0013
 c  ^"
                                                                      January 1992
                                        FINAL





                           DRINKING WATER  CRITERIA DOCUMENT


                                         FOR


^                                    ENDOTHALL
                       Health and Ecological  Criteria Division
                          Office of Science and Technology
                                   Office of Water
                        U.S. Environmental Protection Agency
                                Washington,  DC  20460
                              HEADQUARTERS LIBRARY
                              ENVIRONMENTAL PROTECTION AGENCY
                              WASHINGTON, D.C. 20460

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                                               January 1992
                  FINAL




    DRINKING WATER CRITERIA DOCUMENT


                   FOR


               ENDOTHALL
Health and Ecological Criteria Division
   Office of Science and Technology
            Office of Water
 U.S.  Environmental  Protection Agency
         Washington, DC  20460

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                               TABLE OF CONTENTS
                                                                          Page
      LIST OF TABLES  	  	          v
      FOREWORD	         vi
      AUTHORS, CONTRIBUTORS, AND REVIEWERS  	       viii
  I.  SUMMARY	        [-1
 II.  PHYSICAL AND CHEMICAL PROPERTIES	       II-I
      A.  General  Properties  	       II-l
      B.  Manufacture and Use  	       II-l
      C.  Environmental  Fate and  Stability  	........       Il-i
      D.  Summary  .	       II-4
III.  TOXICOKINETICS	      III-l
      A.  Absorption   	      III-l
      B.  Distribution  	      III-l
      C.  Metabolism   	      III-6
      D.  Excretion	      III-6
      E.  Summary	      II1-8
 IV.  HUMAN EXPOSURE	       IV-1
      A.  Exposure Estimation  	       IV-2
          1.  Drinking Water  	       IV-1
          2.  Diet  	       IV-2
          3.  Air	       IV-3
      B.  Summary	       IV-3
 V.   HEALTH EFFECTS IN ANIMALS 	        V-l
      A.  Short-term  Exposure	        V-l
          I.  Lethality	        V-l
          2.  Other Effects	  .        V-l
      B.  Long-term Exposure	  .        V-5
      C.  Reproductive/Teratogenic  Effects   	       V-10
      D. Mutagenicity  .  .  .	       V-12
          1.  Gene Mutation  Assays  (Category 1)  ..-....•	       V-15
          2.  Chromosome Aberration Assays  (Category 2)  	       V-18
         3.  Other Mutagenic Mechanisms (Category 3)  	       V-19
                                     iii

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                         TABLE OF CONTENTS (continued)
                                                                          Pace
      E.  Careinogenicity	       V-24
      F.  Summary	       V-24
  VI. HEALTH EFFECTS IN HUMANS	       VI-1
      A.  Clinical  Case Reports  	       VI-I
      B.  Epidemic logical  Studies		       VI-1
      C.  High-Risk Groups  	       VI-1
      D.  Summary	'	       vi-1
 VII. MECHANISMS OF TOXICITY	      VII-1
      A.  In Animals   . .  . .	      VII-1
      B.  In Plants	      VII-1
      C.  Synergistic/Antagonistic Effects  .	      VII-1
      D.  Summary	      VI1-2
VIII. QUANTIFICATION OF TOXICOLOGICAL EFFECTS 	     VIII-1
      A.  Procedures for Quantification  of Toxicological  Effects   .     VIII-1
          1.   Noncarcinogenic  Effects 	     VIII-1      a
          2.   Carcinogenic Effects   	     VIII-4      'I
      B.  Quantification of Noncarcinogenic Effects for  Endothall   .     VIII-6
          1.   One-day Health Advisory 	     VIII-6
          2.   Ten-day Health Advisory 	     VIII-6
          3.   Longer-term Health Advisory 	     VIII-8
          4.   Reference Dose and Drinking Water  Equivalent Level   .     VUI-9
      C.  Quantification of Carcinogenic Effects for Endothall   .  .    VIII-11
          1.   Categorization of Carcinogenic Potential   	    VIII-11
          2.   Quantitative Carcinogenic  Risk Estimates	    VIII-12
      D.  Summary  	    VIII-12
  IX. REFERENCES	       IX-1
                                      iv

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                                 LIST OF TABLES
Table No.                                                                  paae
.   II-l   Properties of En'dothall (7-oxabicyclo-(2.2.1)-heptane-
          2,3-dicarboxylic acid)  '	        II-2
  III-l   Percent of Radioactive Dose in Tissues of Rats
          Receiving an Oral Dose of "(^Labeled Endothall and
          Sacrificed at Various Times After Dosing   	       III-3
  III-2   Radioactivity in Tissues of Rats Receiving an Oral  Dose
          of 14C-Labeled Endothall and Sacrificed at Various
          Times After Dosing   .  r-	       III-4
  III-3   Kinetics of Radioactivity Elimination After a Single
          Oral  Dose of 1 mg of 14C-Endothall per Rat  .	•  .       111-5
  III-4   Excretion of Radioactivity by Rats Receiving a Single
          Oral  Dose of 14C Ring-Labeled Endothall   	       III-7
    V-l   Summary of Oral  Lethality Data on Endothall in Rats  ...        V-2
    V-2   Acute Inhalation Toxicity of Endothall  and Formulations
          (Aqueous Aerosols)   ... 	        V-4
    V-3   Primary Dermal Irritation of Endothall  and Formulations
          in Rabbits	        V-6
    V-4   Primary Eye Irritation of Endothall  and Formulations
          in Rabbits  	        V-7
    V-5   Summary of Genotoxicity Data on  Endothall  	       V-13
    V-6   Effect of Aquathol K on Transformation of BALB/3T3
          Cells Without  Metabolic Activation  	       V-21
    V-7   Effect of Aquathol K on Transformation of BALB/3T3
          Cells in the Presence of Primary Rat Hepatocytes    ....       V-22
 VIII-1    Summary of Candidate Studies  for Derivation of the
          Ten-day Health Advisory for  Endothall  	 	     VIII-7
 VIII-2    Summary of Candidate Studies  for Derivation of the  DUEL
          for Endothall  .. 	    VIII-10
 VIII-3    Summary of Quantification of  Toxicological  Effects
          for Endothall	•	    VIII-13

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                            FOREWORD

    Section  1412  (b)(3)(A) of  the Safe  Drinking  Water Act,  as
amended in 1986, requires  the Administrator  of the Environmental
Protection Agency  to  publish  Maximum Contaminant  Level  Goals
(MCLGs) and promulgate  National  Primary Drinking Water Regulations
for each contaminant, which, in  the judgment of the Administrator,
may have an adverse effect on public health and which is known or
anticipated  to occur  in  public water  systems.    The MCLG  is
nonenforceable  and  is set  at  a level  at  which  no  known  or
anticipated adverse health  effects in humans occur and which allows
for an adequate margin of  safety.  Factors considered in setting
the MCLG include health effects  data and sources of exposure other
than drinking water.

    This  document  provides  the  health  effects  basis  to  be
considered in establishing the  MCLG.   To  achieve this objective,
data  on  pharmacokinetics, human exposure,  acute  and  chronic
toxicity to  animals  and  humans, epidemiology, and mechanisms of
toxicity were evaluated.  Specific emphasis is placed on literature
data  providing  dose-response  information.     Thus,  while  the
literature search  and evaluation performed  in  support of  this
document  was comprehensive,  only  the reports  considered  most
pertinent in  the derivation of the MCLG are cited in the document.
The comprehensive  literature data base  in support of this document
includes information published up to  April  1987; however,  more
recent data may have been added during the review process..

    When adequate health effects data exist. Health Advisory values
for lessthan-lifetime exposures  (One-day, Ten-day, and Longer-term,
approximately 10% of  an individual's lifetime) are included in this
document.  These values are not used in setting the MCLG, but serve
as informal guidance  to municipalities and other organizations when
emergency spills or contamination situations occur.

                                                   James R.  Elder
                                                         Director
                         Office of Ground Water and Drinking Water

                                                   Tudor T. Davies
                                                         Director
                                   Office of science and Technology
                                    vi

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                                   FOREWORD
     Section 1412 (b)(3)(A) of the Safe Drinking Water Act, as amended In 1986,
requires the Administrator of the Environmental Protection  Agency to publish
Maximum Contaminant Level  Goals (MCLGs) and promulgate National Primary Drinking
Water  Regulations  for  each  contaminant,   which,   in  the  judgment  of  the
Administrator, may have an adverse effect on public health and which is known or
anticipated to occur in public water systems.  The MCLG is  nonenforceable and is
set at a level  at which no known or anticipated adverse health effects in humans
occur and which allows for an adequate margin of safety.   Factors considered in
setting the MCLG include health effects data  and sources of exposure other than
drinking water.

     This  document  provides  the  health  effects  basis   to  be considered  in
establishing the MCLG.  To achieve this objective,  data on pharmacokinetics,
human exposure, acute and chronic toxicity to animals and  humans,-epidemiology,
and mechanisms of toxicity  were evaluated.    Specific  emphasis is  placed  on
literature data providing dose-response information.  Thus, while the literature
search and evaluation  performed in support of this document was comprehensive,
only the reports considered  most pertinent in the derivation of the MCLG are
cited in the document.  The comprehensive literature data base in support of this
document includes information published up to April 1987; however,  more recent
data have  been  added during  the review process  and in response  to  public
comments.

     When adequate health effects data exist, Health Advisory values for less-
than-lifetime exposures (One-day,  Ten-day, and Longer-term, approximately 10% of
an individual's lifetime) are included in this document.   These values are not
used in setting the MCLG, but serve as informal guidance to municipalities and
other organizations when emergency spills or contamination situations occur.

                                                                James R.  Elder
                                                                      Director
                                     Office of Ground Water and Drinking Water

                                                               Tudor T.  Davies
                                                                      Director
                                               Office of Science of Technology
                                      vi

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                     AUTHORS, CONTRIBUTORS, AND REVIEWERS

     The following Dynamac Corporation personnel were involved In the preparation
of this document:  Nicolas P. Hajjar, Ph.D.  (Department Manager); Norbert Page,
D.V.M.  (Technical  Director); Alberto Pretzel,  Ph.D.  (Principal Author); Nancy
McCarroll 8.S.,  and Michael  Narotsky (Authors); Karen Swetlow, B.S. (Technical
Editor); William McLellan,  Ph.D.  (Reviewer);  Gloria  Fine and Sanjivani Diwan,
Ph.D. (Information Specialists).

     This document was prepared under a  contract  to  Environmental  Management
Support,  Inc.,  with the  Criteria  and Standards Division,  Office  of Drinking
Water, U.S. Environmental Protection Agency (U.S. EPA), Washington, DC  (Robert
Cantilli, Lead Scientist  and Contract Manager).

