GCRI · Health Nexus
Environmental health
Environmental hazards reach health through the air people breathe, the water they drink, the heat their bodies must shed and the chemicals that accumulate over years. Their effects are often diffuse, delayed and shared with other causes, which makes them easy to overlook and hard to attribute. This page sets out how environmental exposure becomes disease, how exposure and effect are measured, and what the evidence serves for health and environment authorities.
Environmental health in seven parts.
- 01The questionEnvironmental health: how the risk develops
- 02CouplingsAir, heat and water link the environment to illness
- 03Reports, standards and contributionsEnvironmental health evidence
- 04IndicatorsWhat is measured, and how well
- 05SourcesWhere the evidence comes from
- 06DecisionsWho decides, and what the evidence serves
- 07Core questionsWhat experts ask
Environmental health: how the risk develops.
Water, air, heat, pollution and health. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
Exposure becomes dose
Ambient concentrations become personal exposure through where people live, work and spend their time, then dose through breathing rate, water intake and duration. Indoor sources such as household combustion of solid fuels can outweigh outdoor levels.
Heat stresses body and system
Heat raises risk for older people, outdoor workers, infants and people with chronic illness. Heatwaves increase hospital demand while reducing staff capacity and straining power for cooling, so bodies and services are stressed together.
Water carries pathogens and chemicals
Floods and failing sanitation spread faecal pathogens; drought concentrates contaminants and pushes people to unsafe sources. Arsenic, fluoride, nitrate and lead cause chronic harm that appears only after long exposure.
Environmental exposure in Africa.
Population density, daytime surface heat and haze over Africa, from NASA GIBS. Each layer carries its own date.
The interactive map needs JavaScript; the layer list and sources are below.
Layers 3
Environmental exposure, for this page
About this layer
- Evidence
- Estimated
- Source
- Gridded Population of the World v4.11 (NASA SEDAC (CIESIN, Columbia University))
- Provider
- NASA SEDAC (CIESIN, Columbia University)
- Licence
- CC BY 4.0
- Vintage
- null; Census-based estimate, static (2020)
- Resolution
- about 1 km grid
- Uncertainty
- Census-based estimate of people per square kilometre in 2020, shown as exposure context; not a count of people affected by any hazard.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (persistent cloud still leaves gaps)
- Source
- VIIRS NOAA-20 Level 3, 8-day (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- 8-day; Satellite 8-day composite; persistent cloud still leaves gaps
- Newest at build
- 2026-09-14
- Resolution
- about 1 km grid
- Uncertainty
- Satellite skin temperature of the ground over the 8 days ending on the date shown, a heat exposure indicator; not air temperature, heat index or a heat warning.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (clouds leave gaps)
- Source
- VIIRS NOAA-20 Deep Blue AOD (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- daily; Satellite retrieval; clouds leave gaps
- Newest at build
- 2026-10-14
- Resolution
- about 2 km grid
- Uncertainty
- Satellite measure of haze, smoke and dust through the whole air column on the day shown; an exposure indicator, not ground-level PM2.5, an air quality index or a health warning.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed
- Source
- VIIRS NOAA-20 corrected reflectance (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- daily; Satellite image
- Newest at build
- 2026-10-14
- Resolution
- about 250 m grid
- Uncertainty
- Satellite image. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (clouds leave gaps)
- Source
- OMI Aura (NASA GES DISC)
- Provider
- NASA GES DISC
- Licence
- NASA open data
- Vintage
- daily; Satellite retrieval; clouds leave gaps
- Newest at build
- 2026-10-10
- Resolution
- about 2 km grid
- Uncertainty
- Satellite column of nitrogen dioxide in the lower atmosphere on the day shown, mostly from combustion; not a ground-level concentration or a health warning.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Modelled (latest year GIBS publishes)
- Source
- MODIS Terra and Aqua land cover (MCD12Q1) (NASA LP DAAC)
- Provider
- NASA LP DAAC
- Licence
- NASA open data
- Vintage
- yearly; Satellite classification; latest year GIBS publishes
- Newest at build
- 2024-01-01
- Resolution
- about 500 m grid
- Uncertainty
- Satellite land cover classes for the year shown, including croplands; a classification with known errors, not a farm register.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
Keyboard, with the map focused
Hold Ctrl or ⌘ and scroll to zoom
Latest available
NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth
Loading the latest NASA imagery.
Drag to move. Ctrl or ⌘ and scroll, pinch or the buttons to zoom; hover for the values under the pointer; reset returns to the region.
