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OCR for page 55
55
ASBESTOS
William M. Stigliani
Part 1: Environmental Protection Agency' s Assessment
of Asbestos-Containing Material in Schools
A. BACKGROUND AND CONTEXT
-
t. Describe the chemical and its uses.
Asbestos is a general term for a group of naturally occurring
hydrated mineral silicates that separate into fibers. Asbestos
minerals used commercially include: chrysotite, amosite9
crocidolite, tremolite, actinolite, and anthophyllite asbestos.
Since asbestos in highly resistant to heat, has high tensile
strength, and moderate to good chemical resistance, it has many
uses ~ These include ~sbestos-cement pipe, asbestos paper,
friction products, vinyl asbestos floor tile, paints, coatings and
sealants, and gaskets and packings.
N : This case study describes assessment procedures and issues and
interpretations raised by others, but it is not intended to present
independent positions or interpretations on either scientific or
policy matters. Me case has been reviewed by individuals outside the
study pro Sect who are directly familiar with the federal analyses and
decisions described; however, responsibility for the paper rests with
the au£J,or, and it does not necessarily reflect the judgment of the
Committee on the Institutional Means for Assessment of Risks to Public
}search or the National Researcl' Council. It has not been subjected to
internal review procedures that apply to reports prepared by NRC
commit tees .
OCR for page 56
56
2. Describe tow the question of risk was elevated to the agency
agenda.
Warnings about 'near th hazards in schools 'nad been raised from
several sources during the 1970s. Dr. William Nicholson and a
team of Mt. Sinai scientists in ~ 1978 study did measurements in
schools in New Jersey showing high levels of asbestos exposure.
At the same t ime 9 the Pub kc Health Service had issued an advisory
concerning the hazard of asbes tos in schools .
Subsequent to these warnings, the Environmental De fens e Fund
(EDF) petitioned the EPA, through section 2L of the Toxic
Substances Control Act, to take regulatory action. The petition
was denied, and El)F sued the EPA. In an agreement settled out of
court, EPA agreed to proceed trite rulemak' ng. The rule became
final June 28, 1982.
3. Under what statutes and agency jurisdiction does the chemical
fall? What statutory tests governed the decision?
The rule falls under the jurisdiction of section 6( a) of the Toxic
Substances Control Act 9 which authorizes the Administrator to
issue warnings and notification if a hazard exists.
The rule requires the governing officials (e. A., superinten-
dent, head of school board, headmaster) to inspect ~11 public and
private primary and secondary schools in the DO SoA. for friable
materials. If such material is found, three samples oust be
analyzed for asbestos by polarized light microscopy from an EPA
recommended laboratory. If abbes tos is found to be present in
these samples, a school must: ( 1) notify the PTA, ~ 2) notify all
employees, (3) post notices in administrative areas, (~) give
guidance for reducing ashes tos exposure to maintenance people and
(5) keep records of all correspondence ~ laboratory information
letters to employees, PTA, etcO ~ .
4. What was the decision schedule? Note any statutory or other
action deadlines.
. .
Advance not ice 0 f proposed
rulemaking
First draft support document
assessing risk of asbestos
in s choot s
Final Rule
September 1980
Oct. 1980
Feb. 1981 ~ postponed)
OCR for page 57
57
Second draf t support document
assessing risk of ashes tos
in schools
Final vers ion of support document
assessing risk of a~be~to.s
in schoo Is
Fina ~ Rule
July 1981
January 1982
June 28, 1982
Final date of compliance to rule June 28, 1983
QUANTIFICATION AND CHARACTERIZATION OF RISK 'to HUMANS
_
(Sections B and C have been combined. )*
I. Cat health endpoints were evaluated?
Lung cancer, pleural and peritoneal mesothelioma, cancers of the
larynx, oral cavity, esophagus, stomach, colon, and kidney.
2. What were the key data available for review? (What additional
data were sought?)
