ML20138D361
| ML20138D361 | |
| Person / Time | |
|---|---|
| Issue date: | 01/07/1993 |
| From: | Blaha J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Gray J NRC COMMISSION (OCM) |
| Shared Package | |
| ML20138D373 | List: |
| References | |
| REF-WM-3 NUDOCS 9302170317 | |
| Download: ML20138D361 (23) | |
Text
p
+
January 7.1993 O
~ i 0
MEMORANDUM FOR: -Joseph' Gray Executive / Legal Assistant, OCM/JC FROM:
Jam (2 L. Blaha-
' Assistant for Operations, OEDO
SUBJECT:
-INFORMATION REQUEST ON RISK HARMONIZATION I am transmitting the following documents in' response-to a request to staff from Kitty Dragonette after the November 25, 1992 meeting between the Environmental Protection Agency (EPA) and staff:
l.
Letter from Raymond Loehr and Oddvar Nygaard, EPA Science Advisory Board to William Reilly, Administrator, EPA, May 18, 1992,.
regarding commentary on harmonizing chemical and radiation risk-reduction strategies.
- 2.
Committee on Interagency Radiation Researd and Policy Coordination (CIRRPC) Science Panel Report No. 8, Jonizing Radiation Risk Assessment - BEIR IV, October 1991.
Orig;nst tk;r.cd tv James L. Blaha Ams L D*3 Assistant for Operations, OEDO
Enclosures:
As stated v:;l a d u.
c cc:
D. Rathbun, OCM/IS S. Coplan, OCM/KR R. Boyle, OCM/FR K. Whitfield, OCM/GO J. Taylor, E00 l
H. Thompson, DEDS OGC SECY
\\
Docume.nt Name: GRAY.CEJ Distribution:
Central File NMSS r/f LLWM r/f EW.Brach JAustin PLohaus JSurmeier MHarvey TCJchnson LBell L
JBlaha LLDR r/f i
l L
PDR:
Yes N o__
Category:
Proprietary
-or CF Caly ACNW: Yes No IG:
Yes No SJBJECT ABSTRACT:'INFORMATION REQUEST ON RISK !:ARMONIZATION OFC -
LLDR 6-LLWM d
LLWM 6lNMSS SEQ 0 NAME.
MWeber*
JAustin*
Bangart*
Bernero*
hlaha DATE
/ /
/ /
/ /
/ /
[/7 /79 g'.3.f,)
- See previous concurrence
]
. f 'N
.. - n 4 o 4
}g h
9302170317 930107 PDR WASTE Iit]-
HM-3 PDR r
o
January 7, 1993 MEMORANDUM FOR: Joseph Gray Executive / Legal Assistant, OCM/JC FROM:
James L. Blaha Assistant for Operations, OEDO
SUBJECT:
INFORMATION REQUEST ON RISK HARMONIZATION I am transmitting the following documents in response to a request to staff from Kitty Dragonette after the November 25, 1992 meeting between the Environmental Protection Agency (EPA) and staff:
1.
Letter from Raymond Loehr and Oddvar Nygaard, EPA Scler.ce Advisory Board to William Reilly, Administrator, EFA, May 18, 1992, regarding commentary on harmonizing chemical and radi ~. ion risk-reduction strategies.
2.
Connittee on Interagency Radiation Research and Policy Coordination (CIRRPC) Science Panel Report No. 8, Ionizing Radiation Risk Assessment - BEIR IV, October 1991.
Ori;;'mi tt,rsd by James L. Blaha J "u l. W4 Assistant for Operations, OEDO
Enclosures:
As stated w/cw. chi cc:
D. Rathbun, OCM/lS S. Coplan, OCM/KR R. Boyle, OCM/FR K. Whitfield, OCM/GD J. Taylor, EDO H. Thompson, DEDS OGC SECY Document Name: GRAY.CEJ Distribution:
Central File NMSS r/f LLWM r/f EWBrach JAustin PLohaus JSurmeier MHarvey TCJohnson LBell JBlaha' LLDR r/f PDR:
Yes No Category:
Proprietary or CF Only ACNW: Yes No IG: Yes No SUBJECT ABSTRACT: INFORMATION REQUEST ON RISK HARMONIZATION
-r -
0FC LLDR LLWM LLWM NMSS
,I)ED0 Maha NAME MWeber*
JAustin*
Bangart* 1 Bernero*
DATE
/ /
/ /
/ /
/
/
[/'/ /f9
- See previous concurrence
MEMORANDUM FOR:
Joseph R. Gray Executive / Legal Assistant for Comissioner Curtiss Office of the. Commission
,/
FROM:
James L. Blaha Assistant for Operations Of fice of the Executive Director for Operations
SUBJECT:
INFORMATION REQUEST ON RISK HARMONIZATION I am transmitting the following documents in response to a req est to staff from Kitty Dragonette after the November 25, 1992, meeting b-tween the 9
Environmental Protection Agency (EPA) and staff:
/
1.
Letter from Raymond Loehr and Oddver Nygaard, EPA ence Advisory Board to William Reilly, Administrator, EPA, May 18, 19 2, regarding commentary on harmonizing chemical and radiatio risk-reduction strategies.
2.
Committee on Interagency Radiation Research nd-Policy Coordination (CIRRPC) Science Panel Report No. 8 "loni ing Radiation Risk Assessment - BEIR IV," October 1991.
Please contact Michael Weber at 504-1298 if u have any questions or desire more information.
