Inconsistency In Blood Count, Elevated RBC, Polycythemia. Could It Be A Result Of A Military Programme?

Hi my father retired from the military in 1991 and worked as a pilot out of Nellis Air Force Base for the last 22 years. He retired in May 2012. When he retired he started having inconsistencies with his blood counts. Extremely elevated RBCs that have been unexplainable to doctors. He s had really bad stomach issues for probably the last 15 years. He s been going to see a hematologist oncologist for the last year having his blood drawn many times a week and then reduced to a couple of times a month to reduce his RBC counts. He has been extremely sick for the last year and passed away this past Sunday due to unexplainable causes. My question is, do you think his condition could be due to his two tours in Vietnam as a pilot flying through the agent orange? We are trying to better understand this tragedy. I have noticed a lot of posts on the Internet in relation to elevated red blood cells leaving the physicians scratching their heads. I know he was diagnosed with polycythemia recently. Any help would be greatly appreciated. Thank you so much.