This fact sheet addresses four common questions concerning residual contamination. Q: What is residual contamination? A: Radioactive material or beryllium that remains at a work site after activities related to nuclear weapons production has stopped. Q: How many sites did NIOSH evaluate for residual contamination? A: 219 Atomic Weapons Employer work sites for residual radioactive contamination and 72 Beryllium-vendor work sites for residual beryllium contamination. Q: Should I be concerned about residual radioactive contamination? A: We would have to know the specifics of your case to answer that question. Generally, exposures from residual contamination are lower than exposures that occurred during the covered work period. The highest exposure occurs during active handling and processing of radioactive materials. Q: What if NIOSH evaluated residual, radioactive contamination at my work site but my dose reconstruction has already been finished and I did not receive payment? A: NIOSH will review your dose reconstruction to see if the information on residual contamination will make a favorable difference in your dose reconstruction. If so, NIOSH will re-work the dose reconstruction to include that information.