ICRP 103 Flashcards
alpha/beta ratio
The dose at which the linear
and quadratic components of cell killing are equal
definition of activity
The expectation value of the number of nuclear transformations occurring in a
given quantity of material per unit time
Activity Median Aerodynamic Diameter (AMAD)
The value of aerodynamic diameter such that 50% of the airborne activity in a
specified aerosol is associated with particles greater than the AMAD
Adaptive response
A post-irradiation cellular response which, typically, serves to increase the
resistance of the cell to a subsequent radiation exposure
Ambient dose equivalent
The dose equivalent at a point in a radiation field that would be produced by
the corresponding expanded and aligned field in the ICRU sphere at a depth of
10 mm on the radius vector opposing the direction of the aligned field
Sievert
Annual intake
The amount of a specified radionuclide entering the human body by ingestion
or inhalation within one year.
Averted dose
The dose prevented or avoided by the application of a protective measure or set
of protective measures
Baseline rates
The annual disease incidence observed in a population in the absence of exposure to the agent under study.
Bioassay
Any procedure used to determine the nature, activity, location, or retention of
radionuclides in the body by in vivo measurement or by in vitro analysis of
material excreted or otherwise removed from the body.
Bystander effect
A response in unirradiated cells that is triggered by signals received from irradiated neighbouring cells.
Categories of exposure
occupational
public
medical
collective effective dose
units: man Sv
sum of effective dose for a subgrouo times number of individuals in subgroup
committed effective dose
The sum of the products of the committed organ or tissue equivalent doses and
the appropriate tissue weighting factors (wT), where s is the integration time in
years following the intake. The commitment period is taken to be 50 years for
adults, and to age 70 years for children.
committed equivalent dose
The time integral of the equivalent dose rate in a particular tissue or organ that
will be received by an individual following intake of radioactive material into
the body by a Reference Person, where s is the integration time in years
derived air concentration
This equals the annual limit on intake, ALI, (of a radionuclide) divided by the
volume of air inhaled by a Reference Person in a working year (i.e., 2.2 103 m3
).
The unit of DAC is Bq m3
.
detriment
The total harm to health experienced by an exposed group and its descendants
as a result of the group’s exposure to a radiation source. Detriment is a multidimensional concept. Its principal components are the stochastic quantities:
probability of attributable fatal cancer, weighted probability of attributable
non-fatal cancer, weighted probability of severe heritable effects, and length
of life lost if the harm occurs.
Detriment-adjusted risk
The probability of the occurrence of a stochastic effect, modified to allow for
the different components of the detriment in order to express the severity of
the consequence(s)
Diagnostic reference level
Used in medical imaging with ioning radiation to indicate whether, in routine
conditions, the patient dose or administered activity (amount of radioactive
material) from a specified procedure is unusually high or low for that procedure.
directional dose equivalent
The dose equivalent at a point in a radiation field that would be produced by
the corresponding expanded field in the ICRU sphere at a depth, d, on a radius
in a specified direction, X. The unit of directional dose equivalent is joule per
kilogram (J kg1
) and its special name is sievert (Sv).
dose modifying factor
ratio of doses with and without modifying agents,
causing the same level of biological effect
Dose and dose-rate effectiveness factor (DDREF)
A judged factor that generalises the usually lower biological effectiveness (per
unit of dose) of radiation exposures at low doses and low dose rates as compared with exposures at high doses and high dose rates.
Dose coefficient
Used as a synonym for dose per unit intake of a radioactive substance, but
sometimes also used to describe other coefficients linking quantities or concentrations of activity to doses or dose rates, such as the external dose rate at a
specified distance above a surface with a deposit of a specified activity per unit
area of a specified radionuclide.
dose commitment
A calculational tool, defined as the infinite time integral of the per caput
dose rate E_ due to a specified event, such as a year of a planned activity
causing discharges
dose equivalent
H=DQ
Q= quality factor for specific radiation type
dose of record
The effective dose of a worker assessed by the sum of the measured personal
dose equivalent Hp(10) and the committed effective dose retrospectively determined for the Reference Person
dose-treshold hypothesis
A given dose above background, below which it is hypothesised that the risk of
excess cancer and/or heritable disease is zero. (See also Threshold dose for tissue reactions).
doubling dose
The dose of radiation (Gy) that is required to produce as many heritable mutations as those arising spontaneously in a generation.
