• Alpha radiation (helium nuclei with 2 protons and 2 neutrons) are large and cannot penetrate skin.

• Beta radiation (electrons) can penetrate upper layers of skin but can be stopped by protective clothing.

• Gamma radiation is very energetic and potentially most damaging; only thick, dense material such as concrete and lead can stop this radiation.

Exposure to radiation can cause tissue damage, leading to radiation damage; it can also cause DNA damage, leading to cancer or birth defects.