Weird I just saw a YouTube video on this like a week ago. Basically you would need to eat an amount that would never be possible by a lot for anything to possibly happen. The other point is we have more radiation than a banana to begin with and are hit by more radiation in 1 day than probably a thousand would even create. Our bodies are able to remove some radiation as well. There are even some parts of the world were people are exposed to higher than normal amounts of radiation and we found that over time the rate of cancer is less than the global average so I would highly doubt being around bananas would cause any risk for cancer.