Glyphosate breaks down to aminomethylphosphonic acid.
Glyphosate and aminomethylphosphonic acid have about the same toxicity according to PESTICIDE RESIDUES IN FOOD - 1997:
AMPA was no more toxic than glyphosate. Similar effects were often found, except for the lesions in the salivary gland seen in the 90-day studies of
toxicity and carcinogenicity with glyphosate in mice nad [sic] rats from the
US national Toxicology Program and the cataracts induced by glyphosate
in a two-year toxicity study in rats. Such effects were not seen in
other studies with glyphosate or AMPA.