James L. Blaha Assistant for Operations Office of the Executive Director for Operations
Enclosures:
As stated cc:
D. Rathbun, OCM/IS S. Coplan, OCM/KR R. Boyle, OCM/FR K. Whitfield,'OCM/GD J. Taylor, EDO
' j[iq 'y/IS H. Thompson, DEDS OGC sc SECY (Ticket 92-XXX)
DISTRIBUTION:
Centr ' Fil -
NMSS r/f pRBangart WBrach JSurmeier Plohaus LLDR r/f
- LLWM r/r MHarvey TCJohnson LBell
- SLE PREVIOUS CONCURRENCE
[0FC: LLDR*
p'DR*
LLWM*
LLWM*
NMSy,
NAME:
MWeber
[JAustin BBrach RLBangart GArjoYtY DATE: 12/28/92 [
12/28/92-12/30/92 12/31/92 E
(/[/q%
- e IDFC: NMy g, EDO NAMhRfrp[ro JB1aha
[/Q
//
DATE:
' Path & Ft'le Name: P:\\ Kitty.mw 0FFICIAL RECORD COPY POR::
YES X
NO Category:
Proprietary-or CF Only-X ACNW:- _YES JL NO-IG:
YES X
' f!0 -
- i
-Q
i MEMORANDUM FOR:
Joseph R. Gray Executive / Legal Assistant s
for Commissioner Curtiss Office of the Commission FROM:
James L. Blaha Assistant for Operations Office of the Executive Director for Operations
SUBJECT:
INFORMATION REQUEST ON RISK HARMONIZATION
/
I am transmitting the following documents in response to a request to staff from Kitty Dragonette after the November 25. 1992, meeting between the Environ'nental Protection Agency (EFA) and staff:
LetterfromRaymondLochrandOddvarNygaard,EPAScienceAdvispr[ Board 1.
to William Reilly, Administrator, EPA, May 18, 1992, reg 6rdi commentary on harmonizing chemical and radiation risk-redt, i on strategies.
/
2.
Committee on Interagency Radiation Research and Polipf Coordination (CIRRPC) Science Panel Report No. 8, " Ionizing Rad 4 tion Risk Assessment - BEIR IV " October 1991.
Please contact Michael Weber at 504-1298 if you havti,iny questions or desire more information,
/
Jim Blaha Assistafit for Operations Offics of/the Executive Director
/6r0erations
Enclosures:
As stated
/
cc:
D. Rathbun, OCH/IS S. Coplan, OCM/KR R. Boyle, OCN/fR K. Whitfield, OCM/GD
/
J. Taylor, EDO
/
H. Thompson, DED)'
/
['
OGC SECY (Ticket 92-XXX) t,/
Cer3 ral file NMSS r/f pRBangart WBrach DISTRIBUTION:
JSurmeier
,M.L'ohau s P
LLDR r/f LLWM r/r MHarvey TCJohnson Bell
- SEE PREVIOUS CONCURRENCE 0FC :
LLDfi*
Lt.OR*
LLW'i LLWM g 9 6
NMSS f
NA)iEIMWeber JAustin BBra'ch RLBa[gk/t GArlotto DATE: 12/28/92 12/28/92 12h/92
/2/3l/92
{//
OFC :
NHSS ED0 NAME: RBernero JB1aha-DATE:
/ /
/ /
Path & File Name: P:\\ Kitty.mw 0FFICIAL RECORD COPY PDR :
YES L
NO Category:
Proprietaiy ___ or CF Only X
ACNW:-- YES X
N0 IG:
YES Xz NO Delu a file after distribution Yes No _
NOTE 10: Joseph Gray Executive / Legal Assistant FROM:
Jin. Blaha Assistant for Operations, OEDO
SUBJECT:
INFORMATION REQUEST ON RISK HARMONIZATION I am transmitting the follrwing documents in response to a request to staff from Kitty Dragonette after the November 25, 1992 meeting between the Environmental Protection Agen-tEPA) and staff:
1.
Letter from Raymond Lochr and Oddvar Nygaard, EPA Science Advisory Board to William Reilly, Administrator, EPA, May 18, 1992, regarding comentary on harmonizing chemical and radiation risk-reduction strategies.
2.
CIRRPC Science Panel Report No. 8, lonizing Radiation Risk Assessinent - BEIR IV, October 199).
Please contact Michael Weber at 504-1298 if you have any questions or desire more information.
Jim Blaha Assistant for Operations, OEDO
Enclosures:
As stated cc:
D. Rathbun, OCH/IS S. Coplan, OCM/KR R. Boyle, OCM/FR K. Whitfield, OCM/GD J. Taylor, EDO H. Thompson, DEDS OGC SECY Distribution:
Central File NMSS r/f LLWM r/f EWBrach JAustin PLohaus JSurmeier MHarvey TCJohnson LBell JBlaha tLDR r/f PDR:
Yes.i_ N o...
Category:
Proprietary or CF Only X ACNW: Yes_%. No IG:
Yes,_ Nof_
SUBJECT AB.sTRACT: INFORMATION REQUEST ON RISK HARMONIZATION 4
c l'
0FC J
Jlh C.
LLWM NMSS OEDO NAME_
MWeber JAustin RBangart RBernero JBlaha DATE
@ GS Q /d$$88
/ /
/f
/,L.
/
L C = C0VER E = COVER & ENCLOSURE N = HO COPY v p p t e. t.w copy G :\\ntry. 4w I
l LL
I ':
.M 9 7. % f d UNITED STATES ENVIRONMENTAL PROTECTION AGENCY i
WASHINGTON.D.C. 20460 N
hiny 18,1992 EPA-SAB RAC-COht 92-007 mFM%og Honorablo Wil' ism K. Reilly Administrator U.S. Environr: ental Protection Agency 401 hi Street, S.W.
