Radioactive waste
Radioactive waste or radioactive residue was a type of hazardous material created as a volatile byproduct of a nuclear reaction. 

In 2268, James T. Kirk suggested Montgomery Scott flush radioactive waste into the ventilation system in an effort to neutralize the dikironium cloud creature. ()

The Orion vessel encountered by the  left trails of radioactive waste in its wake. ()

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Poisonous substances