Hexane is a byproduct of gasoline refining. It is a neurotoxin and a hazardous air pollutant. Many soybean processors use hexane as a cheap solvent to extract oil from soybeans in order to make soy oil and protein ingredients. Whole soybeans are literally bathed in hexane to separate the soybeans’ oil from protein. Many of these companies also market themselves to consumers under a 'green' image and try to appeal to environmentally and health-conscious shoppers.  There are however several companies commited to using “clean” soy ingredients, so lets support them instead. 

More information can be found at Cornucopia.org. This campaign is not affiliated with Cornucpia,org, I just used them for most of my information.