Interim Evaluation, cf Health Risks Associated with


           Emissions of Tetrachlorinated Dioxins


    From i'.unicical Waste Resource Recoverv  Facilities
                     Move-mber 1981 .
                        .**•




Background


     Concern has been raised within  the United States  regarding


the possible emission of trace amounts of highly toxic organic


pollutants as *a consequence of the large scale combustion of


municipal wastes for recovery of energy.  Such resource recovery


facilities are also referred to.as municipal waste combustors.


The concern first came  to a focus at the Herapstead Resource


Recovery Corporation (HRRC) facility in He.mpstead, Long Island,


where in 1979 the owners and operators of the plant permitted


SPA to sample its emissions.  Subsequent analyses indicated that


tetrachlcrodibenzc-p-dioxins (TCDDs), including 2,3,7,3-TCDD,


were present.  However, due to the nature of the sampling method


and the operating conditions of the -plant at the time, only a :


qualitative statement could be made on the presence of these


materials.  Based on these findings  the Agency concluded that


more rigorous testing would-be required in order to quarltitate1


the results.


     3y the time this qualitative information was becoming


available, the Exposure Evaluation Division (EED) of the Office


of Pesticides and Toxic Substances (OPTS) had already  initiated

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a oilot study of emissions front two other municipal waste conbus-



tors in the United States.  In addition, the Office of Solid



Waste  (OSW) had begun a series of similar studies to determine



whether or not ootential problems existed at other municipal
               *"        *^


waste  combustors.  The analytical results from five plants are



now available.


     Even  before  the  above data became  available  to the Agency,



a considerable amount of  information  had been accumulated by



scientists working  on similar and related  facilities outside  the



United States.   In  1979  a  report appeared OP.  the  analysis of  a



number of  micro-pollutants,, including TCDDs,  in  fly ash  from  five



municipal  incinerators  in The Netherlands, Canada, and Japan



 (Siceman,  et. al,  1979).   This was  followed  in the next year by



 an  investigation of fly  ash  and  stack emissions  from  four



 municipal incinerators in Italy (Cavallaro,  et  al,  1930)  and



 by  an  extensive review (Lustenhouwer, et al,  1930)  on  the  amounts



 of  micro-pollutants  found in. the fly ash of  various municipal



 incinerators in Europe.   Amplification of this  information was



 provided in testimony presented during EP.Vs cancellation hearings



 on  the herbicide 2,4,5-T (Hutzinger, 1980).   Each of  these inves-



 tigators reported TCDDs in the emissions and fly ash of muni-



 cipal incinerators.


       The  Agency's  review of  the foreign" data did not suggest the



 existence of any problem that called for precipitous action due to



 the emission of  TCDDs associated with  the combustion of municipal

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wastes.  The Agency continued its program of systematic testing


at municipal waste ccmbustors in order to assess the domestic


situation more completely.


     Mow that the S?A-generate~d emissions data from American
                        *^

municipal waste combustors are available, it is appropriate to


publish an interim assessment of the toxic effects which could


conceivably be associated with TCDDs emissions from municipal


waste combustors in this country.


Overview


     The human health implications associated with the emission


of TCDDs from five municipal waste combustors have been assessed.


The evaluation was based, on the information available on the


estimated levels of the exposure that people living near municipal


waste combustors are likely to experience, and on estimates of


health hazards associated with TCDDs.  The Hempstead, Long Island


plant is not one of the five analyzed as the EPA data for this


plant are r.ot sufficient to support a quantitative evaluation.


     Exposure information on TCDDs was obtained by field sampling


of stac>: emissions from the five municipal waste combustors,


followed by complex chemical analyses for TCDDs.  To obtain an


estimate of the amount of TCDDs that were emitted into the atmo-


sphere, it was necessary to collect and analyze both the flue-gas


and the particulate materials as TCDDs have a tendency to firmly


adhere to small particles (Lustenhouwer, e_t a_l, 1980).