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                                  I.  SUMMARY

     Endothall  is an  organic  acid (7-oxabicyclo-(2.2.1)-heptane-2,3-dicar-
 boxylic acid).   It  is soluble in .water, methanol,  and  acetone and to some
 extent  in  other solvents.   This dicarboxylic  acid  loses water at 90°C to yield
 the corresponding acid anhydride, a powerful  vesicant.

     Endothall  salts  are widely used as defoliants and as herbicides for con-
 trol of terrestrial and aquatic weeds.  Because  of its water solubility,
 endothall  tends to  follow water movement  in the  environment.  In ponds and
 lakes,  the compound disappears from the water and  the hydrosoil within 30 to
 60 days and, often, within  a  considerably shorter  period.  This appears to be
 due primarily to microbial  degradation of endothall.

     One study  was found in the available literature that provides informa-
 tion, although  limited, on  the absorption, distribution, metabolism, and
 excretion  of endothall  in mammals.   In rats administered a single oral dose of
 about 5 ing/kg "C ring-labeled (at C, and  C2)  endothall, approximately 3% of
 the dose was expired  as carbon dioxide, 7% was excreted in the urine, and the
 remainder  (90%)  appeared in the feces.  Total  recovery was 95 to 99% within
 48 hours.  Most of the  compound is  excreted in the feces as the unchanged
chemical,  suggesting  that there is  little gastrointestinal absorption.
Endothall  was also the  only compound detected in the urine.

     Absorbed endothall distributes widely throughout the body tissues.  In
rats that  received a  single oral dose of  1.0  mg  14C-endothall, the highest "C
levels  observed  I hour  after  dosing were  in stomach and intestines (about 95%)
liver (1.1%) and kidney (0.9%) tissues, with  lower amounts (0.02 to 0.1%) in
heart,  lung, spleen,  and brain.  Very low 14C  levels were observed in muscle
and fat.   Tissue residues fell to unmeasurable levels within 48 to 72 hours;
therefore, endothall  would  not be expected to accumulate.
                                      1-1

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     Data on the Intake of endothall from drinking water,  food,  and ambient
air are insufficient for use in determining which of the three sources is the
major contributor to total intake.

     Estimates of the acute oral LD,0 values for endothall  ion in various
endothall formulations In rats range from 31 to 138 mg/kg.  Single intravenous
doses of 5 mg endothall/kg or higher were fatal to dogs and rabbits.  Death
was attributed to either respiratory or cardiac failure.  Inhalation exposure
at levels above 3,000 mg endothall ion/m1 for  1 hour resulted  in lung
congestion and hemorrhage in exposed rats.  Endothall is irritating to the
skin and corrosive to the eyes of rabbits.

     Rats that received oral doses of approximately 400 mg endothall ion/kg
body weight (bw)/day died within 1 week.  Necropsy examination revealed slight
liver degeneration and focal hemorrhagic areas in the kidneys.

     A 2-year toxicity study with disodium endothall in dogs provided a No-
Observed-Adyerse-Effect Level (NOAEL) of 2 mg endothall ion/kg/day and a
Lowest-Observed-Adverse-Effect Level (LOAEL) of 6 mg endothall ion/kg/day
based on increased organ weights and organ-to-body weight ratios for the
stomach and small intestine.

     In a similar 1-year toxicity study in dogs, hyperplastic changes in the
portal tract of the liver and dose-related reactive hyperplastic changes in
the mucosa of the stomach were observed at 14.4 mg/kg/day; at 4.8 mg/kg
endothall ion/day, no effects were observed in the liver,  and marginal injury
to the stomach was observed.

     A 2-year toxicity study with disodium endothall in rats, with small
numbers of animals in control and treated groups, suggests a NOAEL of 100 mg
endothall ion/kg/day, the highest dose tested.  No toxic effects other than
lethality were reported.
                                      1-2

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     A  three-generation  reproduction study with disodium endothall in rats
demonstrated  toxic  effects  and  increased mortality in the offspring at 12 mg
endothall  1on/kg/day in  the maternal diet.  At 4 rag endothall ion/kg/day, no
effects were  observed in either the dams or the offspring.  Although maternal
and  fetal  toxicity  was evident  at  high-dose levels, no abnormalities were
evident in the offspring in any generation.  Thus, a NOAEL of 4 mg endothall
ion/kg/day and a  LOAEL of 12 mg endothall ion/kg/day were established for
developmental/reproductive  toxicity.

     A  teratology study  1n  rats  indicated that endothall (technical 89.5% acid
equivalent) is neither embryo-toxic nor teratogenlc at maternal doses of
30 mg/kg/day  or less during gestation days 6 to 19; however, maternal toxicity
was  observed  at 20  and 30 mg endothall/kg/day.  This study provided a NOAEL of
30 mg/kg/day  for developmental  toxicity, and a NOAEL and LOAEL of 10 and
20 mg/kg/day, respectively,  for maternal toxicity.  A similar study in mice
indicated  that endothall  (technical 89.5% acid equivalent) was teratogenlc at
maternal doses of 40 mg/kg/day;  however, maternal toxicity also occurred at
this dose  and at 20 mg/kg/day.   This study provided a NOAEL and a LOAEL for
maternal toxicity of 5 and  20 mg endothall technicalAg/day, respectively, and
a NOAEL and a LOAEL for  developmental toxicity of 20 and 40 mg endothall
technical/kg/day, respectively.

     Endothall was  not mutagenic in bacterial, fungal, mammalian cell, or
Drosophila assays.   In in vivo  somatic or male germinal cell cytogenetic
assays, within the  nontoxic dose ranges, no clastogenic effects were observed.
Endothall did not induce aneuploidy in plants or increase the frequency of
sister  chromatid exchanges  in human lymphocytes.  Although Aquatol K\ (dipo-
tassium endothall)  exhibited transforming activity in BALB/3T3 cells co-
cultivated with primary  rat  hepatocytes, the results are questionable because
of weaknesses in the study.

     Although endothall  has  not  been shown to be carcinogenic, the present
data base  is  inadequate  to  assess  its carcinogenic potential.
                                      1-3

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     One case report  of endothall poisoning In humans was found in the avail-
able literature.   This  involved  the  suicide of a young man who ingested an
estimated  7  to 8 g of endothall  (approximately 100 mg endothall ion/kg) in a
solution containing 175 g/L.   Repeated vomiting, which occurred after inges-
tion, evidently removed much  of  the  compound and may have resulted in aspira-
tion of the  compound  to the lung.  The autopsy report revealed gross hemor-
rhage in the gastrointestinal  tract  and widespread focal hemorrhages and edema
of the lungs.  No  epidemiological studies of endothall exposure have been
reported.  The mechanism of endothall toxicity in humans is not known.

     No specific information  is  available on the mechanism of toxicity of
endothall  in animals.   Intravenous toxicity studies in dogs suggest that the
cause of death is  cardiac or  respiratory arrest.  One study suggests that
isopropylphenylcarbamate may  antagonize endothall toxicity, but data were not
provided.

     Available data from short-term  oral toxicity studies are essentially
restricted to mortality data  and are not suitable for Health Advisory (HA)
calculations.  A 10-day teratology study provided a NOAEL of 8 mg endothall
ion/kg/day based on a lack of maternal effects and effects in offspring.
Using this NOAEL,  a Ten-day HA for children was calculated to be 800 »g/L.
Since no suitable  data are available for calculation of a One-day HA, the Ten-
day HA value may be used as a conservative estimate of the One-day HA.  There
were insufficient  data for calculation of the Longer-term HA values.  There-
fore, the DWEL adjusted for a 10-kg  child (200.^g/L) may be used to estimate
the Longer-term HA for a 10-kg child; and the DWEL (700 »g/L) may be used to
estimate the Longer-term HA for  a 70-kg adult.  Using a NOAEL of 2.0 mg
endothall ion/kg/day  from a 2-year study in dogs, a Reference Dose (RfD) of
20 ng endothall ion/kg/ day and  a Drinking Water Equivalent Level (DWEL) of
700 »g/L were calculated.  No estimations of excess cancer risk were
performed.
                                      1-4

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     There are no existing guidelines or exposure standards available for
endothall.  Residue tolerances of 0.05 to 0.1 ppm on crops have been estab-
lished.  An Interim tolerance of 200 »g/L has been published for residues of
endothall, used to control aquatic plants, 1n potable water.
                                      1-5

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                      II.  PHYSICAL AND CHEMICAL PROPERTIES

 A.    GENERAL PROPERTIES

      Endothall  is an organic acid  (7-oxabicyclo-(2.2.1)-heptane-2,3-dicar-
 boxylic acid) that is soluble in water,  methanol,  and acetone and to some
 extent in other solvents (Carlson  et al.,  1978).   Its physical and chemical
 properties are summarized in Table II-l.   Endothall  loses water at 90°C to
 yield the corresponding acid anhydride,  which  is a powerful vesicant and eye
 irritant (Carlson et al., 1978;  Windholz et  al., 1983).  Endothall monohydrate
 melts at 144°C,  with loss of water,  to yield the corresponding acid anhydride
 (Carlson et al.,  1978).

 B.    MANUFACTURE  AND USE

      Endothall  is utilized  as a  defoliant  for  a wide range of crops and as a
 herbicide for both terrestrial and aquatic weeds.  Endothall is prepared by
 the Diels-Alder  addition of maleic anhydride to furan to yield the
 dicarboxylic acid (Carlson  et al., 1978).  Commercial formulations generally
 contain the sodium,  potassium, or  N,N-dialkylamine salts of the acid (Simsiman
 et al.,  1976).

 C.    ENVIRONMENTAL FATE AND STABILITY

      Since  endothall  salts  are water soluble,  endothall  tends to move with
water through soil.   Soil texture  and organic  content influence the rapidity
of its movement  (Simsiman et al.,  1976).   Yeo  (1970) reported on the
disappearance of  endothall  from  farm reservoirs.   The water temperature at a
depth  of 30 cm in the reservoirs ranged  from 16.5* to 27.5°C, and the pH
ranged  from 7.2 to 9.1.   In 4 of 14 applications to the farm reservoirs, the
concentration of  endothall  decreased from  initial  values of 0.3 to 1.4 mg/L to
near  the  limit of detection within 8 to 20 days.   In 10 of 14 applications to
the reservoirs, the  decrease was slower, with  an average of 71% of the initial
endothall disappearing  in the first 12 days.
                                     II-l

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          Table II-l.  Properties of Endothall  (7-oxabicyclo-(2.2.1)-
                       heptane-2,3-dicarboxylic acfd)
                                       m
         Property
           Value
CAS No.

