was sometimes overlap) from the ancient civilizations of Greece, Rome, China, Persia and India.  One of the paradoxes of modernity in medicine was that simultaneously there developed an interest in (1) interdisciplinary and holistic approaches while (2) specialization become increasingly entrenched, the latter leading sometimes to a “siloing” in research and data accumulation.  What makes exposome a useful tool is it is a way of expressing the interplay between genetics and environmental factors in the development of diseases with a particular focus on chronic conditions and widely the concept has been applied in many fields of medicine beyond public health.  What it does is calculate the cumulative effect of multiple exposures, allowing researchers to “scope-down” to specific or general gene-environment interactions, producing data to permit a more accurate assessment of disease risk and thus the identification of useful modes of intervention.

Dr Wild’s coining of exposome came about because some word or phrase was needed to describe his innovation which was the application of a systematic approach to measuring environmental exposures to what was coming to be known about the human genome; in a sense it was an exercise in cause and effect, the three components being (1) the external exposome, (2) the internal exposome and (3) the biological response.  The external exposome included factors such as air pollution, diet and socioeconomic factors as well as specific external factors like chemicals and radiation.  The internal exposome included endogenous factors, such as hormones, inflammation, oxidative stress, and gut microbiota.  The biological response described the complex interactions between the external and internal exposome factors and their influence on an individual's physiology and health.

At its most comprehensive (and complex), the exposome is a cumulative measure of all environmental exposures to which an individual has been subject throughout their entire life.  While that’s something that can be modelled for an “imagined person”, in a real-world instance it will probably always be only partially complete, not least because in some cases critical environmental exposures may not be known for long after their effect has been exerted; indeed, some may be revealed only by an autopsy (post mortem).  Conceptually however, the process can be illustrated by example and one illustrative of the approach is to contrast the factors affecting the same individual living in three different places.  What that approach does is emphasize certain obvious differences between places but variations in an exposome don’t depend on the sample being taken in locations thousands of miles apart.  For a variety of reasons, the same individual might record a radically different outcome if (in theory) living their entire life in one suburb compared with one adjacent or even in one room in one dwelling compared with another perhaps only a few feet away.  Conditions can be similar across a wide geographical spread or different despite close proximity (even between people sitting within speaking distance), the phenomenon of “micro-climates” in open-plan offices well documented.  The number of variables which can be used usefully to calculate (estimate might be a better word) an individual’s (or a group’s) exposome is probably at least in the dozens but could easily be expanded well into three figures were one to itemize influences (such as chemicals or specifics types of pollutant matter) and such is the complexity of the process that the mere existence of some factors might be detrimental to some individuals yet neutral or even beneficial to others.  At this stage, although the implications of applying AI (artificial intelligence) to the interaction of large data sets with a individual’s genetic mix have intrigued some, the exposome remains an indicative conceptual model rather than a defined process.

As an example, consider the same individual living variously in New York City, Dubai or Los Angeles.  In each of those places, some factors will be universal within the locality while others will vary according to which part of place one inhabits and even at what elevation at the same address; the physical environment in a building’s ground floor greatly can vary from that which prevails on the 44^th floor:

Lindsay Lohan in New York City in pastel yellow & black bouclé tweed mini-dress.  Maintaining an ideal BMI (body mass index) is a positive factor in ones exposome. 

(1) Air Quality and Pollution: Moderate to high levels of air pollution, especially from traffic (NO₂, PM2.5). Seasonal heating (oil and gas) contributes in winter.  Subway air has unique particulate matter exposure.

(2) Climate and UV Radiation: Humid continental climate—cold winters and hot summers. Seasonal variability affects respiratory and cardiovascular stressors.

(3) Diet and Food Environment: Diverse food options—high availability of ultra-processed foods but also global cuisines. Food deserts in poorer boroughs can reduce fresh produce access.

(4) Built Environment and Urban Design: Dense, walkable, vertical urban environment. High reliance on public transport; more noise pollution and crowding stress.  Lower car ownership can reduce personal emissions exposure.

(5) Cultural and Psychosocial Stressors: High-paced lifestyle, long working hours. High density increases social stress, noise, and mental health challenges.  Diversity can be enriching or alienating, depending on context.

(6) Economic and Occupational Exposures: Highly competitive job market. Occupational exposures vary widely—white-collar vs service industries. Union protections exist in some sectors.

