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OAR Box 1112 

Prepped by Ryan Dugan 

Document Number: 

23) ll-C-1a 

Docket Number: 

A-83-22 

Printed 4/16/2008 9:12:06 AM Sheet 23 of 97 
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83-7.1 

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DESCRIPTION OF THE OAQPS RISK PROGRAM AND THE 

ONGOING LEAD NAAQS RISK ASSESSMENT PROJECT 

Thomas McCurdy 

Harvey M. Richmond 

U.S. Environmental Protection Agency 

Research Triangle Park, North Carolina 

For presentation at the 76th Annual Meeting of the 

Air Pollution Control Association 

Atlanta, Georgia 

June 19-24, 1983 
P.3 

DESCRIPTION OF THE OAQPS RISK PROGRAM AND THE ONGOING LEAD NAAQS RISK ASSESSPROJECT, T. McCurdy and H. M. Richmond, U.S. Environmental Protection Agency, 

Research Triangle Park, N.C. 27711 

EPA's Office of Air Quality Planning and Standards' efforts to develop formal 

quantitative risk assessment methods to aid in making future decisions on alternative 

national ambient air quality standards (NAAQS) are briefly described. The multi-year, 

ongoing risk analysis program is separated into two main divisions: risk assessment 

and risk evaluation. Emphasis of the program to date has been on developing and 

applying alternative risk assessment methods, two of which are more fully described 

in companion papers presented in this session. 

EPA is considering utilizing a formal risk assessment method in the ongoing review 

of the lead (Pb) NAAQS. EPA's initial thinking on the focus and structure of the 

Pb risk assessment project are briefly described. The project plans will be 

reviewed by a Clean Air Scientific Advisory Committee Subcommittee on Health Risk 

Assessment. 

83-7.1 

DESCRIPTION OF THE OAQPS RISK PROGRAM AND THE ONGOING LEAD NAAQS RISK ASSESSPROJECT, T. McCurdy and H. M. Richmond, U.S. Environmental Protection Agency, 

Research Triangle Park, N.C. 27711 

EPA's Office of Air Quality Planning and Standards' efforts to develop formal 

quantitative risk assessment methods to aid in making future decisions on alternative 

national ambient air quality standards (NAAQS) are briefly described. The multi-year, 

ongoing risk analysis program is separated into two main divisions: risk assessment 

and risk evaluation. Emphasis of the program to date has been on developing and 

applying alternative risk assessment methods, two of which are more fully described 

in companion papers presented in this session. 

EPA is considering utilizing a formal risk assessment method in the ongoing review 

of the lead (Pb) NAAQS. EPA's initial thinking on the focus and structure of the 

Pb risk assessment project are briefly described. The project plans will be 

reviewed by a Clean Air Scientific Advisory Committee Subcommittee on Health Risk 

Assessment. 
P.4 

83-7..1 

DESCRIPTION OF THE OAQPS RISK PROGRAM AND THE 

ONGOING LEAD NAAQS RISK ASSESSMENT PROJECT 

Introduction 

The Clean Air Act, as amended in 1977, requires periodic review and 

revision, if needed, of all national ambient air quality standards (NAAQS) to 

ensure that they are based on the latest scientific knowledge. This paper 

briefly reviews the history of the Office of Air Quality Planning and Standards' 

(OAQPS) efforts to develop formal quantitative risk assessment methods to aid 

in making future decisions on NAAQS. After the OAQPS risk program is described, 

the paper focuses on the ongoing risk assessment project for the lead NAAQS 

review. A proposed conceptual framework describing the roles of scientific 

knowledge, risk assessment, and risk evaluation in setting future NAAQS and 

the relationship of this framework to the existing Clean Air Act and current 

standard-setting procedures have been described elsewhere.1'2 

OAQPS Risk Analysis Program 

Since 1977, OAQPS has been developing and exploring the potential future 

use of quantitative health risk assessment approaches to aid in making decisions 

on primary (health-based) NAAQS. EPA's effort to develop a risk assessment 

approach for NAAQS decisions began during the review of the photochemical 

oxidant (later redesignated ozone) ambient standard. In 1977, Thomas Feagans, 

an OAQPS analyst, and Dr. William Biller, an OAQPS contractor, developed a 

health risk assessment approach for analyzing alternative ozone NAAQS. 

