I doubt poison was transferred from dying bugs into your pole beans. Everything I have read says to wait at least 3 days after using Sevin before harvesting. Wash the produce well. In fact, you could add a few drops of very mild detergent to the water, then rinse the produce a second time to remove any soap residue.

There is a natural insecticide: neem oil. It is extracted from the seeds and fruit of the neem tree. As a pesticide it repels a wide variety of adult bugs from crops and kills larval stage bugs. It is not toxic to mammals, birds, earthworms, or beneficial insects such as bees and butterflies as long as it is not applied to the flowers they visit. It's a good idea to wash your produce whether or not you use any pesticide.