What are the negative effects of alpha radiation on humans?
Usually, there are no negative effects associated with alpha particle exposure, but there are a few.
Alpha particles can not penetrate the skin, nor even most clothing. Distances of more than about an inch from an alpha source will stop any dangerous levels of alpha radiation. It is very difficult to expose yourself to dangerous levels of alpha radiation. Having said that:
Radon gas emits alpha particles as it decays. One of the most common effects of alpha radiation is therefore lung disease. If an alpha source, like uranium, is present in water, drinking the water can cause kidney damage.