RTECS Mo.

Synonyms



Molecular formula

Molecular weight

Physical appearance

Melting point

Density

Vapor pressure

pK, (20°C)
pK, (20eC)

Solubility:
    Acetone.
    Benzene
    Dioxane
    Ether
    Isopropyl  alcohol
    Methanol
    Water
145-73-3

RN7875000

Hexahvdro-.3.6-endo-oxy-Dhthalic
acid; 3,6-gndfi-epoxy-l,2-cyclo-
hexanedicarboxylic acid

C,H1005

186.06

White, crystalline solid

Converts to the anhydride at 90°C"

1.43 g/mL

Negligible

3.4
6.7

g acid monohydrate/100 g solvent:
   7.0
   0.01
   7.6
   0.1
   1.7
  28.0
  10.0
•From Windholz et al. (1983).
"Endothall monohydrate melts at 144°C, with formation of the anhydride
 (Carlson et al., 1978).

SOURCE:  Adapted from Carlson et al. (1978) and Simsiraan et al.  (1976),  except
         where indicated.
                                      II-2

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      Sikka and Rice (1973J  reported that  in  a  pond  treated with 2 mg/L
 endothall, the compound was undetectable  within 36  days  in the water and
 within 44 days in the hydrosoil  (silt-loam).   In aquaria studies utilizing the
 same pond water and hydrosoil,  end.othall  (2  to 4 mg/L  initially) was undetect-
 able (<0.01 mg/L) by the end of 7 days.   Levels in  the hydrosoil fell to  below
 0.1  mg/L within 2 to 4 weeks.   When the water  and soil were sterilized  (by
 autoclaving),  endothall showed  an initial  transport into the hydrosoil, after
 which the total system then remained relatively stable.   This indicated that
 the  loss of endothall  from  the  nonautoclaved pond water  and soil was largely
 due  to microbial  degradation.   Sikka and  Saxena (1973) reported that aquatic
 microorganisms readily degrade  endothall,  and  that  one species of Arthrobacter
 could utilize  endothall as  the  sole carbon source.   This organism incorporated
 14C from ring-labeled (at C2 and Cj) endothall into cellular amino acids,
 proteins,  nucleic acids,  and lipids,  and  released '*C as  carbon dioxide.
 After examining the pattern of  label  incorporation  into  intermediary
 metabolites, the  authors  concluded that the  14C from ring-labeled endothall
 was  incorporated  into  glutamic  acid via the  tricarboxylic acid cycle and  by an
 alternative, unknown pathway.

      Sikka and  Rice  (1973)  reported that endothall  disappeared from water in
 three phases:   the initial  rapid  rate of disappearance was attributed to
 adsorption by  the hydrosoil;  a  second, considerably slower rate of disap-
 pearance was attributed to  microbial  metabolism;  and a third, intermediate
 rate  of disappearance  was suggested to be  due  to the proliferation of micro-
organisms  with  the ability  to degrade endothall.  Simsiman and Chesters (1975)
reported that  in  a simulated  lake impoundment,  72%  of  the added endothall
 (3 mg/L) persisted for more than  30 days because of prolonged oxygen depletion
 following  weedkill.  A more rapid degradation  of endothall occurred after the
restoration of  oxygenated conditions; endothall  was not  detectable after
60 days.   Thus, although the  rate of  disappearance  of  endothall in the
environment may vary considerably depending on  conditions, it is usually
cleared from soil  and  water within 30 to 60 days.
                                      II-3

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     Levels of endothall in drinking water and their relationship to human
exposure are reviewed In Chapter IV of this document.

0.   SUMMARY

     Endothall, a water-soluble dibasic organic acid, is used primarily in the
form of its sodium, potassium, or alkylamine salts as a terrestrial and
aquatic herbicide.  Because of Its water solubility and its relatively rapid
degradation rate, it is widely used to kill aquatic weeds.  Natural pond and
aquaria studies demonstrate that endothall is rapidly decomposed by soil and
aquatic microorganisms and has a relatively short half-life in the
environment.
                                     II-4

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                              III.   TOXICOKINETICS

 A.    ABSORPTION

      A study conducted by Soo  et al.  (1967)  in  rats  provides most of the
 information on the absorption, distribution,  metabolism,  and excretion  of
 endothall  in orally dosed laboratory animals.   Each  of six Wistar rats
 (3  months  old; two males, four females) was  administered, by gavage, 1  rag of
 14C  ring-labeled endothall (approximately  3.9 mg endothall/kg for males  and
 5.2 mg endothall/kg for females).   The compound was  radiolabeled in carbons 1
 and 2 of the oxabicyclo ring.   For dosing, the  endothall  was dissolved  in 1 ml
 of  20% ethanol.   For at least  2 weeks prior  to  dosing,  the rats  received
 unlabeled  endothall  in their feed  at  a concentration of 5 mg endothall/kg feed
 (corresponding to approximately 0.254 mg  endothall/kg bw/day for males  and
 0.335 mg endothall/kg bw/day for females).   There were no observed signs of
 toxicity.   Between 85 and 91%  of the  radioactive dose was recovered in  the
 feces as untransformed endothall.   Urinary excretion accounted for approxi-
 mately 7%  of the  dose;  approximately 3%  of  the radioactivity was recovered in
 expired carbon dioxide (see also Section  III.D,  Excretion).  The results
 suggested  that only about 10%  of the oral dose  is absorbed in rats.  It is not
 clear to what extent the use of 20% ethanol  as  a dosing vehicle may have
 influenced the extent of endothall  absorption and metabolism.

 B.   DISTRIBUTION

     Soo et  al. (1967)  reported on  the tissue distribution of WC in Wistar
 rats  after they were administered  an oral dose  (by gavage) of 1 mg of MC
 ring-labeled  compound (approximately 5.2  mg  endothall/kg).  Nine female rats
 (3 months  old) were  maintained on  a regular  laboratory  diet containing
 unlabeled  endothall  at a  concentration of 5  mg  endothall/kg diet (approxi-
mately  0.335 mg endothall/kg bw/day) for  at  least 2  weeks prior to the
 administration of  the radioactive  endothal.l.  Food and  water were available
 ad libitum during  the study period.  After receiving the  oral dose of labeled
                                     III-l

-------
    endothall,  the  rats were sacrificed at  intervals  ranging  from  I to 72 hours
    for  analysis  of radioactivity  in  tissues.

        The results of  this study are shown in Tables III-l and III-2 (Soo
   et al., 1967).  Peak "C  levels in all tissues were observed 1 hour after
   dosing.  Most of the dose (about 95%) was present in the stomach and
   intestine,  with the next highest levels in liver and kidney.   Very low levels
   were observed in muscle,  and levels  in fat were, too low to measure.   During
   the first 4 hours,  "C levels in the  stomach decreased, while levels  in the
   intestines  increased.  After 72 hours,  all  tissue  levels had returned  to zero.
   Only  a  trace of  the  compound remained in  the  Intestinal  tract.

       Calculations by  the authors (Table III-3) indicated a half-life for
  endothall in the intestine and liver of 14.4 and 21.6 hours, respectively.
  Disappearance from the stomach was biphasic, with a rapid half-life of 2.2
  hours and a  slower half-life of 14.4 hours.  The kidney also showed a biphasic
  clearance, with an initial half-life  of 1.6 hours and a slower half-life of
  34.6 hours.

      Soo  et al. (1967) also fed  endothall  to two  lactating  rats  to determine
 whether endothall was secreted in milk.  The animals received daily oral doses
 of 0.2 mg endothall  (nonradioactive,  in a  10%  sucrose solution)  for 1 week
 prior to  parturition.  After  birth, the dams received a daily dose of 0.4 mg
 of 14Cendothall, in a  10% sucrose solution, for 5  consecutive days.  Tissues
 and stomach contents from the pups exhibited no radioactivity, suggesting that
 endothall  was not secreted in the milk of lactating rats.

 C.    METABOLISM

      Soo et al.  (1967)  studied the excretion  of endothall  in the  urine  and
feces of two male  and  four  female Wistar rats (3 months  old) that were
administered a single  oral  dose (by  stomach tube)  of 5 mg  14C-endothall/kg.
Endothall was the only  compound detected in urine  by paper chromatography
using different solvent systems.
                                     III-2

-------
     Table  III-l.
    Percent of Radioactive Dose in Tissues of Rats Receiving
    an Oral Dose of 14C-Labeled Endothall* and Sacrificed at
    Various Times After Dosing
Time of sacrifice
Tissue
1
2
• 4
oostdosina
6
(hours):
8

12
Liver
Kidney
Heart
Lung
Spleen
Brain
Stomach
Intestine
   13
   86
   05
   11
   02
   03
75.18
23.59
   60
   26
   02
   04
   01
   02
68.80
28.75
   56
   27
   02
   04
 0.01
 0.02
40.29
65.85
 0.49
 0.07
  .02
  .02
 0.01
 0.01
 9.46
61.43
0.
0.
,32
,06
,01
,02
,01
,01
,88
          54.05
 0.31
 0.06
 0.02
 0.03
 0.01
 0.00
 0.25
15.97
'Specific activity - 407 counts per minute (cpm)/ng endothall.  Total dose
 1.0 mg/rat (407,000 cpm), equivalent to about 5 mg/kg.

SOURCE:  Adapted from Soo et al.  (1967).
                                         III-3

-------
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                                                  III-4

-------
Table III-3.  Kinetics of Radioactivity Elimination After a Single OralDose
              of 1 rag of 14C-Endothall  per  Rat*
Tissue                       k"   •                   t,,7e
Intestine                   0.048                    14.4

Stomach
  Rapid phase               0.316                     2.2
  Slow phase                0.048                    14.4

Kidney
  Rapid phase               0.446                     1.6
  Slow phase                0.020                    34.6

Liver'                      0.032                    21.6
•Rats received a single oral  dose of 1 mg of "C-endothall, equivalent to a
 dose of about 5 mg/kg bw.
"Elimination rate constant.
eHalf-life  (hours).
"Similar numbers for spleen,  brain, lung, and heart (numerical values not
 reported).

