Millions of Americans in the Midwest and Northeast are at risk of health complications due to degraded air quality. Vulnerable groups include children, older adults, pregnant women, and individuals with respiratory or cardiovascular conditions. Symptoms such as coughing, wheezing, and chest tightness may occur, with long-term exposure linked to increased mortality rates. Air quality alerts have been issued in affected areas, urging residents to limit outdoor activities and take precautions to protect their health.