Taking another course from the original question, if the toxicity of hydroquinone is a concern, you might want to investigate using ascorbic acid, or one of its variants, instead. You can usually achieve similar results with ascorbic acid, although you'll need to adjust quantities of various ingredients, particularly if you use ascorbic acid rather than sodium ascorbate. (Note that "similar" doesn't mean "identical;" if you're very picky about your developers you may find the subtle differences unacceptable.) APUG members Ryuji Suzuki and Pat Gainer have both published several popular formulas that use ascorbic acid, and a few commercial products use it, too (Kodak XTOL, Agfa Neutol Plus, and Silvergrain Tektol spring to mind).