May not have been the primers.
This abstract discusses metal toxicity, in particular from copper and zinc, which are the components of jacket material regardless of primer or propellant. I could see how a frangible bullet might release more Cu particulates on its journey down the barrel.
https://www.researchgate.net/publica..._Cell_Cultures
Passage in here suggests it may not have been the metals in the military training scenario. And Norway, not Sweden.
https://www.bbc.com/news/magazine-19116438
https://www.upi.com/Defense-News/201...7161335383393/
This one is focusing on propellant. Notes the compounds cited in the Norwegian experience discussed previously.
https://onlinelibrary.wiley.com/doi/...prep.201200021
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Related tangent: There was a new indoor range put up a few years ago, located extremely conveniently for me. At first, the ventilation was awesome. But they have not maintained the equipment well, and the AQ has decayed to the point that it's not much better than many others around town. I had a sweetheart deal on membership due to signing up pre-opening, but I let it lapse due to the AQ, among other things. Last time I went, I got kinda used to the smell before my session was over, but noticed I could still smell it a couple hours after leaving.
It's Athena or Saddle River for me from now on, if shooting indoors in Houston.
Hot Wells has shut down everything but shotgun. I should take some skeet lessons.