I am not convinced of there being a vast risk from pepsi, etc. from 4-Me-imidazole...
http://ntp.niehs.nih.gov/index.cfm?objectid=9B956B07-F1F6-975E-79BBCDCCD57001C8Study did find some evidence amongst the highest dosed rats, but at the same time, also studies (I think this one) found that there were also certain decreases in cancers that were statistically greater than allowed for by the decrease in body weight observed at the highest doses.
Bearing in mind also, that these studies used several hundred mg/kg of (rat/mouse) body weight. Average rat weighs between 7-800g-1kg or so (for a really big rat, top end)...whereas a can of the drinks in question, according to wikipedia may contain somewhat over 100mcg.
http://en.wikipedia.org/wiki/4-MethylimidazoleSome of the pubmed articles make me tend to think this is overblown, and that the effects seen may even be species specific, rat hepatic metabolic pathways are somewhat different than those of primates. And without incubation with liver enzymes, seemingly 4-MI didn't appear to cause changes in rat or mouse bone marrow or erythrocytes. Studies (Salmonella typhimurium) for genotoxic properties came up negative.
IMO one would die of caffeine poisoning, or alternately, drowning in coke, LONG before they started to see ill effects from consumption of 4-methylimidazole.
And whats surprising about grumpy going through 1.5-2l of coke a day? granted its probably not HEALTHY but its not difficult to do. I practically live off fizzy crap and go through at LEAST one 2l bottle of fizzy shite a day, two when its hot. And I always have a couple of bottles beside my bed for when I get thirsty at night and don't fancy getting out of bed.