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                               - 4 -


     Computer modeling was used to derive approximate exposure

levels experienced by the population as a result of the dilution

and dispersion that takes place as the flue-gas and particulate

material make their way ,to ground-level after stack emission.

     Estimates of the risk to human health from these TCDDs

emissions were obtained by extrapolating from animal data on the

basis of an important assumption.  The levels of exposure are

far below those causing acute  (short term/ high dose) effects- in
              v-
animals.  Therefore, this assessment focuses on chronic (long

term, low dose) effects with an emphasis on the two most sensitive

toxic effects seen in animals: reproduction and carcinogenicity.

     The fundamental assumption that was made was that if TCDDs

are a human carcinogen, or if  they pose a health hazard due to

adverse reproductive effects in humans, then these effects will

be manifested at  the same relative dose levels as observed in the

recorted animal studies,  taking the relative body surface of

animals and humans into account.  The  inclusion of this

assumption  is essential  in the interpretation of the significance

that animal data  may have with regard  to any human experience.

The exposure data and  the health hazard information on TCDDs were

then combined in  a number of mathematical models to estimate

the risk associated with  human exposure to TCDDs emitted from

municipal waste combustors.

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Toxicitv Data-
     Althouqh there are a total of 22 tetrachlorodibenzo-o-dioxin
(TCDD) isomers, the 2,3,7,3-TCDD isomer has been subjected to the
most extensive testing.  While a variety of studies point to a
range of effects produced by  this material, the appearance of
adverse reproductive  and carcinogenic effects  at very  low doses
in chronic  feeding studies  in animals has  generated special
interest and  concern.
     The effects of a combination of isomers  is  difficult  to
              •=?
assess, but a conservative  assumption  is  that  all  of  the
isomers are as  toxic  as 2,3,7,8-TCDD.   There  are biochemical
reasons, supported by some  'experimental data  (Poland,  et.  a_l,
                                                                 •
1979),  to  suggest  that the  mechanism of toxic action  of 2,3,7,3-
TCDD is associated with the chlorine atoms on the  lateral  ring
positions   (positions  2, 3,  7. and 3).   In fact,  there is no
evidence  to indicate  that  any of the isomers  are more toxic than
 2,3,7,3-TCDD.
      Data on the other chlorinated dioxir.s were insufficient to
 be included in this  interim assessment.
      A.    Reproductive effects of 2,3,7,8-TCDD
            2,3,7,3-TCDD has been investigated and shown to have
      reproductive effects  in numerous  animal  studies.  In one
      of the most recent studies, a  three-generation study in
      rats  (Murray, et,  a_l,  1979), adverse  reproductive effects
      appeared inconsistently in the different generations
      at the  lowest dose tested  (0.001  ug  TCDD /kg /day),

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although this nay be at or very close to the "no-observed
-effect level"  (HOED.  Human epidemiological
studies in this area are limited in number and
statistical power; those that have been conducted do not
demonstrate clear exposure-related effects.
3.   Carcinogenicity of 2,3,7,8-TCDD
     Bioassays  have demonstrated that 2,3,7,8-TCDD is an
animal  carcinogen  in rats  and mice  (Kociba, et al.,- 1978;
national Cancer Institute,  1980), under the test conditions
imposed.  The  information  with  respect  to  human exposure
is  less conclusive.  Epidemiological studies of cohorts
of  workers  engaged  in  chlorophenol  production  and use,
and their exposure  to  TCDDs  in  this  country  (Zack and
Suskind,  I960; Cook,  et  al,  1980),  suggest that any  overall
carcinogenic  effect  on humans  is  small.  A significant
excess of  stomach cancer,  however,  has  been reported in  a
similar cohort of German  workers  (Theiss,  e_t  al,  1931).
 In  addition,  a recent series of reports (P.ardell  and
 Sandstrom,  1979; Eriksson, et al,  1981; Honchar  and
 Halperin,  1981; Cook, 1931) indicate that soft tissue
 sarcomas (a form of cancer) may be associated with  long
 term exposure  to phenoxy herbicides which contain 2,3,7,8-
 TCDD.  The human information available from the  Seveso,
 Italy explosion in 1976 has not indicated that the local
 populations have developed any excess of cancer.   However,

