Answer: Asbestos

If you were a movie star in the early 20th century and you found yourself in a scene that required snowfall, you’d find yourself completely covered in none other than asbestos–the same substance that, in the later 20th century, science would firmly establish as a horrible contaminant responsible for lung cancer and other ailments.

In the early years, however, when the dangers of asbestos were unknown (and it was toted as a wonder material that should be, and was, used for all manner of things), it was used as fake snow on movie sets. Buckets and buckets of dangerous friable asbestos were dumped from the rafters onto actors to simulate snow fall.

It wasn’t just movie stars of the day who were at risk, either. Department stores used asbestos snow to decorate their store front displays and festive home owners would sprinkle the perfectly white powdery fibers over holiday decorations, train sets, and windowsills.

The most bizarre aspect of the decades long use of asbestos as simulated snow is that it replaced cotton batting in the role–a completely harmless and inert substance. Asbestos snow fell out of favor around World War II when the U.S. government began buying up all the asbestos for the war effort.