"...I don't think so; can you explain in more detail?"

"Each caste has separate jobs - I don't know how that's covered in Learning Friends, it's aimed at an age where most information it's educating the audience on is fairly generic. Red jobs are dealing with wastewater plumbing, corpses, and garbage, as well as any functions internal to the neighborhood, like the doctor you saw."

"I see. And 'polluted'," he echoes the word, "is a shared property of wastewater plumbing, corpses, and garbage? I'll admit my first instinct is to treat the problem as an alchemical one..."

"A shared property of those things and also us."

"A property of you because you interact with those things?"

"And have for generations."

"...as I said, I have an alchemist's instincts about this... would it help you at all, do you think, if it turned out that alchemy could remove that property from you, without otherwise affecting you?"

"...probably. That is, it would help in a - vacuum, but it would leave it unclear where we would go on from there."

"How so?"

"If we were still members of our caste, we'd continue doing red jobs. It'd need more magic as maintenance, or at least we'd have to learn procedures for getting ourselves clean after work every day. If we continue doing red jobs, it's not clear if the clean attitude toward us would change much."

"Not even if I could prove to them that the alchemical procedure to remove the property was effective?"

"I don't have enough of a working model of how their thought processes on the subject work to be sure."

"Well, fair enough. And I don't even know if I can do it, I'd have to find out if the property is alchemically detectable or not first. Quite a lot of properties are, though."

"How would you find out?"

"I'd need alchemical tools—the same kind of glassware that works for chemistry is usually fine in a pinch—and some samples of things with and without the property, ideally things that are otherwise very similar to each other. The classic example in introductory alchemy is to leave out two trays of sand under the sky for a week, covering both to begin with and then uncovering one during the day and the other at night, and then alchemically process them to reveal the day-nature and night-nature respectively. Finding 'polluted'-nature will be harder because it's never been done before, but the basic idea is the same. I could do it very slowly using only natural alchemy, or much faster using infernal magic if you didn't mind the tools and samples ending up slightly infernal."

"Is there some reason to mind that?"

"Not in my opinion. It would be inconvenient for you if you ever had to bring those specific objects to Earth, but it seems very unlikely that you'll ever have the occasion to do that."

"We don't have chemistry glassware but the other castes - greens, specifically - will."

"Hmm. I'd like to verify the principle before I leave... I've done alchemy in a mundane kitchen before, in a real pinch, but given the nature of the property under investigation I don't really want to inflict it on anyone's kitchen... even if you all already have it, I imagine you still don't want some of those materials interacting with the tools you use to prepare food...?"

"We keep it away from the food, yes. We're not immune to disease transmission."

"I thought as much. Well—I'll leave it up to you, I think. If someone wants to lend their kitchen to the cause of finding out whether 'polluted'-nature can be alchemically isolated, I'm more than happy to try. I'll clean everything afterward as best I can, of course."

"There may be someone about to update their kitchen, or merge two apartments and repurpose one kitchen. I can find out." She taps her everything.

"Thank you, I appreciate it."

"How long should we expect you to stay in the neighborhood?"

"I'm not sure. Depending on how difficult it is to fix my leg, I might be walking unassisted within the week, or not for several."