dusty environment, no gas cap?

So just wondering if there is any concern with no gas cap living where dirt blows half the days of the year. I would guess they had an objective to keep dirt out when they designed the car, just wondering if anyone knows how. Guessing positive pressure, but still just looks like a big trap door for settled dirt to fall into.

The capless design seems pretty robust and seals well, my 2010 fusion has it and I feel safe opening the fuel door and washing the area out without concerns of water getting in. I couldn't imagine too much dust setting on the top that would fall in on fill ups but if it did you could always just keep a can of air duster in the car and blow it off before sticking the pump nozzle in. Otherwise the fuel filter should take care of any that gets by.

I haven't looked lately, but I think there's a seal between the gas door and body.

The fuel door has a seal around it. I even tried power washing the area and no water got in it.

The fuel door itself has a seal, and more importantly, the filler inlet is sealed until you put a pump filler neck in. When I wash the car, no water gets in.

Thanks guys, I pretty much figured they had it sealed up. Just thought dust might accumulate around the spout and a little gets it at every fill up. I'm sure it would just settle at the bottom if that does happen, and the filter would get any that gets sucked up. Anyone know where the filter is, is it in the tank? I know probably something I'd probably never have to worry about, just thought I'd ask. Thanks again for the reassurance.