Anon is right; the piers were designed this way to accommodate a ravine. If these were actually falling over, the steel bents would be lifted off of the piers on one side. It's plain to see that the bents are built with an offset at the bottom to attach to the concrete piers.
I'm pretty sure those piers are just skewed to compensate for the elevation, it's just the fact that the photograph is also askew that makes it appear as if they're falling over.
Personally I think that this bridge isn't safe for pedestrians or anything else because it's all rusted to heck and the piers are falling over.
In addition, I would like to add that just because it's rusty doesn't mean it's not safe. Rust is common. When it becomes more advanced corrosion, eating through significant portions of the structure or internal bracing, then it's serious. I haven't personally seen this structure yet, but it doesn't appear to be serious.