Effective dose, committed effective dose and sievert

Effective dose (E): sum of the weighted equivalent doses delivered by internal and external exposure to the various tissues and organs of the body. It is defined by the formula:

                              E =∑ w_T H_T =∑ w_T ∑ w_R D_T,R
                                     T              T       R
where
D_T,R is the mean for the organ or tissue T of the absorbed dose of radiation R;
w_R is the weighting factor for radiation R;
w_T is the weighting factor for the tissue or organ T.

The effective dose unit is the sievert (Sv).

Committed effective dose [E(τ)]: sum of the committed equivalent doses in the various tissues or organs [H_T(τ)] following intake, each multiplied by the appropriate weighting factor w_T. It is given by the formula:

                              E(τ) = ∑ w_T H_T(τ)
                                          T

In E(τ), τ is the number of years of integration.

The committed effective dose unit is the sievert (Sv).

The choice made in 1990 by the International Commission on Radiological Protection (ICRP) is to express doses by the effective dose, which is the result of an equivalence calculated in terms of a belated risk of radiation-induced fatal cancers and serious genetic consequences. The effective dose E is the result of a second weighting by a factor describing the relative importance of the effects on the tissues in which the dose is distributed. It is thus already the result of a modelling of the risk. The values of w_T are given in the following table.

Tissue or organ	wT
Gonads	0,20
Red marrow	0,12
Colon	0,12
Lungs	0,12
Stomach	0,12
Bladder	0,05
Breasts	0,05
Oesophagus	0,05
Thyroid	0,05
Liver	0,05
Skin	0,01
Bone surface	0,01
Others1< ?/td>	0,05