No, it is generally not harmful to stand close to a microwave oven when you're cooking something inside of it. Microwave ovens are designed to contain the radiation they emit within the oven itself, so as long as the oven is in proper working condition and not damaged, there should be no significant health risks from standing near it.
Microwave ovens use microwave radiation to heat food by exciting the water molecules present in the food. The microwaves are contained within the oven and do not escape unless there is a malfunction or damage to the oven's seals or doors. However, microwave radiation rapidly decreases with distance, so even if there is a leak, the levels of radiation would be significantly reduced by the time they reach you.
That said, it's still a good idea to follow some basic safety precautions when using a microwave oven:
Maintain a safe distance: While it is generally safe to stand close to a microwave oven, it's a good practice to maintain a reasonable distance, usually at least a few feet away, to minimize any potential exposure.
Use proper cookware: Make sure you're using microwave-safe containers and avoid using metal or containers with metallic accents, as they can cause sparks or damage to the oven.
Follow the manufacturer's instructions: Read and follow the instructions provided by the manufacturer of your microwave oven to ensure safe usage and maintenance.
By following these guidelines and using the microwave oven as intended, you can safely cook your food without significant health risks.