Shiloh Air Quality Index (AQI)

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Shiloh, Illinois, is situated within the Greater St. Louis metropolitan area, a region defined by its position on the Mississippi River floodplain. The city itself occupies a relatively flat terrain, typical of the Midwestern United States, at an elevation of approximately 469 feet above sea level. This low-lying landscape, coupled with the proximity to the Mississippi River, influences local air quality through humidity and potential temperature inversions. Shiloh’s urban character is transitioning, evolving from a primarily agricultural community to a suburban extension of St. Louis. Surrounding Shiloh are extensive agricultural lands, particularly corn and soybean fields, contributing to seasonal particulate matter from harvesting and tilling. To the west lies the heavily industrialized St. Louis metropolitan core, a significant source of pollutants transported eastward by prevailing winds. The urban-rural gradient is pronounced; moving westward increases exposure to industrial emissions, while Shiloh experiences a blend of agricultural and suburban influences. The lack of significant topographical features allows pollutants to accumulate, especially during stable atmospheric conditions. The regional climate, characterized by hot, humid summers and cold winters, further exacerbates pollution events. This geographic setting necessitates careful monitoring and mitigation strategies to protect public health.

Shiloh’s air quality follows a distinct seasonal pattern. Spring brings increased pollen counts, impacting those with allergies, alongside agricultural burning from nearby farms, elevating particulate matter. Warm, humid conditions can trap pollutants near the ground. Summer often sees higher ozone levels, formed through photochemical reactions between sunlight and vehicle emissions, peaking in July and August. Stagnant air masses and high temperatures contribute to this. Autumn offers a brief respite with cooler temperatures and increased wind speeds, dispersing pollutants. However, leaf burning and agricultural harvest activities can temporarily worsen air quality. Winter is typically the period of best air quality, though temperature inversions – where a layer of warm air traps cooler, denser air below – can occur, concentrating pollutants from residential heating sources, particularly wood burning. Sensitive groups, including children, the elderly, and those with respiratory conditions, should limit strenuous outdoor activity during ozone peak periods in summer and inversion events in winter. Monitoring forecasts and adjusting activity levels accordingly is crucial for protecting respiratory health throughout the year. Fog, common in the cooler months, can also exacerbate particulate matter concentrations.