Human Data
The epidemiological data selec ted to be the basis for making quan-
titative estimates of premature death from exposure to asbestos in
schools -~as a large study of asbestos insulation workers (12,0S1
men) reported by Hammond et al. ( 1~ and Selikoff ~2~. Various
other epidemiological s tudies were considered but EPA decided the
insulation workers study was the best one available. Several
reasons were c i ted for this pre ference:
l) the large sample size;
(2) the reasonableness of the estimates of asbestos
exposure levels;
(3 ~ detailed information on various cancer types;
* This section describes the second draf t support document (July
1981~ . The final version of the support documen t (January 1982 ) is
not discussed here since it contains no quant' tative estimations of
risk; the estimates calculated in the second draft were deleted.
OCR for page 58
58
(4) verification of death certificates with supple-
mental information (e.g., autopsy reports,
histo logica ~ s pee imens ~ to de tee t misdiagnosed
mesa the 1 imas;
(5 ~ appropriateness of the control group; and
6) similarities between the material to which the
insulation workers were exposed and the ashes tots
present in schools.
Data on Exposed School Population
EPA gathered information on the presence o f friable asbes tos-
containing materials in public schools and the number of people
exposed by conducting a survey of the nation's school districts.
There was about an 8% response rate. EPA subsequently contacted
school districts that did not respond initial ly for further
informal ion.
Exposure Assessment
The prevalent exposure levels in schools containing friable ashes tos
materials were estimated based on data from a study by Sebastien et
_. (3) of several buildings in Paris. EPA's reasons for choosing
this study were the following:
t) the areas and materials studied are similar to
those in U. S . schools;
(2) the measurements were made by transmission electron
microscopy ~ the only technique whic h is accurate for
environmental sampl ing a ~ low concentrat ion); the
measurements were checked by statistical quality
control techniques 9 and the samples were taken over
relatively long time periods; and
(3 ~ comparisons were made with outdoor air and with a
significant number of buildings that did not contain
ashes tos materials .
EPA fen other studies of U.S. schools did not reeet thee.
criteria. Ilowever, other studies were used to verify that the results
of the Sebastien _ al. study were consistent with data for U.S.
buildings .
OCR for page 59
59
3. To performed the initial analysis? (What was their
background? Available analytic resources? )
Two s taf f members of the Health and Environmental Review Division
of the Office of Toxic Substances at the EPA performed the initial
analysis. One was a Ph.~. epidemiologist; the other had an M.P.H.
degree.
4. To what extent were results presented quantitatively? What
factors influenced the degree of quantif ication^
lathe results were presented in a precisely quantitative fashion--as
lifetime risk and number of premature deaths for students and
adul t empl oyees .
The EPA staff felt there was sufficient data, with reasonable
assumptions, to proceed with a highly quantified assessment.
How was uncertainty described in reaching final interprera-
tions? Were crucial assumptions made explicit?
Uncertainty was described in two important ways . First, utilizing
a linearized dose-response curve, EPA calculated a range of risks
for school occupants, characterizing this range as low, inter-
mediate and high. Me range was based on high, low, and most
likely predict ions of three parameters:
( 1) The cumulative exposure of insulation workers in the
underlying s tudy;
(2 ~ The cumulative exposure of occupants of schools; and
(3) Mortality rates among insulation workers (based on
observed deaths, and deaths calculated from uppper
and lower 95% confidence limits).
Second, EPA considered the pass ibility that risk could be
described by other dose response models, including the threshold
model. The document s tates:
EPA's policy is to select curves that cannot 'ce
ruled out on the teas is of pharmacokinetics or poor
"fit" to available dose-response data and that
display the full range of reasonably possible
increases in risk....EPA is unaware of information
about the pharmacokinetics of ashes tos that would
enable the shape of a dose-response curve to be
OCR for page 60
60
inferred O . ~ .~ should be noted, however, that a
curve could be deve loped to yield virtual ly any
prediction of risk between zero and the leve 1 of risk
predicted by the one-hit model or linear regress ion.
