Risks associated with ionising radiation

The risks associated with ionising radiation depend on the dose of radiation received. A distinction is made between:

• the effects of high doses; and
• the effects of low doses.

Effects of high doses

High doses of radiation can quickly lead to tissue lesions. These lesions only appear if a certain dose is exceeded. The severity of the lesions increases with the dose of radiation. Ionising radiation is measured in 'grays', and its effects are referred to as 'deterministic' effects.

Effects of low doses

Low doses of radiation can result in long-term effects. Effects do not appear systematically, but the probability of long-term effects increases with the dose received.

The dose of radiation is measured in 'millisieverts', its effects are referred to as 'stochastic' effects. The main effects of low doses are:

• risk of cancer;
• hereditary effects.

Risk of cancer

Doses of more than 100 millisieverts

Many scientific studies have shown that doses of ionising radiation in excess of 100 millisieverts are carcinogenic for humans.

Today, it is generally accepted that the risk of radiation-induced cancer is around 5 % per sievert for high doses. On average, there is a risk of 5 additional cancers (due to radiation) if 100 people were to be exposed to a dose of 1,000 millisieverts.

Doses of less than 100 millisieverts

For doses of less than 100 millisieverts, scientific studies have not been able to demonstrate with certainty that ionising radiation has a carcinogenic effect on humans. The main problem with these studies is that cancer is a fairly common disease in our population (spontaneous onset) and, given the number of spontaneous cases (which appear without any obvious cause) that occur, it is extremely difficult to identify cases of radiation-induced cancer.

Currently, the risk is considered to exist, and to be proportional to the dose received, even with very low doses. Thus, the risk of radiation-induced cancer per millisievert is estimated at around 0.005 %.

Risk of hereditary effects

There is a risk that parental irradiation could lead to an increase in severe hereditary genetic diseases in subsequent generations.

Ionising radiation can cause mutations or chromosomal aberrations in parents' germ cells, which can lead to hereditary disorders or diseases.

The risk of genetic diseases in the first 2 generations is extremely low. It is estimated at just 0.0002 % per millisievert.