This is a stupid study by a bunch of “challenged” individuals called epidemiologists who will come up with some statistical method to prove whatever result they want. Most of the ones I know are flaming libs and tree huggers. They love Bambi.
There is one paper that I am aware of where a bullet was left in the synovial fluid of a large joint which resulted in lead poisoning. It was hypothesized that the hyaluronic acid in the synovial fluid decreased the pH just enough to increase the solubility of the lead and increase its normal absorption rate from none to a little.
Glad to hear that, I never shoot them in the joints, so I'm OK.