Ok so the conversation on another thread about safe vs unsafe materials/reactions got me thinking, what useful unsafe materials or technology is missing from DF that was known historically. I'm not looking for game data, just a note saying hey this is unsafe technology/substance was used but it is missing in DF. I may or may not do a mod for this (I don't really have the time or desire to produce or maintain it). So of course I'll start.
Asbestos - 6 types of fibrous rock that were fire proof and could be made into clothing and refractory materials (forge/smelter/blast furnace bricks and crucibles) (carcinogen)
Arsenical Bronze - Copper + 1+% Arsenic (toxic), comparable to Tin Bronze, but need work hardening (tin bronze is naturally hard), could be made into sheets much easier, hard to get the alloy portions correct (arsenic will oxidize and boil off during smelting, producing toxic fumes and if heated to long revert to copper). Arsenic was much easier to obtain and was found in copper ores.
Orpiment - yellow pigments, medicine in China (toxic)
Realgar - pigment, medicine in China and Roman Empire (toxic)
Mercury - refining of gold and silver, extraction of other difficult ores (toxic)
cinnabar - ore of mercury, source of vermillion pigment, Chinese medicine (toxic)
lead - numerous pigments (paint and cosmetics), pewter (pewter formulas used in game are modern formulas), Roman pipes and building construction (used to secure lrion spikes joining stone blocks)), ceramic glazes, stained glass windows (solder), Glass (type of crystal glass), food preservative (both as a substance added and as a container sealant), sling (and firearm) ammunition, farming (pesticides). (toxic)
pitchblende (uranium dioxide) - Uranium (aka Vaseline) glass (pale yellowish-green glass), ceramic glazes (colors: reduction atmosphere green to black, oxidation yellow to orange). ((mildly) radioactive)
Antimony (stibnite) - cosmetics, plumbing, pewter, alloy metals, ceramic glaze, pottery, glass production (toxic)
cobalt (cobaltite) - pigments (glass, glazes and ceramics), cosmetics, alloy metals. (toxic in medium to high doses, mutagenic and carcinogenic, oddly essential for life/vitamin B12)
narcotics - variety of plants, Tobacco, Poppies (opiates), Coca (cocaine), others.
Existing materials with harmful effects but no new uses.
nickel - alloy metals (toxic/carcinogen/dermatitis)
zinc - alloy metals (essential for life, induced copper deficiency, high dosage neurotoxin)