SOURCE:  Adapted from Soo  et al.  (1967).
                                     III-5

-------
        Unchanged endothall  has  also  been found in exposed fish.  Sikka et al.
    (1975)  studied the metabolism of endothall in the bluegill.  This study was
    limited to chromatography of  an extract of whole fish after the animals were
    exposed for 48 hours to 2 mg  14C-endothall/L.  Whole, homogenized fish were
   extracted with methanol, and the extract was concentrated under vacuum.  The
   aqueous residue was extracted twice with petroleum ether to remove lipids.
   The aqueous phase contained essentially all  of the radioactivity,  suggesting
   that no lipid-soluble metabolites  were formed.  .Thin-layer chromatography on
   silica  gel  and cellulose plates revealed  the  presence, of only  unchanged
   endothall.  Thus,  the methodology used by the authors revealed  no metabolites
   of endothall in whole fish.

  0.   EXCRETION

       Soo et al. (1967) investigated the excretion of endothall  in orally dosed
  laboratory animals (rats).  The results are summarized in Table III-4.   Within
  48 hours,  nearly all  of the label could be accounted for by excretion in the
  feces, urine, and  expired air.  . From 2.5 to 2.8% of the  total  dose  was
  excreted  as  carbon  dioxide (all in  the first  24  hours).   About  6 to  7%
  appeared  in  the urine, and  the  remainder (85 to  91%)  appeared  in the  feces.
  Results of this study  suggest that no  significant bioaccumulation or  retention
 occurs.

 E.   SUMMARY

      Following a single oral dose of 1  mg (about 5.2 mg/kg)  endothall  in rats,
 about  10% of the dose was absorbed.   Most of the dose was excreted in the
 feces  as  untransformed endothall, while 7% appeared  in the urine and 3%  was
 eliminated as expired  CO,.   Endothall that was absorbed was distributed  in low
 levels through most  tissues  of the body.  The  tissue with  the highest  levels
 (cpm/100 mg dry  tissue) at  1 hour was the kidney,  but  no marked  preferential
accumulation was apparent.   Clearance of endothall was biphasic  in stomach
(t,,, »  2.2 and 14.2  hours) and kidney.(t1/2 » 1.6 and 34.6  hours),
                                     in-6

-------
           Table  III-4.   Excretion  of Radioactivity by Rats Receiving a
                             Single  Oral  Dose* of "C Ring-Labeled  Endothall
RecoveYv of UC label (X total)



Rat
1
2
3
4
S
6"



Sex
F
H
F
N
F
f
Carbon
Body
weight
(9)
193
250
206
261
206
172




dioxide Urine
Day
1
2.8
2.6
2.S
2.5
2.6
2.6
Day
2
0
0
0
0
0

Day
1
6.7
6.8
5.9
5.3
S.6
3.4
Day
2
0.4
0.5
0.6
0.4
0.3
64.5


Feces
Day
1
71.2
67.1
68.3
67.3
70.6

Day
2
17.7
17.6
20.7
20.1
20.5


48-hour
recovery
(X)
98.8
94.6
98.0
95.6
99.6


72 -hour
recovery
(X)
99.1
94.8
98.5
95. 7s-'
99.6

'Total dose » 1 mg/rat, equivalent to about 5 mg/kg.
"Rat No. S sacrificed 48 hours after dosing.
'Total recovery for rat No. 5 given as 97X in original  reference; however, actual total
 was 99.6X. as shown above.
"Rat No. 6 sacrificed 24 hours after dosing.

SOURCE:  Adapted from Soo et al.  (1967).
                                             III-7

-------
 and monophasic in intestine and liver (t,,, - 14.4 and 21.6 hours,  respec-
 tively).   Total  excretion was greater than 95% of the dose by 48 hours and
 greater than 99% by 72 hours, suggesting that no significant bioaccuimilation
"or retention occurs.
i
                                      III-8

-------
                              IV.  HUMAN EXPOSURE

     Humans may be exposed to chemicals such as endothall from a variety of
sources,  including drinking water,-food, ambient air, occupational settings,
and consumer products.  This analysis of human exposure to endothall is
limited to drinking water, food, and ambient air because those media are
considered to be sources common  to all  individuals.  Even in limiting the
analysis  to these three sources, it must be recognized that individual
exposure  will vary widely based  on many personal choices and on several
factors over which little control  exists.  Where one lives, works, and
travels,  what one eats, and physiologic characteristics related to age, sex,
and health status can all profoundly affect daily exposure and intake.
Individuals living in the same neighborhood or even in the same household can
experience vastly different exposure patterns.

     Information concerning the  occurrence of and exposure to endothall in the
environment is presented in another document entitled "Occurrence of
Pesticides in Drinking Water, Food, and Air" (Johnston et al., 1984).  This
chapter summarizes the pertinent information presented in that document in
order to  assess the relative source contribution from drinking water, food,
and air.

     In the Exposure Estimation  section of this chapter, available information
is presented on the range of human exposure and intake for endothall from
drinking water, food, and ambient  air for the 70-kg adult male.  It is not
possible to provide an estimate  of the number of individuals experiencing
specific combined exposures from those three sources.

A.   EXPOSURE ESTIMATION

1.   Drinking Water

     No data were obtained on levels of endothall in drinking water.  However,
an interim tolerance of 200 pg/L was established for residues of endothall in
                                     IV-1

-------
   potable water from  the  use of  Its potassium, sodium, d1-N,N-dimethylalkyla-
   mlne, and mono-N,N-dimethyla1ky1amine salts to control aquatic plants In
   canals, lakes, ponds, and other potential sources of potable water (U.S. EPA,
   1986).  The maximum Intake of endpthall from drinking water following such use
   was estimated using the tolerance.  Assuming that a 70-kg adult male consumes
   2  liters of water/day, a maximum Intake of 5.7 ?g/kg/day was calculated.
   However,  It should be noted that the Intake of endothall  1n drinking water
   following  other  uses may be higher than  the maximum calculated  here.   In
   addition,  the value  presented does not  account  for variances In Individual
   exposures  or uncertainties  In the  assumptions used to estimate  exposure.

  2.    Diet                                                        '

       No data were obtained on the dietary Intake of endothall In the United
  States.  Tolerances set by EPA for endothall In and on raw agricultural
  commodities are as follows (U.S. EPA, 1986a):
            Commodity,,.
           cottonseed
           potatoes
           rice, grain
           rice, straw
       Tolerance f
100
100
 50 (negligible residues)
 50 (negligible residues)
 These data cannot be used, however, to estimate typical dietary intake.
 3.
      No data were obtained on levels of endothall in ambient air.  Therefore,
 the intake of endothall from ambient air could not be estimated.

 B.    SUMMARY

     Data on the  intake of endothall  from drinking water, food,  and ambient
air are  insufficient  for  use  in  determining which of these three sources  is
the major contributor to  total intake-.
                                     IV-2

-------
                         V.  HEALTH EFFECTS IN ANIMALS

 A.    SHORT-TERM EXPOSURE

 1.    Lethality

      Estimates  of  the acute  oral  LDSO  values for endothall  (technical)  and
 endothall  formulations 1n  rats range  from 31  to 138 mg/kg.  The  data are
 summarized in Table V-l.  The  range of acute  oral  LDSO values  in  rats may  have
 resulted from different absorption rates  for  the various endothall  salts
 tested  or may be attributable, to  unspecified  structural isomers  that might
 have  been  present  as contaminants in  the  various formulations  employed.

 2.    Other Effects

      a.   Oral  studies

      Brieger (1953c)  reported  a study  in which groups consisting of 20 male
 and 20  female rats  were fed  either 1,000  or 10,000 mg disodium endothall/kg  in
 the diet  (approximately 40 or  400 mg  endothall  ion/kg/day, assuming.a body
weight  of  0.40  kg  and daily  food  consumption  of 20 g).  Slight degeneration  of
 liver parenchyma and focal hemorrhagic areas  in  the kidneys were reported for
male  and female  rats  dosed orally with approximately 40 mg endothall
ion/kg/day  for 4 weeks;  most of the rats  receiving approximately 400 mg
endothall  ion/kg/day  died within  one week.

     b.    Intravenous studies

     Srensek and Woodard (1951) reported  (in  an  abstract)  the effects of
intravenous injection  of endothall in  several species.  Dogs that were
administered an iv  injection of 5 to  10 mg endothall/kg bw responded with
                                      V-l

-------
        Table  V-l.   Summary of Oral  Lethality Data on  Endothall In Rats
X Acid
Form tested equivalent Sex
Eridothall 75-86 — »
(technical)
Endothall — M
(technical)
Endothall — -' F -
(technical)
Aquatol K* 28.6 H
(di potassium
endothall)
Aquatol* 15.5
(di sodium
endothail)
Hydrotho! 191* 23.4
{monococoamine
endothall)
Hydout* (mono- 10.0
cocoaml ne
enthothall)
U>J8
ing" formulation/ mg endothall
kg bw Ion/kg bw
51 38-44
57
46 — "
125 36
198-329 31-51
560-590 131-138
GOO 60
Reference
U.S. EPA (1981a)
Gains and
Under (1986)
Gains and
Under (1986)
U.S. EPA (198U);
U.S. EM (19Sla)
U.S. EPA (198Ia)
U.S. EPA (1981a)
'Not specified.
                                        V-2

-------
 immediate scratching of the nose,  intermittent  retching, and vomiting.  Some
 animals recovered,  and some died of respiratory failure.  Electrocardiograms
 demonstrated  no  striking changes until  respiration  ceased.  Cats reacted
 similarly (dose  not reported).   Domestic  fowl were  insensitive to doses four
 times  greater than  those producing toxic  effects in dogs and cats (no data
 presented}.   Rabbits given  25 to 50 mg/kg iv pawed  at their noses, developed
 irregular breathing and,  after 80  to 130  minutes, died of respiratory failure.

