‘Not Roundup. Glyphosate is bad news.’
Allegedly, it’s got a bad press because a lot of the conspiracy nuts have got into. It’s a he’ll of a lot better than the weed killers it replaced. Unless you plan to drink it or bathe in it there’s not really an issue. It’s in the same may cause cancer category as bacon, burnt toast and coffee.
As others have said relay the gravel, a weed membrane will help but ultimately whack it with decent weed killer, ie roundup a couple of times a year. Only needs applying to any visible weeds, spraying the stone is a waste as it breaks down very quickly and he no residual weed killer effects.