Threshold response curve is a point at which a biologic response occurs, so this implies that there is a "safe" amount of dose to be delivered. It starts at a point greater than "0" on the graph.
Non-threshold response curve is described as any radiation exposure can be harmful and cause a response in the body. It implies that there is no safe level of exposure. It starts at "0" on the graph.
Answer:
Vitamin D is dangerous when you take large amounts in short periods, or too much even in long periods.
