But, where is the best or worst air quality? Benton Clean Air Agency Has Issued a Number of AlertsMost of the alerts concern persons with respiratory issues. We checked the readings from the Clean Air Monitoring Stations from across the region, at various times Monday. Benton Clean Air issued several warnings for unhealthy air for persons with respiratory issues. As of Monday evening the 'worst' readings were in Prosser, four of the five monitoring stations were Unhealthy for Sensitive Groups--those with respiratory issues.