Well, whether there is or isn't a separate concern relative to the Potato Spindle Viroid, the article that seaeagle posted is perfectly clear, that the reasons for the ban in NZ is the concern for human health and the environment.
"“
Given the serious effects chlorothalonil can have on human health and the environment, initiating a Red Alert is another way for us to help protect New Zealand and New Zealanders from chemicals that we have concerns about,” says Dr Freeth."
Also I don't know of a ban in Canada, the wiki said that there are high levels of it found in PEI - where potatoes are the main crop - and that some fish kills in PEI had been caused by runoff of the stuff. So the spuds I buy here are likely contaminated with the same residues.
@Carolyn, just browsing I came on this link to "Toxnet" at the NLM. This one really does cite a lot of sources, and covers about everything!
https://toxnet.nlm.nih.gov/cgi-bin/s...rm+@DOCNO+1546