Washington, DC 20460
Subject:
Commentary on Harmonizing Chemical and Radiation Risk Reduction Strategies
Dear hir. Reilly:
The Science Advisory Board's Radh.4on Advisory Committee would like to bring to your attention the need for the Agency _toinelop a more coherent policy for making risk reduction decisions with respect to radiation and chemicalszpo -
sures. As detailed in the attached commentary, Harmonizing Chemical and Radi-ation Rish Reduction Strategies, the regulation of radiation risks has developed -
under a different paradigm than for regulation of chemical risks, and a signi'icant potential exists for EPA deelslons on radiation risk reduction to be seen as u.tusti-iled by the health physics community, the chemical risk management community, or -
both. Our concern has been stimulated by three recent reviews that we have con.
ducted: the Idaho Radionuclides Study (EPA-SAB RAC-LTR-92 004), the Radionu-clides in Drinking Water proposal (EPA-SAB RAC COh!92-003), and the Citizens' Guide to Radon (EPA SAB RAC-LTR 92-005). In the first two reviews, we observed that application of the chemleal paradigm to radiation issues was questioned by many in the radiation protection community. The Agency's treatment of radon in indoor air has been more in line with traditional radiation risk management, but it is inconsistent with the Agency's proposals for control of raden in drinking water.
Although the reasons for the differences between the two paradigms are historical as well as scientlile, an important feature of radiation risk assessment and reduction is the existence of a natural background of radiation in the range'of about 70 to 250 millirem (mrem) per year exclusive ofindoor 1adon. With current EPA risk assessment assumptions, the average background - say,100 mrems per year -
is estimated to produce a cancer risk of about 3 per thousand people over a lifetime Pritstedors Re:y:les Pan
- hehodAL
of exposure. To many radiation scientists, reducing czeess exposures much below 100 mrem /yr seem_s unnecessary and in any case exceedingly dif!1 cult to monitor for compliance because it is within the natural variability of background. By contrast, most EPA programs aimed at reducing risks from chemical exposures strive for risks of one in ten thousand or lower. When this paradigm is applied to radiation exposures, such as from radon in drinking water or radionuclides at Superfund sites, the reduction in radation exposure is in the vicinity of 3 to 5 percent of the total exposure, a figure far below the variability of natural background exposures. In the case of guidelines for radon mitigation in homes, however, the Of! Ice of Radiation Programs appears to use the radiation paradigm. The current benchmark criterion for remediation of radon in homes is an annual average concentration of 4 picoeuries per liter at the lowest lived in area, which translates (again, with standard risk assessment assumptions) to a lifetime cancer risk near one in one hundred.
The Science Advisory Board Report, Reducing Risk: Setting Priorities and Strategies for Environmental Protection (EPA SAB EC-90 021, subsequently refetred.-
to as Reducing Rish), clarly enunciates the principle that EPA's priorities should be directed towards reducing the greatcht risks first, especially when that can be accomplished ec9nomically. The corollary to that principle is that similar risks should be treated similarly, which calls for the harmonization, in so far as is pos-sible, of risk reduction strategies between chemicals and radiation. Harmonization does not necessarily imply identical treatment, but it does imply that any differences in treatment are clearly explained and justiflod.
A resolution to the seeming discrepancy between the radiation paradigm and the chemical paradigm could be achieved in any of several ways: bringing risk-reduction strategies for excess radiation axposures consistently in hue with the chemical paradigm, as appears to be happening in some parts of the Agency; bringing onemical risk-reduction strategies more in line with the radiation paradigm; 1
l or achiang harmony between the two systems by modifying both in appropriate ways, explaining residual differences, and placing more emphasis on what can rea-l sonably be achieved. In the last case, the Enportance of background risk could be t
incorporated and the balancing of the benefits and costs of risk reduction measures could be strengthened while maintaining much of tl.e Agency's current approach to chemicals. If none of these approaches seems appropriate, the Agency should at least explain why the risks from radiation and chemicals are treated differently un.
der specified conditions and in specified exposure settings. The Committee appreci-ates the Agency's difficulty in establishing a coherent risk reduction strategy under the variety of statutes governing EPA.
Tha ideas in this Commentary havs been discussed with the chairs of two other SAB committees, Environmental Health and Drinking Water. While not i
E
4 i
e necessarily in agreement about the virtues of veious approaches to the problem, both of these agree that the issue is important and should be addressed by the Agency. As always, we look forward to receMng your response to this Commentary.
Sincerely, MY $
Dr.
ymond C. Loe Executive Committee Science Advisory Board l
Dr. Oddvar F. N[s/d, Radiation Advisory Committee 1
- -Committee Roster l
Atta:hment 2 Commentary W
e 3
e,
-4
- . ?
Distributi:n List Administratir Deputy Adminintrator Assistant Administrators Director, Omce of Health and Environmental Assessment. ORD Director, Omce of Radiation Programs, OAR Director, Omce of Toxic Substances Director, Omce of Pesticides Proghrams EPA Regional Administrators EPA Laboratory Directors EPA Headquarters Library EPA Regional Libraries EPA Laboratory Libraries e
1 e
t l
l l-T i
i l
I l
s-NN k
---u
.m--
t I
HARMONIZING' CHEAUCAL AND RADIATION RISK-REDUCTION STRATEGIES-A SCIENCE ADVISORY BOARD COMMENTARY htroduction Risk assessment e.nd risk reduction strategies for radiation have developed j
within a markedly different paradigm than has been the case for chemicale. Radi.
ation risk assessment has been based largely on observations in b'umans exposed to relatively well known doses of radiation, while chemical risk assessments are much more oft 4n based on projections from experiments with laboratory animals or on human epidemiology with relatively uncertain determinations of exposure. Perhaps more importantly, radiation risk reduction strategies have developed almost from the start under the assumption that it would be necessary to balance these risks against the benefits of radiation or radiation producing technologies, all witida.:
environment that included unavoidable natural sources of background radiation. By -
contrast, chemical risk reduction strategies evolveded from an initial assumption, developed early in this century for food additives, that public health could be completely protected. Only in the 1960s did a balancing approach beceme well established for chemicals, and (in retrospect) even then it was aimed at reducing risk to levels that would be considered low by almost any criterion, thereby favoring protection of health more than did the.adiation paradigm. Furthermore, for many chemicals, significant natural sources were either absent or given relatively little
. consideration.
