Yes & no. They are synthetically produced; man-made. It is similar to taking an aspirin vs. willowbark infusion (salicin is a constituent of willowbark and a few other plants - the precursor to aspirin.)
Using compost (broken down organic matter) on a plant allows for natural, slow release - just like Mom nature planned
But b/c we live in an "I want it now"/instant gratification world synthetics allow for the quick fix. They are basically salt compounds containing naturally occuring nutrients (nitro, phos, pot, etc.) so they are immediately released - thus the almost overnight greening or blooming. However, using synthetics has its downside and excess salts carry with them many problems - but I will spare you from a plant nutrition lesson 
As for safety - it is up to you. I personally eat as much home grown and/or bought organic f's & v's as do my feeders, thus Luna, but that is my own choice; not only for putting fewer chemicals into my own and my animals bodies, but to avoid the environmental problems as well. But that is me 
To ward of a debate, I am not saying that all synthetically produced things are bad.
Probably more then you needed to know...
lele & her organic cham LOL!
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0.1 veiled - Luna
0.2 felines - Kyndra and Líta
1.0 African Clawed Frog - Skipper
0.5 Mad. Hissers (for summer - all girls, no little ones, whew!)