The Spanish government is having all of the cheapest olive oil which is made from the skin of olives (called orujo) removed from store shelves because of a concern that it might contain carcinogens.
There is absolutely no problem with the better qualities (such as Virgin or Extra Virgen).

Hi, everyone. I just wanted to mention re this topic that I learned on a recent visit to Spain that if buying olive oil to look for a number on the bottle which indicates acidity. You want a low number, definitely a 3 or less! The number 1 indicates Extra Virgin, although some that I purchased are labeled extra virgin and show a number 3, indicating 3% acidity. However, the lower the number the better. Hope this helps! ( I love Pan con Tomate, with the drizzle of good olive oil.)

I's not all that hard to determine the quality of olive oil. Take a sip. If it turns your throat to flame, don't buy it.
Cantabene