Incorporating some of the techniques and principles developed in the field of 

decision analysis, the approach involved eliciting judgmental probabilities 

from health and air quality experts to represent the major uncertainties whi.ch 

give rise to health risks associated with attainment of alternative NAAQS. 

Results of the ozone risk assessment were summarized in the proposed 

rulemaking notice and a document describing the application of the method to 

ozone was issued in July 1978.3>4 In the proposal notice EPA acknowledged 

that the method had not received adequate peer-review and EPA concluded in the 

promulgation notice that the method required further study and development.*^ 

At OAQPS's request, EPA's Science Advisory Board (SAB) established a 

Subcommittee on Health Risk Assessment to review the ozone and other risk 

assessment methods being used or developed within the Agency. After its first 

meeting in April 1979, the Subcommittee commended EPA for recognizing the need 

for and undertaking development of quantitative subjective decision aids for 

use in assessing health risks associated with NAAQS.' The Subcommittee, 

however, strongly recommended that EPA not apply the risk assessment method 

developed during the ozone review until the approach was further developed, 

better explained, and published in peer-reviewed journals. The Subcommittee 

also recommended that OAQPS develop and evaluate other risk assessment methods 

in addition to the approach used in ozone. 
P.5 

83-7.1 

In response to the SAB Subcommittee recommendations, OAQPS developed an 

expanded risk analysis program in the fall of 1979.8 The risk analysis program 

involves both risk assessment and risk evaluation projects. However, the 

major emphasis of the program to date has been on risk assessment, which is 

defined as the process of making risk estimates and describing the severity of 

harm associated with adverse events. Risk evaluation is defined as the process 

of evaluating how much risk is acceptable in light of all relevant circumstances. 

The first project undertaken in developing alternative risk assessment 

approaches was a highly interactive effort involving six groups of distinguished 

researchers from a variety of disciplines, including decision analysis, 

biostatistics, and behavioral psychology. The objectives of this project were 

to (1) develop conceptual risk assessment approaches suitable for use by EPA in 

reviewing ambient air standards, and (2) narrow down these alternatives to 2-

3 approaches for further development. 

A two-day kick-off public meeting was held in April 1980 at which information 

and views were exchanged on the problem of developing a suitable risk assessment 

approach for NAAQS. At the conclusion of the project, the SAB Subcommittee 

reviewed the six conceptual approaches and concluded that two approaches 

particularly warranted further development.9«10 

In parallel with the alternative conceptual approaches project, Feagans 

and Biller developed further the method that had been used for the ozone risk 

assessment (hereafter "F/B Risk Assessment Method").11 In May 1981 the SAB 

Subcommittee reviewed a report describing the F/B Risk Assessment Method and 

concluded that, "while the F/B approach may have commendable aspects as a 

research effort, it is not, in its present form, an implementable tool for 

public policy decision making . . ."12 The Subcommittee also recommended 

that the authors publish their work in peer-reviewed journals so that others 

in the professional community could judge the merits of their viewpoint. The 

authors are following the Subcommittee's recommendations to publish their 

work, but only the first of a planned series of papers has been published so 

far.13 

In an effort to further develop the two promising alternative conceptual 

approaches recommended by the SAB, OAQPS awarded separate contracts to SRI 

International and Woodward-Clyde Consultants in June 1981. These developmental 

projects were oriented toward an illustrative application of the two conceptual 

approaches using carbon monoxide (CO) as the pollutant of interest, one of the 

six pollutants for which NAAQS exist. Reports describing the two illustrative 

application projects have been completed and will be reviewed by a Subcommittee 

recently created by the Clean Air Scientific Advisory Committee (CASAC).14,15 

The two projects are summarized in two other papers in this session.1 6*

17 

OAQPS has undertaken an interagency agreement with Argonne National 

Laboratory to conduct a risk assessment for alternative lead (Pb) ambient 

standards. The approach used by Argonne will be based on the best features 

of the developmental efforts discussed above and the recommendations of 

the CASAC Subcommittee. The next section of this paper discusses in more 

detail the Pb NAAQS risk assessment project. 
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Lead NAAQS Risk Assessment Project 

OAQPS believes that the risk assessment program is now at a stage where 

an application project for an on-line standard-setting effort is desirable. 