DS02
Dosimetry System 2002, a system for estimating gamma and neutron exposure
under a large variety of situations and which allows the calculation of absorbed
dose to specific organs for members of the Life Span Study
effective dose
uses tissue weight factor
Sv
sum of tissue weighting factor times equivalent dose for all organs
equivalent dose
dose multiplied by radiation weighting factor
excess absolute risk
The rate of disease incidence or mortality in an exposed population minus the
corresponding disease rate in an unexposed population. The excess absolute
risk is often expressed as the additive excess rate per Gy or per Sv
excess relative risk
The rate of disease in an exposed population divided by the rate of disease in an
unexposed population, minus 1.0. This is often expressed as the excess relative
risk per Gy or per Sv.
Exposed individuals
The Commission distinguishes between three categories of exposed individuals:
workers (informed individuals), the public (general individuals), and patients,
including their comforters and carers.
Incidence (incidence rate)
The rate of occurrence of a disease in a population within a specified period of
time, often expressed as the number of cases of a disease arising per 100,000
individuals per year (or per 100,000 person-years).
Induced genomic instability
The induction of an altered cellular state characterised by a persistent increase
over many generations in the spontaneous rate of mutation or other genome-related changes.
intake
Activity that enters the body through the respiratory tract or the gastrointestinal tract or the skin.
– Acute intake
A single intake by inhalation or ingestion, taken to occur instantaneously.
– Chronic intake
An intake over a specified period of time.
LD50
dose that is lethal for half of exposed individuals
life-span study
The long-term cohort study of health effects in the Japanese atomic bomb survivors in Hiroshima and Nagasaki.
lifetime risk estimates
1) the excess lifetime risk (ELR) which is the difference between
the proportion of people who develop or die from the disease in an exposed
population and the corresponding proportion in a similar population without
the exposure; 2) the risk of exposure-induced death (REID) which is defined as
the difference in a cause-specific death rate for exposed and unexposed populations of a given sex and a given age at exposure, as an additional cause of death
introduced into a population; 3) loss of life expectancy (LLE) which describes
the decrease in life expectancy due to the exposure of interest; and 4) lifetime
attributable risk (LAR) which is an approximation of the REID and describes
excess deaths (or disease cases) over a follow-up period with population background rates determined by the experience of unexposed individuals. The LAR
was used in this report to estimate lifetime risks.
linear dose response
A statistical model that expresses the risk of an effect (e.g., disease or abnormality) as being proportional to dose
Linear-non-threshold (LNT) model
A dose-response model which is based on the assumption that, in the low dose
range, radiation doses greater than zero will increase the risk of excess cancer
and/or heritable disease in a simple proportionate manner.
Linear-quadratic dose response
A statistical model that expresses the risk of an effect (e.g., disease, death, or
abnormality) as the sum of two components, one proportional to dose (linear
term) and the other one proportional to the square of dose (quadratic
term) .
Mendelian diseases
Heritable diseases attributable to single-gene mutations
Multifactorial diseases
Diseases that are attributable to multiple genetic and environmental factors.
Multistage tumorigenesis
The stepwise acquisition of cellular properties that can lead to the development
of tumour from a single (target) cell.
Mutation component
A quantity that provides a measure of the relative change in disease frequency
per unit relative change in mutation rate, i.e., a measure of responsiveness; MC
values differ for different classes of heritable disease.
Nominal risk coefficient
Sex-averaged and age-at-exposure-averaged lifetime risk estimates for a representative population.
non-cancer diseases
Somatic diseases other than cancer, e.g., cardiovascular disease and cataracts.