The discordance er lack of harmony between these different paradigma was not particularly evident until the Environmental Protection Agency (EPA) started to deal with radiation issues in the context of decisions that also needed to be made about chemicals, for example with respect to radionuclides as hazardous air.pollut-ants under the Clean Air Act, or at hazardous waste sites, or in drinking water supplies where chemicals are also present. The application of standard chemical risk reduction criteria to radionuclides in these situations leads to limitations on excess radiation dose that are small in comparison to natural background radiation.
Knowing the history of the radiation paradigm, it should come as no surprise that sonie radiation scientists see such limitations on radiation exposures as unworkable or even misguided. Some chemical risk assessors who observe radiation protection
'u nua ta aanmamatal maucm.=t, harm =hbt k a werd u a =t.uha17 h rurop w at u exh in the Ua.W 8tates Harmon! ation does not r@ that all aantonmantal pEcles be Weatkal or even wheth a:esatant. p:L:sas a.ro in harinony when they are ma as la tune with as mrsl2 strategy and not discordant.
1
--am m-
&-e--w-e--
m
l guidelines corresponding to risks greater than one in a thousand are similarly puzzled: how can such high absolute risks be tolerated?
Given this situation, some resolution of the discordance between the two paradigms is needed. The resolution could simply be to assert that radiation and chtmicals are fundamentally different and should be arsessed and managed differ-6atly, or some synthesis could be reached that takes into account both background issues and absolute risk levels. As an example of the latter approach, Kocher and
~,,(
Hoffman (1991) have recently proposed a specific risk management strategy that may be applied to both radiation and chemicals. The following sections describe the radiation and chemical paradigms in more detail and suggest some possible ap-proaches to resolve the discordance between them.
The Radiation Paradigm Current risk assessment approaches for radiation, whether from radionuclides or from other sources, developed out of the atomic energy program. It both served as a framework for radiation protection for atomic workers (and later for the gener-al public) and, under the rubric of " damage assessment," was used to predict fatal-ities and residual health impacts from the radioactive fallout from nuclear weapons.
In assassing risk, health physicists, radiobiologists, and radiation epidemi-clogists have been able to maka rish estimates of relatively high precision from human data.
While cancer risk estimates for radiation entall substantial uncertainties, especially at low doses and dose rates, they are seen as being sufficient to justify making a best estimate of risk within a statistical uncertainty factor of about 2 for all cuseers com-bined for whole body external radiation if the dose is known accurately (NCRP, 1989).* These best estimates of risk are used directly without further safety factors of any kind. Because best estimates are used and the degree of uncertainty is oniy moderate, risk assessment result-for radiation can be compared with risk cHteria for control decisions with some confidence.
Radiation risk aasessment was heavily influenced by the thinking of physi-cists; in fact, " health physicists" are more likely to be involved in the practice of radiation protection tha.n are the "radic'alologists" who study the fundamental bio-logical aspects of radiation. Typically, the description of radiation risks smulated the mathematical treatments of physical systems, often using phenomenologic
- maes.ci.r,unt, sarc uku-w the w ar =mauwm aseos rm., b. mad. er tout 4 d.w em e
10 rua If the hnaar dm rwpme hypcGesis is scorpted far low &ee extrapohtlou, howme, b rish a,cumnas an ruhtiveh preew In this nport & units of rad sad rsa han tesa w+d rabr thma b corrwposi!=g f'I urJts of of mad 84.
Ter esreien to & knar trJts a:1 sumert.al vdves an dmied bj cc.s huaced.
2
models with consideration of biological theory only as a secondary factor. The fit of curves to cancer data from radiobiological experiments were interprettd as reflecting linear, simple quadratie, or linear quadratic dose-response relationships, and the un.
l derlying mechanisms were described by " target theory" as "one hit" or "two hit" and j
so on. Later, it was postulated that radiation created breaks in DNA which, if not repaired, could result in somatic tnutations and eventually in cancer..While it is i
now believed that additional mechanisms - e.g., radiation effects on oncogenes -
may play a role, the mutation bypothesis for radiation carcinogenesis still heavily i
influences radiation r:sk assessment and management (NCRP,1989).
The analysis of epidemiologie information followed simuar models, whether the data were from acuto doses of whole body gamma irradiation (Hiroshima and 1
Nagasak]), fractionated X 1rradiation (tuberculosis patients, for example), or j
protracted irradiation from internally deposited radionuclides (the radium dial painters and the uranium miners). Issues arono about the existence of thresholds
- for radiation carcinogenesis (e.g., in the dial painters) or at least " practical thresh.
olds" (e.g., the idea that cancer lateney was inversely related to dose such that manifestation of risks at low doses could be delayed so long that no cancers would occur during a normallifetime).
Underlying all this development was the knowledge that background expo-sures to radiation in the range of about 70 to 250 mD11 rem per year (mrem /yr) and i
averaging perhaps 100 mrem / year dose equivalent (NCRP,1987) were inescapable.
At legst initially, these background exposures were generally assumed not to confer significant risks. Thus, as recommended radiation standards became more strin-gent with the discovery of adverse effects at ever lower levels of protracted exposure, 4
the radiation scientists kept in mind the difficulty of caparating excess exposures from natural exposures when the former did not substantially exceed the latter.
Consequently, cancer risk reduction strategies for excess radiation exposures have very probably included comparison to background radiation in addition to the comparison of risks and benefits reaching from radiat# n producing technologies, 0
even though the background exposure issue has usually not been explicitly presented in such decisions.
