<<Disclaimer: Verify this information before applying it to your situation.>> I am very concerned about the safety of mushrooms. A few years ago, I became sick more than once after eating specialty mushrooms at a favorite restaurant. I didn't catch on right away, because I thought that it just couldn't be the mushrooms. Then I saw an article in a local newspaper about a local mushroom grower who said that he grew his mushrooms in wheat straw. I have asked two other mushroom growers at our farmers' market what medium they use. One said wheat straw, the other said compost, but couldn't or wouldn't say what the compost might contain. Now, I buy only common white mushrooms, and only those if they are very clean, with caps tightly attached to the stems. I also wash them before cooking. Margaret