NORM
Radioactive material containing no significant amounts of radionuclides other
than naturally occurring radionuclides. Material in which the activity concentrations of the naturally occurring radionuclides have been changed by
some process are included in NORM.
personal dose equivalent
An operational quantity: the dose equivalent in soft tissue (commonly interpreted as the ‘ICRU sphere’) at an appropriate depth, d, below a specified point
on the human body. The unit of personal dose equivalent is joule per kilogram
(J kg1
) and its special name is sievert (Sv). The specified point is usually given
by the position where the individual’s dosimeter is worn.
planned exposure situations
Everyday situations involving the planned operation of sources including decommissioning, disposal of radioactive waste and rehabilitation of the previously
occupied land. Practices in operation are planned exposure situations
PRCF (potential recoverability correction factor)
Everyday situations involving the planned operation of sources including decommissioning, disposal of radioactive waste and rehabilitation of the previously
occupied land. Practices in operation are planned exposure situations
principles of protection
A set of principles that apply equally to all controllable exposure situations: the
principle of justification, the principle of optimisation of protection, and the
principle of application of limits on maximum doses in planned situations.
Progenitor cell
Undifferentiated cell capable of limited proliferation.
projected dose
The dose that would be expected to be incurred if no protective measure(s) – were
to be taken.
protection quantities
Dose quantities that the Commission has developed for radiological protection
that allow quantification of the extent of exposure of the human body to ionising radiation from both whole and partial body external irradiation and from
intakes of radionuclides.
what has Q been superseeded by?
Q has been superseded by the radiation weighting factor in the definition of
equivalent dose, but it is still used in calculating the operational dose equivalent
quantities used in monitoring.
radiation detriment
A concept used to quantify the harmful health effects of radiation exposure in
different parts of the body. It is defined by the Commission as a function of several factors, including incidence of radiation-related cancer or heritable effects,
lethality of these conditions, quality of life, and years of life lost owing to these
conditions.
Radiation weighting factor, wR
A dimensionless factor by which the organ or tissue absorbed dose is multiplied
to reflect the higher biological effectiveness of high-LET radiations compared
with low-LET radiations. It is used to derive the equivalent dose from the absorbed dose averaged over a tissue or organ.
reference level
In emergency or existing controllable exposure situations, this represents the level of dose or risk, above which it is judged to be inappropriate to plan to allow
exposures to occur, and below which optimisation of protection should be
implemented. The chosen value for a reference level will depend upon the prevailing circumstances of the exposure under consideration.
relative life lost
The ratio of the proportion of observed years of life lost among people dying of
a disease in an exposed population and the corresponding proportion in a similar population without the exposure.
relative survival
The ratio of the proportion of cancer patients who survive for a specified number of years (e.g., 5 years) following diagnosis to the corresponding proportion
in a comparable set of cancer-free individuals.
representative person
An individual receiving a dose that is representative of the more highly exposed
individuals in the population (see Publication 101, ICRP 2006a). This term is
the equivalent of, and replaces, ‘average member of the critical group’ described in previous ICRP Recommendations.
residual dose
The dose expected to be incurred after protective measure(s) have beenfully
implemented (or a decision has been taken not to implement any protective
measures).
risk constraint
This risk is a function of the probability of an
unintended event causing a dose, and the probability of detriment due to that
dose.
sensitivity analysis
This aims to quantify how the results from a model depend upon the different
variables included in it.
source region
An anatomical region within the reference phantom body which contains the
radionuclide following its intake. The region may be an organ, a tissue, the contents of the gastrointestinal tract or urinary bladder, or the surfaces of tissues
as in the skeleton, the alimentary tract, and the respiratory tract.
Specific absorbed fraction
The fraction of energy of that emitted as a specified radiation type in a source
region, S, that is absorbed in 1 kg of a target tissue, T.
statistical power
The probability that an epidemiological study will detect a given level of elevated risk with a specified degree of confidence.
stem cell
Non-differentiated, pluripotent cell, capable of unlimited cell division
Stochastic effects of radiation
Malignant disease and heritable effects for which the probability of an effect
occurring, but not its severity, is regarded as a function of dose without
threshold.
treshold dose for tissue reactions
Dose estimated to result in only 1% incidence of tissue reactions.
tissue weighting factor
factor of each tissue (add up to 1) for effective dose
The factor by which the equivalent dose in a tissue or organ T is weighted to
represent the relative contribution of that tissue or organ to the total health
detriment resulting from uniform irradiation of the body
Track structure
Spatial patterns of energy deposition in matter along the track from the passage of ionising radiation
transport of risk
Taking a risk coefficient estimated for one population and applying it to another population with different characteristics.