Environmental exposure, framed on Africa.Satellite and model products as NASA publishes them, each with its own date. They are indicators, not assessments of any place.
Data: NASA GIBS · ASTER GDEM · Blue Marble · © OpenStreetMap contributors · Natural Earth · NASA EONET · ESA Copernicus Sentinel-5P TROPOMI · NASA JPL OPERA DIST-ALERTSources and licences
- We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Center for International Earth Science Information Network (CIESIN), Columbia University. 2018. Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 11. NASA Socioeconomic Data and Applications Center (SEDAC). Licensed under CC BY 4.0. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). doi:10.7927/H49C6VHW. CC BY 4.0
- VIIRS near-real-time products (flood, land surface temperature, snow cover, corrected reflectance), NASA LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- MODIS and VIIRS atmosphere products, NASA LANCE and LAADS DAAC; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- OMI nitrogen dioxide (Aura) and OMPS aerosol index (Suomi NPP), NASA; distributed by the NASA GES DISC; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- MODIS land products (vegetation indices, gross primary production, land cover), NASA LP DAAC and LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- ASTER GDEM is a product of METI and NASA (ASTER Global Digital Elevation Model V003, NASA LP DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). Cite as: NASA/METI/AIST/Japan Spacesystems and U.S./Japan ASTER Science Team (2019). ASTER Global Digital Elevation Model V003. doi:10.5067/ASTER/ASTGTM.003. NASA open data
- Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. Public domain
- © OpenStreetMap contributors (ODbL), via NASA GIBS (coastlines, boundaries, roads and place names). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). ODbL
- Blue Marble, NASA Earth Observatory; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Context on the globe and flat map: coastlines, boundaries, roads and place names from NASA GIBS reference layers (OpenStreetMap data, ODbL, © OpenStreetMap contributors); Blue Marble imagery as an optional base; 3D terrain and the elevation read-out from the ASTER GDEM elevation colour index (5 m to 200 m classes, exaggerated for legibility). Boundaries are drawn as published and imply no position on any territory.
- Live events: NASA Earth Observatory Natural Event Tracker (EONET); events are indicative and keep their original source links.
- Live: NASA EONET Events are indicative, not authority warnings.
- Observed (EO): ESA Copernicus Sentinel-5P TROPOMI (contains modified Copernicus Sentinel data 2026). We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- Observed (EO): NASA JPL OPERA DIST-ALERT (contains modified Copernicus Sentinel data 2026). We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- NASA GIBS: We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- Air quality forecast, 5 days, PM2.5 (CAMS via Open-Meteo): Contains modified Copernicus Atmosphere Monitoring Service information 2026.
- Past year, daily temperature (ERA5 via Open-Meteo): Contains modified Copernicus Climate Change Service information 2026.
- Weather data by Open-Meteo.com (https://open-meteo.com/), licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).
- Optional layers (14 sources in the layer list: live, forecast, observed and context) print their provider credit on the map and here when switched on; forecasts are model output and derived indices are estimates.
Layers and dates
- Population density, 2020: Population: CIESIN, Columbia University, Gridded Population of the World v4.11 (2018), NASA SEDAC, CC BY 4.0 · static
- Land surface temperature, day, 8-day composite: VIIRS NOAA-20 Level 3, 8-day, NASA LANCE · 14 Sep 2026
- Aerosol optical depth, daily: VIIRS NOAA-20 Deep Blue AOD, NASA LANCE · 13 Oct 2026
- True colour: VIIRS NOAA-20 corrected reflectance, NASA LANCE · 13 Oct 2026
- Nitrogen dioxide, lower atmosphere column: OMI Aura, NASA GES DISC · 10 Oct 2026
- Land cover type (IGBP), yearly: MODIS Terra and Aqua land cover (MCD12Q1), NASA LP DAAC · 2024
Air, heat and water link the environment to illness.
| Domain | How it couples here | What to watch |
|---|---|---|
| Energy | Combustion for power, transport and cooking is the main source of fine particulate pollution; heat stresses power systems. See heat and cooling. | Fine particulate concentration in micrograms per cubic metre |
| Water | Contaminated water carries chemical and microbial hazards. See drinking water and sanitation. | Contaminant exceedances against WHO guideline values |
| Food | Contaminants and residues enter diets; heat affects food safety. | Residue monitoring results |
| Biodiversity | Urban green space and trees reduce heat and filter air. | Tree canopy cover by neighbourhood |
The WHO global air quality guidelines (2021) set guideline values for fine and coarse particulate matter, ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide, expressed in micrograms per cubic metre over stated averaging times. Heat-health warning systems follow WMO and WHO guidance (2015), which ties thresholds to local evidence of excess mortality.
