Lead poisoning symptoms take weeks to months to emerge. It would show in a blood sample.

Not really a concern outdoors. Ben Stoeger, world shooting champion and firearms trainer who shoots a lot, said his blood lead levels are normal and attributes it to shooting outdoors.

n=1

One counterexample may be sufficient to disprove a hypothesis. If you claim a certain quadratic equation has no roots and I give you one root, you can’t say “n=1”.

It is a strong datapoint, but he may be using meaningfully different weapons / ammo compared to seals.

Math avoids this kind of uncertainty.

The guns are different, but primers are mostly the same.

Claims about populations in medicine are not very much like math theorems. There are too many exceptions for a single case study to settle the question.

i don't think that is true of lead poisoning

plenty of troops shooting a lot outdoors. enlisted grunts shooting a machine guns, etc. lots of civilian shooters as well.

lead is also easy to detect in blood, or via things like hair samples. no doubt SF types are getting more residue than most, but again fairly easy to notice