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                               -. 7 -



     it nay.be too early to evaluate the long term effects



     from this exposure (Reggiani, 1980) in view of the short



     period of time that has'elapsed since the Seveso incident



     and the generally longer latency period for cancer develop-



     ment,  itore definitive work to address, this question has
                        *^ -


     been initiated by the National Institute of Occupational



     Safety and Health (MIOSH) and the National Cancer Institute



     (MCI).



Exposure Data



     There are* about 40 municipal waste corabustors in the



country.  A. large number of additional units are under consider-



ation for construction, some of them involving very different



technologies.  Consequently, the recently obtained emission



data from the stacks of five municipal waste combustors cannot



be said to characterize totally the industry today nor what



the industry is likely to become (see Tables 1 and 2).  However,



the data can give some indication of current conditions and



what niicht ce expected in the future as data collection, proceeds.



In order to analyze these data more completely, information is



needed on the interaction between the various factors that may



affect the output of dioxins from municipal .waste combustors.



Included among these are the .nature of the combustible materials,



temperature, flow rate, process, stack heights, local topography,



and/or combustion chamber design.

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                                -  a  -





      In the present  estimates,  the  relation between the emission



data  and  the maximum concentration  to which people in the sur-



rounding  area are likely to be  exposed has been obtained-throuch



a theoretical air dispersion model, PTMAX  (EPA, 1977).  This



computer  program calculates the location and magnitude of the



maximum short term  (1  hour) concentration  in the area around



the stack.  Data from  the five  sampled sites provided the



input.  Basically,  the results  show.the ground concentration



to be a slowly varying function of  stack height, temcerature,
              «*


diameter, and exit  velocity.  To obtain annual maximum average



ground level concentrations, reasonable, if rough, estimates



were  made on the assumption that the maximum annual average



concentration is 1/40  of" the maximum hourly concentration (see



Table 3)  (Tikvart,  19SI).  While there is  no guarantee that the



results of future studies (some are already in progress and



will  continue through  FY 32) will fall within these ranges,



the current data can be used to suggest the range of variations



that  is expected to  be encountered.



Toxicity  and Exposure  Assumptions



      Emission data  can be used  with other data to estimate



potential human exposure to TCDDs from municipal waste combustion



sources.  However,  many unanswered  questions relating to TCDDs1



toxicity  and exposure  remain.   Since there are insufficient data



to answer these important questions and because this information



is needed to assess  the risk to people breathing emissions from

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                             - 9 -

the stack, the Agency has adopted a series of assumptions which
are designed to represent the "worst case" possible.  Some of
these questions and related assumptions are presented below:
     1.   What are the tpxicological properties of the different
          TCDD isomers?  (There are considerable experimental
          data on the properties of 2,3,7,3-TCDD, but relatively
          little on the other 21 isomers.  The evidence that
          does exist, however/ suggests that they may be less
          toxic than 2,3,7,8-TCDD.)
          In the absence of data the assumption  is:
          The carcinogenic properties and reproductive effects
          of all TCDDs are the same as that of 2,3,7,8-TCDD.

      2.   Given the'concentration  and composition of TCDDs mea-
          sured in emissions  from  a stack, what  are  the resulting
          air concentrations  and compositions at ground level to
          which people would  be  exposed?  In  the  absence of  data
          the assumption is:
          The PTMAX air  dispersion model  (EPA 1977)  and the
          factor  used  to convert to the  annual concentration,
          adequately represent  the transport of  the  emissions
          to ground  level.  The composition  of emission produces
          found at  ground  level is identical to  the  composition
          (but  not  the concentration)  in the stack.

