Page "Photographic processing" Paragraph 49

Developing agents are commonly hydroxylated benzene compounds or aminated benzene compounds, and they are harmful to humans and experimental animals.

Some are mutagens.

They also have a large chemical oxygen demand ( COD ).

Ascorbic acid and its isomers, and other similar sugar derived reductone reducing agents are a viable substitute for many developing agents.

Developers using these compounds were actively patented in the US, Europe and Japan, until 1990s but the number of such patents is very low since late-1990s, when the digital era began.