Slight audio bug: when returning to the main menu, the music starts to double up on itself. Don't forget to tell the AudioSource to Stop() before you Play() it again!
But as for the gameplay itself, I thought it was a wonderful game that very quickly overwhelmed me. I did notice that putting workers where they would be happy (that is what the smiley face means, right?) didn't seem to raise the Happiness meter -- a lack of Happiness is what ended up causing an accident.
I'd love for there to be more a soundscape: a "shoomp" when workers pop out of the tube, the sounds of their balls clinking together, the whir and roar of the tube processors, alarms when a meter gets critically low -- you have a lot of potential here to really bring out the most in your mechanics.
Great job overall! Very well done!