Well yes it is. Because as a very short lived element with a half-life of a few days it is an energetic emitter of alpha radiation (helium nucleus) that can cause cell damage. That radiation can’t get past a sheet of paper or your skin, but more delicate cells inside the body can be damaged.
As a gas, it gets into the body via the lungs. Hence lung cancer.
But it would never be ingested. Only inhaled.
