Could PNP (Silicon) transistor be toxic when exposed to air\light?
The semiconductor itself is harmless, but, since you heard some sizzling, it is possible that a getter, such as an alkali metal, was in the metal-cased component. There is a patent for getters to be used with semiconductors, http://patentimages.storage.googleapis.com/pdfs/US3259490.pdf, though I've never seen one in use.

More likely, you heard the glass header breaking.