I use these troughs for planting, have so for years.
Here in Germany, they are the cheapest alternative to big pots. To be honest, I am not sure on the aspect of possible leakage of the material. However, it can't be really dangerous as many people use them and show pictures and I hear no warnings, as in the case of wooden sleepers which were used some decades ago but which are not used anymore due to the dangerous coating they have.
I will keep my eyes open and post here if I find something definitive.
I am only one, but still I am one. I cannot do everything, but still I can do something; and because I cannot do everything, I will not refuse to do something that I can do. (E.E.Hale)
Acetylsalicylic acid is aspirin. This could be handy too: