(a) Introduction. For each radionuclide, Table I indicates
the chemical form that is to be used for selecting the appropriate
ALI or DAC value. The ALIs and DACs for inhalation are given for an
aerosol with an activity median aerodynamic diameter (AMAD) of 1 micrometer
and for three classes (D,W,Y) of radioactive material, which refer
to their retention (approximately days, weeks, or years) in the pulmonary
region of the lung. This classification applies to a range of clearance
half-times for D of less than 10 days, for W from 10 to 100 days,
and for Y greater than 100 days.
(1) The class (D, W, or Y) given in the column headed
"Class" applies only to the inhalation ALIs and DACs given in Table
I, Columns 2 and 3. Table II provides concentration limits for airborne
and liquid effluents released to the general environment. Table III
provides concentration limits for discharges to sanitary sewerage.
(2) The values in Tables I, II, and III are presented
in the computer "E" notation. In this notation, a value of 6E-02 represents
a value of 6 x 10^{-2 } or 0.06, 6E+2 represents
6 x 10^{2 } or 600, and 6E+0 represents 6
x 10^{0 } or 6. Values are given in units
of microcuries (µCi) or microcuries per milliliter (µCi/ml),
as indicated.
(b) Table I, "Occupational Values". Note that the columns
in Table I of this appendix captioned "Oral Ingestion ALI," "Inhalation
ALI," and "DAC," are applicable to occupational exposure to radioactive
material.
(1) The ALIs in this appendix are the annual intakes
of a given radionuclide by "reference man" that would result in either
a committed effective dose equivalent of 5 rems (0.05 sievert) (stochastic
ALI) or a committed dose equivalent of 50 rems (0.5 sievert) to an
organ or tissue (non-stochastic ALI). The stochastic ALIs were derived
to result in a risk, due to irradiation of organs and tissues, comparable
to the risk associated with deep dose equivalent to the whole body
of 5 rems (0.05 sievert). The derivation includes multiplying the
committed dose equivalent to an organ or tissue by a weighting factor,
w_{T }. This weighting factor is the proportion
of the risk of stochastic effects resulting from irradiation of the
organ or tissue, T, to the total risk of stochastic effects when the
whole body is irradiated uniformly. The values of w_{
T }are listed under the definition of "weighting factor" in §336.2
of this title (relating to Definitions). The non-stochastic ALIs were
derived to avoid non-stochastic effects, such as prompt damage to
tissue or reduction in organ function.
(2) A value of w_{T }= 0.06
is applicable to each of the five organs or tissues in the "remainder"
category receiving the highest dose equivalents, and the dose equivalents
of all other remaining tissues may be disregarded. The following parts
of the GI tract--stomach, small intestine, upper large intestine,
and lower large intestine--are to be treated as four separate organs.
(3) Note that the dose equivalents for an extremity,
skin, and lens of the eye are not considered in computing the committed
effective dose equivalent but are subject to limits that must be met
separately. When an ALI is defined by the stochastic dose limit, this
value alone is given.
(4) When an ALI is determined by the non-stochastic
dose limit to an organ, the organ or tissue to which the limit applies
is shown, and the ALI for the stochastic limit is shown in parentheses.
The following abbreviated organ or tissue designations are used:
(A) LLI wall = lower large intestine wall;
(B) St wall = stomach wall;
(C) Blad wall = bladder wall; and
(D) Bone surf = bone surface.
(5) The use of the ALIs listed first, the more limiting
of the stochastic and non-stochastic ALIs, will ensure that non-stochastic
effects are avoided and that the risk of stochastic effects is limited
to an acceptably low value. If, in a particular situation involving
a radionuclide for which the non-stochastic ALI is limiting, use of
that non-stochastic ALI is considered unduly conservative, the licensee
may use the stochastic ALI to determine the committed effective dose
equivalent. However, the licensee shall also ensure that the 50-rem
(0.5 sievert) dose equivalent limit for any organ or tissue is not
exceeded by the sum of the external deep dose equivalent plus the
internal committed dose equivalent to that organ (not the effective
dose). For the case where there is no external dose contribution,
this would be demonstrated if the sum of the fractions of the nonstochastic
ALIs (ALI_{ns }) that contribute to the committed
dose equivalent to the organ receiving the highest dose does not exceed
1 (i.e., Sigma (intake in µCi of each radionuclide/ALI_{ns }) < 1.0). If there is an external deep-dose
equivalent contribution of H_{d }, then
this sum must be less than 1 - (H_{d }/50),
instead of < 1.0.
