416 S. State St. Hwy 1- West Union Air Monitoring Station, Clark County, Illinois

416 S. State St. Hwy 1- West Union is an air monitoring station located in Clark County, Illinois, United States. Operated under the oversight of the Indiana Department of Environmental Management's Office of Air Quality, this facility is part of a broader network that tracks ambient air pollution levels. The station is currently operational and contributes to regional air quality assessments. The station operates within the framework of the U.S. EPA's Air Quality System (AQS), which sets standards for criteria pollutants such as ozone, particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. Monitoring stations like this one are sited to ensure representative sampling of local air quality, often in accordance with EPA siting criteria. The station's last reported sample date is September 30, 2025, indicating ongoing data collection. Environmental monitoring at this location supports public health protection by providing data used to determine compliance with National Ambient Air Quality Standards (NAAQS). The data also informs local air quality trends and helps guide emission reduction strategies. As part of the Illinois-Indiana border region, the station plays a role in understanding cross-state air pollution transport.

Clark County, Illinois, is a rural area with agricultural land use and some light industry. Air monitoring in this region focuses on background pollutant levels and potential transport from nearby urban and industrial centers. The station's location along State Highway 1 allows for representative sampling of regional air quality, including impacts from traffic and agricultural activities. Monitoring parameters typically include criteria pollutants, with potential for additional speciation depending on network priorities.