The exposome: beyond one exposure at a time

Your home isn't exposed to one thing. On any given day it might hold a little lead in the windowsill dust, something from the gas stove, whatever came in on the dog, and the cleaner you used on Sunday. You live with all of it at once.

Environmental health research didn't always look at it that way. For most of its history, the field studied one exposure at a time: lead¹, asbestos², tobacco smoke³. Those studies taught us a lot. So when, and why, did scientists start looking at many exposures together?

The traditional approach: one exposure at a time

Studying exposures one by one produced some of public health's clearest findings.

But the one-at-a-time approach has limits. Complex diseases rarely trace back to a single cause⁷, so it's hard to pin one on lead alone. And it misses how exposures interact. Crude oil, for example, is itself a mixture of thousands of compounds. Organic chemicals and metals can also behave differently together than either does alone⁸.

Introducing the exposome: the bigger picture

In 2005, cancer epidemiologist Christopher Wild proposed a new idea: the exposome. Where the genome is everything you inherit, the exposome is everything you encounter⁹.

The integrated compilation of all physical, chemical, biological, and psychosocial influences that impact biology.

That's the widely used definition today¹⁰. In plain terms, it's the full mix. That includes chemicals like lead and PFAS, a family of long-lasting synthetic chemicals. It also includes things that don't come in a test tube, like how stressed you are and how much social support you have.

That mix isn't fixed. It shifts with where you live and work, what you do, and your stage of life. How sensitive you are to a given exposure can shift too^11,12.

Why studying exposures together matters

Exposures don't always just add up¹³. Two together can have:

The classic example: people exposed to both tobacco smoke and asbestos have a far higher risk of lung cancer than people exposed to either one^14,15. In another line of research, controlled studies found that diesel exhaust amplified airway inflammation from allergens in people with allergies¹⁶.

Looking at many exposures at once also reveals patterns. Combustion-related chemicals, for instance, often rise and fall together because they share a source, like traffic^17,18. Spotting those clusters helps researchers trace exposures back to where they come from, and focus on the combinations that matter rather than one chemical at a time.

What the exposome means for your home

Exposome research is mostly done in labs and large studies, but the idea behind it is practical. Your overall exposure picture can tell you more than any single chemical.

Say a particular condition runs in your family, or you're simply curious about one exposure. Looking at the related exposures together, not just the one you've heard about, gives you a clearer sense of what's worth addressing first.

That picture comes from more than one place. Measuring your home, your wider environment, and your body each adds something the others can't. Your home is the easiest place to start, because it's where you spend the most time and where you can actually change things.

Sources

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15. 15.Ngamwong, Y. et al. Additive synergism between asbestos and smoking in lung cancer risk: A systematic review and meta-analysis. PLoS One 10, e0135798 (2015).
16. 16.Carlsten, C. et al. Diesel exhaust augments allergen-induced lower airway inflammation in allergic individuals: a controlled human exposure study. Thorax 71, 35–44 (2016).
17. 17.Patel, C. J. & Manrai, A. K. Development of exposome correlation globes to map out environment-wide associations. Pac. Symp. Biocomput. 20, 231–242 (2015).
18. 18.Tamayo-Uria, I. et al. The early-life exposome: Description and patterns in six European countries. Environ. Int. 123, 189–200 (2019).

Nestwell screens your home environment. Results describe your water, air, or dust and are not a medical diagnosis.