(6) The DAC values are derived limits intended to control
chronic occupational exposures. The relationship between the DAC and
the ALI is given by:
Attached Graphic
(7) The DAC values relate to one of two modes of exposure:
either external submersion or the internal committed dose equivalents
resulting from inhalation of radioactive materials. The DAC values
based upon submersion are for immersion in a semi-infinite cloud of
uniform concentration and apply to each radionuclide separately.
(8) The ALI and DAC values include contributions to
exposure by the single radionuclide named and any in-growth of daughter
radionuclides produced in the body by decay of the parent. However,
intakes that include both the parent and daughter radionuclides shall
be treated by the general method appropriate for mixtures.
(9) The values of ALI and DAC do not apply directly
when the individual both ingests and inhales a radionuclide, when
the individual is exposed to a mixture of radionuclides by either
inhalation or ingestion or both, or when the individual is exposed
to both internal and external irradiation (see §336.306 of this
title (relating to Compliance with Requirements for Summation of External
and Internal Doses)). When an individual is exposed to radioactive
materials which fall under several of the translocation classifications
of the same radionuclide (i.e., Class D, Class W, or Class Y), the
exposure may be evaluated as if it were a mixture of different radionuclides.
(10) It shall be noted that the classification of a
compound as Class D, W, or Y is based on the chemical form of the
compound and does not take into account the radiological half-life
of different radionuclides. For this reason, values are given for
Class D, W, and Y compounds, even for very short-lived radionuclides.
(c) Table II, "Effluent Concentrations". The columns
in Table II of this appendix captioned "Effluent Concentrations,"
"Air," and "Water" are applicable to the assessment and control of
dose to the public, particularly in the implementation of the provisions
of §336.314 of this title (relating to Compliance with Dose Limits
for Individual Members of the Public). The concentration values given
in Columns 1 and 2 of Table II are equivalent to the radionuclide
concentrations which, if inhaled or ingested continuously over the
course of a year, would produce a total effective dose equivalent
of 0.05 rem (0.5 millisievert).
(1) Consideration of non-stochastic limits has not
been included in deriving the air and water effluent concentration
limits because non-stochastic effects are presumed not to occur at
or below the dose levels established for individual members of the
public. For radionuclides, where the non-stochastic limit was governing
in deriving the occupational DAC, the stochastic ALI was used in deriving
the corresponding airborne effluent limit in Table II. For this reason,
the DAC and airborne effluent limits are not always proportional.
(2) The air concentration values listed in Table II,
Column 1, were derived by one of two methods. For those radionuclides
for which the stochastic limit is governing, the occupational stochastic
inhalation ALI was divided by 2.4 x 10^{9 } ml,
relating the inhalation ALI to the DAC and then divided by a factor
of 300. The factor of 300 is composed of a factor of 50 to relate
the 5-rem (0.05 sievert) annual occupational dose limit to the 0.1
rem (1 millisievert) limit for members of the public, a factor of
3 to adjust for the difference in exposure time and the inhalation
rate for a worker and that for members of the public; and a factor
of 2 to adjust the occupational values (derived for adults) so that
they are applicable to other age groups.
(3) For those radionuclides for which submersion (external
dose) is limiting, the occupational DAC in Table I, Column 3, was
divided by 219. The factor of 219 is composed of a factor of 50 and
a factor of 4.38 relating occupational exposure for 2,000 hours/year
to full-time exposure (8,760 hours/year). Note that an additional
factor of 2 for age considerations is not warranted in the submersion
case.
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