     Goldstein (1952)  reported  in  an abstract that  intravenous injections of 5
 mg  endothall/kg  were often  fatal in both  dogs and rabbits, and doses of
 10  mg/kg were always fatal  in both species.  This report suggested the heart
 as  the primary organ of failure, as evidenced by symptomatology, pathology,
 electrocardiogram,  blood pressure  recording, and respiration rate (data not
 presented).   These  findings are in contrast with those of Srensek and Woodard
 (1951),  who attributed death of the animals to  respiratory failure.

     c.   Inhalation studies

     Since endothall  is  often applied by  spray  techniques, inhalation exposure
 is  a potential hazard.   Acute inhalation  exposure to endothall formulations at
 levels above  20,000 mg/m3 (>3,000 mg endothall  ion/m1} resulted  in lung
 congestion and hemorrhage in exposed rats.  A number of deaths resulted from a
 high-level exposure to these formulations of 1  to 6 hours' duration
 (Table V-2).  Exposure to airborne endothall at lower levels produced
 respiratory'and  eye irritation.
     d.   Skin and eve irritation

     Goldstein (1952) reported that a 1% solution of endothall applied to the
unbroken skin of rabbits produced no effects.  The  same solution applied to
scarified skin resulted in mild  skin lesions.  Solutions  (10-20%) or applica-
tions of the pure, powdered material to intact or scarified skin resulted in
more severe skin effects, including necrosis, and the death of some treated
animals.
                                      V-3

-------
              Table V-2*   Acute Inhalation Toxicity of Endothall  and Formulations
                          Aqueous Aerosols)
                                                                        i


% Acid
Form tested equivalent
Endothall 75-86
(technical)


Aquathol* 15.5
(di sodium
endothal 1 )

Aquathol* 15.5
(di sodium
endothal 1)

Aquathol* 28.6
(dipotassium
endothal 1)

Exodsure (mct/nrM

Endothall
Formulation ion Species
50 40 Guinea
- pig


200 31 Rat



20,970 3,250 Rat



20,780 5,940 Rat




Effect
(duration of
exposure)
Respiratory arti
eye irritation!;
recovery (6-hoiiir
exposure)
Irritation; il:l
survived (duraij
tion of exposure
not specified) :
Lung congestion,
hemorrhage; 2/ijO
died (1-hour
exposure)
§'
a«ab.u.. 	 »*..>
rats; 4/10 died'
(1-hour exposure)
Hydrothol 191*
(monococoami ne
endothal1)
23.36
22,120
5,170
Rat
Hemorrhage, con-
gestion in most
rats; 4/10 died'
(1-hour exposure)
SOURCE:  Adapted from U.S. EPA  (1981b).
                                              V-4

-------
      Additional  studies of endothall  and  various  formulations  (Table V-3) also
 demonstrated the skin-irritant capacity of this compound.   Solutions contain-
 ing the sodium or potassium salts were-mildly irritating to rabbits, while
 several organic amine salts produced  severe skin  irritation and,  in some  in-
 stances, fatalities.

      Endothall  salts  produced  severe  eye  irritation  in rabbits when small
 quantities were applied to the conjunctiva.   These data are shown in
 Table V-4.  All  formulations tested were  capable  of  producing  corneal damage.

 8.    LONG-TERM  EXPOSURE

      Brieger (19535)  orally treated nine male dogs (one dog/dose  level) with
 doses of 1,  2,  3,  5,  10,  20, 30,  40,  and  50  mg  disodium endothall/kg bw/day
 (0.8  to 40 mg endothall ion/kg/day},  in capsules,  for up to 6  weeks.  All dogs
 administered doses greater than 20 mg disodium  endothall/kg bw/day died within
 3 to  11 days.  The remaining dogs were  sacrificed  at the end of 6 weeks.
 Pathological  changes  were  found- in the  gastrointestinal tract  of  all dogs.
 These changes,  particularly conspicuous in  the  dogs  at the  four highest dose
 levels,  included necrotic  areas at the  highest  dose  and varying degrees of
 ulceration and edema  at the lower doses,  and they  may have  resulted from
 contact of the  undiluted compound (administered in capsules) with  the walls of
 the gastrointestinal  tract.  Other than the  gastrointestinal effects, no  other
 treatment-related  findings were observed.

     Brieger  (1953a)  reported  the results of a  2-year feeding study in Wistar
 rats.   Groups of 10 male and 10 female  rats  were fed diets  containing 0,  100,
 300,  1,000, or 2,500  mg disodium endothall/kg of diet (approximately. 0, 4, 12,
 40, or  100 mg endothall  ion/kg bw/day,  respectively, assuming  food intake of
 20 g/day and mean  body  weight  of 0.4  kg).  No toxic  effects, other than
 lethality, were  reported,  but  the use of a larger  number of animals in each
group could have given  a stronger assessment.   Mortality by the end of the
 study was 60 to  90% for all  groups  except for the  high-dose female group,
where mortality  was only 30%.   The  initial group of  female  controls was
                                      V-5

-------
Table V-3.  Primary Dermal Irritation of Endothall and Formulations in
% Acid
Form tested equivalent
Endothall 1-10
(Di sodium)
Aquathol* 15.5
Aquatho! K® 28.6
Hydrothol 191* 23.4
Hydout® 10.0
Dose
Endothall
Formulation ion (mg) Effect
0.5 ml 5-50 Irritation; no
sensitization
0.5 ml 77.5 . No irritation at 24-72
hours
0.5 ml 143 Slight erythema and
edema in 1/6 rabbits at
24 hours; negative at
72 hours
0.5 mL 117 6/6 animals died at 24
hours
0.5 g 50 2/6 abraded skin sites;
severe irritation
SOURCE:  Adapted from U.S. EPA (1981a).
                                      V-6

-------
  Table V-4.  Primary Eye  Irritation of Endothall and Formulations in Rabbits
Form tested
                                     Dose
  % Acid                   Endothall
equivalent  Formulation    ion  (mg)
                              Effect
Endothall
(Technical)
Aquathol®
(Disodium
endothall)
Aquathol K®
(Dipotassium
endothall)
  75-86
0.1 g
  15.5
0.1 Hi
  28.6
0.1 ml
Hydrothol 191®    23.36
(Monococoamine
endothall)
              0.1 ml
75-86      In unwashed eyes:
           conjunctiva! opacity;
           lethality within 24
           hours.  In washed eyes:
           reversible conjunctival
           inflammation or a
           prolonged reaction with
           corneal opacification.

15.5       Severe conjunctival
           inflammation, chemosis;
           delayed corneal
           clouding.  No
           differences between
           washed and unwashed
           eyes.

28.6       Conjunctival
           irritation; irre-
           versible corneal
           clouding at 7 days in
           unwashed eyes.
           Reversible conjunctival
           inflammation and iridal
           congestion in washed
           eyes.

23.4       Corrosive; 3/6 dead at
           72 hours.

SOURCE:  Adapted from U.S. EPA (1981b),
                                      V-7

-------
 reduced  to eight rats  because one escaped and another accidentally died.
 However,  the surviving animals were maintained until they were 27 months old.
 Brieger  considered  age of death  for each rat, and ranges of mean (t standard
 deviation) ages of  death were 20.1 to 23.8 (t 2.8 to 6.1) months for all male
 groups and 18.9 to  21.6 (t 5.6 to 7.0) months for all female groups.  Due to
 the high  mortality  and the small number of animals, this study is considered
 to be Inadequate for assessment  of endothall toxicity.

     Keller (1965)  reported the  results of a 24-month.study on the effects of
 d1sodium  endothall  in  male and female beagle dogs.  Purebred beagles (6 to
 9 months  of age) were  divided into four groups of six dogs each (three males,
 three females).  One group served as control and received only the basal lab-
 oratory diet.  The  other three groups were fed diets containing 100, 300, or
 800 mg disodium endothall/kg diet, respectively.  According to the author,
 these levels of endothall in the diet correspond to dose levels of approxi-
 mately 2, 6, or 16  mg  endothall  ion/kg bw/day, respectively.  In the high-dose
 group, the dietary  intake was increased from 800 to 1,000 mg disodium endo-
 thall/kg  diet (20 mg endothall ion/kg bw/day) at the end of the 19th month; to
 1,300 mg  disodium endothall/kg of diet (26 mg endothall ion/kg bw/day) at the
 end of the 20th month;  to 1,600  mg disodium endothall/kg diet (32 mg endothall
 ion/kg bw/day) at the  end of the 21st month; and, finally, to 2,000 mg
disodium  endothall/kg  diet (40 mg endothall ion/kg bw/day) at the 22nd month.
The study was terminated after 24 months.

     No gross signs of toxicity  were observed in any test animals throughout
the study.  Dealth  of  one female dog at the intermediate dose level was
attributed to pneumonia.  Body weight gains and food consumption were within
normal limits throughout the study.  One high-dose dog showed a net weight
loss of about 1 kg.  Hematology, liver function, and urinalysis results of t-
est animals were comparable to those of controls throughout the study.
Necropsies at 24 months showed no gross pathology that could be attributed to
the test  compound.  Organ weights and organ-to-body weight ratios of test
animals in the low-dose group were comparable to those of controls.
 Intermediate- and high-dose level dogs exhibited increased eight and organ-to-
body weight ratios  of  the stomach and small intestine.  The effect appeared to
                                      V-8

-------
 be dose related..  Microscopic examination of tissue sections revealed no
 significant or consistent pathological  changes  that could be attributed to
 ingestion of the disodium endothall  in  the diet.  Changes, such as bile duct
 proliferation in the test dogs, were considered to be incidental; they were
 comparable to controls and within  normal limits.  This study, therefore,
 identifies a LOAEL of 6 mg endothall  ion/kg bw/day and a NOAEL of 2 mg
 endothall  ion/kg bw/day.

      In  a  more  recent  12-month dietary  study in dogs, disodium endothall was
 fe'd to  groups of four male and four  female beagle dogs at levels of 0, 150,
 450,  or 1350 ppm (Greenough et al. 1987).  After 6 weeks of dosing, the
 dietary level  at the highest dose  was reduced to 1000 ppm because'of anorexia,
 decreased  food  consumption and body  weight loss.  Compound intake in the low-,
 mid-  and high-dose groups  was approximately 6,  18 and 35.8 mg/kg/day.  Five
 high-dose  dogs  (two  males  and three  females) were sacrificed moribund at 62
 and 103  days (males  and at 104, 193,  and 263 days (females).  The sacrificed
 dogs  had subdued behavior  and were in poor condition.  Histologically, they
 showed  acute necrosis  of the esophageal epithelium and necrosis of the fundus
 and pylorus  of  the stomach.

     After the  highest  dose  had been  reduced to 1000 ppm, a partial recovery
 of  the weight loss was  observed, but  the overall weight gain remained lower
 than  in  controls.  No  effects on weight gain were observed at 150 or 450 ppm.
Clinical laboratory  studies  showed a  marked reduction of hemoglobin
concentration in high-dose dogs; this was considered secondary to the
debilitated  state  of the dogs.  Several dogs in the high-dose group also had
elevated levels  of serum aspartic  aminotransferase and alanine
aminotransferase.  At gross  examination, the livers of high-dose males and
females were noted with a  nodular  granular surface, and ascites were apparent
in  the abdominal cavity.  Oval cell  hyperplasia in the portal tract and
hepatocyte shrinkage was observed  histologically in the liver of all high-dose
dogs and 6/8 dogs  fed 450 ppm endothall.  No effects on the liver were
observed at the  lowest  dose  tested.   No necrotic changes in the esophagus or
stomach were observed in high-dose animals that survived, but reactive
hyperplastic changes were observed in the gastric mucosa of the stomach.

