This study examines the effects of solid waste and its leachate (from a sanitary landfill in Kirkuk City) on air quality in Iraq. The landfill site and its surroundings, extending to the nearest residential area, were tested to measure the leachate pollution index, air quality index, and air pollutant levels (PM10, PM2.5, CH4, CO, CO2, SO2, H2S, VOCs, and NO2). Eleven test sites were selected based on their distance from the centre of the sanitary landfill site. Additionally, the test period was extended from February to October 2024 to examine the impact of the city’s climatic variance on air quality. According to the GIS contour maps, the concentration of pollutants was highest in the centre of the landfill and progressively declined as one moved toward the nearest residential neighbourhood. The effective pollutants in the study area were PM10, PM2.5, CH4, SO2, and H2S; the ranges of the highest and lowest concentrations of the respective pollutants are given as follows: 139–169 mg/L, 87–137 mg/L, 617–1997 mg/L, 0.033–0.547 mg/L, and 0.037–1.621 mg/L. Moreover, the study revealed that the leachate pollution index values (25.529–41.928) were higher than the permitted level, and the landfill site’s air quality index values ranged from 141 to 281, both of which were deemed extremely unhealthy and unhealthy for the sensitive population living in the surrounding areas. The findings of the correlation study indicated a robust relationship between contaminants and the reduction in their concentration based on increasing one’s distance from the landfill site. Hence, this study suggests using cell systems with robust engineering and scientific techniques to treat leaching and gases that affect the environment in and around sanitary landfills.