I found this growing in my herbs this am. Im concerned because there is a superfund site presently resuming construction. It was halted by EPA due to toxins in air . The site is below me. I live up on the cliff. What is this? I dug it out and threw out the herb.
This looks like a Leoucocoprinus mushroom, a common and harmless mushroom that is digesting the bark or other organic material in the potting mix. It's actually called a flowerpot dapperling because it is so often found in potted plants. It is not harmful to you or the plant. Of course, you should never eat mushrooms without an expert ID of an actual specimen (not just an image). Wikipedia has a decent page on this genus in case you want to look it up.