                                      V-9

-------
    Similar but less severe histologic findings were observed in all eight dogs
    fed 450 ppm.  At 150 ppm, very mild injury to the epithelium of the stomach
    with Separative hyperplasia" was observed.

         Based  on  the histologic changes  in  the liver and  reactive  hyperplastic
    response  in the  gastric mucosa,  the  LOAEL .is  450 ppm (14.4 mg/kg endothall
    ion/day), and  considering  the marginal effects on the  stomach at the lowest
    level, the  NOAEL  is probably slightly lower than 4.8 mg/kg endothall ion/day.
   C.   REPROOUCTIVE/TERATOGENIC EFFECTS
        A three-generation study on the effects of disodium endothall  on
   reproduction in rats was reported by Scientific Associates (1965).   The study
   utilized 120 Sprague-Dawley-derived weanling rats (40 to 55 g).   Groups of
   20  females  and  10  males were fed 0,  100,  300,  or 2,500 ppm disodium endothall
   (approximately  0,  4,  12,  or 100  mg  endothall  ion/kg/day,  respectively).   Diets
  were available  a4  libitum throughout  the  study.   Animals  were housed indi-
  vidually, except during mating.   When the animals were 100 days old,  they were
  bred to produce F1t litters.   Ten days after weaning the Ft. progeny,  the
  animals were rebred to produce F,B litters; 20  female  and  10 male  F,b weanlings
  were selected to continue the study.  Using similar procedures,  F,b progeny
  were bred to produce  Fa and F2b litters, and F2i) progeny were bred  to produce
  Fj. and FJ6 litters.  Selected  F3b  weanlings were necropsied and examined  histo-
  logically.   Observations for all  litters included litter size, pup weight, pup
 survival, 'sex distribution,  and gross  abnormalities.

      Parental toxicity In  this study was demonstrated  at the high-dose level
 by unthriftiness, reduced  food "acceptance" (the  animals pawed through their
 food), reduced body weight gains,  olive to dark-brown  discoloration of the
 kidneys, and pale adrenals.  Reproductive or developmental toxicity was
 demonstrated at the high-dose level by reduced litter size, pup weight, and
 pup survival,  and toxic effects in offspring included emaciation,  tremors,
 nasal  scabs,  diarrhea,  or peri anal necrosis.   Excessive pup mortality at the
 high-dose  level resulted  in only one  surviving Frt offspring; this dose level
was .therefore terminated.   At the  mid-dose  level,, no parental  toxicity was
L
                                     v-io

-------
 observed.  However, at the raid-dose level,  signs of reproductive/developmental
 toxlclty Included reduced pup survival  in the F18, f^, and FJb litters; "poorer
 quality" of survivors was noted at weaning.   No adverse  effects were  attri-
 buted to endothall  at the low-dose level.  This study provides a  NOAEL and a
 LOAEL of 12 and 100 mg endothall  ixin/kg/day,  respectively,  for parental
 toxicity, and a NOAEL and a LOAEL of 4  and  12 mg endothall  ion/kg/day,
 respectively,  for developmental/reproductive  toxicity.

      In  a teratogenicity study, 4 groups  of 40 female Sprague-Oawley-derived
 rats  (202 to 273 g) were mated and then fed,  by gavage,  0,  10, 20, or 30
 mg/kg/day aqueous endothall  (technical  89.5%  acid equivalent) on  days 6 to 19
 of gestation (Science Applications,  Inc., 1982).   Doses  of  test material were
 prepared by using a base factor of 1.12 to  adjust for purity.  On day 20, most
 females  (25 or 26 per group)  were killed, and their litters were  delivered by
 cesarean section.   Implantation data were recorded,  and  fetuses were  weighed,
 sexed, and examined for alterations.  The remaining dams were allowed to
 deliver,  and 10 to  13 litters per group were  examined for postnatal
 development and behavior.   Examinations included  physical appearance  and
 development,  body weight,  eye opening,  surface righting  reflex (pups  were
 placed on their backs and  allowed 15  seconds  to right themselves), and
 pivoting locomotion (change  in compass  direction  of the  body midline  produced
 by forelimb motion).   The  pups were  necropsied on postnatal day 21.   Two dams
 died  at  the 20-mg/kg  bw/day dose,  and 10  dams died at the 30-mg/kg bw/day dose
 level.   No  clinical  signs  were noted  prior to death,  and no gross lesions were
 observed  at  necropsy.   Endothall  (technical)  was  not embryotoxic  or terato-
 genic at  maternal doses  of 30 mg/kg  bw/day or below,  and no patterns  of
 behavioral  dysfunction were observed  in any group.   The  researchers concluded
 that  the  lack of developmental  toxicity at dose levels that were  fatal to a
 number of dams  indicated that the maternal organism is more susceptible to
endothall than  the  conceptus.   This  study provides  a NOAEL  of 30  mg endothall
technical/kg bw/day for  developmental toxicity,  and  a NOAEL and a LOAEL of 10
and 20 mg endothall technical/kg  bw/day,  respectively, for  maternal toxicity.
                                     V-ll

-------
     In another study, endothall technical (89.5% acid equivalent) was
administered by gavage to 4 groups of 25 pregnant Charles River CD-I mice on
gestation days 6 though 16 at doses of.O (control), 5, 20, and 40 mg/kg bw/day
(IRDC, 1981).  Doses of test material were prepared using a base factor of
1.12 to adjust for purity.  Blended whole egg with water (4:1, v/v) was used
as the vehicle.  Dams were killed on day 17, and the numbers of uterine
implantations were recorded.  Fetuses were weighed, sexed, and examined for
alterations.  Maternal mortality occurred in 0/25, 0/25, 2/25, and 8/25
females in the control and low-, mid-, and high-dose groups, respectively.  In
surviving dams, no signs of maternal toxicity were reported.  The incidence of
vertebral and rib malformations in the progeny was increased, but was not
statistically significant, at 40 mg/kg bw/day.  Although the effect was not
statistically significant, the authors suggest the results of this study
indicate that endothall was teratogenic at 40 mg/kg bw/day because the
incidence of vertebral and rib malformations in their laboratory is extremely
low.  They also concluded that since the malformations were produced at a dose
level that was lethal to approximately 30% of the pregnant females, the
possibility of other factors (maternal toxicity) involved in the etiology of
the reported malformations could not be ruled out.  No other signs of
developmental toxicity were demonstrated at the lower doses.  This study
provides a NOAEL and a LOAEL for endothall technical for maternal toxicity of
5 and 20 mg/kg bw/day, respectively, and a NOAEL and a LOAEL for developmental
toxicity of 20 and 40 mg/kg bw/day, respectively.

D.   MUTA&ENICITY

     Relatively few studies investigating the genotoxic potential of endothall
have appeared in the published literature.  This section includes the
published experiments as well as a series of unpublished assays that were
performed to meet U.S. EPA registration requirements.  These are categorized
into gene mutation assays (Category 1), chromosome aberration assays  (Category
2), and studies that assess other mutagenic mechanisms (Category 3).  The
findings are discussed below and summarized in Table V-5.
                                     V-12

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                                                            V-I5

-------
1.   Gene MutationAssays (Category 1)

     a.   Reverse mutation in orokarvotes

     Andersen et al. (1972) surveyed 110 herbicides including the commercial
grade of endothall in spot tests with eight unidentified histidine-requiring
mutant strains of Salmonella tvphlmurium.  Endothall (dose not reported) was
listed as negative; however, only qualitative results.were presented.

     Schechtman et al. (1980a) performed an S. tvohimurium mammalian microsome
reverse mutation assay (Ames test) on crystalline endothall (89.5%).  Results
of the plate incorporation assay indicated that five doses (50 to 5,000
Mg/plate), either with or without Aroclor 1254-induced rat liver S9, were
neither cytotoxic nor mutagenic in $. tvphimurium TA1535, TA1537, TA1538,
TA98, or TA100.

     b.   Lower eukarvotes

     The potential of endothall (purity not given) to induce recessive lethal
mutations in Neurosoora crassa was evaluated by Sandier and Hamilton-Byrd
(1981).  No mutations were observed following a 5-day exposure of asexual
spores, either in suspension or on solid medium, to five doses ranging from
200 to 12,800 ppm.  The slower than normal rate of cell growth in the
12,700-ppm.suspension and 12,800-ppm solid medium treatment groups suggests
that cytotoxicity was achieved at these levels.

     c.   Mammalian cells

     A crystalline preparation of endothall (89.5%) was investigated by
Schectman et al.  (1980b,c) for the potential to Induce ouabain-resistant
(ouan) mutants in the in vitro BALB/3T3 mouse embryo cell forward mutation
assay.  Based on  a preliminary cytotoxicity screen, cells  in  suspension
cultures were exposed to  1.0, 3.0, or  10.0 *g/mL  1n the  absence  of S9  activa-
tion or 0.01, 0.1,  and 1.0 /ig/mL  in the presence  of S9 activation.  The  S9
                                      V-16

-------
 activation system was obtained from liver  of Arochlor  1254-induced rats.
 Following treatment,  cells were plated  directly for cytotoxic effects or
 allowed a recovery period and  subsequently selected for oua" mutants.  In both
 the presence and absence of S9 activation,  endothall was  assayed to  a cyto-
 toxic  dose with-no increase in oua" colonies  compared  to  controls.

     d.    Sex-linked recessive  lethal mutations in Drosophila me!anooaster

     Sandier and Hami Iton-Byrd (1981) performed sex-linked recessive lethal
 mutation studies with endothall (purity not given).  The  larval feeding
 portion of the study  was conducted  with 50, 100,  and 200  ppm, and the adult
 feeding was performed with 400, 800, and 1,600  ppm.  Dose selection  for both
 assays was governed by preliminary  results  showing  reduced survival  for both
 growth stages at high levels.

     Following the larval  and  adult feeding exposures, males were collected
 and mated with untreated females.   F, progeny were permitted one round of
 brother-sister mating, and the resulting progeny  (FJ were scored for lethal
 mutations.   In the larval  feeding study, which  represents germ cells treated
 in  the early stages of spermatogenesis,  slight  but  neither dose-related nor
 significant increases  in the lethal frequencies were observed at 50  and
 100 ppm.   Based  on the control  frequency and sample size  (approximately
 2,600/group), the slight increases  should  not be  considered  to indicate a
 positive  response.  No significantly increased  lethal  frequencies were
 observed  in the  adult  feeding  study. Progeny resulting from this exposure
 correspond  to germ cells that  were  primarily sperm  at  the time of treatment.
 The  combined results  of  these  studies indicated that endothall treatment of
 germ cells  at different  stages of spermatogenesis did  not elicit a mutagenic
 response.

