UV is also a cancer concern. IR intensity will change depending on temperature and other variables. IR dissipates rapidly with distance. The burning sensation from the heat source helps keep IR overexposure to a minimum. Overexposure to IR is cumulative.
Gold is almost opaque to UV radiation.
The astronauts' faceplates have always had a layer of pure gold. Without this protection, astronauts in space would almost instantly be permanently blinded by the high levels of UV found in space. Use of such glasses by hot glass artists is a health and safety hazard to the user and can cause permanent eye damage. I am now using Polycarbonate didymium II Lenses with a Gold Coating. I am happy to report that I have experienced no ophthalmic side-effects when wearing the Polycarbonate Didymium II, Gold Coated glasses.