All crucial assumptions in describing these uncertainties, were
explicitly stated.
6. How were Qualitative factors dealt with
Mechanism of action, associated thresholds
E ffec ts on population subgroups
- Other confounding factors
EPA was unaware of information about the pharmacokineeics of
asbestos that would provide definitive evidence about the shape of
the dose-response curve ~ or the existence of thresholds O
EPA did consider biological susceptibility to asbestos as a
function of age O After reviewing the literatures EPA determined
that there was little confirmatory evidence to assume that
children were more susceptible to asbestos exposure than adults.
EPA made the assumption that annual incidence rate is not affected
by age at first exposure. The longer retraining life expectancy of
children compared wi th that o f adults was the only factor that was
inco rpora ted in t o the q cant i ~ a ~ ive ri s ~ e s t ima te .
EPA did consider the greater risk of lung cancer from asbestos
exposure among smokers Data for the smoking-asbestos interaction
was incorporated into the risk assessment.
The effect of fiber size and type on carcinogenic response was
considered. Experimental evidence s trongly sugges ts that fibers
of certain sizes that reach the pleura g regardless of chemical
composition, are more potent in producing mesothelioma than fibers
of other sizes. EPA assumed that its use of data from the study
of asbestos insulation workers avoided any major uncertainties
that might otherwise have been presented by this finding. Because
there were no data indicating that the fiber types or sizes to
which the insulation workers were exposed were substantially
different from those present in schools, the types and sizes in
both settings were assumed to be similar.
OCR for page 61
61
What qualitative factors affected the weighting of data? Were
such criteria explicit and in accord with any general ouide-
lines ?
-
The calculated risk estimates were based on a linear, nonthreshold
dose-response curve. SPA acknowledged that these estimates were
conservative with respect to other models that could have been
used, particularly the threshold model. EPA stated that "the
existence of a threshold is theoretically possible but not
demonstrated." EPA cited evidence, primarily in the form of
mesot'nelioma case reports, that nonoccupational levels of
exposure, perhaps as low as those found in schools, are sufficient
to elevate risk. Other reasons cited by EPA for use of the linear
mode! were: the fact that the authors of two major studies of
asbestos workers believe their data for increased respiratory
cancer risk are best described by the linear nonthreshold
relationship, the fact that reviewers of the asbestos literature
have recommended the use of this dose-response curve for lo~dose
extrapolations, and that for quantitative risk assessments of
carcinogens in general, the EPA Interim Guidelines (EPA 1976,
Albert _ al . 1977 ~ Cal is for the use of the 1 inear nonthreshold
dose-re s pans e curve .
As another issue EPA stated that peak exposures were not
included in the risk assessment because their frequency could not
be estimated. However, "for some individuals, custodians and
maintenance workers in particular, the impac ~ of peak exposures
might dwarf the effect of exposure to prevalent asbestos concen-
trations....Custodians could easily double their cumulative
exposure by spending less than 3 minutes per day dry sweep-
ing....Vies~ed in this manner, the inability to incorporate peak
exposures into the risk assessment may underestimate custodians'
exposure (and therefore risk) by more than an order of magnitude."
EPA estimated that 6% of the exposed school children were
smokers, and sub ject to the interaction between smoking and
asbestos in the elevation of lung cancer risk. This estimate
assumes that interaction wit 1 not take place in exposed students
who become smokers after leaving school. If the interaction
actually does occur, then the risk to school children predicted by
EPA could be s ignif~cantly underestimated.
Another assumption was that the estimate of premature death
when only 16: of the workers have died (observation period of the
cohort study) will be the same when all 12,051 have died. This
assumption may underestimate the risk.
