Peru Air Quality
Lima sits beneath a permanent coastal marine inversion — a meteorological lid that traps vehicle exhaust below 1,000m for 6–8 months per year, making it one of the most polluted capitals in the Americas.
Monthly AQI — Lima
May–October austral winter: marine inversion at its most persistent
La Garúa: The Grey Sky of Lima
Lima's iconic “garúa” — a persistent coastal mist — is caused by the same meteorological system that traps air pollution. The cold Humboldt Current offshore chills the marine boundary layer, creating a temperature inversion that caps atmospheric mixing at 800–1,200m for 6–8 months per year (May–November).
Above the inversion lid, the sky is clear and sunny. Below it — where Lima's 11 million people live — the city is sealed under a grey ceiling. All vehicle exhaust, industrial emissions, and dust get recirculated within this shallow layer. The garúa's fine water droplets also deposit pollutants on surfaces rather than washing them away like rain would.
During austral summer (December–April), the inversion weakens. Sea breezes and occasional rain improve air quality significantly. Lima's cleanest months are January–March, when PM2.5 averages drop to 10–12 μg/m³.
Urban Pollution Sources
Informal Transport
Lima's chaotic informal minibus (combi) network uses thousands of old diesel and gas-converted vehicles. Many fail emission standards but operate without enforcement. The 'guerra de centavos' (penny wars) between competing routes causes aggressive acceleration and heavy exhaust.
Industrial Zones
Ventanilla (northern Lima) and Ate-Vitarte (east) host industrial corridors. Cement, metal, and chemical factories emit PM10, SO₂, and heavy metals that mix into the marine inversion layer.
Sea Salt + Dust
Pacific Ocean sea spray generates coarse salt particles. Desert dust from Lima's surrounding cerros (hills) adds PM10. Both contribute to Lima's high total suspended particulate readings even outside rush hours.
Open Burning
Waste burning in peripheral districts (conos) is still common. SENAMHI identifies burning as a significant PM2.5 source in the northern and southern expansion zones where municipal waste collection is irregular.