In mid-January 2009, in advance of the inauguration of President Obama, a radiological survey of downtown Washington, DC was conducted at the request of the Secret Service.
No statistically significant man-made radiological activity was detected in the survey. Typical variations in natural background radiation were found, along with slightly elevated readings at the National World War II Memorial and elsewhere “caused by the building materials containing naturally occurring radioisotopes.”
See “Radiological Survey of Downtown Washington DC for the 2009 Presidential Inauguration” (large pdf), National Nuclear Security Administration, March 2009.------------------------------
The elevated readings at the National World War II Memorial are clearly shown on Page 8-9 (Figure 3 & 4). These variability is explained on Page 3...
The exposure rate variability observed within the map is typical of that produced by differences in geology, building and paving materials, and natural ground cover. The map in Figure 3 shows an exposure rate “bullseye” (5.2-7.0 uR/hr) caused by The National World War II Memorial. The elevated exposure rates from mobile data shown in Figure 4 are all of natural origin, caused by the building materials containing naturally occurring radioisotopes.