Prepare the copper same as for ferric chloride etching. I use
either acetate or PnP, whichever is handy, with equally good
results. That part of the process has been discussed a lot lately
so I won't go into it again.
As for the chemical itself, I use the same precautions as with
ferric chloride -- work under a fume hood, wear a mask and gloves,
etc. One should always get a copy of and read the relevant MSDS
sheet. Mine says "avoid runoff into ... sewers which lead into
waterways. Water runoff can cause environmental damage." And to
dispose "...according to local regulations." I live on 5 acres in
the country in Canada and have no idea what regs might apply in a
city or other countries.
I don't mean to minimize the risks in any way but as etchants go,
this one appears to be RELATIVELY benign. For me the main advantage
over ferric chloride lies in how much cleaner this process is.