I mix using only diketone free flavors, and I mix all of my own flavors. I don't buy .... from Premium vendors who don't even list the lab certicication on the bottle. Mix your own, and be safe. And stay under 100 watts for god sakes.
Do you test your DIY? That's the only way I'm aware of that can claim diacetyl / diketone free. Precussers can combine to create a reaction when mixed. Steeping can accelerate that reaction. Nicotine can contain precussers. I haven't seen a nic supplier that tests for diketones yet, but there goes the idea that unflavored is free from diketones..
I seriously think this does need further study, but the idea that all juices need to be diketone free has been blown out of proportion and maybe impossible at this moment in time. I think it's quite likely many juices are submitted for testing when they are freshly mixed, getting low results and as the juice ages, diketones grows = part of the reason many tast better after steeping. If the same juice was tested a month or 3 months later the results would show a very different amount of diketones present. This is my therory after reviewing what brewers know about diacetyl forming.
The jury is still out on how much of a health risk diacetyl is to begin with. The OSHA regs came at the request of a labor union, not scientific studies. That may still be valid however, but it's not conclusive. Medicine is still gathering information on how much a threat OB is, whether it's been under dignosned in the past, particle sizes, actions in the lungs and it could be a combination of factors. I have seen many medical assumptions in medicine that sound as if they have the answer turn out to be wrong upon further investigation/clinical studies. We just don't know yet.
Do I dare mention there was a recent study showing butyric acid aids in the asorbtion of diketones?
Sometimes jumping on the diactyl causing harm bandwagon seems very close to what ANTZ is doing to ecigs. They are drawing conclusions without looking into the situation further. Of course everyone should have the facts to make their own choice and if a manufacturer knowingly is selling juice with diketones in it, they should tell the consumer - but I'm not convinced that manufacturers are doing that when they test freshly mixed juice and the results are negative, but the results are positive from another lab at a later date. Why would a lab lie? Are they falsifying results?