Yes, there have been a few studies. There are not many studies on that, but there has been some proof that the heating of some of these flavourings, what we call thermal decomposition, produces some cytotoxic products. That is true, but it's very difficult to gauge exactly what the importance is in terms of the final impact on health.
These comments were made more than anything to indicate that there are some concerns about toxics and cytotoxics that should be taken into account, especially as Professor Britton was saying, in order to regulate these products, to maximize the benefits but also to minimize their harms.
You can only do that through regulation. That's why one of the recommendations from the WHO is to minimize those harms through appropriate regulation and not on a voluntary basis.