unit of rem
RBE-weighted sum of absorbed dose in rads
uses quality factor
eventually replaced by Sv
difference between quality factor and radiation weighting factor
quality factor only considers LET
weightinf factors are based on RBE at inducing stochastic effects at low doses
weighting factors replaced Q- dose equivalence becamse equivalent dose
2 types of hardmful radiation effects
High doses will
cause deterministic effects, often of an acute
nature, which only appear if the dose exceeds a threshold value. Both high and low
doses may cause stochastic effects (cancer or heritable effects), which may be
observed as a statistically detectable increase in the incidences of these effects occurring long after exposure.
deterministic effects (harmful tissue reactions) due in large part to the killing/ malfunction of cells following high doses; and stochastic effects, i.e., cancer and heritable effects involving either cancer development in exposed individuals owing to mutation of somatic cells or heritable disease in their offspring owing to mutation of reproductive (germ) cells
what is the system of protection based on?
a) reference
anatomical and physiological models of the human being for the assessment of
radiation doses, b) studies at the molecular and cellular level, c) experimental animal studies, and d) epidemiological studies
how is the linear non treshold model used by the commission?
At radiation doses below around 100 mSv in a year, the increase in the incidence of stochastic effects is assumed by the Commission to occur with a small probability and in proportion to the increase in radiation dose over the background dose
source-related vs individual-related assessments
individual considers all sources the person is exposed to
source considers all people the source exposes
3 fundamental principles of protection
Justification.
Optimisation of protection.
Application of dose limits.
3 situations where radiation exposure can happen
planned
emergency
existing exposure
where are the rules exempt or excluded?
- cannot be regulated
- need not be regulated (based on low risk)
dsecribe deterministic effects
treshold dose
above treshold dose, severity of injury increases with dose
dose below which no tissues show impairment
100 mGy
This judgement applies to both single acute doses and to situations where these low doses are experienced in a protracted form as repeated annual exposures
describe stochastic effects
in the low dose
range, below about 100 mSv, it is scientifically plausible to assume that the incidence
of cancer or heritable effects will rise in direct proportion to an increase in the equivalent dose in the relevant organs and tissues
linear-non-treshold (LNT) model
are cellular adaptive responses, bystander signalling, or other biological models considered?
No, evidence is too uncertain
since the estimation of
nominal cancer risk coefficients is based upon direct human epidemiological data, any
contribution from these biological mechanisms would be included in that estimate
DDREF
dose and dose-rate effectiveness factor
used by
UNSCEAR to project cancer risk determined at high doses and high dose rates to
the risks that would apply at low doses and low dose rates
cancer risk at low dose and low rate is reduced by DDRF factor (usually 2)
detriment adjusted nominal risk coefficients for stochastic effects after
exposure to radiation at low dose rate
cancer: 0.055/ Sv for whole, 0.041/Sv for adults;
heritable effects: 0.002/Sv for whole, 0.001/Sv for adults
is radiation shown to cause heritable effects in humans?
No, but it is shown to do so in animals and is thus included
what data is used for studying heritable effects?
human and mouse studies
but radiation not yet shown to cause heritable effects in humans
approach to heritable risks
-doubling dose, obtained from actual human data
-recoverability of mutations in live births
is allowed for in the estimation of DD
Commission’s present estimate of genetic risks up to the second generation
- 2%/Gy whole population
0. 1%/Gy adult workers
differences in how nominal probability for cancer risk wa calculated in ICRP 103 vs 60
The present estimate is based upon data on cancer incidence weighted for lethality and life impairment, whereas in Publication 60 detriment was based upon fatal cancer risk weighted
for non-fatal cancer, relative life lost for fatal cancers and life impairment for nonfatal cancer
overall fatal risk coefficient recommended by commission
5%/Sv
could genetic cancers impact apparent radiation risks?
