My parents spent 10 years living aboard their boat at the Gangplank Marina in the Washington Channel in DC and I spent a couple of years working on a yacht there - which is maybe a half- to a mile from DCA as the pigeon flies and just outside the flight paths. Every morning, I had to wash down the decks to rinse off a layer of black "dust" from jet fuel exhaust. I am sure the amount of exhaust dust in the air on the airfield where the mobile lounges operate is dramatically higher that where the boats are. So, yeah, air quality around an airport is not great at all. And while the filters you photographed don't look great, it does not surprise me that the ML air filters get very dirty quickly. but having dealt with the managers of the mobile lounge shop in the past, I know they are on top of it and wouldnt consider that "failing."