MANAGEMENT OF NORM IN THE PETROLEUM INDUSTRY Akpojevwa Tega Naomi, october 2016 | Page 35

• For both radiation-induced cancer and heritable disease it is the
probability of the occurrence of the effect, not its severity that depends
upon the dose
• The general risk model for radiological protection is that the risk of
these stochastic effects increases linearly with dose, without a threshold
dose (also known as linear no-threshold or LNT model).
2.2.1 Sources of Exposure
There are two ways in which a person can be exposed to radiation emitted by
radioactive material, including NORM. Irradiation from external sources and
contamination from inhaled and ingested sources.
Figure 2.2: Exposure to NORM form internal and External (OGP report, 2016)
Irradiation from external sources occurs when the material emitting radiation is
located outside the human body. Irradiation from internal sources occurs when
the material emitting radiation is located inside the human body. Internal
24