"Building an arch in proximity to a nuclear leak has its fair share of challenges. Before construction of the NSC began, workers helped decontaminate the area by removing the top layer of soil along with any potential radioactive material that might have been left behind. After that they poured a layer of concrete over a large area and erected a wall closest to the sarcophagus. During peak construction times, there are around 1,200 employees at the site from over 27 nations. To ensure they are safe from radiation exposure, the millisievert (mSv), or the average accumulated back-ground radiation exposure dose, is closely monitored. The average dental X-ray exposes someone to about 0.014 mSv. A worker in the New Safe Confinement arch is exposed to 0.0075 mSv’s per hour. A new, state-of-the-art changing facility with a capacity for 1,430 workers was built onsite and offers medical and radiation protection facilities. There also is an ambulance on duty, in case of emergencies. In addition, the Chernobyl Shelter Fund provides training facilities, radiation monitoring and medical equipment as well as a medical screening program for the workers, according to the EBRD. All work on site is carried out under the strictest health and safety regulations by a specially trained workforce, according to Bouygues and Vinci. So far there has not been a single case of exposure beyond permissible limits, according to the EBRD."