Health authorities believe that the hepatitis-A cases recently traced to Chi-Chi's restaurants are due to Mexican green onions. Reuters reports that they are being held up at the border.
I wonder if food irradiation has been tried with green onions. It can kill off pathogens deep beneath the surface of foods without adding a lot of processing time. It doesn't work well with everything though - as I understand it each individual product to be irradiated must be studied to find the appropriate doses and particulars about feed rates, orientation, packaging, etc. In some cases taste and texture can be affected.
Somebody had better do something quickly though. This is the kind of thing that could impact green onion sales for years.