On Tue, 8 Jul 2008 16:04:56 +0100, Rusty Hinge 2
wrote:

The message
from "Emrys Davies" contains these words:

I know how glyphosate works on a plant and the soil but I am wondering
if it is safe in the following circumstances:

If it is applied to weeds on concrete paths, allowed to completely dry
and then it rains is there a danger that the residue can then be carried
on shoes onto grassed areas and thus cause damage?

No. Once in the soil it becomes locked-in and harmless.

Incidentally, on the Farming Programme recently (IIRC) I heard a farmer
refer to it repeatedly as 'glyphosphate'...


The OP did say it was on concrete paths rather than on soil, but I
think the answer will be the same because having dried out and then
been further diluted by rain it will be very much weakened.
I think the farmer's mistake is because he will be used to dealing
with other sorts of phosphates as fertilisers.