Yes, and don't confuse Selenium in toner with sodium selenite - the actual compound that the selenium is in, in the toner. None the less, sodium selenite is pretty toxic orally - around 5 mg sodium selenite per kg of subject body weight for rats, mouse, and rabbit was a lethal dose in 50% of the test subjects. Assuming the same toxicity for people, that would be about .3 g total oral dose for a 70 kg human... So don't ingest any. See http://www.jtbaker.com/msds/englishhtml/s4946.htm for more info.
Originally Posted by KenM
But the trick to cleaning up this spill is to keep the work area wet - use a mop and wash the area thoroughly several times. If you see any residue when it starts to dry, wash it again several times.
I would not use Aggie's suggestion to wash the area with acetic acid - a simple wash with lots of fresh water should suffice. After the area has dried, if you are still concerned, seal off the area of the spill by repainting the area or replacing the flooring, but that may not need to done with a thorough water wash.
You should probably wash your shoes and the clothing that you were wearing while cleaning up the spill, to remove any contamination from them. After all, why clean up the spill on the floor and then track it back into the house, where you actually live...