Hi Janina. When you are dealing with chemicals like this, you are always in the position that most people will not react at all and a few might have a reaction. As a general statement, your government is more restrictive than ours is. Both governments have done a pretty good job in keeping out products that are harmful to most people. Pretty much, if you can buy it commercially, it will be pretty safe. If a manufacturer knows that he will be sued for everything it owns and everything it ever had, they would not be too smart to knowingly put a dangerous product on the market.
I don't know a lot about log cabins but I do know that there are a lot of magazines about them on the news stand. I'm sure that they have articles and their website have indexes and more information on this.
The safest system that I have seen was on the *** **** boat storage series. Plywood panels with foam between 2 sheets of plywood were attached to the rafters. Since this was more on the outside of the roof than on the inside, I would think that any fumes from the foam would go up and out and not down and into the house. Your particular roof structure would dictate if you could use this system and how much work it would be to install. Log cabins move a lot too so the manufacturer should be questioned if the panels will adapt to the movement.