What you’re smelling in a public restroom might well be other products though — the urea and VOCs in the urine, and the byproducts of bacteria feeding on the ur

What you’re smelling in a public restroom might well be other products though — the urea and VOCs in the urine, and the byproducts of bacteria feeding on the urine — so it isn’t really an indication of what is in the bowl. And on a longer flight, those bathrooms might have been used by 100 people before you, likely far more than a ground side bathroom with regular cleaning crew visits.