(7) Healthcare Access and Public Policy: Robust healthcare infrastructure, but disparities remain by borough and income. Medicaid and public hospitals provide some safety net.

Lindsay Lohan in Dubai in J.Lo flamingo pink velour tracksuit.  A healthy diet and regular exercise are factors in one's exposome. 

(1) Air Quality and Pollution: Frequently exposed to dust storms (fine desert dust), high PM10 levels, and air conditioning pollutants. Limited greenery means less natural air filtration.  Desalination plants and industrial expansion add further exposure.

(2) Climate and UV Radiation: Extreme desert heat (45°C+), intense UV exposure, little rain. Heat stress and dehydration risks are chronic, especially for outdoor workers.

(3) Diet and Food Environment: High import dependency. Abundant processed and fast foods, especially in malls. Dietary pattern skewed toward high sugar and fat content.  Cultural fasting (eg Ramadan) introduces cyclical dietary stressors.

(4) Built Environment and Urban Design: Car-centric city. Pedestrian-unfriendly in many areas due to heat and design. Heavy air conditioning use is a major indoor exposure pathway.

(5) Cultural and Psychosocial Stressors: Strict social codes and legal restrictions influence behavioral exposures. Expat life often means social disconnection and job insecurity for migrant workers.

(6) Economic and Occupational Exposures: Large migrant workforce faces occupational health risks, including long hours in extreme heat. Labor protections are inconsistent.

(7) Healthcare Access and Public Policy: Healthcare access stratified—good for citizens and wealthy expats, less so for low-wage migrants. Private sector dominates.

Lindsay Lohan in Los Angeles in 2005 Mercedes-Benz SL65 AMG (2005-2011) Roadster (R230, 2002-2011).  Smoking is a factor in one's exposome.

(1) Air Quality and Pollution: Known for smog due to vehicle emissions and topography (valley trap). Ozone levels high, especially in summer. Wildfire smoke increasingly common.

(2) Climate and UV Radiation: Mediterranean climate with mild, dry summers. High UV exposure, though moderated by coastal influence. Drought conditions affect water quality and stress.

(3) Diet and Food Environment: Strong health-food culture, organic and plant-based diets more common. Yet fast food and food deserts remain in less affluent areas.  Hispanic and Asian dietary influences prominent.

(4) Built Environment and Urban Design: Sprawling, suburban in many parts. High car dependence means more exposure to vehicle exhaust.  Outdoor activities more common in certain demographics (eg, beach culture).

(5) Cultural and Psychosocial Stressors: Cultural emphasis on appearance, wealth, and entertainment may increase psychosocial pressure.  Homelessness crisis also creates variable community stress exposures.

(6) Economic and Occupational Exposures: Gig economy widespread, leading to precarious employment. Hollywood and tech industries also introduce unique workplace stress patterns.

(7) Healthcare Access and Public Policy: California’s public health programs are progressive, but uninsured rates still high. Proximity to cutting-edge research centers can boost care quality for some.

So one's exposome is a product of what one wants or gets from life, mapped onto a risk analysis table.  In New York City, one copes with urban pollution and persistent subway dust in an increasingly variable climate marked by periods of high humidity, a dietary range determined by one's wealth, the advantage of a good (if not always pleasant) mass transit system and the possibility of a “walking distance” lifestyle, albeit it in usually crowded, fast-paced surroundings.  Employment conditions are mixed and access to quality health care is a product of one's insurance status or wealth.

In Dubai, one lives with frequent dust storms, months of intense heat and UV exposure, a dependence on food imports, the constant temptation of fast food (FSS; fat, salt, sugar).  The car-centric lifestyle has created a built environment described as “pedestrian-hostile” and there are sometimes severe legal limits on the personal freedom especially for migrant workers who are subject to heat exposure and limited labor rights (even those which exist often not enforced).  The health system distinctly is tiered (based on wealth) and almost exclusively privatized.

