5 US Cities with Cleanest Air and Water

2. Urban Honolulu, HI

Population: 1,000,890

Annual Particle Pollution (2019-2021): 3.7µg/m3

Water Quality Score: 72.4

Urban Honolulu has generally good air quality, with fresh Pacific Ocean breezes contributing to clean air. The city sources its water from underground. The pH value for its inland stream is 5.5-8.0, while for open coastal, it ranges from 7.0 to 8.1.