The Effects of Radiation on Living Things

Health Physics

What types of radiation are harmful?

Why is ionising radiation harmful?

Radiation

Radiation may be absorbed by the medium it passes through.

All living things contain living cells. We have many different types of cells which perform different functions including:

Skin cells. Red blood cells (they transport oxygen around the body) White blood cells (they fight infection). Nerve cells. Muscle cells. Brain cells.

Radiation can kill living cells or change the nature of living cells.

Ionising radiation can kill or change the nature of living cells.

The effects of the damage inflicted by the ionising radiation may:

be severe and cause immediate effects, or not become apparent for a long time.

The biological effect of radiation depends on:

The type of radiation. The type of body tissue or body organ that absorbs the radiation. The total amount of energy absorbed.

The Effects of Ionising Radiation

Long-Term Effects of Radiation

These effects take longer to become apparent and can be caused by much lower levels of radiation.

Uranium miners tended to get lung cancer due to breathing in gases which emitted alpha particles.

People who painted the dials of clocks with luminous paint developed one cancer from using their lips to make points on the brushes.

One of the most important long-term effects of radiation is that of cancer in various parts of the body.

Dose Equivalent

The DOSE EQUIVALENT is a measure of the biological effect of radiation and it takes account of the type and energy of the radiation as well as how the radiation is distributed.

REMEMBER, the biological effect of radiation depends on:

•The type of radiation.•The type of body tissue or body organ that absorbs the radiation.•The total amount of energy absorbed.

Because 1 Sv is a very large dose of radiation which could only happen as a result of a very serious nuclear accident or explosion, doses are given in millisieverts (mSv) or microsieverts ( Sv).

The DOSE EQUIVALENT is measured in sieverts (Sv).

Rolf Maximilian Sievert (1896 – 1966)

Suppose that 100 people all receive a dose equivalent of 1 Sv spread over the whole body. It is estimated that, of the 100 people on average 4 of them would eventually die as a result of the radiation.

But precisely who would die, or when they would die, or what illness they would die of, cannot be predicted.

Background Radiation

Radiation is all around us!

Background radiation is radiation that is naturally occurring.

The limits on effective dose (dose to the whole body) introduced by the IRR99 to replace the limits set previously by the IRR85 are: for employees aged 18 years or over, 20 millisieverts in a calendar year (except that in special cases employers may apply a dose limit of 100 millisieverts in 5 years with no more than 50 millisieverts in a single year, subject to strict conditions);

for trainees, 6 millisieverts in a calendar year; and for any other person, including members of the public and employees under 18 who cannot be classed as trainees, 1 millisievert in a calendar year.

The dose limit for the skin now applies to doses averaged over an area of skin not exceeding 1 cm2.

Natural Sources of Radiation

Source Annual Dose (Sv)

Radon and thoron gas from rocks and soil

800

Gamma rays from ground 400

Carbon and potassium in your body 370

Cosmic rays at ground level 300

Total = 1870

Man-Made Sources of Radiation

Source Annual Dose (Sv)

Medical uses – x-rays, etc. 250

Chernobyl (first year) 50

Fall-out from weapons testing 10

Job (average) 5

Nuclear industry (e.g. waste) 2

Others (TV, aeroplane trips, etc.) 11

Total = 328

Radiation Dosage

The limits on effective dose (dose to the whole body) are:

For employees aged 18 years or over, 20 millisieverts in a calendar year (except that in special cases employers may apply a dose limit of 100 millisieverts in 5 years with no more than 50 millisieverts in a single year, subject to strict conditions)

For trainees, 6 millisieverts in a calendar year

Any other person, including members of the public and employees under 18 who cannot be classed as trainees, 1 millisievert in a calendar year.

Death Risk - Cause

Death Risk - Cause Death Risk – 40 Year Old

All causes 1 per 500

Smoker – 10 per day 1 per 2000

Road accidents 1 per 5000

Home accidents 1 per 10 000

Work accidents 1 per 20 000

All radiations 1 per 27 500

Medical Radiations 1 per 240 000