# Radiation and cancer

We were doing a radiation experiment, in my physics class. Obviously, all of the students why crying in fear of getting cancer.

The brief explanation given by my teacher, as to how radiation exposure can lead to the development of cancer, was the ionising nature of radiated matter. I assume this ionising damages DNA leading to mutations, such as cancerous cells.

How would Gamma-radiation cause this, then, it's simply a high energy photon - how would a photon ionise an atom?

Does Gamma-radiation not cause cancer, and is it just Alpha and Beta?

• Required reading: xkcd.com/radiation Note, in particular, the non-trivial natural background (around $1 \,\mathrm{mrem/day}$) and what that means about the relationship between the exposure during the laboratory exercise and the average yearly exposure of people living in the developed world. Also compare to, say, a dental x-ray. Feb 25 '17 at 0:09
• -1. No research effort. Feb 25 '17 at 3:15

Gamma is a high energy photon. It interacts with an electron in an atom and kicks it free since it is so energetic. The atom remains behind ionized.

Yes, any of them can interact with atoms and molecules and ionize them or even kick an atom out of a molecule and hange the molecule. It can break up genes and cause the mutations. How much and how likely depends not only on the individual energies, but also on how many. The rems in @dmckee's comment measures exposure.

I read that radiation consists of several types of subatomic particles that can easily penetrate deep inside the human body, damaging some of the biological cells of which the body is composed. This damage can cause a fatal cancer to develop. Experiments on laboratory animals injected with radioactive materials clearly show the reduced risk at low dose, but other than inducing cancer, the most significant health impact of low-level radiation is causing inherited disabilities in later generations, often called genetic defects. So I think we should pay more attention to this problem. After my trip to Chernobyl three years ago I bought radiation detector for home use at https://ecotestgroup.com/press/blog/best-radiation-detector-for-home-use/ to check the level of radiation at my house 'coz I realized that radiation can be everywhere. Radiation can cause terrible diseases and we should do everything to avoid it.

Different kinds of radiation interact With the body in different ways. Alpha can't penetrate your skin and is harmless outside the body but if you ingest it it'll destroy you. Betas are pretty bad all around but can be stopped by clothing. Gammas can penetrate just about anything, because of this most of gamma radiation will go through you without ever interacting. But that which does is interact is still pretty bad.

Radiation is all around you. You're breathing it in right now. You cannot avoid it. Some of it is caused by man but a lot of it is just natural, around since the planet formed. But like fighting diseases your body has ways of protecting you from small amounts. DNA is damaged all the time during cell replication. So the body has enzymes to repair DNA when this happens. The whole reason for our double helix DNA is to have a template to repair one side if the other is damaged.

Gamma damages cells when the photon gets absorbed by an electron in a DNA molecule. This massive energy boost causes the electron to shoot off. This disrupts the bond holding the molecule together and the molecule breaks.

But it takes a lot of it for enough damage to occur to cause cancer, which is likely impossible with the source being used in your class, unless you decided to eat it. Even then that cancer could take 20 years to develop.

Don't just ignorantly fear radiation because it's the R word. Learn about it, try to understand it so you can make intelligent decisions.

I assume this ionising damages DNA leading to mutations, such as cancerous cells.

Correct, ionising radiation creates double strand breaks of DNA which leads to mutations.

How would Gamma-radiation cause this, then, it's simply a high energy photon - how would a photon ionise an atom?

Gamma rays and x-rays (photons) are non-charged particles, they are called 'indirectly ionising radiation'. Electrons (beta) and alpha particles are charged particles meaning they interact directly with matter through Coulomb forces. They quickly loose energy which is why these particles have short ranges.

There are a few ways that photons can interact with matter, each resulting in a release of electrons, which are 'directly ionising radiation', this is where the damage is done.

Photons can interact through:

Compton scatter

The photon interacts with the electron cloud of an atom and is 'scattered', loosing some energy and changing direction in the process. The lost energy release an electron from the electron cloud and this electron goes on to deposit energy in the matter.

This is the predominant interaction for high energy photons, its probability also depends on the atomic number of the material.

Photoelectric absorption

When the photon has a sufficiently low energy (usually after undergoing several Compton scattering events) it can be absorbed by an atom. To compensate for this an electron is ejected from its shell again and will go on to deposit energy. The photon ceases to exist after this interaction.

There are other by-products of these interactions such as characteristic x-rays or Auger electrons due to the reshuffling of the electrons in various shells.

TL/DR

Photons are massless uncharged particles that have to interact with matter to generate electrons (beta). Electrons are charged particles that deposit energy quickly in matter through Coulomb interactions, this can lead to DNA damage which causes mutations.