     In another  sex-linked  recessive lethal  assay,  Wilson et al. (1956)
 exposed adult male D.  melanooaster  to-an unreported vapor concentration of
 19.2%  endothall  for 24 hours.   Following treatment,  males were serially mated
with untreated females for 9 days;  three brother-sister paired matings were
                                     V-17

-------
 allowed for the F, progeny, and the F, progeny were scored for lethal
 mutations.   The same authors  also conducted  larval  feeding  studies with 100
 and 250 ppm endothall  (19.2%).   Eggs  were  collected,  and  surviving males were
 mated with  untreated females  as  described.   From the  results,  Wilson et al.
 concluded that  "even by conservative  estimates,  endothall must be considered
 as  a mutagen when  administered either as a vapor or a food  ingredient."
 However,  the authors based  this  conclusion on  findings from extremely small
 sample populations.   For example,  the highest  percentage  of induced sex-linked
 recessive lethals  (0.8%) occurred in  the vapor exposure study  with adult
 males;  this value was  derived from one mutation  in  128 flies  (chromosomes)
 tested.   When the test results were compared to  the control (0 mutations in
 64  chromosomes), the increase was  reported to  be approximately ninefold.
 Interpretation  of JJ. melanooaster sex-linked recessive lethal  assay results
 relies  heavily  on sample size, since  the precision  of the assay to provide
 meaningful  information is directly related to  the background frequency of
 spontaneous mutants  and the number of tests  (chromosomes  examined} performed.
 Wurgler et  al.  (1977)  developed  sample size  tables  to determine the power of
 the  test  and the degree of  confidence in the result.   Comparing the data of
 Wilson  et al. (1956) against  these tables  shows  that  at least  1,000 chromo-
 somes  in  both treatment and control groups should have been analyzed for the
 endothall-vapor study  results to  have any biological  significance.  There is a
 similar problem of inadequate sample  size with the  larval feeding study data.
The  findings of this study  should  be  considered  inconclusive evidence of a
mutagenic response.

2.   Chromosome Aberration  Assays  (Category  2)

     a.   Somatic cells fin vivo)

     Dietary preparations containing  150, 300, and  600 ppm disodium endothall
 (15.8% acid  equivalent) were  administered to 12-week-old male  rats of strain
CRL:COBS CD(SO) Br (five/group) for 5 days in  the bone marrow  cytogenetic
assay performed by Brusick  (1977a).  'Animals were sacrificed 6 hours after
final dosing, bone marrow cells were  harvested,  and prepared metaphases
                                     V-18

-------
              (40 to SO/animal) were scored for structural chromosome aberrations.   The
              administered doses were neither toxic, cytotoxic, nor clastogenic.  The lack
              of toxicity at the highest dose, however, indicated that a maximum  tolerated
              dose (MTD), which could have provided a stronger test, was not achieved.

                   b.   Germinal  cells  (in  vivoh   dominant  lethal  assay

                   Brusick (1977b)  also used similar doses of disodium endothall  in  conjunc-
              tion with a 5-day feeding regime to determine potential clastogenic effects on
              germinal cells of male rats of strain CRLrCOBS CD(SO) Br.  Following  exposure,
              males were mated sequentially with untreated females for 7 weeks.-  The number
              of females in treatment groups ranged from 10 to 18.  No relevant increase in
              dominant lethal parameters was observed from matings timed to correspond with
              the entire period of spermatogenesis; however, the test doses were  not overtly
              toxic.   Similarly, no adverse effects on fertility or total implantation rates
              were seen.  However,  this study is weakened by the low number of matings
              (20/group/week) and the inability to establish that an MTD was achieved or
              that the test material reached the target cell (gonads).
                                                                           V
              3.   Other Mutaoenic  Mechanisms (Category 3)

                   a.   Aneuoloidv

                   Roots of AIlium  ceoa. Vicia faba. and Pi sum sativum var alaska were
              exposed to'o.l, 0.2,  0.5, and 1.0 ppm endothall (19.2%) (Wilson et  al.', 1956).
              Results were presented only for P. sativum. but the authors stated  that the
              findings for the other plants were comparable with those for £. sativum.
              Although the high dose suppressed mitosis, suggesting cytotoxicity, no defini-
              tive "C-mitotic" effect,  which is an indirect measurement of aneuploidy, was
              observed.
                                                   V-19
_

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     b.   |n vitro sisterchromatid exchange

     Vigfusson (1981) exposed human lymphocytes to four concentrations
(0.01 to 10 *g/mL) Aquathol K* (potassium endothall, 28.6% endothall Ion),
both 1n the presence and absence of S9 activation system obtained from rat
liver (it was not specified whether or not the rats had been pretreated with a
microsomal enzyme inducer).  Higher doses were completely cytotoxic; at
10 tig/ml (+/- S9), a slight cytotoxlc effect was reported.  Following treat-
ment, cells were permitted one round of replication, harvested, stained, and
evaluated for sister chromatid exchange (SCE) Induction (50 metaphase cells/-
dose).  Slight but not significant elevations in SCEs were scored-at nonacti-
vated 1.0 ng/mL and 59-activated 10 #g/mL.  The remaining doses were negative.

     c.   In vitro transformation

     Doses of Aquathol K® (28.6% endothall Ion) ranging from 1.25 to 50 nL/mL
(approximately 0.36 to 14.3 ng/mL endothall) without exogenous metabolic
activation (Table V-6) and concentrations of endothall spanning a range of
0.78 to 25 nL/mL (approximately 0.22 to 7.2 /»g endothall/mL) in the presence
of freshly isolated rat hepatocytes (Table V-7) were evaluated in the BALB/3T3
In vitro transformation assay by Rundell and Matthews (1981).  Results of a
preliminary screening test, to establish dose levels for the transformation
assay, showed that nonactivated doses greater than or equal to 62.5 nL/mL
caused severe reductions in cell survival; levels greater than or equal to
31.25 nL/mL were cytotoxlc.  Monolayer cultures either with or without rat
hepatocytes were exposed to the selected doses of Aquathol K?, washed, allowed
a 4-week incubation period, stained, and scored for the number of transformed
foci.  In the absence of metabolic activation, endothall produced a signifi-
cant (p <0.01) increase in transformed foci at a single dose  (12.5 nL/mL).
                                      V-20

-------
     Table V-6.  Effect of Aquathol K on Transformation of BALB/3T3 Cells
                 Without Metabolic Activation
Test material
Approximate
dose (ng endo-
thall/mL,
Number
of foci
Number of
foci/plate
Number of
pi ates
with foci
Aouathol K« fnL/mll
      0
      1,
      6.
     12.5
     25.0
     50.0'
25
25
0
0.36
  79
  60
  20
            14.40
Positive Control

3-Methylcholanthrene

      5.0 »g/ml_
 7
 9
 6
19**
 5
 2
                              33*
                                                   Initial Assay
0.25
0.56
0.38
1.19
0.31
0.13
 6/28
 9/16
 6/16
10/16
 5/16
 2/16
                            2.2
                          15/16
                                                   Repeat Assay
Aouathol K® fnL/mU

      0
      2.0
      4.0
      8.0
     16.0
     32.0

Positive Control

3-Methylcholanthrene

      5.0
             0
             0.57
               ,14
               .20
               .56
1,
2.
4.
             9.12
8
5
15**
16**
2
1
0.21
0.26
0.75
1.80
0.11
0.05
6/39
5/19
7/20
9/20
2/19
1/19
                              49
                                **
                            2.45
                          20/20
  'Higher doses were found to be cytotoxic (<10% survival) in preliminary
   studies.
"Significantly different from the negative control at p  sO.Ol.

SOURCE:  Adapted from Rundell and Matthews (1981).
                                     V-21

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     Tab"v'7-
Test material
Aouathol K* fnl
0
0.78
3.13
6.25
12.50
25.00-
Approximate
dose (ng endo-
thall/mL)
./ml)
0
0.22
0.90
1.79
3.60
7.20
Number
of foci
39
82**
56**
91**
53**
44**
Number of
foci/plate
1.3
5.13
4.31
6.07
3.31
2.75
Number of
plates
with foci
22/23
16/16
13/13
15/15
14/14
16/16
Positive Controls
Oimethylnitrosamine
      1.25 ML/mL
Cyclophosphanride
      2.2 *g/mL
103
133
6.44
8.31
16/16
16/16
 'Higher doses  were found to be cytotoxlc  (<10%  survival) In preliminary
  studies.
**Sign1ficantTy different from the control at p sO.Ol.
                                     V-22

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Confirmation of  this  response was demonstrated at two levels (4 and 8 nL/mL)
in  a  repeat study  (Table V-6); however, the transformation frequency was
comparable at both dose levels.  In the presence of rat hepatocytes, signifi-
cant  (p <0.01) but not dose-related increases in transformed foci were scored
over  the entire  0.78  to 25 nL/mL treatment range; the greatest increase
(6.07 foci/dish) occurred at 6.25 nL/mL.  The frequency at the 6.25 nL/mL
level is only slightly lower than that calculated for the positive control,
dimethylnitrosamine (DMN) at 1.25 «L/mL.  The authors concluded that
Aquathol K® both with and without rat hepatocyte-medfated activation was
active in the BALB/3T3 in, vitro transformation assay.

     Although Aquathol K® was assayed in accordance with generally accepted
procedures, the  findings of this study can be questioned for the following
reasons:  (1) the effect was not dose related; (2) the response elicited in
the presence of  primary rat hepatocytes suggests that Aquathol K* is com-
parable in transforming activity to the potent carcinogen, DMN (the response
at 6.25 nL/mL (1.8 »g endothall ion/mL) is actually of a higher magnitude than
DMN at 1.25 ML/mL (approximately 92.6 *ig/mL)); (3) the in vitro results are
not supported by the  findings of long-term carcinogenicity bioassays and
mutagenicity tests with endothall; and (4) the rat hepatocyte metabolic
activation phase for this test system has not been validated (Heidelberger
et al., 1983).

