I am a carbon printer so my opinion may be biased. But in my opinion there is very little risk involved with dichromates in carbon printing. The major risks are ingestion (not likely that you would drink it) and breathing the powder when making a solution, which can be easily avoided. After the dichromate is in solution the risk is primarily dermatolgical, so you wear gloves.
The dichromate is out of the print after warm water development and clearing with sodium bisulfite, or sodium or potassium metabisulfite.
In practice you use very little dichromate in carbon printing. For example, to sensitize a 9X12 tissue I use only 8ml of a 10% ammonium dichromate solution. That is with brush sensitizing. Some people sensitizer in a tray and use more, but it is not necessary.
Originally Posted by ronlamarsh