Heat-health and equity watch.
The screen a team would use to follow this subject: its measures, states and decisions. Names are examples and values are illustrative.
Heat-health and equity watch
Environmental health · Summer season · District 4
Daily maximum temperature
Outreach to at-risk groups
| People over 75 living alone | 1048 | 76 | Behind |
| Outdoor workers | 1932 | 45 | Behind |
| Care homes | 39 | 99 | On track |
Actions
- A-1Open cooling centres, district 4Civil protectiontoday
- A-2Adjust outdoor work hoursLabour inspectorate1 d
Environmental health evidence.
Exposure and heat-health analyses are designed for the Country Quarterly series. The Global Centre for Risk and Innovation (GCRI) sets no exposure limits and issues no heat warnings. Monitoring datasets would carry NS-3b metadata under the proposed Nexus Standards. Useful contributions: low-cost sensor data with co-location calibration, and heat-health outcome studies.
Model environmental health as a system. Run the cascade.
Assembled from the Nexus Standards area profile Health security and One Health: the hazards it names, the systems and sectors that carry the loss, the controls that dampen it and the data that observe it. Choose the components, pick an initiating hazard and step through the cascade. The Map view places the run on an example geography with open data. Every coupling weight is a stated assumption you can change. A teaching model, not a forecast, an assessment or a certification. To model a place of your own choosing, open the full System Builder.
Hazards
- Antimicrobial resistance
- Tuberculosis surge (set off downstream)
- Typhoid and paratyphoid fever (set off downstream)
- Health-system overload (set off downstream)
Systems and couplings
- Health security and One Health
- Biological hazard standards Mechanism
- Biodiversity and nature risk standards Common driver
- Food and agriculture risk standards Mechanism
- Global and systemic risk Cascade
Controls
NS-0Constitution and principlesNS-3Risk record UNIs (grammar, legacy crosswalk, allocation authority)NS-9Contextual UNIs (deployments, instances, programme instances)NS-10Policies and clauses (machine-readable obligations: definition, binding, evaluation and enforcement)NS-11Verification and monitoring (evidence, attestations, zero-trust conformance observation)NRS-H83Hazard family: Health system capacity failure (NHS-1 health.system)NRS-H42Hazard family: Rare and persistent human infections (NHS-1 health.other-human)NRS-H41Hazard family: Animal-to-human spillover (NHS-1 health.zoonotic)NRS-H43Hazard family: Livestock and aquaculture epizootics (NHS-1 health.animal-health)NRS-D3Humanitarian response and resilient recoveryNRS-H46Hazard family: Environmental and product harm to people (NHS-1 health.harm)
Observation
- WHO Disease Outbreak News (listed for reference)
- WAHIS animal health events (listed for reference)
- WorldPop gridded population (listed for reference)
- International Health Regulations capacity and health emergency preparedness
- Percentage of bloodstream infections due to selected antimicrobial-resistant organisms
Example geography
- West Africa: 59 hexagonal cells
- Night lights tonight, outages (VIIRS Day/Night Band), NASA GIBS
- Surface water through cloud, 30 m (OPERA DSWx-S1 radar), NASA GIBS
- Rain rate, last half hour (IMERG), NASA GIBS
What is measured, and how well.
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Annual mean fine particulate matter | micrograms per cubic metre | annual | Ground monitors fused with satellite and model estimates | MODELLED |
| Population above the WHO air quality guideline | persons | annual | Exposure surfaces on gridded population | ESTIMATED |
| Heat stress | universal thermal climate index, degrees Celsius | daily | Reanalysis and weather forecasts | MODELLED |
| Heatwave exposure | person-days of heatwave exposure | seasonal | Temperature records on gridded population | ESTIMATED |
| Heat-related excess deaths | deaths above expected | seasonal | Vital registration against modelled baselines | ESTIMATED |
| Reliance on polluting cooking fuels | percent of population | annual | Household surveys, SDG indicator 7.1.2 | ESTIMATED |
| Drinking-water contaminant exceedance | percent of samples above the guideline value | monthly | Water quality surveillance | OBSERVED |
| Blood lead concentration | micrograms per decilitre | per survey | Biomonitoring surveys | OBSERVED |
How environmental health is modelled, measured and tested.
The model, its assumptions, its data and its uncertainty, in the form a scientist or engineer would check. Structures follow published methods. The values drawn are illustrative, not findings.