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                        - 10 -





3.    How does the ground level concentration vary relative




     to the position from the stack?  In the absence of



     data the assumption is:



     All of the exposed population is subjected to the



     maximum average annual concentration found at the



     point of concentration.





4.    How do the TCDD concentrations in the air behave when



     they- are breathed by humans? (The TCDDs in the stack



     gases are generally associated with particulate matter



     from which they are difficult to remove in the labora-



     tory) .  In accord with available data  (ICR?, 1963)



     the assumption is:



     Seventy-five percent of  the  inhaled particles are



     retained  in  the body.



     In  the  absence of  data the  assumption  is:



     All  the TCDDs  that  are retained  in  the  respiratory



     tract are biologically available to the organism.





 5.   How  often and  for  how  long  will  people  be subject to  a



     given level  of exposure?  (The  lifetime of  municipal



     waste  combustors  is  approximately  30 to 40  years.)



     Even given  this  approximation,  the following is  assumed;



     The copulation is  exposed  to this  maximum average



     annual  concentration from the  source  for  24 hours a



     dav throuchout a 70 year lifetime.

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                             -  11  -
     6.    What  is  the  relative  sensitivity  of  man versus  the
          animals  used in these studies?
          In the absence of data the  assumption is:
          Man is of comparable  sensitivity  to  animals for
          reproductive and carcinogenic effects, taking body
          surface  areas into account.
Health Risk Estimates
     The health risk estimates were calculated using a variety
of mathematical models - linearized multi-stage  (Crump, 1981):
probit, logit, Weibull and gamma multi-hit (Food Safety Council,
1980) - which were applied to the rat carcinogenicity data
(Kociba,  1978) and the TCDDs exposure data associated with  the
emissions from municipal waste combustors".   The  results from
the models  were consistent  in estimating low  risks.
      Potential reproductive effects were assessed by comparing
the  calculated  levels  of  exposure from TCDDs  to the  lowest
level tested in animals  (Murray,  et  al,  1979).   The  anticipated
levels  of TCDDs to which  humans may  be exposed are  far below
the  level used  in the  animal study.
Summary
      An evaluation of the public  health  considerations  related
to TCDDs  emissions has been made  by  applying  the various  mathe-
matical models to the data.from the  five US sites under  the
many combinations of  assumptions  that must be made  in  analyzing

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                               - 12 -


the data.  Those estimates suggest that the present emissions
levels of TCDDs from  the five municipal waste combustorg
described in this report do not present a public health hazard
for residents living  in the immediate vicinity. . In addition,
the health risk estimates presented in the assessment indicate
that as long as emission levels of TCDDs do not greatly exceed
the emissions measured at the five US sites evaluated in this
interim assessment, there should be no reason for concern.  This
              •i»-
conclusion is valid for all toxicological effects (including
reproductive and cancer) for which the available animal and
human data have been analyzed.
     This is an interim report and EPA intends to periodically
monitor representative resource recovery facilities such as these
for emissions of TCDDs.   EPA will take steps to regulate TCDDs
emissions if it appears necessary.  However, at the present
time, this need has not been demonstrated.

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  References


/  Cavaliaro, A.', et al.  1980.  Chemosphere, 9_, 611.

  Cook, R.R., et al.  1980.  J. Occup. !1ed. , 22, 530.

  Cook, R.R.  1981.  Lancet/ 618.

  Crump, K.S.  1981.  "An Improved Procedure for Low Dose
                         * -
       Carcinogenic Assessment from Animal  Data".-  MISHS

       Contract No. MIH S-S-77-22.  J. Environ. Path, and Tox. £, 675

/x-Eiceman, G.A. , et al.  1979.  Anal. Chem. , 51,f 2343.

  Srikson M., et al.  1981.  J.  Ind. tied.,  38,  27.

