The safety of railroad proximity?

I've been considering the issue of foraging while walking along an active railroad. Does anyone know about issues of environmental contamination (either from the materials used in construction of the railroad or the running of the trains) and how that factors into safe foraging distances?

I've found several admonitions not to forage "adjacent" to railroads (like this one: https://www.saltandprepper.com/learn/food/urban-foraging) but nothing that defines how big a space to exclude with any authority. (That document does say to leave a 30-foot buffer from roads.)

I wouldn't forage too close to it.

No idea what they were spraying from that pretty yellow trundler, but it's a fair bet it counts as toxic gick...

In the USA what really concerns me RR wise are those trails that follow extinct RR beds that were in active use 40+ years ago. There is simply no way to know what the trains were hauling in the 1920s, 30s, etc. not to mention what undocumented mishaps took place. Of course, there is the issue of RR ties.

Railroads spray a gnarly mixture of stuffs to keep down vegetative growth for long time periods. I believe spray easements can go out about a hundred foot from the track but actual treated zone would be something around thirty foot out from the tracks.

I only harvest plants I don’t tend to find in any other convenient places, like prickly ash. This is however an inactive, abandoned railroad, which likely was no longer in use by the time that sort of thing came around. It still may have some lingering ickiness from the coal, but it has been a while.