When first shown in the UK it was preceded by a warning for "people of a nervous disposition".
Cord Wainer Bird was a pseudonym used by Harlan Ellison, who was unhappy with the final product made from his script.
"Trekkies" will recognize David Opatoshu (Dr. Reisner) as Anan 7 from A Taste of Armageddon (1967) and Jill Ireland (Julie) as Leila Kalomi from This Side of Paradise (1967). An additional Star Trek connection is author Harlan Ellison, who wrote the first treatments for this story and The City on the Edge of Forever (1967), but was notably dissatisfied with the final products. (However, Gene Roddenberry did not allow Ellison to use his Cordwainer Bird pseudonym for "City," as he feared that would give Star Trek a bad reputation for author treatment.)
At one point, Nelson says that anaerobic bacteria live on air. Actually he has it backwards. Anaerobic bacteria thrive in the absence of oxygen.
This episode takes place in the 1970s.