High + Very High Risk Pop224.7MNPWEI >= 60 - Annual Mean
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Population Exposure & Health Risk
Urban NO₂ health burden across West African cities - NPWEI tiers - 2019-2025 - Annual Mean
% Urban Pop High Risk61.5%of urban West Africa - Annual Mean
High-Risk Cities1of 27 cities - NPWEI >= 60
High-Risk Countries2of 15 countries - NPWEI >= 60
Population by Risk Tier
Risk Tier Population
Urban pop (millions) per NPWEI tier
Annual vs DJF vs JJA High-Risk Population
Population at NPWEI >= 60 (millions)
City-Level Exposure Summary
Lagos
- Country
- Nigeria
- NPWEI
- 100/100
- Risk
- Very High
- Urban Pop
- 15.85M
- DJF / JJA
- 100 / 100
Abuja
- Country
- Nigeria
- NPWEI
- 49/100
- Risk
- Moderate
- Urban Pop
- 5.53M
- DJF / JJA
- 55 / 45
Ibadan
- Country
- Nigeria
- NPWEI
- 44/100
- Risk
- Moderate
- Urban Pop
- 7.24M
- DJF / JJA
- 44 / 47
Abidjan
- Country
- Côte d'Ivoire
- NPWEI
- 42/100
- Risk
- Moderate
- Urban Pop
- 5.91M
- DJF / JJA
- 32 / 57
Bamako
- Country
- Mali
- NPWEI
- 39/100
- Risk
- Low
- Urban Pop
- 5.47M
- DJF / JJA
- 22 / 50
Aba
- Country
- Nigeria
- NPWEI
- 35/100
- Risk
- Low
- Urban Pop
- 13.19M
- DJF / JJA
- 33 / 40
Port Harcourt
- Country
- Nigeria
- NPWEI
- 35/100
- Risk
- Low
- Urban Pop
- 9.61M
- DJF / JJA
- 34 / 40
Onitsha
- Country
- Nigeria
- NPWEI
- 34/100
- Risk
- Low
- Urban Pop
- 10.75M
- DJF / JJA
- 39 / 35
Kano
- Country
- Nigeria
- NPWEI
- 32/100
- Risk
- Low
- Urban Pop
- 11.34M
- DJF / JJA
- 14 / 68
Enugu
- Country
- Nigeria
- NPWEI
- 31/100
- Risk
- Low
- Urban Pop
- 7.61M
- DJF / JJA
- 39 / 33
Dakar
- Country
- Senegal
- NPWEI
- 30/100
- Risk
- Low
- Urban Pop
- 3.58M
- DJF / JJA
- 18 / 66
Benin City
- Country
- Nigeria
- NPWEI
- 28/100
- Risk
- Low
- Urban Pop
- 3.43M
- DJF / JJA
- 36 / 24
Kaduna
- Country
- Nigeria
- NPWEI
- 23/100
- Risk
- Low
- Urban Pop
- 2.96M
- DJF / JJA
- 19 / 33
Ouagadougou
- Country
- Burkina Faso
- NPWEI
- 22/100
- Risk
- Low
- Urban Pop
- 5.10M
- DJF / JJA
- 6 / 42
Warri
- Country
- Nigeria
- NPWEI
- 22/100
- Risk
- Low
- Urban Pop
- 4.75M
- DJF / JJA
- 29 / 23
Accra
- Country
- Ghana
- NPWEI
- 20/100
- Risk
- Low
- Urban Pop
- 5.44M
- DJF / JJA
- 26 / 21
Health Risk Insights
Highest Burden Country
Nigeria records the highest NPWEI (100/100) driven by dense urban-industrial activity.
Dry Season Health Burden
An additional ~43.7M people enter high-risk zones during the dry season (DJF) due to Harmattan-suppressed vertical mixing.
Very High Urban Hotspots
Cities at Very High tier include Lagos. Residents face chronic NO₂ exposure likely exceeding WHO 2021 guidelines.
Vulnerable Populations
Children, elderly, and people with respiratory conditions in high-exposure zones face disproportionate health risk.
Wet Season Relief
Monsoon ventilation during JJA reduces NO₂ burden across most cities, a natural seasonal respite.
Data Basis
All estimates use Sentinel-5P TROPOMI NO₂ columns (2019-2025), population-weighted via NASA Gridded Population 2020 at >=50 ppl/km2.