I have plenty of facts and data to "back up" the claim that shooting in an indoor range without a respirator will elevate your serum (blood) lead levels. In my case, it's about 10 years of records tracking changes in my own serum lead. I used to spend about 4 evenings a week in indoor ranges. My all-time high was 31 mcg/dl, reduced to 16 mcg/dl after one year of respirator use, then to about 8 mcg/dl a year later. Bounced back up to 16 mcg/dl when I thought newer and stronger exhaust fans at our range would solve the problem (they didn't). I put the respirator back on, and the levels came down again. I also have data from others on my shooting team(s) that show the same, the worst case being one individual at over 60 mcg/dl, reduced similarly with respirator use.

Your are correct about washing after handling lead and lead-contaminated objects as a good means of decreasing exposure to environmental lead.

I spent many years working as an environmental, safety & health consultant and know a good bit more about this stuff than the average bear. The lead issue is real - sure, there are plenty of other more important health risks, but it's real, and can be avoided with a few relatively simple behavioral modifications.