When in the early days the critical endpoints for radiation protection were i
effects seen only at what are now considered to be high (e.g., erythema) doses, the allowable excess doces were easDy separable from normal variability in background i
radiation. The standards have been tightened as the assumption of no threshold for '
radiation carcinogenesis and the possibility of a linear dose response relationship j
have taken hold among most radiat'on risk assessors. These assumptions have been i
l 1
c l
-l
employed in the development of radiation protection policy. Scientists have also learned, however, that many people are experiencing exposures to the lutgs from radon and its progeny thet confer risks several times that from the 100 mrem / year that arises from cosmic radiation, terrestrial gamma radiation, and internal potassi.
um-40 radiation, averaging perhaps 200 mrem /yr (NCRP,1987). And, at least for a time., medical diagnostic and therapeutic rs:Hation increased the tverage radiation dose shout 100 miem/ year on the averaga.
The International Commission on Radiologier.1 Protection (ICRP) currently recommends limiting excess environmental radiati*on exposures to a total of 100 mrem /yr for the general population GCRP,1991). In addition, the ICRP requires that there be a net positive benefit and that the ALARA principle be adhered to that is, that exposures should be kept As Low As Reason 2bly Achjavable when economic and social factors have been taken into account. The AI. ARA concept appears to be the radiation protection community's equivalent of feasible technology based standards for chemicals.
l The potential cancer burden from 100 mrem /yr exposure is not always made l
explicii, b radidon protection guidance. If continued over a lifetime, however,100 mrem,97 is calculated with EPA's current risk coefficient for radiation carcinogene-eis to cause cancer risks of alzeost 3 in a thousand (3 x 101 (NAS/NRC,1990).
l Some analyses would pred!ct risks up to three times higher, i.e., close to one in one hundred.
The Chemical Paradigm l
For chemicals, the paradigm is different. }.fost cancer risk assessments are based on the results of bloassays in eheh dosed with chemicals at levels thou-sancis of times those expected in the environment, not from human data of high
~
reliability. To deal with the uncertainty, EPA in particular has adopted the use of the upper confidence limit on the slope of the linearized multistage model to project l
rbks at low doses and has used a conservative procedure - the surface area sealing rule - to project from animal bioassays to assumed human responses. Both of these l
procedures are widely believed to produce risk estimates that are more likely to overestimate than underestimate human risk (EPA 1986; 1989). Thus rish esti.
mates for chemicals are biased high (even though such may not be the case with evcq chemical). This conservative method of dealing with uncertainty ensures that in the vast mejority of cases, the actual risk level achieveil will be lower than the l
risk criterion used in a control decision.
I 4
Furthermore, the prototype chemical carcinogens were synthetic substances with no or limited natural sources. In calculating excess risk from human sources of a chemical, background levels, if any, are therefore frequently seen as irrelevant, even though in actuality background levels from either natural sources or anthropo-genic sources other than the one being considered often exist.
Rhk e.ssessment for chemicals developed from the ideas of medical epidemi-olcgists, biostatisticians, experimental biologists, and.. perhaps most importantly -
public health regulators. Again the idea was to prottet people from the adverse eirects of chemicals on health, most particularly potential carcinogen! city. Here the tradition was chemical safety, deriving from the early food and drug protection ideas to keep chemical exposures low enough to protect health with a substantial margin of safety. This was typically accomplished by finding some "no-effect level" and then dividing by " safety factors" with the goal of achieving nearly absolute safety. This approach is still used for non-carcinogenic chemicals.
The idea that some chemicals might be a little dangerous at any level of exposure (the no threshold idea, applied especially to what were ther. called " radio-mimetic chemicals") came as quite a shock to the regulators. Congress responded in
~
1958 by attaching the "Delaney Clause" to the amendments for the Food, Drug, and Cosmetics Act, which prohibited the addition to the human food supply of any chemical that can cause caneer in htmans or =Mah. The idea remained to provide absolute protection.against cancer risk.
l From the start, however, FDA scientists and others realized that assuring complete absence of carcinogens in the food supply was impossible, particularly in view of the rapidly advancing ability of the analytic chemists to detect ever, lower levels of chemicals in foodland the abundance of naturally occurring carcinogens.
Almost from the outset of the Delaney era, therefore, the FDA was looking for the practical equivalent to absolute safety in a world where thresholds for carcinogenesis could not be assured. FDA and NIH sdentists soon proposed that if risks calculated under the no-threshold assumption were below some small value, the carcinogen was effectively not present in the food and the Delaney Clause would be satisfied. The first proposal for a " virtually safe dose" was to limit cancer risk to one in 100 million t
(10% over a lifetirrte of exposure (Rodricks et sl.,1987). The idea was clearly tied to the assumption that all the people in the United States could be exposed at or near the virtually safe dose; at the then-current population of.about 150 million, only one or two people surrently alive could be 'affected even if all the conservative assump-tions about exposure and poterey proved to be true.
5
Shortly thereafter, it was realhed that the 10' criterion itaalf put an altsost impossible burden on the regulator for assuring the safety of food additives with considerable benents. Almost as a reflex, the idea arose that one in a million (10')
was a lifetime risk that most people would find negligible. At that level, everyone in the nation could be exposed and only about 3 excess cancer casesperyear would be incurred, again even if the riak estimates were accurate and not conservative. Given that everyone would not be so exposed if one calculated the risk for a reasonably highly exposed person, the resulting cancer toll would clearly be fraisible r.ad, for most people, the risk insignificant.
