I don;t have time this moment to read the blog, but here's my take from past readings:
iron phosphate: very low toxicity
EDTA: very low toxicity (it's used in toothpaste among othe things.
BUT, iron phosphate PLUS EDTA: slight toxicity. The EDTA helps the iron enter through the guts of snails and mammals, so that it is POSSIBLE to get a harmfull dose if you work at it.
I know that my perspective on toxicity is unlike most people's. I used to work in a chemical factory, and when we said "toxic", we meant either fall-down-promptly, burns-your-hair-off, or Class 5 carcinogen. f it was something where it took chronic exposure over months to have a moderate effect, yeah, we avoided exposure, but didn't think of those as "toxic". Just "not good to absorb too much".
So YMMV. And people outside the chemical industry have the luxury of treating everything even slightly toxic as "AVOID COMPLETELY".
Funny: at that job I was considered the nut who wore ALL the protective gear, and was laughed at for us. But I read the scientific papers about our carcinogens and knew they were not like "the nitrites in hot dogs", as management wanted us to believe.
But among "green" gardeners, I'm fairly far out in the direction of asking "well, just HOW toxic is that?" before I worry.
