This study describes a series of air monitoring measurements of particle number (PN), black carbon (BC) and PM 2.5 mass concentrations in the vicinity of the Los Angeles International Airport (LAX)(roughly 150 m downwind of the LAX's south runways) as well as on-road measurements of the aforementioned pollutants using a mobile platform on three major freeways (ie, I-110, I-105, and I-405) during May–July 2016. All measurements were performed in the “impact zone” of LAX with the predominant westerly winds from coast to inland. The overall impact of aircraft emissions from the LAX airport and its facilities in comparison to vehicular emissions from freeways on air quality was evaluated on a local scale (ie areas in the vicinity of the airport). PN concentration was, on average, 4.1±1.2 times greater at the LAX site than on the studied freeways. Particle number emission factors for takeoffs and landings were comparable, with average values of 8.69× 10 15 particles/kg fuel and 8.16× 10 15 particles/kg fuel, respectively, and indicated a nearly 4-fold statistically significant reduction in PN emission factors for takeoffs during the past decade. BC emission factors were 0.12±0.02 and 0.11±0.01 g/kg fuel during takeoffs and landings, respectively. Additionally, the mean PM 2.5 emission factor values for takeoffs and landings were also comparable, with values of 0.38±0.04 and 0.40±0.05 g/kg fuel, respectively. Within the impact zone of the airport, an area of roughly 100 km 2 downwind of the LAX, measurements indicated that the LAX daily contributions to PN, BC, and PM 2.5 were approximately 11, 2.5, and 1.4 times greater than those from the three surrounding freeways. These results underscore the significance of the LAX airport as a major source of pollution within its zone of impact comparing to freeway emissions.