Possible Origins of the trope
The association of "green glow = radioactive and toxic" may derive from an infamous Radioluminescent Paint
that helped cement the dangers of radiation in the public consciousness.One of the earliest and most visible applications of radiation the public encountered was a common copper- and zinc sulfide-based paint that glowed an intense bright green thanks to the addition of trace amounts of radium. Considered a wonder of modern technology at the time, a paint that could make Tron Lines on any surface was understandably popular, especially so for things like watch dials and instrument panels where the ability to read them in the dark is useful as well as cool.
While reasonably safe in the manner it was intended to be used (small dabs of the stuff sealed into a metal and glass case), the danger was downplayed to the workers (mostly young women) hired to paint the delicate items, and tragedy ensued. Unaware that ingested radium is incorporated into bones and builds up to lethal levels over time, they carried out (and were often encouraged to use) common painters' habits like licking brushes to create a fine point and handling paint directly with one's fingers. Many also amused themselves by painting their nails and teeth with the cool glowing paint, and "borrowed" it for use as makeup for nights out on the town.
When they realized that their employers had knowingly poisoned them and continued to deny responsibility, an explosive and highly public trial taught the world to associate the bright green glow of watch dials with the disfigured and dying Radium Girls- and the callous companies that tried everything from destroying their reputations to bribing and coercing medical professionals to help with the coverup to get off the hook.
