EPR-Public CommunicationsL-02

Communicating Basics of Radiation

Simple

Challenge

• Communicating with the public about radiation is challenging;

• Communicate in plain language;• You will communicate better with people if

you can think as they are thinking.

Sources

• Radiation is naturally present in the environment. This is called natural background radiation;

• People are exposed to natural radiation from outer space, the air, food and drink;

• People may also be exposed to artificial radiation from medical treatment, consumer products and occupational exposure;

• Often, medical exposures from diagnosis and in treatment account for the largest dose from artificial sources.

Cosmic radiation and dose rates of exposure

Types of radiation

Alpha radiation (α) Beta radiation (β) Gamma radiation (γ)

Radiation that has a short range in air and can be stopped by paper or skin. This radiation can be hazardous if it enters the body by inhalation or ingestion because large exposures can result in nearby tissues.

Radiation that can penetrate further into materials or tissue, but can be stopped by plastic, glass or metal. This radiation does not normally penetrate beyond the top layer of skin but large exposures can cause skin burns and is also hazardous if it enters the body.

Very penetrating radiation for which only dense material such as steel or lead can provide an effective shield. It can deliver significant doses to internal organs without needing to be taken into the body.

Types of radiation

Exposure pathways

Inadvertent ingestion

Common exposure pathways for a small radioactive source

Quantities and units

Measuring radiation

The becquerel (Bq) is a unit used to measure radiation.

When ionising radiation interacts with biological tissue, it deposits energy there. The amount of energy deposited per unit mass of tissue is called the absorbed dose: the unit of this dose is called the gray (Gy).

Since equal exposures to different types of radiation expressed as Gy do not necessarily produce equal biological effects, these doses are weighted to give units of dose as the effective dose, or sievert (Sv). The sievert determines the probability that an ill-health effect will ensue. Regardless of the type of radiation, 1 sievert of radiation produces the same probability of biological effect (cancer or hereditary effects). Sievert is calculated and not measured.

Dose of radiation

The amount of radiation – the “dose” – received by people is measured in sieverts (Sv). This takes into account the type of radiation and how a person is exposed to that radiation.

Example: A typical dose received due to the natural sources of radiation is 3 milliSieverts in a year (written 3 mSv or 0.003 Sv).

The sievert belongs to the same family as the litre and kilogram. To explain the prefix “milli” compare with commonly used units such as litre (l) and millilitre (ml).

Dose rate

Dose rate is the rate at which dose is received. It is often used to calculate the intensity of a radiation source.

Example: The dose rate at one metre from a source is 50 microsieverts per hour (written 50 µSv/h). If a person stood in this radiation field for 2 hours, he/she would receive a total dose of 100 µSv.Here, a µSv is a million times smaller than a Sv and a thousand times smaller than a mSv.

Effects of radiation

• Deterministic: short term, occurring early after exposure;

• Stochastic: long term, occurring years later.

Recognizing a radiation source

Trefoil radiation warning symbol

New standard ionizing radiation warning supplementary symbol

Radiation protection

• Time• Distance• Shielding

Am I safe?

In addition to dose and dose rate quantities the following questions must be answered:

• What was measured or reported? • How was the person exposed (exposure

scenario)?• Who was exposed?

Potential health effects

• Death;• Severe health effects (severe deterministic

effects):• Severe burns;• Other non-fatal effects.

• Health effects to foetus;• Cancer risk.

Health effects from being near an unshielded radioactive source

HEALTH EFFECTS FROM BEING NEAR AN UNSHIELDED RADIOACTIVE SOURCE - BASED ON EXTERNAL DOSE TO THE WHOLE BODY

1000 mSv

100 mSv

Death Possible* Severe

health effects

possible*

Health effects*possible in the fetus

HEALTH EFFECTSEXTERNAL DOSE TO THE WHOLE

BODY

2 mSv

10 mSvAverage annual dose to the public

Very small increase in cancer risk

if any**

* Medical follow-up byan expert is warranted.

** No increase in cancer incidence has been detected below about 100 mSv

Health effects from carrying an unshielded radioactive source

HEALTH EFFECTS FROM CARRYING AN UNSHIELDED RADIOACTIVE SOURCE - BASED ON DOSE RATE

100 mSv/h

Death and other severe health effects* possible from carrying

an unshielded source for:

HEALTH EFFECTS DOSE RATE OF SOURCE at 1 m

10 mSv/h

1.0 mSv/h Health effects*

possible in the fetus from woman carrying an unshielded source

0.1 mSv/h

hours

minutes

* Medical follow-up by an expert is warranted.

Severe burns* possible from carrying an unshielded

source for:

hours

minutes

Health effects from being near an unshielded radioactive source

HEALTH EFFECTS FROM BEING NEAR AN UNSHIELDED RADIOACTIVE SOURCE - BASED ON DOSE RATE

5000 mSv/h

1000 mSv/h

100 mSv/h

Death and severe health effects* possible

from exposure for:

HEALTH EFFECTS DOSE RATE

10 mSv/h

1.0 mSv/h

Health effects*possible in the

fetus from exposure for days

days

weeks**

0.1 mSv/h

hours

minutes

* Medical follow-up by an expert is warranted.

** Severe health effects have not been seen in past emergencies from being near a source with a dose rate < about 10 mSv/h @ 1 m.

Let’s practice

• Some questions…