Yes, it can be harmful to put bamboo in the microwave. Bamboo is a type of grass, and like other organic materials, it contains moisture. When bamboo is exposed to microwave radiation, the moisture within it can heat up rapidly, leading to steam buildup and potential steam explosions.
Microwaving bamboo can cause the material to dry out unevenly and become extremely hot. The steam buildup can create pressure within the bamboo, leading to the risk of the bamboo splintering or bursting apart, which can be dangerous. It can also cause damage to your microwave, such as warping or scorching the interior walls.
To avoid any potential hazards, it is generally recommended not to put bamboo or any other wooden materials in the microwave. It's best to use alternative methods for heating or cooking bamboo-based products.