The NAAQS pollutant selected to apply the OAQPS risk assessment method is lead 

(Pb). The existing Pb standard was set in 1978 and is now up for review under 

§109(d)(l) of the Clean Air Act. A Subcommittee of CASAC is assisting the 

full Committee in reviewing the Pb risk assessment project. The Subcommittee's 

views and guidance will be very important in the conduct of the Pb project. 

For this reason, the ideas and approach described below are tentative and may 

be altered. In fact, whether or not the risk estimates derived as part of the 

project will be used in the Pb NAAQS review depends upon CASAC's review, public 

comments regarding the technical adequacy of the approach, and EPA management's 

evaluation of the usefulness of the technique. 

Focus of the Pb Risk Project 

Final judgments on the scope and focus of the risk assessment will be based 

on a review of the scientific evidence presented and evaluated in the revised 

Pb criteria document. Based on a preliminary review of the scientific evidence, 

OAQPS is considering narrowing the scope of the Pb risk project in the manner 

described below. 

1. Exposure and risk extimates will be obtained for only 10 cities 

(due to limitations on availability of Pb air quality data for 

urbanized areas) and for a representative sample of areas surrounding 

selected major point sources of Pb emissions (primary and secondary 

smelters, battery manufacturing plants, etc.). Thus, exposure and 

risk estimates will not be applicable to the nation as a whole. 

2. Exposure and risk estimates will be provided for two potentially 

sensitive population groups: children 6 years old and younger and 

pregnant women. 

3. Risk estimates will be provided for up to eight general health effects 

indicators: heme biosynthesis, cognitive/behavioral effects, 

electrophysiological effects, renal function, reproductive and 

developmental effects, delivery complications, erythropoietic effects, 

and cardiovascular and immunological functional impacts. 

The Pb risk project will investigate all significant environmental 

pathways of Pb exposure, including water and food ingestion, other ingestion 

(such as pica for paint), and inhalation. Finally, the impact of varying the 

averaging times for the standard will be investigated. The current averaging 

time is a calendar quarter. 

Structure of the Pb Risk Project 

The overall structure of the Pb risk project is depicted in Figure 1. 

There are five major components of the project. The first two component models 

are focused on predicting total Pb exposure for the sensitive groups of concern 

in the geographical areas of interest (see above). Inputs to the first component 

model include alternative Pb air quality standards under consideration, existing 
< 

Alternate 

Pb Ambient 

Standards 

Point 

Source 

Modeling 

Component 

Model 1. 

Ambient air 

quality 

model. 

Time Series 

Analysis of 

Ambient Air 

Data 

/Predicted \ 

- X Pb Ambient V J 

\ Levels / 

Human 

Activity 

Data 

"S * 

Component 

Model 2. 

Urban areaspecific human 

exposure 

model (NEM). 

/•» 

Population & 

Travel 

Data 

/Tota 

-X Expo 

\Estii 

Total Pb 

sure 

mates 

Figure 1. Flow Chart of the Lead NAAQS 

Risk Assessment Project. 

EXPOSURE 

REPORT 

S-

> 

RISK 

REPORT 

Component 

Model 3. 

Physiological 

uptake model. H

'Estimated 

Physiologic 

^Indicator; 

Health 

Expert 

Encoding 

Component 

Model 4. 

Dose-effect 

relationship 

models. 

Component 

Model 5. 

Area-specific 

risk 

assessment 

model. 

