[JBrunner]

"The dose makes the poison" -- a statement first made in the 1600s, I think, and that still holds today for most substances (some hormone-like organic small molecules violate the rule). Selenium is indeed considered a "micronutrient" -- many otherwise toxic elements are too -- but IMO you can't use that fact to diminish the potential health risks of working with these kinds of substances.

Indeed. If you eat enough fresh green spinach, it will kill you.

FWIW- I always wear nitrile gloves in the darkroom, have good ventilation, and wear a mask when mixing powders. These measures are common sense. Some of the things in my darkroom are toxic, so I eliminate as much exposure as possible.

Common sense in personal protection, safe handling, responsible storage, and proper disposal of chemicals goes a long way, very much farther IMHO than worrying about the individual toxicity of a given compound. That said, it behooves one to know what one is handling, as well.

J