System model
The couplings between the systems in environmental health: signs of influence, a reinforcing and a balancing loop, and cross-links where stress jumps.
Where the evidence comes from.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| WHO Ambient Air Quality Database | Annual mean particulate matter and nitrogen dioxide from city monitors | Open, attribution, WHO terms of use |
| OpenAQ | Harmonised real-time and historical air quality measurements | Open; licence per contributing source |
| Copernicus Atmosphere Monitoring Service | Reanalysis and forecasts of aerosols, ozone and wildfire smoke | Free and open, attribution |
| ERA5 and ERA5-HEAT (Copernicus) | Temperature and thermal stress indices, the universal thermal climate index included | Free and open, attribution |
| WHO and UNICEF Joint Monitoring Programme | Drinking water, sanitation and hygiene service levels | Free and open, attribution |
| IHME Global Burden of Disease | Modelled burden attributable to environmental risk factors | Free for non-commercial use, attribution |
| Lancet Countdown on health and climate change | Indicators of heat exposure, health impacts and adaptation | Published report and data, terms per indicator |
Who decides, and what the evidence serves.
Health Nexus prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| Ministries of health and environment | Which pollutants and sources to regulate first, and which populations to protect | Exposure surfaces against guideline values; attributable burden with uncertainty |
| Municipal health and emergency authorities | When to activate heat-health action plans and where to open cooling centres | Heat stress forecasts with their skill; exposure of vulnerable groups by neighbourhood |
| Drinking-water regulators and suppliers | Which supplies need treatment, a source change or public advisories | Contaminant exceedance by supply; seasonal and flood-related contamination risk |
| Hospital systems | How to prepare staffing, cooling and admissions for heat and smoke episodes | Seasonal exposure outlooks; past admission patterns during episodes |
Outputs this topic produces
- Exposure surfaces for air, heat and water hazards with their error
- Heat-health evidence for action plans and hospital preparedness
- Attributable burden estimates with model assumptions stated
- Combined-exposure profiles for districts and facilities
What experts ask.
Environmental health connects a measured exposure to a health outcome.
- How do temperature extremes affect illness and death, and who is most sensitive?
- What health burden comes from air pollution, including wildfire smoke?
- When does flooding or drought compromise drinking water and sanitation?
- Which chemical and pollutant exposures matter most, and at what levels?
- How do exposures combine, for example heat with poor air quality?
Mechanisms and drivers.
Extreme heat strains the body’s ability to regulate temperature and places stress on the heart, kidneys and lungs. Older people, infants, outdoor workers, people with chronic illness and those without cooling are most at risk, and much of the harm occurs on hot nights when the body cannot recover. Cities amplify heat through the urban heat island effect.
Fine particulate air pollution penetrates deep into the lungs and bloodstream and is associated with respiratory and cardiovascular disease. Floods spread contamination and disrupt treatment works; drought concentrates pollutants and reduces water for hygiene. Many exposures act together, and their combined effect can exceed the sum of their parts.
How it is studied, and where the methods stop.
| Method or data | What it shows | Limits |
|---|---|---|
| Time-series and case-crossover studies | Short-term associations between exposure and outcomes | Confounding and exposure misclassification from fixed monitors |
| Cohort studies | Long-term effects of chronic exposure | Expensive, slow and dependent on follow-up quality |
| Exposure modelling with monitors and satellite data | Where and when people are exposed | Personal exposure differs from outdoor concentrations |
| Heat-health and air-quality early warning evaluation | Whether warnings change outcomes | Hard to separate warning effects from weather variation |
How it is studied, and what the methods cannot say.
- 01Epidemiology and public health scienceSurveillance design and evaluation · Nowcasting under reporting delayApplied here
- 02Causal inference and impact evaluationEvaluating public health measures · Exposure-response for heat and airApplied here
- 03Probability and statisticsSurvey-weighted and small-area estimation · Expected baselines for excess mortalityApplied here
- 04Data engineering, interoperability and stewardshipLinking health information systems · Privacy-preserving publicationApplied here
- 05Complex systems and agent-based modellingContact and mobility networks · Cascades across health and infrastructureApplied here
Where this page’s references lead.
The bodies and documents this page is read against. Status and editions change; each link goes to the issuing body.
Questions and answers.
What is a WHO air quality guideline?
Can a death be attributed to heat or air pollution?
Why combine exposures instead of studying each one?
Where can I get advice about my own exposure?
Why are heat deaths hard to count?
Do warnings work?
Does Health Nexus set exposure limits?
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