The air quality in Los Angeles greatly has improved since the 1970s but climate change has resulted in the more frequent intrusion of smoke from wildfires and the prevailing UV exposure tends to be high; the climate is not as “mild” as once it was rated.  While there are pockets in which walkability is good, Los Angeles mostly is a car-dependent culture and the coverage and frequency of mass-transit has in recent decades declined.  Although this is not unique to the city, there's heightened awareness of a sensitivity to specific cultural pressures based on appearances and perceptions of lifestyle while housing stress is increasing.  Economic pressures are being exacerbated by the growth of the gig economy and traditionally secure forms of employment are being displaced by AI (bots, robots and hybrids).  Although California's healthcare system is sometimes described as "progressive", on the ground, outcomes are patchy.

So each location shapes the exposome in distinctive ways and the potential exists for the process better to be modelled so public health interventions and policies can be adjusted.  Of course, some risks are global: anywhere on the planet there’s always the chance one might be murdered by the Freemasons but some things which might seem unlikely to be affected by location turn out also to be an exposome variable. Because planet Earth is (1) roughly spherical, (2) and travels through space (where concepts like up & down don’t apply) and (3) constantly is exposed to meteoroids (every day Earth receives tons of “space dust”), it would be reasonable to assume one is equally likely to be struck by a meteoroid wherever one may be.  However, according to NASA (the US National Aeronautics and Space Administration), strikes are not equally likely everywhere, some latitudes (and regions) being more prone, due to several factors:

(1) Because Earth’s rotation and orbital motion create a bias, meteoroids tend more often to approach from the direction of Earth’s orbital motion (the “apex direction”), meaning the leading hemisphere (the side facing Earth's motion, near the dawn terminator) sees more meteoroid entries than the trailing hemisphere.  On a global scale, the effect is small but is measurable with the risk increasing as one approaches the equatorial regions where rotational velocity is greatest.

(2) Because most meteoroids approach from near the plane of the Solar System (the ecliptic plane), there’s what NASA calls a “latitude distribution bias”: Earth’s equator being tilted only some 23.5° from the ecliptic, meteoroids are more likely to intersect Earth’s atmosphere near lower latitudes (the tropical & sub-tropical zones) than near the poles.  So, those wishing to lower their risk should try to live in the Arctic or Antarctic although those suffering chronic kosmikophobia (fear of cosmic phenomena) are likely already residents.

(3) Some 70% of the Earth’s surface area being the seas and oceans, statistically, most meteoroids land in the water rather than in land so the lesson is clear: avoid living at sea.  The calculated probability is of course just math; because sparsely populated deserts accumulate meteorites better because erosion is low, a large number have been found in places like the Sahara and outback Australia but those numbers reflect a preservation bias and don’t necessarily confirm a higher strike rate.  The lesson from the statisticians is: Don’t dismiss the notion of living in a desert because of a fear of being struck by a meteoroid.

(4) Gravitational focusing, although it does increase Earth’s meteoroid capture rates (disproportionately so for objects travelling more slowly), is a global effect so there is no known locational bias.  While there is at least one documented case of a person being struck by a meteoroid, the evidence does suggest the risk is too low to be statistically significant and should thus not be factored into the calculation of one’s exposome because one is anywhere at greater risk of being murdered by the Freemasons.

Ms Ann Hodges with bruise, Alabama, September. 1952.  Painful though it would have been, she did get  her “15 minutes of fame” and eventually sold the fragment for US$25 so there was that.

In the narrow technical sense, many people have been struck by objects from space (as estimated 40+ tons of the stuff arrives every day) but most fragments are dust particles, too small to be noticed.  The only scientifically verified injury a person has suffered was an impressively large bruise a meteorite (the part of a meteoroid that survives its fiery passage through the atmosphere to land on Earth’s surface) on 10 September 1954 inflicted on Ms Ann Hodges (1920-1972) of Sylacauga, Alabama in the US.  Weighing 7.9 lb (3.6 kg), the intruder crashed through the roof of her house and bounced off a radio, striking her while enjoying a nap on the sofa.  The meteoroid was called Sylacauga and, just as appropriately, the offending meteorite was named the Hodges Fragment.  Anatomically modern humans (AMH) have been walking the planet for perhaps 300,000 years and we’ve been (more or less) behaviorally modern (BMH) for maybe a quarter of that so it’s possible many more of us have been struck,  In the absence of records, while it’s impossible to be definitive, it’s likely more have been murdered by the Freemasons that have ever been killed by stuff falling from space although, as the history of species extinction illustrates, a direct hit on someone is not a prerequisite for dire consequences.