A new study reveals the tourist cities with the highest pollution levels anywhere worldwide.

Based on the study conducted by DIPNDIVE, Egypt’s Cairo came out on top, despite attracting 14.9 million visitors annually.

Meanwhile, Los Angeles, the world’s third most visited city with more than 49 million tourists annually, is the second most polluted destination, while top Asian destination Hong Kong ranked third.

The analysis identified these destinations based on their average annual number of visitors.

Pollution levels were assessed using key indicators, including the Air Quality Index, PM2.5 concentrations, water quality index, and noise levels. These metrics were then combined into a pollution score to rank cities by environmental conditions.

A representative from DIPNDIVE remarked: “Travel is one of the most enriching experiences, but it’s important to recognize how environmental factors can impact our journeys and the destinations we visit. Cities like Los Angeles and Bangkok demonstrate the challenges of managing air quality and noise in highly urbanized tourist hubs. On the other hand, destinations like Cancun remind us that even seemingly pristine locations can face unique environmental concerns, such as high noise pollution. Understanding these dynamics enhances traveler awareness and underscores the need for sustainable tourism practices globally.”

Where the conditions are the worst

Cairo, which welcomes 14.9 million annual visitors, recorded the highest pollution levels among the analyzed destinations. Cairo’s Air Quality Index (AQI) stood at 160, reflecting unhealthy air conditions, while PM2.5 concentrations, referring to tiny air particles harmful to human health, reached 68.4 µg/m³—well above the WHO’s recommended safe limit of 5 µg/m³.

Los Angeles, attracting 49.1 million visitors annually, is the second most polluted city on the list, with a score of 51.17. As the third most visited city worldwide, Los Angeles has serious issues with air quality. The city comes right after Cairo with an AQI of 116 and PM2.5 levels averaging 41.5 µg/m³.

Hong Kong, welcoming 14.7 million visitors annually, had a pollution score of 50.33, which is the third highest on the list. The city recorded an Air Quality Index of 83, indicating polluted air conditions. PM2.5 concentrations were measured at 26.5 µg/m³, five times exceeding the WHO’s recommended safe limit of 5 µg/m³. The city’s water quality index was reported at 69.

Bangkok, with 12.2 million visitors annually, is the fourth most polluted city on the list, with a score of 48.97. The city recorded an AQI of 91, indicating polluted air quality. PM2.5 levels reached 30.8 µg/m³, more than six times exceeding the safe limit.

San Diego, attracting 31.8 million visitors annually, ranks as the fifth most polluted city on the list, with a pollution score of 40.04. The city recorded an Air Quality Index of 73, with PM2.5 concentrations reaching 20.8 µg/m³, significantly exceeding the WHO’s recommended safe limit of 5 µg/m³. Noise and water pollution also contribute to its overall environmental challenges.

Phuket, which welcomes 8.4 million visitors annually, is the sixth most polluted city on the list, with a pollution score of 40. The city recorded an AQI of 58, with PM2.5 levels measured at 13.1 µg/m³. Noise levels averaged 71 dBA, while the water quality index stood at 54, further highlighting environmental challenges in this popular tourist destination.

Athens, attracting 6.4 million visitors annually, is the seventh most polluted city on the list, with a score of 39.87. The city recorded an Air Quality Index of 81 and PM2.5 concentrations at 25.1 µg/m³, five times above the WHO’s safe limit. With noise levels reaching 55 dBA and a water quality index of 63, Athens faces significant environmental challenges impacting its appeal as a tourist destination.

Cancun, welcoming 10.8 million visitors annually, ranks as the eighth most polluted city on the list, with a pollution score of 36.66. The city recorded the highest noise pollution in this list, with levels averaging 103 dBA. Its AQI of 15 reflects relatively good air quality, but other factors, such as noise and water quality, contribute to its overall pollution challenges.

Dubai, which draws 16.8 million visitors annually, is the ninth most polluted city on the list, with a pollution score of 36.12. The city recorded an Air Quality Index of 66, while PM2.5 concentrations were measured at 17 µg/m³, over three times the WHO’s recommended safe limit. Noise and water quality issues also contribute to its pollution score.

San Francisco, attracting 23.1 million visitors annually, ranks as the tenth most polluted city on the list, with a score of 34.15. The city recorded an Air Quality Index of 82, and PM2.5 concentrations reached 25.9 µg/m³, significantly exceeding the WHO’s safe limit. While noise and water quality are relatively better, air pollution remains a major concern.