Even water is toxic if you have too much. How do we keep a potentially harmful but necessary nutrient like boric acid at safe levels in our buildings and our bodies?
What do you do about a substance that is a biologically necessary trace nutrient, long considered nontoxic, and in a multitude of products--but that is also now listed on a major European Union chemical hazard list due to evidence that it is toxic for reproduction?
It's one of those riddles that I can imagine toxicologists love to play with but that drives everyone else crazy. Here's the story, and our approach to answering the riddle--for now.