A question on Cooking SE brought up the fact that:
One study showed that 91.7% of green coffee beans were contaminated with mold. This is before they were processed, which allows even more mold to grow. Another study showed 52% of green coffee beans and almost 50 percent of brewed coffees are moldy. SOURCE
The studies quoted by the answer indicated that there might be some toxins that make it to the ground used in brewing coffee but did not address if there were any problems with toxins actually in the coffee.
I thought the question may be better addressed by our learned folks that share their knowledge and research here at Skeptics :)