possibly
not enough evidence to be able to study this
radiation and other diseases
heart disease, stroke, digestive disease, and respriatoru dsease increased in survivors of atomic bomb
- data don’t suggest they should be included in risk from radiation doses for dose < 100 mSv
- UNSCEAR also saw no detriment for dose < 1 Gy
- risk is uncertain and no specific judgement is possible
risk to emrbyo/fetus for D < 100 mSv for malformation
insignificant
treshold for severe mental retardation in prenatal period (8-15 week)
300 mSv
even in
the absence of a true dose threshold, any effects on IQ following in-utero doses under
100 mGy would be of no practical significance
life-time
cancer risk following in-utero exposure
similar to that of childhood exposure
3 X population
absorbed dose distribution for radionuclides emitting alpha particles, soft beta particles, low-energy
photons, or Auger electrons
highly heterogeneous
radiation weighting factors for photons, protons etc/
photons and electrons = 1
protons and charged pions= 2
neutrons= function of neutron energy
alpha particles = 20
what are the remainder tissues
thymus gallbladder heart prostate cervix/uterus adrenals kidneys extrathoracic region lymph nodes muscle oral mucosa pancreas small intestine spleen
wt for bone marrow, colon, lung, stomach, breast, remainder tissues
0.12 each
wt for gonads
0.08
wt for Bladder, Oesophagus, Liver, Thyroid
0.04 each
wt for Bone surface, Brain, Salivary glands, Skin
0.01 each
reference radiation for RBE measurements
200 kV photons
LET of photons, electrons, and muons
10 keV/um
describe plot of wr for neutrons vs energy
peaks at about 20 at 1 MeV -at about 5 for 100 MeV falls off to ~ 2.5 for 0.1 and 10000 MeV -continuous function to account for fact that most neutron exposures involve a range of energies -empirical
why is wr low (2.5) for lower energy neutrons?
large contribution of secondary
photons to the absorbed dose in the human body
proton energy assumed for wr
. In the proton component of cosmic radiation fields or fields near high-energy particle accelerators, very high-energy protons dominate
> 10 MeV
these penetrate the skin
what are pions
negatively or positively charged or neutral particles encountered in
radiation fields resulting from interactions of primary cosmic rays with nuclei at high
altitudes in the atmosphere.
These particles contribute to exposures in aircraft.
They
are also found as part of the complex radiation fields behind shielding of high-energy
particle accelerators
energy distribution is broad; use wr of 2 for pions
how are humans exposed to alpha particles?
internal
emitters, e.g., from inhaled radon progeny or ingested alpha-emitting radionuclides
such as isotopes of plutonium, polonium, radium, thorium, and uranium
what does RBE depend on for alpha particles, fission fragments?
biological end-point under consideration
wr= 20 for all
where are doses from fission fragments and heavy ions important?
internal dosimetry for fission fragments
aviation for heavy ions, space exploration
what does RBE depend on for heavy ions?
wr of 20 is conservative
The radiation quality of heavy charged
particles incident on and stopped in the human body changes markedly along the
track of the particle
reference male and female models
computational
wt is sex and age averaged?
yes
equivalent doses are averaged and multiplied by wt to get effective dose
operational quantities
measured in lieu of equivalent and effective dose since equivalent and effective dose cannot be measured directly
provide conservative estimate
ambient dose equivalent and directional dose equivalent are used for area monitoring
personal dose equivalent is used for individual monitoring
personal dose equivalent depth
d= 10 mm for effective dose and 0.07 mm for skin and hands and feet dose
operational quantities for internal dosimetry
non exist
biokinetics models are used to estimate dose with measurements of radionuclides
From the intake, equivalent
or effective dose is calculated by using reference dose coefficients (doses per unit intake, Sv Bq1
) recommended by the Commission
-these are based on models to describe the entry of various chemical forms
of radionuclides into the body and their distribution and retention after entering the
blood
where can radionuclide intake be estimated from?
feces
environmental samples
external monitoring
assumption of using personal dosimeters
the body is irradiated uniformly
equation for total occupational exposure
Hp(10) + E(50)
where Hp(10) is the personal dose equivalent from external exposure and E(50), the
committed effective dose from internal exposure
E(50 is sum of ingested or inhaled radionuclides times their corresponding coefficients
Account may
be taken of the physical and chemical characteristics of the intake, including the
activity median aerodynamic diameter (AMAD) of the inhaled aerosol and the
chemical form of the particulate matter to which the specified radionuclide is
attached. Otherwise, the dose coefficnets do not depart from that of the reference male and female
what if there is a wound and radiatioactive material enters through it?
not included in regular internal dosimetry
has to be recorded and investigated separately
do aircrew have dosimeters?
