Thank you for your question concerning lead paint on the radiators in your home. Cast iron radiators were used for steam and hot water heat. Neither produces heat high enough to vaporize lead oxide.
- Lead oxide begins to vaporize at temperatures higher than 525-degrees Fahrenheit.
- So vapors are not something that should concern you.
You should be concerned with lead paint chips and/or lead paint dust though. Keep the painted surfaces in good repair. If they start to oxidize, creating dust or chips have them repainted to protect the health of your family.
Removing lead-based paint from cast iron radiators is not a homeowner experience. While lead paint can be remove chemically in place it is a job for a professional.
In the interim keep the paint in good condition and sleep well.
For more information:
Read "I am concerned about lead. I know our house has lots of it." a Q&A answered by Cynthia Phakos.