As long as rice turns sour, it is all caused by bacteria, just like brewing and vinegar-making rice. As long as the rice meets the strain of sour porridge, it will not be moldy, and it will not be for several months. Good things occupy rice, and harmful things do not exist. If beneficial bacteria cause cancer, then wine and vinegar also count.
Chongzuo has four longevity towns, and Fusui is one of them. Almost every household in Fusui raises sour porridge, and it is not perfect for duck and raw fish to have sour porridge.