At least some of the signs were desgined by Anders Sandberg:

• Warning Signs for Tomorrow

I found the image on Bruce Sterling’s Tumblr.

The source is from u/FuckMyHeart’s (reddit user) comment, which has a bit more info:

• FuckMyHeart comments on Fringe Science Warning Signs

From the same comment and user:

• zip file containing each symbol as its own indexed png with transparency