Sentence:  Cadamore believes the mess came from an airplane. In the airline industry, it's euphemistically known as <WSD>blue ice</WSD>. Most people have far less judicious names for it. Such waste apparently is caused by leaks in airplane lavatories. 
Meaning of the word marked with <WSD> tags:  Human waste that has leaked from an aircraft, frozen at high altitude, and fallen to earth.