Radioactivity - The Changing Arctic Environment: The Arctic Messenger - page 72

um-40 is the main source of internal irradiation. The average global effective dose
is approximately 0.3 mSv a year.

The acronym used for naturally occurring radionuclide material is NORM. As we have
seen, the ultimate sources of NORM include the primordial radionuclides we met in the
introduction to this chapter, including cosmogenic radionuclides, such as carbon-14 and
tritium ( 3 H or hydrogen-3). Cosmogenic radionuclides rarely reach levels that pose risks
to human health or the environment. However, NORM derived from potassium-40 ( 40 K)
and from primordial isotopes of elements from the radioactive series originating from 238 U
(uranium series), 235 U (actinium series) and 232 Th (thorium series) can in certain circum-
stances lead to significant radiation exposure. Each of these series includes many interme-
diate radionuclides until arriving at lead - their final stable and nonradioactive destination.
In industrialized societies, health authorities are very interested in knowing when
people may be exposed to more NORM than is “normal”. To explain this apparent contra-
diction, we will need to greet another acronym. This is TENORM, or technologically en-
hanced NORM. Since Earth's formation, geological processes have tended to concentrate
potassium-40 ( 40 K) and uranium and thorium series nuclides in “favoured” minerals and
geological formations that have limited contact with the biosphere. TENORM is produced
when humankind disturbs these enriched geological formations of rocks, soils, water or
other natural materials, bringing their radionuclides into contact with the biological envir-
onment. The types of human activity that can produce TENORM include uranium mining,
phosphate and elemental phosphorus production, phosphate fertilizer production, coal ash
generation, oil and gas production, drinking water treatment, metal mining and processing
and geothermal energy production.
The radiological exposure to individuals from TENORM wastes occurs in three main
categories:

· Associated with onsite disposal of wastes, such as mine tailings. This type of dis-

posal can lead to groundwater contamination and to airborne releases of radioact-
ive particulates and radon gas.

·