Although quas!.scientifle arguments have been offered to justify the one-in.a-million criterion for acceptable risk, we must not forget that it originated as a number of convenience. Nevertheless, it became Institutionalized over the next several years and, when cancer risks from environmental exposures became recog.
nized in the late '60s'and early '70s, the concept of negligible risk at 10' was applied there.* Early on, the types of risks of most concern were widespread ones such as exposures to PCBs or pesticide residuos in the environment. Later, the same risk criteria began to be applied to much less widespread riska such as around industrial facilities or hazardous waste disposal areas.
d Eventually, it became evident that 10 was a very stringent criterion when relatively few people wara exposed. Studies of EPA decision making show that EPA often has chosen not to require reductions in exposure when the calcu'ated risks 4
4 were as high as 10 or even 10 when the population exposed was smdl (Travis et al.,1987; Rodricks et al.,1987).'
hioreover, some of the statutes that govern chemical regulation by EPA and other agencies allow or even require a balancing of the risks against the besefits of the technologies involved and the cost of control strategies in determining what risk is acceptable in a speelfic situation. Others simply demard action whenever risks are determined to be " substantial" or "significantl' and many judicial battles have been fought over the meaning of these directives. For example, in the Vinyl Chloride case litigated under the Clean Air Act, the court ruled that chemical safety did not imply a complete and unambiguous freedom from risk, but also that the
' nu 1, ) aria lstau. e a d sun w not, r.rdad la no encar mal haahh ama where, teh b vime a a
arguabh vohastary rkk smA by poemdent freue moo eanese rkhs, a Efetime rkk creerba of abms one la a Gousand 6s considated renambh far acupadomal erposure to santnegene (see Rodrkhs et al,1987, pp. 314) Ena la the oseupadual arena. howwer, radiatlan agarut, hmita are less twtrkthe la risk tanns than are rAamka2 expoeurs hat.a. Currer4r aDowaus roEstlua danos, it a:tua2)y incurred. = mud lead to a 1/ethas rkk ct es over one la a hundred pihape rechly one in tsa (See NASMRC,1990, pp.172).
6 l
'4\\ I, primary safety decision had to be made without considering benefits and control costs (Whipple,1989) Later, risk / benefit balancing could be appUed in determining an adequate margin of safety. Such risk-benefit balancing is conducted in the same spirit as the optimization principle in the radiation community, but at a different balance point, with radiation protection requiring lower expenditures per cancer avoided.
Recently, Don R. Clay, EPA's Assiskut Administrator for Solid Waste r.nd Emergency Response (which includes the soprfund program) has indicated that remediation at hazardous waste sites need not be undertaken when cancer risks for lifetime exposures are calculated to be below 10 (Clay,1991). Cancer risk levels at d
d or above 10 are aho accepted in setting Maximum Contaminant Levels (MCLs) for carcinogens in drinking water (e.g., for chloroform from water disinfection) when limiting them further is not technically or economically feasible. Even so, many EPA programs still apply a risk criterion in the 10 to 10" range to a (sometimes 4
only hypothetical)
- maximally exposed individual" or " reasonable maximum expo-sure." This "individur! risk" focus does not place as much weight on the overall protection of public health (individual risk times number of people exposed at that risk level) as does a " population risk" focus. Whether the Agency's judgment is focused on individual risk or on population risk for a speelfie situation depends on the provisions of the enabling legislation and the traditions of the EPA eilice imple-menting it. Risk based legislation is more likely to result in an indMdual risk focus, whereas technology based standards to some extent skirt the individual risk issue and impileltly favor a population risk approach.
Some chemical regulators and environmentalists are convinced that risk levels above one in a million are not acceptable for any person, invoking argumend regarding equity: why should any person bear a cancer risk for the benefit oi other people? Why should all people not be afforded equal protection? Why should carcinogens be allowed in the environment at all? And everyone would agree that all opportunities to reduce risk should be seized as long as the costs - economie, social, or other -- are not too high.
Progress toward such goals 3 much easier to measure when there is no natural background exposure. Synthetic organic chsmicals often would not b observed in the environment at allif not for human activities; even when natural 7
1 i
~.
sources can be identified, the risk levels for the natural levels of exposure are often not high when calculated with the linearhed multistage model or an equivalent.'
Notwithstanding these altrularities to the radiation paradigm, the chemical carcinogen paradigm tends to view any risk levels above 10", even to a very few individuals, as potentially excessive and therefore requiring action to reduce exposure and risk.
Discordance between ths Paradigms Although similarities and differences in risk assessment techniques for chemicals and radiation have been dheussed, (NCRP,1989) and although the difference in the rbk reduction strategins between these two paradigms has been recognhed by some scientists and regulators for several years, the prosinces of the health physicista and the chemical risk managers stayed relatively distinct until recently. As the EPA gradually took on greater and greater responsibility for reguhting radiation sources as well as chemical ones, the discordance became more visible.
The diniculty became evident in several EPA program areas. When EPA had to promulgate Nationel Emhslons Standards for Hazardous Air Pollutanta (NESHAPs) for radionuclides, it needed to harmonhe the residual risk levels with those allowable for other carcinogenic air pollutants such as benzene. In the course of analyzing sources of airborne radionuclides, more stringent controls were pro-posed for them than would have been thought necessary to keep radiation doses to 100 mrem /yr or somewhat leas. Furthermore, EPA had to wrestle with the fact that prior emissions from (or other practices of) these facilities may have left residual radioec'tivity in communities across the country producing radiation doses with calculated sisks greater than one in ten thousand..The Radiation Advisory Commit-tea (SAB,1992a) recently commented on the Idaho Radionuclides Study, in which l
some people may have received creess gamma radiation of the same magnitude as typleal background radiation levels, i.e., about 100 mrem /yr, from uranium. series i
i radionuelides in elemental phosphorus slags distributed in their community.
l Elsewhere, EPA is dealing with radon emanations from phosphoD'psum stacks or l
with rs.dionuclides from processing of rare earths for radium, thorium, or non, radioactive materials.
l IR 4 $FW aftuttiana.* SJ1af34 !& drhding 99 tar 80240 tb 8,1Dd a. the calctdated riallevels of natural eKposure hit high.
