The amount of oil in the pomace is so minuscule that it cannot be extracted by pressing, but only through the combined use of chemical solvents (such as hexane) and extremely high heat.
The quality standards laid down by the International Olive Council, the United Nations of olive and olive oil producing countries, make it abundantly clear that olive oil, to be considered genuine, cannot be obtained using solvents or 'reesterification processes'.
Hexane is introduced in the production process to dissolve the fats in the pomace (it amounts literally to squeezing the last drop of oil) and the oil that comes out of this exercise has to be subject to heat treatment to remove the solvent.
If the process is unregulated and the heat level crosses the acceptable 90 degrees C, it's not a cause for worry (except that the resultant 'olive oil' certainly doesn't have the health benefits of extra virgin olive oil).
The problem starts if the producers get greedy and increase the heat levels to get 'better oil' - that leads to the production of cancer-causing 'polycyclic aromatic hydrocarbons' such as benzopyrene. It was this concern that led Spain to ban olive pomace oil in 2001, and its lead was followed by several countries in varying degrees, most notably New Zealand and Germany.
(This article is taken from India Today published in December 2011) more