Bitter Pistachios

I recently got a 5 lb bag of fresh domestic pistachio nuts in a Woot!-Off. In going thru these, it seems 2% or more are bitter or sour. I recalled a conversation I had years ago with a food science prof who had sworn off eating peanut butter because of aflatoxin risk. Aflatoxins are a class of mycotoxins, and among the most potent naturally occurring carcinogens, found in moldy nuts, grains, fruit, and veggies. Cream hundreds of peanuts together in a jar of peanut butter and who knows how many were moldy or contained aflatoxins. So I started wondering about the safety of these sour pistachios; maybe the bitter taste was because of some mold growing on the pistachio? How would one tell? I don't think I could tell mold from any of the other odd colorations characteristic of roasted & salted pistachios.

I did a little Google-ing on "bad pistachios" and came upon multiple Yahoo! Answers about sour/bitter pistachios. The question was whether eating bitter or sour pistachios was bad for you. To my amazement, the responders replied to a tune that they were NOT bad for your health and some even went so far to say that there was nothing in pistachios that was bad to eat. I wanted to post a follow-up reply, but Yahoo! closes the responses after 4 days.

Some more digging found this quote from the US Dept of Agriculture:
"Aflatoxin contamination of tree nuts (almonds, pistachios and walnuts) is a significant mycotoxin-related problem, now."

So now, while (as of today) I am still eating pistachios and peanut butter, I am much more selective of the nuts I eat. If I encounter a sour or bitter pistachio, I spit it out, gargle, drink glass-after-glass of water, take antioxidants, etc.--maybe all these would be useless against my ingestion of aflatoxins, but I figure it's about all that I can reasonably do if I'm going to eat the things. And maybe I'm ingesting aflatoxins anyway in nuts that seem fine; I just don't know. For peanut butter, I stick to the name brands, as I figure the risk of getting bad peanuts in off-brand labels is higher, especially if those peanuts are acquired as sub-quality rejects from the name brand manufacturers.