In an ideal world, we would all eat only organic, locally grown produce.  But trying to balance that lofty goal against a budget isn't always possible.  Although there are many reasons to buy organic, if you're trying to avoid ingesting pesticides, choose organic when you're buying "the dirty dozen," as identified by the Environmental Working Group: peaches, pears, nectarines, apples, grapes, strawberries, cherries, bell peppers, celery, lettuce and kale – and other produce where you're eating the outer surface, especially if it's hard to clean.  For non-organic, you're safest with fruits and vegetables where you don't eat the outer surface, and the lowest levels of pesticides are found on onions, avocados and sweet corn.