We know that some sheep-dip chemicals have caused problems, but there's very little evidence that agro-chemicals in general are a causitive problem for mental ill health.

Suicide prevention talks about access to means and methods.

Internationally agro-chemicals are a problem because they're one of the most commonly used methods for death by suicide.

But in the US there's easy access to guns, and so restricting access to agro-chemcials is unlikely to have much effect.