McCain may have -- probably was -- exposed to Agent Orange. There are several appeals made to the Board of Veterans Appeals that uphold a possible connection between AO exposure and glioblastoma.

The cancer senator McCain has been diagnosed with is glioblastoma multiforme (GBM). Despite extensive research, no one has been able to find a cause. GBM is more likely to occur in older people, but there are plenty of young cases as well. Everything from pesticide exposure to diets has been examined in the hunt for a cause without any significant links having been found. There is zero evidence for Agent Orange, a mixture of the herbicides 2,4-D and 2,4,5-T being a factor in GBM. Of course there will be a number of Vietnam vets who have been afflicted with GBM but that is because there are a lot of Vietnam vets. The question is whether the incidence of GBM is greater among the veterans than the general population. There is no indication that this is so. One study did suggest an association with occupational exposure to magnetic fields. Researchers determined that telephone cable splicers, welders, electricians and electric utility workers had a slightly higher incidence, but there were confounding variables and the study was never duplicated. Basically, the cause of this dreadful disease is just not known.