In such caaee, tha kina of onmparsson to ha hswnd of chamle.sl c.sidnepuns le more laalt to be invekad. oA4a by etlpdat.iy that thare is no azoena arporm if amW cencantratier.a are not beyerd the anSdesen Ihrlts es O e Lattentica et ha:1 ground concentrations.
8
A second area of discordance grew out of the recognition of waste problems invoMag radioactive materials that were under the puulew of EPA cr state environmental agencies rather than the Nuclear Regulatory Commisalon or thw nuclear / radiation safety agencies in agreement shtes. The most striking of these are the radioactiva or mixed waste problems at sites that have been placed on the Nationn! Priority List for attention by the Superfund Program. Here ths wastes of most concern are often the radionucildee of the uranium or thorium series that are also found in nature, and which have for the most part been " technologically -
anhanced" by human activities, rather than created by them.
The facilities of the Department of Energy that are part of the nuchar weapons complax form another group of probism sites where radenuclides are a significant or even dominating part of the cancer risk equation. Whether these facilities are treated as Superfund (CERCLA) problems or current waste disposal sitas under the Resource Ocaservation and Recovery Act (RCHA), the treatment of
, radioactive materfah is seen as necessarily being subject to the same types of risk analyses and remedial responses that EPA has used for chemica.ls. The document
' Risk Assessment Guidelines for Superfund" (RAGS), for example, contains a section on how to assess the cancer risks from exposure to radionucildes, but does not suggest any different rbk reduction strategies than for carcinogerde chemicals. The.-
)
implication is that remedfation is expected if the lifetime rbks from radionuelider are calculated to exceed about 10" (or lower in some proposals for radiation sites).
The differences in the radiation and chemical paradigma have also become -
apparent in EPA's actions with respect to radon in homes. The current EPA guidance (" action level") for home remediation is 4 pCi/L of radon in air in the-lowest lived in area, which by current EPA rbk assessment methods translates to a lifetime risk of over 1 in 100 or 10,000 in e million (1 x 10) for an average. person i
(smokers and nonsmokers combined) (EPA,1991a). The Agency is creatly not implying that such a level of risk is acceptable in an absolute sense, but appears to be applying a rule of practicality based on the dimeulty of reducing exposure levels much below 4 pCi/L within a reasonable budget. EPA atino must work on the radon
{
issue without a clear legislative mandate encouraging the Agency to regulata homeowners' choices.
EPA has reacted differently to the legislative requirement to control levels of radon in drinking water. Using an approximation of the chemical paradigm, the i
Osce of Drinking Water ha. proposed that public water utilities must treet water j
that contains radon above 300 pCi/L (EPA,1991b), a level yielding a risk in the vicinity of one in ten thousand (1 x 10"), even though this level of risk is two orders 1
9 i
of magnitude lower than what is recommended for radon in air and the cost per calculated life saved is substantially greater than for remediation of radon in household air (SAB,1992a).
It can be argue 6 that the discordance between radiation and chemical risk.
i reduction strategies is simply another manifestation of necessary differences in regulatory cholees in different situations. Indeed, good reasons exist to make all risk. reduction Ocisions within a framework intended to reduce overall risk levels without excessive attention to keeping the risks from any one situation within inflexible guidelines. Clearly, the requirements of the various statutes enabling EPA's regulatory activities force the Agency to formulate and apply some discordant and seemingly inconsistent policies. Nevertheless, the Committes believes that the differences between the chemical and radiation paradigms are more troublesome than the variation within each area of regulation.
In each new case of radiation risk management, EPA can follow the chemical -
tradition of regulating risks to the vicinity of 10" or lower or the radiation tradition i
of tolerating (where inexpensi e remedies are not readily available) an approximate' doubling of the riska from natural background radiation, which are in the vicinity of 3 ' 10 for background exclusive of radon and nearly one in a hundred (10 ) when l
radon is included. This dispa.rity can and has led to considerable lack of under-standing and conflicts betwe3n health physicists and chemical risk managers.. Even the existence of an analogy in the chemical world to_the radionuclide problem - the ba;kground levels of carcinogenie inorganic substances such as arsenic and the existence of substantial quantities of natural organic carcinogens in foods (Ames and Gold.,1990)- has not brought about any resolution of this discordance.
1 Need for Harmonization 4
Clearly, EPA needs to adopt policies that will allow its staff, the regulated community, scientif!c consultants to both parties, and the general public all to know what to expect in EPA's regulation of residual radioactivity and other radiation issues. The Radiation Advisory Committee does not claim any specialinsight in how the resolution should be accomplished, but does emphasize the importance of achieving such harmonization. InteresUn the comparative risks of radiation and 1CRP, %d is now becoming more chemicals has a MetM wta widespread her and Hoffman, ly
/
m One approach could be to assert that radiation.nnd chemical regulations are fundamentally different, perhaps because of the unavoidability of background 10
radiation. The guidance of the ICRP on dose limitation (currently,100 mrem /yr whenever the AI. ARA principle does not result in lower levels) could become the c
expUcit poucy of the Of!!ce of Radiation Programs (ORP), and other branches of EPA could explicitly defer to ORP on radiation and radioactivity issues.
A second set of alternative approaches would strive for clear consistency between the radiation and chemical risk reductic3n strategies. The two extreme cases are:
a.
Use the optimization principle along with background risks from radiation as guidance for how much excess risk can be tolerated from any, source, be it chemical or radiation. Excess risks in the range of 10 or a bit higher would be used as a criterion for remedial actions or regulations whers remediation is expensive and not easily achieved.
Use the ALARA principle whenever it appUes, that is, when risks can be reduced without excessive penalties in terms of social or economic costs. Make provisions for dealing with hazards in those cases where 4
exposures even at the calculated 10 risk level are not detectable or distinguishable from background (i.e., AIARA should apply'whenever risk reduction can be reasonably anticipated evt.n though it cannot be measured).