No
an assessment of effective dose may be
obtained from values of the quantity ambient dose equivalent, H*(10)
for medical exposure of patients, is effective dose used?
No, it can be limiting
Effective dose can be of
value for comparing doses from different diagnostic procedures and for comparing
the use of similar technologies and procedures in different hospitals and countries
as well as the use of different technologies for the same medical examination.
However, for planning the exposure of patients and risk-benefit assessments, the equivalent dose or the absorbed dose to irradiated tissues is the relevant quantity
problems with calculating effective dose from medical tests
heterogeneous doses when only part of an organ are irradiated
difficult to interpret
main applications of effective dose
prospective dose assessment for designing protection
retrospective analysis for ensuring compliance
effective dose is for individual specific dose?
no its for a reference person
where can effective dose parameters deviate from the reference values?
direction of exposure
physical
and chemical characteristics of inhaled or ingested radionuclides. In such cases it is
necessary to clearly state the deviation from the reference parameter values.
can effecrve dose be used to asses cancer risk in exposed individuals?
No
Effective dose is intended for use as a protection quantity on the basis of reference values and therefore is not recommended for epidemiological evaluations, nor
should it be used for detailed specific retrospective investigations of individual exposure and risk
Absorbed dose and bioknietics modelling should be used for individual assessment. Organ or tissue dose is required.
what model is collective effective dose based on?
LNT
linear non trshold
what is collective effective dose used for?
n instrument for optimisation, for comparing
radiological technologies and protection procedures
dose rate and time period should be specified
not for epidemiological studies- would be biologically and statistically very uncertain- not the intent for this function
what to do with collective effective dose when the range
of individual doses spans several orders of magnitude
divide into several ranges of individual dose, each covering only 2-3 orders of magnitude
population size, mean individual dose,
and uncertainty is considered separately for each range
what do you do when the collective effective dose is smaller than the reciprocal of the relevant risk detriment
he risk assessment
should note that the most likely number of excess health effects is zero
define uncertainty
level of confidence that can be placed in a given parameter value
accuracy of measurements as dose decreases
accuracy decreases
what is variability
quantitative differences between
individual members of the population in question
accuracy of measurements as complexity of the system increases
accuracy decreases
uncertainties of assessments of radiation doses from internal exposures vs external exposure
internal exposure uncertainty is greater than external
The degree of uncertainty differs between various radionuclides
uncerainty in ICRP parameters
difficult to quantify because it varies for the parameters and circumstances. However internal exposure has larger uncertainties than external exposure
How does ICRP handle uncertainties wrt compliance
(167) Regulatory compliance is determined using point estimates of effective dose
that apply to a Reference Person, regarding these point estimates as subject to no
uncertainties. In retrospective assessments of doses that may approach or exceed limits, it may be considered appropriate to make specific individual estimates of dose
and risk, and aso to consider uncertainties in these estimates.
(168) If ICRP standards change, previous assessments of equivalent dose or effective dose
should be considered adequate. In general, the Commission does not recommend
re-computation of existing values with the new models and parameters
3 types of exposure situations
planned
emergency
existing
guide for pregnant worker
additional dose to embryo/fetus after declaration of pregnancy should not exceed 1 mSv
-females should not be involved in potential emergency situations that could expose them to high dose
-dose to fetus and dose to breast-feeding child are small compared to dose to reference female
how is the exposure to airline crew monitorred?
-control of routes and flying time
does the effect of dose from a source impact the effect of dose from a different source?
no, as long as you are under treshold dose for deterministic effects
difference between dose constraint, risk constraint, and reference level
For planned exposure situations, the source-related restriction to the dose that
individuals may incur is the dose constraint. For potential exposures, the corresponding concept is the risk constraint. For emergency and existing exposure situations, the
source-related restriction is the reference level
dose limits vs constraints and reference levels
dose limit= protect individual from all sources in a planned exposure situation
dose constraints and reference levels = protect the public from a source in any situation
principle of justification
Any decision that alters the radiation exposure situation should do more good than harm.
