Judging from the literature of the era, “fallout” was a major concern for the populace, and forced the citizens to spend their socializing time deep underground in protective bunkers. Here we see the forced, almost desperate gaiety of people whose world has been immeasurably poisoned, yet believe they must carry on as before.
We assume this work was one of a series that revealed the Mystery of the Party Quarts, a term we know only from the advertisements. The fellow in the foreground, with whom the viewer is supposed to identify, is pouring the sacramental lager into two glasses, not three. The man in the back may possibly consume a different beverage - a Seven and a Seven, perhaps - and then there will be sexual intercourse intended to repopulate the world.
Or maybe they’ll just play canasta.