  EPA.  1977.  ^Guidelines  for Air Quality  Maintenance  Planning

       and Analysis".  Vol.  10 (Revised):  Procedures for  Evaluating

       Air Quality Impact  of New Stationary Sources.

  Food Safety Council.  1980.  Final  report of  the

       Scientific  Committee.

  Hardell,  L. and  A.  Sandstrom.   1979.   Br. J.  Cancer,  3_9,  711.

  Honchar,  ?. and  W.E.  Ealperin.   1981.   Lancet,  268.

  Hutzinger, 0.   1930.  Testimony submitted to EPA administrative

        hearings on the  cancellation,  of  2,4,5-T and silvex.

   International Commission on Radiation Protection (ICR?)

        Publication No.  10  Report of  Committee IV.  1968. 3.

   Kociba, R.J., et al.  1978. Tox.  Appl. Pharm.,  4±,  279.

   Lustenhouwer, J.W.A.,  et al.  1980.  Chemosphere, .9,  501.

   Murray, F.J., et al.  1979.  J. Appl. Pharm, 5£, 241.

   National Cancer Institute.  1980.   Publication

        Number  (NIH) 80-1757 and 80-1765.

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                               - 2 -

Poland, A., et al.  1979.  Ann. NY Acad. Sci., 32®.' 214'
Reggiani, G.  1980.  Oral  testimony in EPA 2,4,5-T Cancellation
     Hearings, Transcript  pages 16-761 - 16766.
Theiss, A.M., efc al.   1981.   In press.
Tikvart, J.  1981.  Personal  Communications with Randolph
     ChrisTnon.
Zack, J.A, and R.R. Suskind.   1980.  J. Occup. Med, 22, H-

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                            TABLE 1




                 RANGE OF STACK CONCENTRATIONS



     Pollutant(s)                             Range (ng/dscm~)



     2,3,7,8-TCDD                              MDh - 3.5C



       TCDDsd                                  ND - 3.5



a - ng = 10~^ grams; dscm = dry standard cubic meter

              •*:
b - "I7D" not detected at a detection limit of 0.25 ng/dscm.


c - The analytical method used could not distinguish 2,3,7,8-TCDD


    from several of the other TCDD isorners.  It is recognized


    that some molecular forms may be co-eluting with the 2,3,7.3

                  f
    isomer; therefore this value could be an overestimate of the


    amount of 2,3,7,3-TCDD actually present.


d - "TCDDs" includes any and all of the tetrachlorodibenzo-?-dioxin


    isomers present.

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                       TABLE  2





              RANG5 OF STACK  PA3AF1ETSRS



     REPRESENTED 3Y THE FIVE  COKBL'STQRS  TESTED


           •
                   <^




     Parameter                         Range





Stack Height  (meters)                  10 -  75





Stack Temperature (Centigrade)         139 - 232
          
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                            TA3LS 3
 RANGE OF  ANNUAL MAXIMUM AVERAGE GROUND LEVEL CONCENTRATIONS
                      OF* DIOXIM ISOMSRS

        ESTIMATED FOR FIVE US SOURCES SAMPLED TO DATS
          USING PTMAX COMPUTER AI3 DISPERSION MODEL3

           Pollutant (s)             Range (ng/m3)b
             
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                  Unitea States            Press Office £-107)
                  Environmental Protection      Washington DC 20460
                  Agency
                    invifonmenta!
R-153
     FOR RELEASE:  THURSDAY, NOVEMBER 19,  1931

     INTERIM  SPA EVALUATION FINDS NO
     DIOXIN HAZARD AT RESOURCE
     RECOVERY FACILITIES

         U.S.  Environmental Protection Agency Deputy

     Administrator John W. Hernandez, Jr.  today said  that  an

     interim  evaluation of resource recovery facilities  at five

     locations indicates  that  tetrachlorinated dioxin emissions

     from  the combustion  of municipal wastes are "far below the

     level of a credible  health  risk."

