Hope you guys aren't too tiered of me putting up suggestions, because I have no plans on stopping. Thanks to toady for reading our suggestions, not many devs do stuff like this.
I did a search and I couldn't find this suggestion anywhere, but let me know if I missed something.
Many metals and other substances in real life are poisonous, one theory about how Rome fell is the massive amount of lead they used in their water systems. However in dwarf fortress there is no lead poisoning, or any poisoning at all that doesn't come from creatures (as far as I know). This of course, could be explained away by saying dwarfs are immune because they live underground, but what fun is that? So I'd like to propose poisonous environments and objects. Here are a few syndromes I thought up, if you have any you'd like to add please do so. These are only ideas, and I don't expect to see all of them (or any really, unless toady likes it) happen.
Argyria: Caused by wearing +finely crafted+ silver jewelry or lower, or using +finely-crafted+ or lower silver weapons for a long time. Areas in contact with silver turn blue and become more vulnerable to damage. Goes away with time. Can be fixed by smelting into sterling silver or nickle silver. I would also like to suggest sterling silver be made weapons-grade to balance this.
Arsenic poisoning: Results from drinking from a aquifer in an area that has a sulfuric compound in the rock or soil above it, near a volcano, or nearby metal ores. Causes dizziness and drowsiness at first, then later vomiting, blood vomit and pain. In the final stages lungs, kidneys, and livers break down entirely, resulting in death.
Copper poisoning: Excessive use of copper in Barrels, goblets, kitchens, butcher shops, fisheries, and stills can lead to copper poisoning. Only causes vomiting at first, but continued exposure can make dwarfs vomit blood and irritable, leading to sudden bad thoughts and even tantrums.
Iron poisoning: Caused the same way as copper poisoning. Note that this is NOT Tetanus. Causes pain and vomiting, and blood vomiting at first, then disappears for a short time. If not treated immediately and stopped from eating food made at iron kitchens or drinking iron goblets, it re-emerges as liver and brain damage (permanent, but not deadly) if left alone to long, the dwarf COULD die from liver failure.
Lead Poisoning: Caused by having lead objects associated with food/drink. Additionally, if a dwarf is hit by any lead object and begins bleeding, there is a chance to get stage 1 lead poisoning. At first, it causes sadness, pain, and loss of appetite. As it progresses it causes kidney failure, anger, confusion, pain, and sterilization in men. At it's final stages it can cause brain damage, dehydration, loss of grip/ability to stand (hands and feet go numb) and complete insanity. Eventual death by brain damage (swelling)
Mercury poisoning: Not sure how it would be caused, I'm just listing it for fun. Symptoms include loss of vision, hearing, and/or speech, as well as general confusion depending on amount of exposure.
Nickle Poisoning: Caused by drinking out of nickle goblets, barrels, or stills, but takes a long time to build up. (IOW you should be fine as long as you don't make every single goblet and barrel out of nickle) Causes Anger, dizzyness, and lack of sleep. Later stages cause pain, rapid dehydration, and eventually death unless treated. Can be fixed by smelting into nickle-silver.
Poison Ivy/Oak: Grows naturally in some areas. Gives thinking creatures bad thoughts and blisters on exposed skin. NPCs will try to path around it like a wall, but will go through if there is no other way
Tetanus or Lockjaw: While iron rust hasn't been introduced yet, I believe toady said it was possible for a future update. Randomly caused by being injured with a rusty iron object(%chance of getting sick) A Dwarf with Lockjaw will randomly go into spasms where they will lay on the ground and flail their limbs around with indwarven strength. It starts off with low pain, but after a week it developed into uncontrolled spasms can tear at the dwarfs muscles, break his bones, and presents a major hazard to anyone close by, as well as rapid dehydration. While tetanus itself is survivable, the spasms often end up killing dwarfs who break their own backs or necks or collapse their lungs, and doctors helping them are at risk of having their heads knocked off.
Tin poisoning: Caused by storing food and drink in tin barrels for to long. Causes minor pain, vomiting, dizzyness, and chills (coldness bad thought? Idk)
Zinc Poisoning: Caused by repeatedly drinking out of zinc cups, barrels, or stills. Takes a long time to build up. Pain and vomiting.
Things that would have to be done:
Food items need to be able to be "tainted" without the player knowing what ones are toxic and what's safe to eat. Each food item taken to say, a lead kitchen would haft to leave with either:
A. a % chance of making a dwarf sick (each meal has a .5% or so chance to give lead poisoning)
B. a certain "toxicity value" that is applied to the food that when eaten is subtracted from a dwarfs "tolerance level". This stat would gain value over time untill it hit a cap affected by physical modifiers, but when it reached 0 the dwarf would become sick, and if he continued it would go down into the negatives. For instance, if Urist has a lead tolerance level of 500, and each meal has a toxic level of 50, it would take 10 meals cooked at the lead kitchen to make Urist sick, and further meals would make him take longer to recover. The longer he is below 0, the sicker he will get.
Of course, you need a different tolerance level for each metal and for poison oak, as different metals need more or less to make people sick. Rust, if ever implemented, would do better with the % chance of sickness than a tolerance level, however.
Wow I spent way longer writing this than I thought I would. Thanks for reading this and be sure to let me know what you think.