-source related
principle of optimisation of protection
the likelihood of incurring exposures,
the number of people exposed, and the magnitude of their individual doses should
all be kept as low as reasonably achievable, taking into account economic and
societal factors
-source related
principle of application of dose limits
The total dose to any individual from
regulated sources in planned exposure situations other than medical exposure
of patients should not exceed the appropriate limits recommended by the
Commission
-individual related
is the most optimal option always the one with the lowest dose?
not necessarily
Optimised protection is the result of an evaluation, which carefully balances the detriment from the
exposure and the resources available for the protection of individuals
2 instances where dose limit is used
planned exposure: occupational exposure
planned exposure: public exposure
3 instances where dose constraint is used
all planned exposure
occupatonal exposure
public exposure
comforters and carers, research volunteers in medical exposure
4 instances where reference exposure is used
diagnostic reference level for patients- planned exposure
emergency exposure- occupational
emergency exposure- public
existing exposure- public
risk constraint vs dose constraint
dose constraint is for planned exposures
risk constraint is for potential exposures
-source related restriction on individual dose
band 1 mSv or less
Individuals are exposed to a source that gives them little or no individual benefit but benefits to society in general.
for example- hospital treating cancer with radiation exposes non-cancer patients
band 1-20 mSv
Individuals will usually receive benefit from the exposure situation but not necessarily from the exposure itself.
ex: constraints for people caring for patients with radiopharmaceuticals
constraints for occupational exposure in planned situations
band 20-100 mSv
Individuals exposed by sources that are not controllable, or where actions to reduce doses would be disproportionately disruptive.
ex: reference level set for highest planned residual dose from a radiological emergency
public exposure limit for the year (effective dose)
1 mSv/yr
under special circumstances, could exceed this, as long as average over 5 year period if not more than 1 mSv
for NEW, 20 mSv/year on 5 year average, no more than 50 mSv in one year
Limits on effective dose are for the sum of the relevant effective doses from
external exposure in the specified time period and the committed effective
dose from intakes of radionuclides in the same period. For adults, the
committed effective dose is computed for a 50-year period after intake,
whereas for children it is computed for the period up to age 70 years.
dose limit for eye lens
equivalent dose
50 mSv occupational (CNSC)
15 mSv public
dose limit skin
equivalent dose
500 mSv occupational
50 mSv public
averaged over 1 cm2 area of skin regardless of area exposed
dose limit hands and feet
equivalent dose
500 mSv occupational
none for public
why are dose limits for tissues given in equivalent dose?
Commission assumes that the relevant RBE values for the deterministic
effects are always lower than wR values for stochastic effects. It is, thus, safely
inferred that the dose limits provide at least as much protection against high-LET
radiation as against low-LET radiation. The Commission, therefore, believes that
it is sufficiently conservative to use wR with regard to deterministic effects
consideration for transient workers
potential shared reposnsibility fo several employers and licensees
when there are planned discharges of long-lived radionuclides to the environment, how can we avoid build-up i the environment that evetually exceeds a constraint?
do the math
if too uncertain, take 0.1 mSv/yr as reasonable
if it is natural radioactive material, the limit isn’t mecessary
3 types of potential exposure events
-Events where the potential exposures would primarily affect individuals who are
also subject to planned exposures
-Events where the potential exposures could affect a larger number of people and
not only involve health risks but also other detriments, such as contaminated land
and the need to control food consumption. ex. nuclear reactor accident, malicious use of source
-Events in which the potential exposures could occur far in the future, and the
doses be delivered over long time periods, e.g., in the case of solid waste disposal
in deep repositories
risk constraint for poential exposure of workers, and public
2 x 10^-4 /yr for workers
1 X 10^-5/yr for public
how is the management of long-term contamination resulting from an emergency sitation treated as?
existing exposure situation
reference levels for radon-222
600 Bq/m3 for domestic dwellings
1500 Bq/m3 for workplaces
Radon exposure at work at levels above the national reference level should
be considered part of occupational exposure whereas exposures at levels below
should not. In the interest of international harmonisation of occupational safety
standards, a single action level value of 1000 Bq m3 was established in the BSS
(IAEA, 1996)
where are dose coefficients for the embryo/fetus due to intakes of radionuclides by the mother?
