Well, actually... the only mulch you'd be getting with arsenic in it would most likely come from your local landfill where they take treated pallets, grind them up and sell them back as "mulch". Or they'd be taking in lumber from demolition projects, etc. And that's if the lumber comes from commercial construction where the "old" treated lumber is still allow, containing chromated copper arsenate. The newer treated lumber available to home owners no longer is treated that way but basically has a large amount of copper in it for its treatment.
Any bagged mulch from the garden centers, box stores, etc, will most likely contain hardwood or softwood mulch and those won't have any treated lumber/arsenic in them. Keep in mind, arsenic is naturally present in nearly all soils but the type and quantity will not have deleterious effects.
Lastly, you should also be comfortable using leaves, straw, even pine straw as a safe mulch if you choose to get away from any type of wood mulch. This will (unlike cedar mulch) break down faster and feed your soil, the soil life, and contribute to feeding your fruit trees. And if you're a new fruit tree grower it is best to keep the mulch, whichever kind you choose to use, a few inches away from the trunks of your trees so you don't set up more troubles.
Best to you and yours!
Shoe
