At the moment, anyone can easily claim their juice is organic. It doesn't actually mean anything. The nicotine, we know, is just nicotine and is not harmful (though it is addictive). The vegetable glycerin/propylene glycol CAN be broken down into two aldehydes (bad for you, carcinogenic) if the temperature is too high. The flavorings are the only thing truly in question.
The short answer: The information doesn't exist to say if there's a "safe" e-liquid out there.
The long answer:
There is quite a lot of worry about diketones nowadays, although Dr. F's most recent study seems to show that we were inhaling far more diketones as cigarette smokers than we ever will be inhaling with e-liquid. That said, he does see diketones as an avoidable risk in juice, and is pushing for the removal of all diketones from e-liquid.
Diketones are a set of molecules that are common in flavorings. In particular, the most common ones, are diacetyl and acetylacetone. These can cause bronchiolitis obliterans (complete destruction of the lungs) in high enough doses. Factory workers who were exposed to the stuff for long periods of time, 8 hours a day, suffered many negative side effects. So as you can guess, this stuff is not good, and should be avoided at all costs. Diketones tend to give juices a creamy/custardy/eggy/buttery taste. There are also a slew of other flavorings that are questionable in terms of what they may or may not do down the line. 10 years from now, we might find out that some common flavoring is extremely harmful to you. The science just hasn't gotten there, and vaping is still relatively new.
Some companies claim that they're able to achieve the same custardy/creamy flavor profiles without the use of any diketones (usually they specifically name diacetyl and acetylacetone). The problem is, this is a VERY hard thing to prove. Some companies get their juice lab-tested, but in this case, they usually only test for one specific diketone (ie: ONLY diacetyl, or ONLY acetylacetone, or both) which leaves out the slew of other molecules that we might not want to be inhaling.
Maybe in the future, once we have a solid list of the chemicals to avoid in flavorings, we'll be able to buy at-home "test kits". Dip a strip in a bit of e-liquid and if it turns x color, it has y ingredient. I don't know. For now, it's kind of a toss-up. For me, personally, I try to stay away from the creamy/custardy juices whether or not the manufacturer tests the juice for diacetyl or not. I tend to stick to NET juices and fruity juices (both of which still may have nasty stuff in it, for all we know), but I do have some "guilty pleasure" e-liquids that are certainly in the "diketone" flavor profile (cheesecake, strawberry custard, some other delicious choices).
Hope that helps. Welcome to ECF!