In calculating the cumulative exposure of the insulation
workers, EPA assumed an induction period 10. Therefore, only
exposures 10 years prior to the beginning of the observation
period were considered '~wasted. " There is convincing evidence
that the induction period may be longer, perhaps 20. Thus E P.\
may have overes timated the cumulative exposure, thereby unter-
estimating the risk at a given cumulative exposure.
OCR for page 62
62
8. Describe any internal, internal-ad~risory (e.g., EPA' s SAB), and
external (e.g., NAS) scientific review of the initial analysisO
What, if any, cri ticism was incur ed?
In early 1980, a draft risk assessment was reviewed by four
outside medical authorities. In the proposed rule ~ September
1980), public comments regarding health risks were solicited. In
November 1980, there was a public rulemaking bearing in which
comments were invited. In December 1980, there was a meeting with
the Toxic Substances Subcommittee of the EPA's Science Advisory
Board ~ SAB) to evaluate the risk assessment document .
Me SAB raised the issue of the lack of definitive scientific
evidence for choosing one dose-response curare in preference to
another. Whey suggested that the risk assessment incorporate
several different extrapolations. They also urged the authors to
incorporate more evidence from qualitative epidemiologic data
showing the incidence of mesoehelioma occurring at extremely low
levels of asbestos exposure. This data they suggested was the
best evidence that a threshold did not exist. The SAB also
suggested that more emphasis be given to peak exposures, which
they believed caused an inordinately high risk to school
maintenance workers. Finally, they strongly urged the El?A to
incorporate the separate ef fects of ashes tos exposure on smokers
and nonsmokers into the risk assessment.
9. How were the issues raised in the reviewks) accommodated?
In the revised draf ~ (July 1981) EPA included a more extensive
discussion of different dose-response models. In particular, EPA
focused on the question of a threshold response to asbestos
exposure. EPA did not dispute its possible existence, but
presented information that would argue against such a contention.
In particular, the revised risk assessment included more
comprehensive documentation of cases of mesothelioma occurring
after only short periods of exposure to asbestos.
The revised draft also discussed the importance of peak
exposures. Although these were not factored into the risk
assessment, EPA acknowledged the possible great underes timation of
risk due to this omission ~ see Q. C . 7 ~ .
Data on ashes tos exposure among smokers and nonsmokers was
made available to EPA, and this information was incorporated in
the revised risk assessment. The new data lowered the estimated
risk since the incidence of smoking among school children is much
lower than the incidence among insulation workers.
OCR for page 63
63
10. What other issues arose concerning scientific data and their
use? Briefly describe dissenting opinion.
Representatives from the Asbestos Information Association (AIA)
also attended the December 1980 meeting. At that time the AIA
argued the t:
the exposure data was taken from only one French
study which was not representative of all the
schools in the U. S.;
there was no evidence that a threshold d id no ~
exist, and therefore a scientifically valid risk
assessment could not be made until the issue was
reso lved; and
(3) the risk assessment was seriously flawed because
no attempt was made to separate out the effect of
smoking in the ana ly s i s .
L1. Is the substance subject to past or possible future regulatory
i_
ordinate W1 th o ther agencies or programs ?
The Air and 'hater Offices at EPA each have established standards
for asbestos. Also, OSHA, CPSC and FDA have all promulgated
rules, pertaining to various aspects of asbestos use. Asbestos is
subject to future regulatory actions or revis ion of current
s tandards in each o f the four agencies .
Mere was an asbestos working group established by the
Interagency Regulatory Liaison Group to coordinate activities
under the Carter Administration, but this group was disbanded in
September 1981.
D . INTE RPRETATION
1. fat role did ri sk assessment have in the final agency
document where s tandards were established to control the
che~nica 1 ?
'the quantitative risk assessment played no identifiable role in
the final rule. In fact the calculations and estimation of
numbers at risk were removed from the f inal rifle assessment
document.
OCR for page 64
64
Were there variations--over time or across agency programso-in
the assumptions used? Were these variations significant to
the final risk assessment?