publication 88
recommendation for public exposure from radioactive waste disposal
= 0.3 mSv/yr
allowed public exposure due to prolonged exposure
between 1 and 0.3 mSv/yr as a limit
allowed public exposure from prolonged component from long-lived nuclides
= 0.1 mSv/yr
dose constraints for volunteers for biomedical researc
minor societal benefit: < 0.1 mSv
intermediate societal benefit: 0.1-1 mSv
moderate societal benefit: 1-10 mSv
-substantial societal benefit: > 10 mSv
dose constraints for comforters of patients
5 mSv per episode
young children, infants, and people not involved in direct care should be subject to 1 mSv/yr limit
occupational reference levels in emergency sitatons
- life-saving (informed volunteers)- no restriction if benefit to others outweight rescuer’s risk. . Effective doses below 1000 mSv should avoid serious deterministic effects; below
500 mSv should avoid other deterministic effects. - other urgent rescue operations:1000 or 500 mSv’
- other rescue operators: = 100 mSv
reference levels for public exposure to foodstuff, distribution of idine, sheltering, temporary evacuation, permanent relocation
In planning, typically
between 20 and 100 mSv/year
according to the situation
reference levels for radon
< 10 mSv/yr
<600 Bq/m3 at gome
< 1500 Bq/m3 at work
reference levels for NORMS
between 1 and 20 mSv/yr depending on the situation
what happens if say an operation is abandoned and the oeprators disappeared?
national regulatory authority or some other designated body will have to accept some of the responsibilities usually carried by the operating management
if a consultant is hired, with whom does the respinsibility lie?
still with the operating organization
for medical exposure, is limitation of the dose to the individual patient recommended?
No, because it
may, by reducing the effectiveness of the patient’s diagnosis or treatment, do more
harm than good. The emphasis is then on the justification of the medical procedures and on the optimisation of protection
why are dose constraints for medical exposure inappropriate?
depends on the medical test
required for the patient
-diagnostic reference levels are used to manage appropriate dose instead
3 levels of justification for use of radiation in medicine
- radiation in medicine is accepted as doing more good than harm to the patient
- procedure will improve the diagnosis or treatment
- application of procedure to the individual patient should be justified
do diagnostic reference levels apply to radiation therapy?
No
should absorbed doses below 100 mGy to the amrbyo/fetus be considered a reason for terminating a pregnancy?
No
above this the woman should receive info about risks
defence in depth
a focus of accident prevention
use multiple defences against the consequences of failure
is unintentinal exposure of members of the public in waiting rooms and
on public transport high enough to require restrictions on nuc med patients?
No, unless being treated with radioiodine
how soon can cremation occur if a patient had I-125 implants?
1 year
reference animals and plants
for protection of environment
intent of the commission wrt environmental protection
- does not intend to implement dose limits
- plans to set out data for reference animals and plants, upon which further action can be taken
- get more data and info
complex clustered damage
DSB and SSB and damaged DNA bases combine in clusters
ferquency and complexity of clustered damage depends on the LET of the radiation
conclusions for adaptive responses of cells
- not universal feature of cells
- lots of variation
- no evidence it is trigered by a few tens of mGy
- no consistent animal evidence of adaptive responses that reduce adverse health effects
doserate dependence for mutations
linear-quadratic for low LET and tend towards linearity as LET increases
epigenetic response to radiation
post-irradiation cellular responses that appear to
result in genomic change and/or cellular effect without an obvious requirement for
directly induced DNA damag
Includes:
radiation induced genomic instability- genomic damage are expressed persisently over many post-irradiation cell cycles as opposed to just the first couple
post-irradiation bystander signalling between cells
can cytokines and growth factors modify the onset of deterministic effects
yes
factors that affect dterministic effects
- cytokines and growth factors, biological response modifiers
- structures of tissues and organs- parrallel organs can sustain a lot more
stages of tumor growth
Tumour initiation – the entry of a normal cell into
an aberrant cellular pathway (pre-neoplastic state) that can lead to cancer; b) Tumour promotion – enhancement of the growth and development of a pre-neoplastic
clone of initiated cells; c) Malignant conversion – the change from a pre-neoplastic
state to one where cancer development is likely; and d) Tumour progression – the
later phases of tumorigenesis where cells gain properties that allow more rapid development and the acquisition of invasive characteristics
pt of action of radiation in multistage tumour development
initatiation state of tumorogenesis is likely
high-penetrance genes
single-gene human genetic disorders where excess spontaneous cancer is expressed
