A thermonuclear test by North Korea was inadequately performed on September 3, 2017, greatly weakening site ground structure and integrity. This raises the risk of land slides and structural collapse, and thus, the risk of release of radioactive materials into the environment.
Of particular concern are radioisotopes such as strontium-90 and caesium-137, which are long lived, and can be ingested through food and water.
The dispersion of such radioactive materials in the event of structural collapse, and extent of fallout on a global scale, would be determined, in part, by meteorological patterns, including the path of the jet stream.
Typical historical jet stream patterns suggest the regions most affected by a potential fallout would be Japan, immediately followed by Vancouver Island and the Vancouver/Lower Mainland area (British Columbia, Canada). Variations in jet stream patterns could also result in substantial fallout in Alaska and the Western United States.