Well, those people may be living longer, if you are speaking of the russians who are effectively finding refugee in the zone from various crap that happens in Russia. I mean, if the mafia is after you, you may go to zone and avoid getting killed by mafia, and thus live longer.
It really is reminiscent of the anthropogenic global warming. The industry always denies effects of the pollutants, tries to bribe scientists with 'research grants' (some, successfully), etc. The people in zone living longer? It's primarily old folks in the zone! (And just a very few young folks whom are hiding from something) No **** if you take average age, or average age at death even, it'll be larger.