XL 

ead Count 

Risk 

Estimates 

> 

•>! 
P.8 

83-7.1 

air quality distributions (as supplemented by time series analysis to obtain a 

complete data set), and point source modeling outputs. The prime product of 

Component Model 1 is estimated daily air quality concentrations at specified 

geographical areas (called neighborhood types) for each of the ten cities and 

major point sources being analyzed. 

Component Model 2 develops area-specific total exposure estimates for 

subject population groups. Both air and non-air exposures will be accounted 

for, and the output of the model will be in the form of (1) distributions of 

exposures experienced by sensitive groups, and (2) the expected number of 

people exposed to various concentration levels. The prime inputs to Model 2 

are the air quality estimates from Model 1, information on people's activity 

patterns, and probablisitic "additive factors" of Pb contributions for each 

environmental pathway of Pb that will be modeled. For a more thorough discussion 

of the exposure components of the OAQPS risk assessment procedure, see Biller 

et al. (1981 ). 1 8 

Component Model 3 tranforms total Pb exposure estimates into distributions 

of blood and dentine Pb in sensitive population groups in the analyzed areas. 

This "uptake" physiological model itself contains two submodels: (1) an absorption 

model relating Pb exposure estimates, disaggregated by environmental pathway, 

to Pb retained in the body, and (2) an equilibrium model relating the interchange 

of Pb among body organisms. The absorption model provides a daily estimate of 

Pb retained in the body. The equilibrium model produces daily and time-averaged 

estimates of blood Pb and dentine Pb (in shed teeth). To accomplish this 

requires that the interaction among bone, tissue, blood, and other pools of 

body Pb be explicity modeled. Component Model 3 outputs will be in the 

form of distributions of blood and/or dentine Pb in sensitive population groups, 

and in the form of expected numbers of people having a specified level of blood 

or dentine Pb concentrations. 

The prime outputs of component models 4 and 5 are probabilistic estimates 

of health risk to sensitive population groups associated with alternative Pb 

NAAQS in the geographical areas being analyzed. (For a more thorough discussion 

of probablistic risk estimates, also called benchmark and head count risk, see 

references 19 and 20). Model 4 is primarily focused upon developing doseresponse relationships for the health effects categories noted above. An 

important part of this task pertains to the probabilistic encoding of health 

expert judgments regarding uncertain functional linkages and variables of the 

dose-response relationship. Model 5 integrates the outputs of Model 4 with 

the exposure/uptake modeling results from Model 3 to produce the needed risk 

estimates. 

Results of the project will be described in two reports. The first report 

will be focused on exposure modeling results, while the second will summarize 

the exposure information and describe outputs of the uptake and risk assessment 

models. These reports will be submitted to the CASAC Subcommittee and the 

public for review. If these reviews are favorable from a scientific and 

technical perspective, OAQPS will integrate the risk assessment results with 

its other on-going Pb standard-setting activities, such as the OAQPS 

"staff paper." (The OAQPS "staff paper" reflects the staff's interpretation 

of the key studies and scientific evidence described in the criteria document 
P.9 

83-7.1 

and identifies critical uncertainties and judgments that must be addressed in 

the standard-setting process.*^1) If that occurs, the risk assessment outputs 

will be a formal part of the Pb NAAQS review process and the full CASAC will 

also review the risk reports and results as part of the overall review of 

the OAQPS staff paper. In addition, the reports will be submitted to the 

public for review and comment. Thus, there will be numerous opportunities for 

interested parties to review and comment on OAQPS's Pb risk assessment approach 

and results. This hopefully will ensure an open and technically valid project 

as OAQPS further improves its techniques to aid standard-setting decisions. 
P.10 

83-7.1 

REFERENCES 

1. T.B. Feagans and W.F. Biller, A General Method for Assessing Health 

Risks Associated with Primary National Ambient Air Quality Standards, 

U.S. EPA, Research Triangle Park, N.C , May 1981. 

2. H.M. Richmond, "A framework for assessing health risks associated with 

national ambient air quality standards." The Environmental Professional 

3_(3):225 (1981). 

3. 43 Federal Register 26962 (June 22, 1978). 

