I work for the Sagarmatha Pollution Control Commission. We're very busy during the peak seasons — March/April and October/November — our garbage collectors have far more to do, and so does the visitor centre. I'm glad so many tourists come, honestly; it shows they care about the environment and are willing to support the park's conservation.
The big amount of garbage is only indirectly caused by tourists — it's mostly the local teashop and lodge owners who throw things away where they shouldn't.
Beyond the usual garbage problems, there's also sanitation, and even bodies abandoned on the mountain peaks. We've tried to educate local shop and lodge owners about why the environment matters, and in some ways it's worked — but many still seem to think keeping things clean is our job, not theirs, since that's what SPCC exists for, as they see it.
What I mean by "indirectly responsible" is that tourists consume the products that create the waste, but they're rarely the ones who dispose of it badly. Some even play an educational role — sharing what they know about the environment with local people. And in a roundabout way, tourists are the ones funding us: SPCC was founded with WWF money, but now runs on funding from the Nepal Tourism Board, which collects the 2% tourism tax paid by almost every tourism business here.
The waste piles up locally — but paying for the cleanup runs straight back to the visitors.