"Safe", it seems, is subjective. In other posts you've mentioned the levels required to cause death, but sometimes "death" is not the worst that can result from exposure.
"In a two-generation study on rats over the effects of myclobutanil on reproduction, researchers found a decrease in pup weight gain, increased incidence of stillborns, and atrophy of the testes and prostate (#EPA). Myclobutanil is listed as a developmental toxin in the Toxics Release Inventory (#PANNA).
Chronic toxicity tests on rats found decreased body weight and changes to brain and spleen weight, in addition to reproductive effects (#EPA)."
Link
It also states that myclobutanil is environmentally mobile (found in surface water and rain). This means that it can leave the plant during transporation and that it is in the air you are breathing while watering the plants, don't forget about the dried particles that enter the air from the floor/walls/medium/plant surface/etc.
Just how much does it take to shrink your nuts/brain and cause erectile dysfunction (also attributed to pesticide use/exposure)? It wouldn't matter if the manufacturers answer to that was "1 US gallon", I don't want any amount of it near my person... for my dick's sake, I worry about grey matter as well (but to a much lesser extent than my man parts).
I know that you said that you haven't used it in a couple years, just keep this in mind if you ever go to reach for it (double entendre there).
I too have a "safe" method of eradicating PM, but my "safe" means that I can get it all over my person, drink it even, without any worries at all. I haven't seen PM since I stopped gathering genetics via "clone collecting", but if it ever pops up, I know exactly how to quickly resolve the issue.