Radiation Dose Limits for Adult Subjects

Radiation Dose Limits for Adult Subjects

Henry D. Royal, M.D.

Associate DirectorDivision of Nuclear Medicine

Mallinckrodt Institute of Radiology

Professor of RadiologyWashington University School of Medicine

St. Louis, MOFDA Meeting 11/16/04

Past and Present Experiences

IAEA International Chernobyl ProjectSeveral NAS CommitteesPresidential Advisory Committee on

Human Radiation ExperimentsImmediate Past President, SNMVeterans Advisory Committee for

Environmental HazardsBoard of Directors, NCRPUS Delegate to UNSCEAR

Overview

Current RegulationsLimitations of Current RegulationsCommunicating RisksAnswers to QuestionsOther Comments

Whole Body, Active Blood-forming Organs, Lens Of The Eye, And Gonads:

Rem

Single dose 3

Annual and total dose commitment

5

Other Organs: Rem

Single dose 5

Annual and total dose commitment

15

Limitations

Linked to Occupational ExposureWhole Body DoseNo Adjustment for AgeNo Adjustment for Life Expectancy

Linked to Occupational Exposure

Rationale UnclearSince Subjects Will Not Directly

Benefit From RDRC Studies, Risk Should be Minimal

Unfortunately, Minimal Risk is Ambiguously Defined

Whole Body Dose

Should Be Replaced By EDDose is a Surrogate for RiskDose Limits Should Be Modified To

Adjust For Age And Life Expectancy

ConsumerProducts

0

200

400

600

800

1000

1200

1400

1600

0 10 20 30 40 50 60 70 80

Leukemia

Cancers

Age

Can

cers

per

10

4 P

ers

on

-Gy

Females

BEIR V 1990

Can

cer

Rate

Age (Years)0 20 4

0 60 80

Exposure

Latent Period

Baseline Cancer Rate

Communicating Risks

The Magnitude of a Risk Depends on Framing

Common Approach:

Radiation Increases the Risk of a Fatal Cancer by 4%-5% per Sievert (100 rems)

For a 5 Rem ED

Participation In this Research Study Will Increase Your Chances of Getting Cancer (Dying) by 2/1000

Communicating Risks

What’s Wrong With This Approach?

Very Difficult For Most People to Think in Terms of Numerical Risks

Does Not Distinguish Between Immediate Deaths and Delayed Deaths

Does Not Account for Age or Life Expectancy

An Alternative ApproachDays of Life Lost

2/1000 Times 15 Years = 10.95 Days

Cologne et al: Lancet 2000; 356:303-07

>

Loss of Life

< 1 Gy – 2 Months

>1 Gy – 2.6 Years

60% Cancer

30% Other

10% Leukemia

Cologne et al: Lancet 2000; 356:303-07

Alc

oh

olic

Poor

Socia

l S

tatu

s Gra

de S

ch

ool D

rop

-Ou

t

Can

cer

20%

Overw

eig

ht

Hig

h

Ris

k J

ob

Orp

ah

ned

Povert

y

Sm

okin

g -

Male

Heart

D

isease

Moto

r V

eh

icle

Accid

en

ts

1,000

2,000

3,000

4,000

Cohen: Health Physics 61:317-335, 1991

5,000

6,000Loss o

f Lif

e

Exp

en

tan

cy (

Days)

Catalog of Risks

Su

icid

e

Dri

nkin

g W

ate

r

Fir

e,

Bu

rns

Alc

oh

ol

Mu

rder E

nerg

y C

on

serv

ati

on

Moto

r V

eh

icle

Accid

en

ts

Loss o

f Lif

e

Exp

en

tan

cy (

Days)

50

100

150

200

Catalog of Risks

Cohen: Health Physics 61:317-335, 1991

Air

Pollu

tion

Sm

all C

ars

AID

S

Rad

on

Pesti

cid

es

Pois

on

Natu

ral H

azard

s

Bic

ycle

s

Sp

ou

se S

mokin

g

Dro

wn

ing

Rad

iati

on

Work

er

250

300

An Alternative Approach

Variations in Background Radiation

±100 mrem X 70 Years = 7 remNot Possible to Measure the Risk Directly“…the possibility that there may be no

risks from exposures comparable to external natural background radiation can not be ruled out.”

BEIR V 1990 Page 181

Unintended Consequences

Some Populations Will Not Benefit From Medical Research

Increased Collective Dose to Obtain the Same Information

Opportunity Costs

Answers to Questions

Current Dose Limits (5 Rem Annual Dose) Are Appropriate

Should Adjust for Age and Life Expectancy So That Dose is A Better Surrogate For Risk

Other Comments

Get Rid of Organ Doses Accounted for in EDShould be Limited Out of Concern for

Deterministic Effects Only

Keep Regulations Are SimpleAvoid Unintended Consequences