Ionizing radiation can cause either deterministic or stochastic effects on human tissue. Deterministic effects have thresholds and their severity increases with dose, causing cell damage or death leading to tissue impairment. Examples include skin erythema and necrosis after certain doses and cataracts after years. Stochastic effects have no threshold and risk increases linearly with dose, causing hereditary effects like Down Syndrome and cancer. Non-ionizing radiation from sources like microwaves, infrared, and ultraviolet can also damage tissues in high doses, with UV light linked to skin cancers after excessive or even moderate exposure.

1. Radiation protection

2. Effect of ionizing and non ionizing radiation
The deleterious effect ionizing radiation has
on human tissue can be divided into two
types:
 non-stochastic (deterministic) or
 stochastic effects.

3. Deterministic (Non-Stochastic) Effects
 Deterministic effects only occur once a threshold of
exposure has been exceeded. The severity of deterministic
effects increases as the dose of exposure increases.
 Deterministic effects are caused by significant cell
damage or death. The physical effects will occur when the
cell death burden is large enough to cause obvious
functional impairment of a tissue or organ.

4. Examples
 Skin Erythema/Necrosis/Epilation
Erythema occurs 1 to 24 hours after 2 Sv have been received. Breakdown of the
skin surface occurs approximately four weeks after 15 Sv have been received.
Epilation is reversible after 3 Sv but irreversible after 7 Sv and occurs three
weeks following exposure.
 Cataract
Cataract occurs due to accumulation of damaged or dead cells within the lens.
 Cataract occurs after 2 to 10 Gy have been received, but may take years to
develop.

5.  Radiation Sickness
Radiation sickness (correctly termed acute radiation syndrome) involves nausea,
vomiting, and diarrhea developing within hours or minutes of a radiation
exposure. This is due to deterministic effects on the bone marrow, GI tract, and
CNS.
 Fetal Death
Deterministic radiation exposure effects during pregnancy depend not only on the
radiation dose received but also on the gestational age at which it occurred.
 High levels of radiation exposure in pregnancy can lead to growth retardation

6. Stochastic Effects
 Current thinking is that stochastic effect
occurrence follows a linear no-threshold
hypothesis. This means that although there is no
threshold level for these effects, the risk of an
effect occurring increases linearly as the dose
increases.

7. Examples
 Hereditary Defects (e.g., Down Syndrome)
 Cancer

9. Effect of non ionizing radiation
 We use and are exposed to nonionizing radiation sources every day. Microwave
ovens use microwaves to heat food,
 toasters use infrared waves to heat and sometimes burn our toast, and we watch
television,
 talk on cell phones, and listen to the radio through the use of radio waves. These
are all nonionizing forms of radiation.
 Visible light, radar, laser light, and ultraviolet light also fall into this radiation
category

10.  Some forms of nonionizing radiation can damage tissues if we are exposed too
much.
 For instance, too much ultraviolet (UV) light from lying out in the sun is known to
cause some skin cancers; even moderate amounts can cause skin burns.
 With enough energy, lasers can cause biological damage, which is why they are
useful in medicine to remove warts and some skin cancers and even to break up
kidney stones.