P b.
Regulate radiation risks exactly as chemical risks are now regulated.
Use 10" as a standard criterion for remediation or regulation, regard-Icss of how the corresponding standards compare with background levels of exposure. Use the absolute value of risk in excess of back-ground risk as a criterion, not the fractional increment relative to background risk. Make practical exceptions for the inabiUty to detect some of the regulated exposures at the selected level of risk,just as is done for chemical substances when the detection limit exceeds the target for regulation, as is the case for dic,xin in water. Take costs and benefits into account where the appucable legislation provides for that possibility.
The Radiation Advisory Committee recognizes that neither of these latter
. options may be practicable given the history of how the two paradigmr developed.
Probably more likely to be accepted would be a third option that seeks a compromise risk reduction strategy with an intermediate risk acceptance criterion or criteria.
11
i 8
4 As a third option, the Agency could determine that, because the phyalcal i
characteristics of the two types of agents are so different and because the approach-es to monitoring and regu ating them have developed so differently, bringing the two areas into rigid conformity in the near term is very likely not possiblo, however societally or ethically desirable as a long term goal. The Radiation Advisory Committee strongly suggesta in this case that the two appronebes be harmonized-that is, fitted into a common policy framework aimed at aggregate risk reduction but not necessarily achieving such reductions in identical ways or with identical risk criteria in every case (see Deisler,1984, for an example of harmonization in the chemical safety IIeld). The harmonization between chemical and radiation risks of different types could occur by clearly and explicitly taking into account the differene-es in risk reduction criteria or strategies between hazards that have natufal sources (rather than, or in addition to, anthropogenic sources) and those that have only anthropogenic sources. For example, risk criteria for substances with no natural sources (including radionuelides such as plutonium or americium) could be different from those used for substances that have natural sources (including carcinogenic inorganic substances and organic materials with signifIcant natural sources).
r Whatever the nature of harmonization between the radiation and chemical paradigms, it will need to incorporate as well the differences among ambient environmental and indoor and occupational exposures, and the distributions of risks and benefits among exposed individuals and the sources of the exposure.
t Clearly, the choice among these options - and others that may exist -is a l
policy choice that transcends scientific analysis.
The leadership of the Environ-mental Protection Agency has the authority and the responsibility to make the choice. We urge the choice to be artleulated clearly so that the scientists who assess j
the risks of radiation and chemicals can understand the basis for subsequent l
decisions about risk reduction.
i 5
9 5
12
\\
-+-w.-c t-e-t-
.c
. - - - r
.r.m,_
,e v-y wm-
.,c.,
.m
.. m m.
m
o s.
REFERh.4CES i
Ames, B.N., and L.S. Gold,1990. Too Many Rodent Carcinogens: Mitogenesis Increases Mutagenesis, Science 249:970-971, Clay, D.R.,1991. Role of the Baseline Mk Assessment in Superfund Remedy Selee-tion Decisions, Environmental Protection Agency Memorandum, April 22,1991, p.1 1
Deisler, P.F. Jr.,1984. Reducing the Carcinogenic Mks in Industry, Mercel-Dekker, pp. 135 158.
\\
EPA,1986. Environmental Protection Agency, Guidelines for Carcinogen Mk Assessment, Fed. Reg. 51:33992 34003, September 24,1986..
)
EPA,1989. Environmental Protection Agency, hk Assessment Guidance for Superfund, Vol.1, Human Health Evaluation Manuel (Part A), EPA /540/189/002, pp. 8-6.
~
EPA,1991a. Environmental Protection Agency, Proposed Revisions in EPA Esti-mates of Radon, Mks and Associated Uncertaintia.
I EPA,1951b. Environmental Protection Agency, National Primary Drinking Water Regulations; Radionuclides; Proposed Rule, Fed. Reg. 56:33050 33127, July 18, 1991, pp. 33051.
ICRP,1991. International Commission on Radiological Protection, Radiation Protection: 1990 Recommendations of the International Commission on Radiological Protection, ICRP Publication 60, Pergamon Press.
Kocher, D.C., and F.O. Hoffman,1991. Regulating Environmental t..ecinogens:
Where Do We Draw the Line?, Env. Sci. Technol. 25:19861989.
NAS/NRC,1990. National Research Council, Health Effects of Exposure to Low Levels ofIonizing Radiation (BEIR V). Report of tht. Committee on the Biological Effects ofIonizing Radiations, National Academy Press, pp.172173.
NCRP,1987. National Council on Radiation Protection and Measurements, Expo-sure of the Population of the United States and Canada from Natural Background Radiation, NCRP Report 94.
13
NCRP,1989. National Counch.n Radiation Protection and Measurementa, Com.'
parative Carcinogenicity of Ionizing Radiation and Chemicals, NCRP Report No. 96, pp.2.
SAB,1992a: Science Advisory Board, Radiation Advisory Committee,1daho Radionu.
clide Study, EPA SAB RAC LTR 92 004, January 21,1992.
SAB,1992b: Science Advisory Board, Radiation Advisory Committee, Reducing hks from Radon; Drluking Water Criteria Documenta, EPA.SAB RAC-COM 92 003, January 29,1992.
Rodricks, J.V., S.M. Brett, and G.C. Wrenn,1987. Significant Ek Decisions in Federal Regulatory Agencies, Reg. Toxicol. Pharmacol. 7:307-320,.1997, p. 308,310 313 Travis, C.C., et al.,1987. Cancer hk Management, Eny-Sci. Technol. 21:415420.
Whipple, C.,1989. Courts Speak on hk issue, Forum Appl. Research Publ. Policy, 4:96 99.
o e
14 1
- - - - -. - -. - _ _ - _ _ _ _ - _ _ _