These data together provide clear evidence that molluscicides containing iron phosphate combined with either EDTA or EDDS can have adverse effects on earthworm activity or growth and may possibly be toxic to them.
FWIW, it is the chelating agent EDTA in Sluggo that creates any toxicity. Otherwise consumption of the iron phosphate in this and other similar molluscicides would be as "safe" and non-offensive for slugs and snails as it supposedly is for any other creatures.
This product should be used with caution around pets and kids as iron poisoning is a distinct possibiity if consumed in quantity (i.e., keep bags/containers secure and out of reach).