Originally posted by lytrytyr I understand the Wiki entry quite well (strong background in chemistry) and still fail to see the issue for most home darkroom use. Mitigation for commercial operations is well-established, is detailed in the article, and is mandated by law based on the volume of waste they produce. I could answer point-by-point for each of the substances listed, but it would be wasted key-strokes.
To be quite honest, a home darkroom for B&W* present less risk than the witches brew of cleaning supplies, pharmaceuticals, dietary supplements, cosmetics, and partially processed food (feces) that constitute normal household sewage**.
Steve
* Home processing for C41 color is marginally more of a problem, but only marginally.
** Almost all of the listed chemicals in the Wikipedia section are common constituents of household waste streams. The exceptions might be the reducing agents used in some developers. For what its worth, hydroquinone (reducing agent in HC 110 developer) is found naturally in beer and coffee.