         The  interim evaluation  was made from data collected  on

     municipal resource  recovery facilities in Arkansas,

      Illinois, Iowa, Florida,  and Ohio.  EPA said there are

      about 40 resource  recovery  combustors  in the United States

      and that a number  of additional  units  are being planned,

      some  of them involving very different  technologies.

      The interim data do not totally  represent the industry,

      although  the data  do give some indication of current

      conditions, and what might be  expected in the future.

          "The  approach used in EPA's  analysis,"  Dr.  Hernandez

      said, "is extremely conservative,  in  that  the assumptions

      err on  the side of public health protection.  The

      conclusions reached concerning public health risks are

                                 (more)

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R-168
                                    -2-



        lifcely  to  be applicable  to  similar  facilities when those



        facilities are  properly  designed, constructed and



        operated."



           Hernandez cautioned  that EPA has not developed anything
                              *»


        that should be  interpreted  as an emissions standard for



        tecrachlorinaced  dioxins, nor should the levels measured at



        the five facilities  be  interpreted  as an upper boundary in



        terms of setting  emissions  limitations.



           "Setting*, such a  standard would  involve a long and



        complex rulemaking process  which, given  the results of our



        interim analysis,  is not deemed  to  be necessary,"



        Hernandez  said.   "The agency intends to  periodically



        monitor representative  resource  recovery facilities/"



        he added,  "and  if we find that the  emissions are



        significantly greater than  those evaluated in this



        assessment, we  will  consider the need for regulatory



        action."



           Concern first arose  at  the Hempstead Resource Recovery



        Corporation facility in  Hempstead,  N.Y.   In 1979 the



        operators  of the  plant  permitted EPA to  begin sampling



        emissions. However, in  an  unrelated action, the village of



        Herapstead, late in 1979, ordered the facility closed



        because of odor problems.   It has not been reopened.  The



        Hempstead  facility is not included  in the interim



        evaluation because EPA  had  not collected



        sufficient data before  the  facility was  closed.



                                 (more)

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                                     -3-



            There are a  tocal of  22  different  forms  (isomers)  of



        tetrachlorinated dioxins; only  the  cetrachlorodibenzo-o-dioxin


        (2,3,7,3-TCDD) isomer has been  subjected  to  extensive



        testing.  EPA said  there  is  no  scientific  evidence  that any
                                *&•


        of the  isomers are  more toxic than  2,3,7,8-TCDD.



        Therefore,  for the  purposes  of  the  interim evaluation, EPA



        said it made the conservative assumption  that  all  the



        isomers are as toxic as 2,3,7,8-TCDD.



            Since there  are insufficient  data  to  completely answer



        questions relating  to TCDD's toxicity  and  exposure,  and



        because this information  is  needed  to  assess  the risk  to


        people  breathing emissions from the  stack, SPA said  it



        conducted its analysis by adopting  a  series  of assumptions



        designed to represent the "worst  case"  possible.



            The specific isomer,  2,3,7,8-TCDD  has  been shown to



        have effects on  the reproductive  systems  of  various animal



        species.  Bioassays have  demonstrated  that 2,3,7,8-TCDD is



        an animal carcinogen in rats and  mice.  Existing



        epidemioloyical  studies do not  demonstrate clear



        exposure-related reproductive effects, in  humans.  "Other



        epidemiological  studies suggest an  association between



        exposure to 2,3,7,8-TCDD  and certain  types of  human cancer.



        Further studies  are underway to address this question.  In



        its assessment EPA  assumes that all  of  the tetrachlorinated



        dioxir.s found in the emissions  were  carcinogenic.
         (For  further  information  on  technical  aspects  of  the

         evaluation, contact  Dr. Don  Barnes,  senior  science  advisor,

         Office of  Pesticides  and  Toxic  Substances,

         tel.  (202)382-2897.)


R-16 8

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