The Exposome: A New Way to Think About Your Health

In 2003, a cancer epidemiologist named Christopher Wild was thinking about why the Human Genome Project had failed to explain most human disease. The sequencing was done. The genes were mapped. And yet: genome-wide association studies were finding that common genetic variants accounted for only a small fraction of the variance in disease risk for most common conditions. Something large was missing from the picture.

Wild proposed a name for what was missing: the exposome. He defined it as the totality of environmental exposures a person encounters from conception to death. Not one chemical. Not one pollutant. The entire cumulative sum of everything — air quality, diet, water, chemical exposures, radiation, the microbiome, stress, socioeconomic factors — that the human body encounters across a lifetime.

The word itself was a deliberate parallel to genome. Just as the genome is the complete set of genetic instructions a person carries, the exposome is the complete set of environmental inputs that shape how those instructions are expressed. Both matter enormously for health. The difference is that for most people, the genome is fixed at conception while the exposome is continuously shaped by choices, circumstances, and environments — and is therefore the more actionable of the two.

Measuring the exposome presents a challenge that dwarfs the technical difficulty of sequencing DNA — and researchers have approached it through two complementary strategies.

The external exposome This is the environment surrounding a person: air quality at their home and work, water contaminants in their supply, chemicals in their food and consumer products, noise, heat, radiation, and psychosocial stressors. It can be measured through environmental monitoring, exposure modelling, and questionnaire data. This is the approach PollutionProfile takes — linking your locations and activities to environmental databases to estimate your external exposome over time.

The internal exposome This is the biological imprint of those external exposures within the body. Biomonitoring approaches — measuring blood, urine, and tissue levels of environmental chemicals and their metabolites — capture the internal exposome at a snapshot in time. Blood PFAS levels, urinary phthalate metabolites, blood lead concentrations — these are internal exposome measures.

The two approaches are complementary. The external exposome tells you what you were likely exposed to; the internal exposome tells you how much of it got in. Together, they provide the most complete picture of environmental health risk.

Omics technologies and the exposome The most ambitious exposome research combines environmental exposure data with metabolomics (the full set of metabolites in a biological sample), proteomics, and epigenomics to trace the biological pathway from exposure to altered physiology to disease. This is active research at the frontier of environmental health science — tools like mass spectrometry and machine learning are making it possible to detect and interpret environmental signals in biological samples at scales that were impossible a decade ago.

The exposome concept has several implications for disease prevention that differ substantially from the genetic risk model that has dominated medicine since the 1990s.

Most disease is not primarily genetic The landmark statistic in exposome science comes from a 2010 paper by Rappaport and Smith in Science: analysing twin studies and heritability estimates, they calculated that environmental factors account for approximately 70–90% of disease risk for most common chronic diseases. Genetics loads the gun; environment pulls the trigger — and for most people with most diseases, the environment is doing the most work.

This is not an argument against genetic research. It's a reframing of where the greatest opportunity for prevention lies.

The timing dimension The exposome model naturally incorporates developmental timing in a way that single-exposure risk models don't. A person's exposome includes the chemical environment in utero, in infancy, during puberty, during peak occupational exposure years, and in later life — each period carrying different implications for different disease outcomes. A cardiologist looking at a 60-year-old patient who grew up near a smelter, worked 25 years in a building with PCBs, and lived near a major highway for 20 years is looking at an exposome that explains far more than their LDL cholesterol or family history.

The actionability advantage Unlike genetics, the exposome is modifiable. Not entirely — you can't change your childhood exposures — but significantly. Reducing current exposure, choosing lower-toxin products, filtering water, improving indoor air quality, spending more time in nature, managing occupational exposures — these are all interventions on the exposome. They don't change the past accumulation, but they change the future trajectory.

PollutionProfile is, at its core, an exposome tool — designed to help you build, understand, and act on your personal environmental exposure history.

What the Historical Exposure Recorder captures: • Every address you've lived at, linked to historical air quality and water quality data • Proximity to Superfund sites, industrial facilities, and pollution sources at each location • Occupational exposure history across your working life • Significant known exposure events

How the app translates this into a risk report: The cumulative exposure data from your history is matched against dose-response relationships from the epidemiological literature to generate exposure-specific risk estimates. These aren't predictions of disease — no tool can tell you whether you'll get cancer. They're risk contextualisation: here is how your exposure history compares to population-level exposure and risk data, here are the specific exposures that contribute most to elevated risk estimates, here are the conditions most associated with your specific exposure profile.

The clinical translation The report generated by PollutionProfile's Historical Exposure Recorder is designed to be useful in a clinical conversation — not as a diagnostic tool, but as an exposure summary that a physician can use to order targeted investigations, weight differential diagnoses, or direct preventive screening. A 50-year-old who worked for 15 years in a dry-cleaning facility has a specific PERC (perchloroethylene) exposure history that is relevant to their kidney function, liver function, and cancer screening — and a PollutionProfile report makes that history explicit and communicable.

Starting your exposome record Begin with the addresses. Even approximate years and ZIP codes allow the app to link historical air quality and contamination data to your residential history. The occupational history can be added incrementally. The output gets more detailed with each piece of information added — but even a partial history is more informative than no history at all.