,
By the spring of 1982 g EPA, CPSC and OSHA all had developed
(draft) quantitative risk assesses The author of this case
study compared the values of premature deaths quoted in these
draft reports ~ standardized to an accumulated exposure of 2
f~bers/cc, 20 years, 40 hours/week) . Specifically, the calculated
risks, in premature deaths per 1 9 000 were:
OSHA*
EPA
CPSC
8-260
.
1,000
57-348
1, 000
19-338
1 9 000
It thus appears that there was significant agreement among the
agencies in Else calculation of risk from abbes tos.
To the extent there were issues/concerns about questions of
science, would the outcome have been improved by:
A better system of in-house scientific review?
Review by an outside scientific organization?
Coherent federal guidel ines on carcinogenic risk assessment
Better agency guidelines on the performance of risk
assessment?
- Improved agency decis ion procedures ?
Me calculated numbers for school occupants at risk, present
in the July 1981 draft, were deleted in the final version of the
risk assessment (January 1982~. Apparently, the decision to
remove the numbers was made by the Deputy Ass istant Administrator
for Toxic Substances without consultation with the Toxic Sub-
~ Lances Subcommittee o ~ the EPA' s Science Advisory Board ~ SAB) .
* OSHA's estimates were quoted with no supporting information provided
(FR. Jan. 13, 1982, 1807) .
OCR for page 65
65
(For the role of the SAB, see Q. C. 8) . There were reports of
concern among the SAB members, that the deletion and the bypassing
of the advisory panel could reduce the credibili ty of EPA risk
assessments. This break in communication may have been averted
had es tab L ished procedures on the ro le o f the SAB in individual
risk assessments been better formulated.
PERFORMANCE CONSIDERATIONS
.
1. Ability to obtain relevant scientific information.
EPA staff probably utilized the best scientific late available to
them at the time the assessment was made. The major gap in
information was lack o f good comprehensive exposure data for U. S.
schoo 1 s .
2. Credibility of assessment; 1 ikel infold that interested parties
would accept them as definitive.
The draft risk assessment (July 1981) is credible only to the
extent that a nonthreshold linear low dose extrapolation is deemed
to be credible. EPA s taff was following EPA policy and guidelines
in use since the mid-1970s. Since the choice of a model is based
in part on a policy decision and not on complete scientific
knowledge, some interested parties, quite predictably, attacked
the use of the model.
~~ ~ _~
~ _-
the assessment group itself? That was the degree to which
interest pressures could be exerted from outside the
assessment group? '~hat was the respons iveness of the
assessment to these diverse interests?
The assessment group was made up of staff from EPA's Health and
Environmental Review Division of the Office of Toxic Substances.
The SAB, which played a key role in reviewing the document, was
made up of academicians and various medical experts. None of
these appeared to have any direct association with the asbestos
industry. Early in the review process, representatives from the
Asbestos Information Association (AIA), an industry trade
association, expressed strong opposition to various aspects of
EPA's quantitative risk assessment (see Q. C. 10), and voiced
their objections on numerous occasions.
OCR for page 66
66
After completing of the second draf t of the quantitative risk
assessment (July, 1981), the Deputy Assistant Administrator for
Toxin Subs tances asked the asses sment group to remove the
calculated number e of school occupants at risk from the risk
an sessment O The fine ~ vers ion o f the s upport document ~ January
1982) reflected this deletion. T'nis change was done apparently
without prior consultation with the SAB, and -~as reported to have
had the wholehearted support of the AIA. Some interested members
of Congress have harshly criticized the deletion, citing evidence
float SPA of ficials consulted only the ALl before making the change.
See also QO I). 3 and QO E. 7.
4. What were the time and resources necessary to complete the
risk assessment?
Three to three and one-half person years was needed to complete
the risk asses sment .
5. Responsiveness of assessment agenda to public concerns,
interest group concerns, professional concerns, and emergence
of nest scientific information.
