She asks: “I’m also making one tiny addition to Harmful Organisms and Substances. After ‘harmful substances at toxic levels,’ I’m adding, ‘including mold, EMF, and all environmental hazards’ because I’m particularly concerned with those.” Is this addition helpful, or risking confinement of the prayer to the stated list alone?

There is no great danger in adding the extra examples because you are stating that you are including these with the other categories and this will be construed by the divine realm as serving as some examples, albeit of greater concern to the requester than others unstated. You are allowed to request anything you like but in the case of ambiguity, we will do less and not more. So this would be an example of a practitioner’s particular list of bad actors representing things to be given a high priority but not meant to be comprehensive, so it is safe as is.