Avoiding Poison Mushrooms (at the Market)

Not all edible organic mushrooms are safe to eat.  As +Paul Stamets points out in Mycelium Running - How Mushrooms Can Help Save the World, some mushrooms from China, for example, might have accumulated heavy metals from the high degree of ambient pollution where they were grown, yet still be considered organic. The draft standards for Certified Naturally Grown (CNG) mushrooms should mitigate this problem, as hyperaccumulation of heavy metals is built into its safeguards. To wit:

• Substrate may not be directly placed on any surface contaminated with heavy metals or other synthetic pollutants. 

For growers, CNG offers a clearer path to producing wholesome mushrooms than the organic program followed by most other agricultural producers. The National Organic Program (NOP) requirements may take measures beyond what should reasonably be applied to an organic mushroom farm, since fungi are nourished and cared for differently than plants and animals. However, if a beginning grower could convince themselves that they comply with the CNG standard, and try to align that with the NOP requirements, as long as they are not grossing over $5,000 of organic product sales per year, then they should self-certify as "organic." 

Beyond $5K in sales, official certification is required. At that point, I would probably opt for the CNG certification, rather than organic. After an inspection by one of the incumbent experts (possibly +Tradd Cotter, himself), as the only CNG grower in my area (the closest is vegetable grower, Working Over Thyme Farm in Brandywine), I could then be an inspector of new mushroom farms seeking the CNG label.

As far as buying mushrooms, my advice is to try to buy organic mushrooms, and when the certified naturally grown label for mushrooms becomes available, opt for that. In either case, you'll be safeguarding yourself from pesticides and other poisons that you could get in mushrooms which seem to eat about anything fed to them.