For exposome research to make a difference, it must be diversified and translate into policies that protect health.

The exposome, which sets out to capture everything in the environment that affects health over a lifetime, turns 20 this year. First proposed by Christopher Wild in 2005 (ref. 1), after completion of the Human Genome Project, this ambitious idea was designed to match the importance of the genome. It has since grown into an active scientific field, made possible by new technologies and better ways of integrating data.

Despite rapid progress, the exposome can sometimes be thought of as little more than a measure of a few air and chemical pollutants. This narrow view has policy consequences. As Ji et al. note, international regulatory frameworks such as the EU Ambient Air Quality Directive set safety limits for only a handful of air pollutants: particulate matter 2.5 μm or less in diameter (PM2.5), sulfur dioxide (SO2) and ozone (O3). But more than 180 other hazardous air pollutants remain largely overlooked. Missing too are environmental factors such as the built environment, occupational hazards, social inequities and climate-related stressors such as extreme heat — which all have strong evidence of interacting with air pollutants and health outcomes. To truly capture how environment shapes health, the exposome must move beyond this reductionist focus and embrace a broader view.

One attempt to move into this direction is the US National Institutes of Health’s Human Exposome Project, which aims to use environmental sensors to systematically track all environmental exposures across the life course. However, its emphasis remains largely on identifying hazardous chemicals, leaving many other environmental determinants unaddressed.

But evidence shows that the exposome extends far beyond chemicals. Ibanez and colleagues, for example, analyzed data from 40 countries to examine the exposome of healthy adults and those showing signs of accelerated aging. The authors found that beyond air quality, social and political conditions— such as gender inequality, level of democracy and factors related to migration— were critical determinants of aging. These findings highlight the fact that health is shaped by multiple interacting factors, which effective policies must address collectively. Urban greenspaces and sustainable housing offer clear examples; they improve air quality, reduce heat and noise, and narrow socioeconomic disparities, all of which benefits both physical health and mental health.

Another problem is that most exposome research still draws heavily on cohorts in North America and Europe, even though exposures can look very different elsewhere. Studies are needed on the millions of people in low-resource settings who live in informal settlements, cook over open fires or work near rare-earth mining sites — conditions that bring heavy exposure to pollutants. Without data from these populations, key risk factors could go unrecognized and policies risk being misaligned.

To fill these gaps, projects such as EXPOSOC in Thailand and the H3Africa AWI-Gen Collaborative from Burkina Faso, Kenya, Ghana and South Africa are underway to measure environmental exposures in under-represented populations. Expanding this reach builds a more representative picture of the exposome and ensures that the evidence guiding policy reflects the realities of those most at risk.

Equally important is digging deeper into how these exposures affect the body. Within exposome research, this means studying biological markers and pathways that connect specific exposures to health outcomes. Johnson et al. have illustrated this potential by mapping immune changes that capture the broad health effects of exposure to wildfire smoke and its pollutants. By tracing the connections between environmental exposures, molecular changes and disease development, exposome research provides stronger, causal evidence for regulations and can help inform prevention programs.

Realizing this potential, however, will ultimately require close collaboration across disciplines — from environmental science and biology to public health — supported by breaking down siloed research funding, creating common research platforms and open data sharing. Turning science into action also requires bringing together policymakers who can act on the best evidence, legal experts to design enforceable regulations, and stakeholders in urban planning and agriculture to reduce the environmental hazards that harm health. The resultant regulations must also be safeguarded from undue corporate influence from harmful and polluting industries.

But right now, evidence is not being translated into action, as regulations on well-established environmental hazards — air pollution, climate change and deforestation — are being eroded. Since late 2023, the European Union has weakened parts of the European Green Deal2, while in the USA, the Trump administration has similarly slashed protections, dismantled the Environmental Protection Agency and withdrew from the Paris Agreement3. Its forthcoming Make America Healthy Again report exemplifies this retreat, avoiding regulations on ultra-processed foods and pesticides despite acknowledging their health risks4. Global efforts to establish a legally binding plastics treaty collapsed after objections from the USA and several petrochemical-producing nations5. There is a wide gap between knowledge and action — a gap exposome research must now help close, with the commitment of leaders outside of the research sector.

As we look ahead to the next 20 years of exposome research, the question will be not just what will be discovered but what difference it will make. For exposome research to matter, it must go broader, capturing the full spectrum of exposures in diverse populations, and deeper, mapping these exposures to the molecular signatures and health outcomes over a lifetime. In a world in which political will too often falters, only strong cross-sector collaboration, coupled with clear, persistent evidence that cannot be buried or ignored, can close the gap between denial and accountability. This will leave policymakers with fewer excuses for inaction.