All of this furor claiming that A&T gave no reference.
Well, if you read A&T, you would find that they DID give a reference. It is a citation by Gordon Hutchings who said that "They may be the most toxic chemicals in the darkroom". I would personally amend that to say "second to selenium".
None of the above are severly toxic if, as Ian has pointed out, you observe safe handling procedures in mixing, use and disposal.