I'm an environmental consultant and have dealt extensively with lead-based paint issues. Here are my thoughts:
1. You're an adult so you would need a very large dose to cause you issues. I doubt that sanding waste from a bike frame would represent enough volume to provide you a significant dose. If you have no symptoms (google them), don't worry about it. However, children are highly susceptible to permanent neurological impacts from paint dust. Be sure that you wet mop or HEPA vacuum (NOT regular vacuum) any areas where you sanded to get rid of the dust.
2. Lead-based paint is primarily found on house paints, structure paints, and ship paints, with lead content decreasing through the years before complete bans in the 1980s. There's a good chance that there is no lead or very low lead on your bike frame.It's more likely that lead-based paint dust from window and door trim from your pre-1990s house have impacted the floors and areas around your house than your bike frame has.
Last edited by davester; 12-24-20 at 08:50 PM.