Human health

Ionising radiation

Radionuclides are released into the atmosphere during the nuclear fuel cycle and other activities such as the burning of coal. These radionuclides (especially if they are long-lived) eventually end up in the food or water of humans where their ionizing radiation causes damage to ‘Human Health’.

 

Cause-effect pathway

 

Radionuclides can be emitted to different environmental compartments (freshwater, seawater or air). Depending on the emission compartment and the radionuclide the human population will be exposed to a larger or smaller part of the ionizing radiation.

 

Modeling approach

 

Because no cancer incidence data is available for low exposure levels an average approach is used to calculate the extra incidence of cancer as a result of medium- to high dose exposure (resulting from nuclear accidents). This factor is then corrected to take into account the fact that at low exposure levels the additional cancer incidence per dose is lower than at medium/high levels. The correction factor is called the Dose and Dose Rate Effectiveness Factor (DDREF). By making this correction a marginal approach is approximated.

 

 

Value choices

 

A number of choices have been made for the calculation of the characterization factors, namely:

  • The time horizon over which effects are assessed

  • By how much the effect factor (derived at high exposure levels) should be corrected

  • Which types of cancer to include (some types are certainly caused by ionizing radiation, for other cancer types it is uncertain whether they can be caused by ionizing radiation)

 

 

High level of robustness

Low level of robustness

Time horizon

100 years

100 - 100000 years

DDREF

10

2

Included cancer types

Thyroid, bone marrow, lung and breast cancer

Hereditary disease

bladder, colon, ovary, skin, liver, oesophagus, stomach, bone surface and remaining types of cancer

 

 

Spatial variability

 

Currently, no spatially explicit models are available to estimate the global spread of the radionuclides and the resulting exposure. Instead the models used are based on standardized situations, resulting in 3 characterization factors (one for each emission compartment).

 

 

Characterisation factors

 

The following equation can be used to calculate the characterisation factors (CF):

 

CFx,i,TH = CDx,i,TH ∙ EF

 

where CD stands for collective dose, and EF for effect factor for radionuclide x, environmental compartment i and time horizon TH.

 

The collective dose (unit: man.Sv) is a measure for the total exposure to ionizing radiation in the human population as a result of the emission of 1kBq of a radionuclide. By multiplying this total dose by the EF the CF can be calculated. The EF (Daly/Man.Sv) itself is the summation of the additional incidence of different cancer types (and hereditary disease) multiplied by their severity.

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