Lois question has been answered in Questions A.2, C.8, C.9, and
E.3 .
6. Ability of the risk assessment to identify research needs.
An exposure s tudy of ashes tos in Ho us ton schools was undertaken.
This was done in part to answer the criticism incurred when EPA
used data from a Parisian building as the basis for an exposure
assessment. The Houston data, in fact, provided numbers that were
quite similar to those obtained in Paris.
7. Extent to which risk assessment impeded or facilitated
regulation?
Initially EPA was planning to require school districts to take
corrective actions to protect occupants of schools from asbestos
exposure. Such a rule would have been very expens ire to inact .
Under the Toxic Substances Control Act (TSCA), the cost of imple-
menting a rule must be balanced by the benefits accrued from it.
~us, it would have been necessary under TSCA, for EPA to demon-
strate that the health risk was sufficiently great to merit such
action. A quantitative risk assessment probably would have been
helpful to illustrate the number of lives that could 'he saved by
the actions A1SO9 other actions limiting the use of asbestos were
being contemplated by SPA. It was under this percept ion, that SPA
proceeded with the quantitative risk assessment, believing that it
could be useful for a number o f contemplated regulatory ac tions .
OCR for page 67
~7
The final asbestos rule dealt only with identification and
notification of the presence of asbestos in schools. The rule
requiring school districts to take corrective action was abandoned
by EPA in April 1981. The Deputy Assistant Administrator (DAA)
for Toxic Substances, who called for the deletion of the
quantitative risk assessment from the July 1981 draft, cited two
reasons for doing so. One was that the cost of the identification
and notification rule is "very little", and thus a detailed
quantitative risk assessment to support the rule was not needed.
Secondly, it was important "to get the rule out. " Controversy
over the quantitative risk assessment was holding up progress.
The asbestos industry, which was not opposed to the identifica-
tion and notification rule per se, was quite opposed to the
quantitative risk assessment supporting the rule, and its
promulga t ion .
Some members of Congress disagreed with the DAA's judgment.
For example, the chairman of the House subcommittee on Labor
standards felt that without the numbers, the "sense of urgency" in
implementing the rule is lost for local officials, parents and
schoo 1 emp layees .
8. Were related risk assessments consistent?
-
See Q. D. 2.
9e Extent to which there Is an explicit distinction between
weights accorded to scientific factors and policy factors.
The July 1981 draft made very explicit distinctions between
scientific and policy factors utilized in the quantitative risk
assessment. The distinctions were particularly clear regarding
the use of dose-response models. See also, Q. C. 5 and Q. C. 7.
10 Mode and frequency of communication between assessors and
.
regulators .
There appears to have been some problem of communication between
the regulator and the assessor. See Q. D. 3 and Q. E. 3.
OCR for page 68
~8
REFERENCES
.
Albert, Roll. ~ R. Train, and E. Anderson. 1977. Rationale developed
by EPA for the assessment of carcinogenic risks. J. National
Cancer Into 9 5801537-154~.
EPA (Environmental Protection Agency). 1976. Health risk and economic
impac t assessments of suspected carcinogens: interim procedures
and guidelines. Fed. Reg. 41: 21402-21405.
Hammond, EoC. ~ I.J. Selikoff, and H. Seidman.
exposure, cigarette smoking and death rates.
330 :473~490.
1979. Asbestos
Ann. MY Acad. Scio
Selikoff, I.Jo, EoC. Hammond, H. Seidman. 1979. Mortality experience
of insulation workers in the United States and Canada, 1943-1976.
Ann. NY Acad. Sci 3300 91-1160
Sebastien, P., A. Gaudichet 9 G. Dufour, G. Bonnaud, J . Bignon, J. Tori.
19780 Metrological survey of atmospheric pollution inside buildings
insulated by asbestos projection. Paris, France: Paris University
Laboratory De par~cmen t ~ EPA ~ rans let ion) .
Representative terms from entire chapter:
insulation workers