4. U.S. Environmental Protection Agency, Office of Air Quality Planning and 

Standards, A Method of Assessing the Health Risks Associated with Alternative 

Air Quality Standards for Ozone, U.S. EPA, Research Triangle Park, N.C , 

June 1978. 

5. 43 Federal Register 26962 (June 22, 1978). 

6. 40 Federal Register 8202 (February 8, 1979). 

7. U.S. Environmental Protection Agency, Science Advisory Board, Subcommittee 

on Health Risk Assessment, Review of "A Method of Assessing the Health 

Risks Associated with Alternative Air Quality Standards for Ozone," 

U.S. EPA, Washington, D.C , September 1979. 

8. U.S. Environmental Protection Agency, Office of Air Quality Planning 

and Standards, Risk Analysis Program Plan and Accomplishments, U.S. EPA, 

Research Triangle Park, N.C , February 1981. 

9. U.S. Environmental Protection Agency, Office of Air Quality Planning and 

Standards, Conceptual Approaches to Health Risk Assessment for Alternative 

NAAQS, U.S. EPA, Research Triangle Park, N.C , May 1981. 

10. U.S. Environmental Protection Agency, Science Advisory Board Subcommittee 

on Health Risk Assessment, Approaches to Health Risk Assessment for 

Alternative National Ambient Air Quality Standards, U.S. EPA, Washington, 

D.C , December 1980. 

11. T.B. Feagans and W.F. Biller, A General Method for Assessing Health Risks 

Associated with Primary National Ambient Air Quality Standards, U.S. EPA, 

Research Triangle Park, N.C , May 1981. 

12. U.S. Environmental Protection Agency, Science Advisory Board Subcommittee 

on Health Risk Assessment, Review of "A General Method for Assessing 

Health Risks Associated with Primary National Ambient Air Quality Standards," 

U.S. EPA, Washington, D.C , September 1981. 

13. T.B. Feagans and W.F. Biller, "Risk assessment: describing the protection 

provided by ambient air quality standards." The Environmental Professional 

3. (3): 235 (1981). 
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83-7.1. r 

14. R.L. Keeney et al., Development and Application of a Risk Assessment 

Methodology to Study Alternative National Ambient Carbon Monoxide 

Standards, U.S. EPA, Research Triangle Park, N.C , March 1982. 

15. A.E. Smith, P.C. McNamee, and M.W. Merkhofer, Development of Decision 

Analysis Methodology for Health Risk Assessment: An Illustrative 

Application to Alternative Air Quality Standards for Carbon Monoxide, 

U.S. EPA, Research Triangle Park, N.C , March 1982. 

16. R.L. Keeney, R.K. Sarin, and R.L. Winkler, "A risk assessment model 

for the study of alternative national ambient carbon monoxide standards," 

paper to be presented at the 76th Annual Meeting of the Air Pollution 

Control Association, Atlanta, 1983. 

17. P.C. McNamee, M.W. Merkhofer, and A.E. Smith, "Illustrative application 

of decision analysis methodology to health risk assessment of ambient 

air quality standards for carbon monoxide," paper to be presented at the 

76th Annual Meeting of the Air Pollution Control Association, Atlanta, 1983. 

18. W.F. Biller, et al., "A general model for estimating exposure associated 

with alternative NAAQS," paper 81-18.4 presented at the 74th Annual 

Meeting of the Air Pollution Control Association, Philadelphia, 1981. 

19. T.B. Feagans and W.F. Biller. A General Method for Assessing Health 

Risks Associated with Primary National Ambient Air Quality Standards, 

U.S. EPA, May 1981. 

20. H.M. Richmond, T. McCurdy, and B. Jordan, "Risk analysis in the 

context of national ambient air quality standards," paper 82-9.3 

presented at the 75th Annual Meeting of the Air Pollution Control 

Association, New Orleans, 1982. 

21. J. Padgett and H.M. Richmond. "The process of establishing and revising 

national ambient air quality standards." JAPCA 33(1): 18 (1983).