Why are ultraviolet, X-rays and gamma rays dangerous to the human body?

Ultraviolet, X-rays and gamma rays are dangerous to the human body because ultraviolet waves increase the risk of skin cancer and cause the skin to age prematurely. While x-rays and gamma rays are ionising radiation so they knock electrons off atoms when they are absorbed. This can cause mutations of genes, increasing the risk of skin cancer. Although the effect of radiation depends on the dose, that is measured in sieverts (Sv) or millisieverts (mSv).