Are there any minors (persons under 21) in your household? They may be at risk from the glass and aluminum if they play or work in the yard, esp. the glass. Yikes!
Even adults can be injured despite precautions like wearing sturdy shoes, long pants, and leather gloves while working in such surroundings.
And...I almost hate to suggest it, but as a technical editor, and in light of some of the geoscience/engineering reports I've read over the last many years, I feel honor-bound to bring it up:
If the previous owners thought nothing of throwing glass, aluminum, steel cans, etc. out onto the property, might they also have blithely disposed of inconvenient paints, motor oil, or other such chemicals? If so, and you run into paints, motor oil, or other chemicals in the soil, consult your real-estate agent about the seller's disclosure obligations in the State of Washington and how to proceed with the necessary clean-up.
I would also suggest, if you run into such chemicals, that you STOP WORKING near them immediately. Just leave them in place; consult professionals (starting with the real-estate agent and seller liability) before proceeding.
With any luck, though, these people just chucked empty containers outside.... ::fingers crossed::
Sunset Zone 17, USDA Zone 9