exclusion zone around the site and thousands have been evacuated around fukushima. but research about radiation poisoning is still in its infancy. most research comes from the atom bomb attacks in japan in 1945 and recently from the accident in chernobyl in 1986, where wide-spread contamination caused few casualties from the 600,000 exposed. >> the world health organization estimates 4,000. the sun kills 8,000 miles per hours alone per -- 8,000 americans alone per melanoma. >> it's measured in sieverts in your home you receive average dose of .0036 sieverts per year, unless you live at a higher altitude where you receive .0050 sieverts. flight crews in the northern latitude receive .0058 sieverts per year. the maximum allowed for nuclear workers is .05 sieverts. 4.0 sieverts is acknowledged to be a standard that would kill 50% of exposed population in 30 days.