Why are xrays dangerous?

Answer 1

X-Rays take the picture you see using a type of radiation. Any type of radiation can cause abnormal cell growth (cancer). This is why a lot of the time, depending on where the X-Ray is, and how powerful the machine the doctors are using is, they have you wear that heavy chest guard, which is full of lead, to stop the X-Rays from penetrating your body.

X-rays are an ionizing radiation that produce free radicals when they pass through the body. Free radicals are very dangerous molecules that can cause cell damage, and they might react with DNA causing the cell to replicate very fast, this in turn might generate tumors like leukemia in children.

ADDITION:

X-Rays can cause the biological injuries/damage as with other forms of radiation. Overexposure and long-term exposure to X-rays can cause radiation poisoning, skin burns, even cancer. It also can cause a mutation in healthy body cells and it can cause deformities or aborting of a fetus.