     In addition, the possibility that other components in the preparation may
have been responsible for the positive response should not be discounted.
Studies published by Brusick (1986) indicate that excess monovalent ions such
as Na* and  K*, which are introduced into the culture medium when salts of test
compounds are assayed, have led to erroneous false positive results; transfor-
mation in BALB/3T3 is responsive, to this ionic effect.  Brusick (1986) further
indicated that "false positives" in the in vitro transformation assay could be
attributed to ionic alterations in the treatment conditions.  Although the
findings of this study are questionable, 'no definitive conclusions can be
reached; further testing is required to clarify, the potential, if any, of
endothall to induce in vitro cell transformation.
                                     V-23

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 E.    CARCINOGENICITY

      In a 2-year study,  Brieger (1953a)  exposed  10 male and 10 female rats per
 dose level to endothall  in the diet at levels  ranging  from 100 to 2,500 mg
 disodium endothall/kg food (about 4 to 100  mg  endothall ion/kg/day, assuming
 food intake of 20 g/day  and mean body weight of  0.40 kg).  After 2 years,
 there were no differences in the number or  types of tumors in exposed animals
 in  comparison to control  animals.  Two treated male rats developed lung
 tumors, but statistical  significance of their  presence was not assessed and
 tumor type and dose group were not given.   As  previously indicated in Section
 V.B,  Long-term Exposure,  this study by Brieger (1953a) is  deficient owing to
 the small  number of animals available for assessment.

 F.    SUMMARY

      The  acute oral  toxicity LDM values  for endothall  ion  in various
 endothall  formulations range from 31 to  138 mg endothall ion/kg bw.  Single
 intravenous doses of 5 mg endothall/kg bw or higher were fatal to dogs and
 rabbits.   Death was attributed to either respiratory or cardiac failure.
 Inhalation exposure,  at  levels above 20,000 mg endothal1/m3 for 1  hour,
 resulted  in lung congestion and hemorrhage  in  rats.  Endothall is irritating
 to  the  skin and corrosive to the eyes of rabbits.

      Rats  that received oral  doses of approximately 400 mg endothall ion/kg
 bw/day  died within 1  week.   The animals  exhibited slight liver degeneration
 and focal  hemorrhagic areas in the kidneys  at  necropsy.

     Oral  administration  of disodium endothall to male dogs in doses ranging
 from  0.8 to 40 mg  endothall  ion/kg bw/day for  up to 6  weeks produced patho-
 logical changes in the gastrointestinal  tract  of all dogs.  These changes
 ranged  from inflammation  to necrosis,  and may  have resulted from contact of
the undiluted  compound (administered in  capsules) with the walls of the
gastrointestinal  tract.
                                     V-24

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     In a chronic study, no gross signs of toxicity were evident in dogs dosed
with 2, 6, or 16 mg endothall ion/kg bw/day and necropsied after 24 months.
Weight gain, food consumption, hematology, liver function tests, and urinaly-
ses were comparable in treated and-control groups.  The organ weight and
organ-to-body weight ratios of the stomach and small intestine were increased
above those for controls for the intermediate- and high-dose level animals.
Microscopic examination did not indicate changes that could be attributable to
the ingestion of the compound in the diet.  The low-dose level of 2 mg endo-
thall ion/kg bw/day was the NOAEL, whereas the 6-mg endothall ion/kg bw/day
dose level produced changes in organ weight and was considered to be the LOAEL
in this study.

     A 2-year toxicity feeding study with disodium endothall in rats at an
intake of 0, 4, 12, 40, or 100 mg endothall ion/kg bw/day was available for
evaluation.  The study used a small number of animals in control and treated
groups, and lethality was reported at all doses tested.  This study was
inadequate to evaluate toxicity or set an effect level.

     In a three-generation reproduction study in rats fed endothall at 4, 12,
and 100 mg endothall ion/kg bw/day, no apparent effect was observed in dams or
any offspring at the lowest dose.  At approximately 12 mg endothall ion/kg
bw/day in the diet, reduced pup survival and "poor quality" of weanlings were
noted, and at 100 mg endothall ion/kg bw/day in the diet, reduced litter size,
pup weight, and pup survival were noted.  This study provides a NOAEL for
reproductive-effects of 4 mg endothall ion/kg bw/day and a LOAEL for reproduc-
tive effects of 12 mg endothall ion/kg bw/day.

     Results from a teratology study in rats indicated that endothall
(technical 89.5% acid equivalent) is neither embryotoxic nor teratogenic at
maternal doses of 30 mg/kg bw/day or less, whereas maternal mortality occurred
at 20 and 30 mg/kg bw/day. It appears that the dams are more susceptible to
endothall than the developing conceptus.  This study provides for endothall
technical a NOAEL of 30 mg/kg bw/day for developmental toxicity, and a NOAEL
and a LOAEL of 10 and 20 mg/kg bw/day, respectively, for maternal toxicity.
Similarly, in mice, maternal mortality occurred at 20 and 40.mg endothall
                                     V-25

-------
 technical/kg  bw/day.  Malformations were reported  at 40 mo/kg bw/day.  The
 authors  stated  that more malformations occurred among control animals in their
 laboratory; however,  they  also  considered that these effects were associated
 with a high incidence of maternal-mortality.  The  NOAEL and LOAEL for maternal
 toxicity are  5  and 20 mg/kg bw/day, respectively,  and the NOAEL and LOAEL for
 developmental toxicity are 20 and  40 mg/kg bw/day, respectively.

     Endothall was not mutagenic in bacterial, fungal, mammalian cell, or
 Drosophila mutagenicity tests.  In vivo somatic or male germinal-cell cyto-
 genetic  assays  performed with the  disodium salt showed no clastogenic effects
 within the investigated nontoxic dose ranges.

     Endothall did not induce aneuploidy in plants, and Aquathol K®
 (dipotassium endothall) did not increase the frequency of SCE in human
 lymphocytes.  Although Aquathol K® exhibited transforming activity in BALB/3T3
 cells both in the presence and  absence of primary  rat hepatocytes, the results
 can be questioned because  of Issues regarding procedure and Interpretation.

     Although endothall  has not been shown to be carcinogenic, the present
data base is inadequate to assess  its carcinogenic potential.
                                     V-26

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                              VI.  HEALTH EFFECTS IN HUMANS

 A.    CLINICAL  CASE  REPORTS

      The  only  information on  endothall toxicity  in humans is a case report of
 the  suicide  of a young  male  (54  kg) who  ingested an estimated 7 to 8 g of
 disodium  endothall  (approximately  102  to 118 mg  endothall ion/kg bw)
 (Allender, 1983).   Repeated vomiting,  which may  have resulted in some
 aspiration of  the compound, occurred after ingestion of the solution, which
 apparently removed  much of the material  from the gastrointestinal (GI) tract.
 At autopsy,  the stomach contents contained only  4 mg endothall/100 mL stomach
 contents.  Levels of 1.7 and  1.0 mg endothall/100 g tissue were observed in
 the  liver and  blood,  respectively.  The  autopsy  report revealed gross hemor-
 rhage of  the GI tract and widespread focal hemorrhages and edema in the lungs.
 The  latter may have resulted  from  aspiration of  the compound during vomiting,
 since the compound  does have  a local irritating  capacity.

 B.    EPIDEMIOLOGICAL  STUDIES

      No epidemiological  reports  concerning endothall exposure were found in
 the  literature.

 C.    HIGH-RISK  POPULATIONS

     No data identifying any  high-risk population were found in the
 literature.

 D.   SUMMARY

     Little  information was available on human health effects of endothall.
There are no reports  of adverse  health effects in individuals who manufacture
or apply this compound.  A single  suicide report  indicates that oral ingestion
by humans produces  effects observed in animals.  The human autopsy report
 indicated gross hemorrhage of the  GI tract and widespread focal edema and
hemorrhage,  of  the  lung.
                                     VI-1

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                             VII.  MECHANISMS OF TOXICITY
    A.   ANIMALS
        The mechanism of endothall toxicity in animals is not known,  Goldstein
   (1952) reported that the cause of death following intravenous injection of 5
   or 10 mg/kg bw in dogs was cardiac arrest.  In an earlier study (Srensek and
   Woodard, 1951), death in dogs or rabbits dosed with 5 to 50 mg/kg bw was
   attributed to respiratory failure.   No other data are available  on the
   mechanism of action in animal species.

   B.   PLANTS

       Studies of the effects of endothall in plants indicate that it may have
  several actions.  Mann and Pu (1968) reported that endothall (5 *g/mL} caused
  an approximate 40% inhibition of incorporation of malonic acid into the lipid
  fraction of hypocotyl segments of Hemp sesbania fSesbania exaltata).  Maestri
  and Currier (1966)  suggested that endothall  produced a variety of membrane
  effects  that  resulted in wilting and drying  of leaf tissue.   The  authors  also
  reported increased  respiratory rate  in  leaves  sprayed with endothall.
  However,  these  studies  do not  provide a  clear  understanding  of  the mechanism
  of action of  this compound  in  plants.

 C.   SYNERGISTIC/ANTAGONISTIC EFFECTS

      Gzhegotskii and Martynyuk (1966) reported on the toxicity of Murbetol, a
 combination herbicide containing 142.4 g endothall  and 85.5 g isopropy1-
 phenylcarbamate  (isopropyl N-phenylcarbamate;  propham) per liter.   Although
 specific  data  were not presented,  14  times as  much  Murbetol was  required to
 produce the same toxic response in albino rats,  mice,  and  guinea pigs as
endothall alone.  This was attributed to  the  "antagonistic interaction" of the
components.  The endpoints utilized as measures  of  the toxic  response were  not
reported.
                                     VIM

-------
0.   SUMMARY

     No specific Information Is available on the mechanism of  toxicity  of
endothall in animals.  Intravenous toxicity studies in dogs  suggest that the
cause of death is cardiac or respiratory arrest.  One study  suggests that
isopropylphenylcarbamate may antagonize endothall toxicity,  but no data were
provided.
                                     VII-2

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                VIII.  QUANTIFICATION OF TOXICOLOGICAL EFFECTS .

     The quantification of toxicologlcal effects of a chemical consists of
separate assessments of noncarcinogenic and carcinogenic effects.  Chemicals
that do not produce carcinogenic effects are believed to have a threshold dose
below which no adverse, noncarcinogenic health effects occur, while carcino-
gens are assumed to act without a threshold.

A.   PROCEDURES FOR QUANTIFICATION OF TOXICOLOGICAL EFFECTS

1.   Noncarcinoqenic Effects

     In the quantification of noncarclnogenic effects, a Reference Dose (RfD),
formerly called the Acceptable Dally Intake (ADI), Is calculated.  The RfD Is
an estimate (with an uncertainty spanning perhaps an order of magnitude) of a
dally exposure of the human population (Including sensitive subgroups) that Is
likely to be without an appreciable risk of deleterious health effects during
a lifetime.  The RfD Is derived from a No-Observed-Adverse-Effect Level
(NOAEL), or Lowest-Observed-Adverse-Effect Level (LOAEL), Identified from a
subchronic or chronic study, and divided by an uncertainty factor(s).  The RfD
is calculated as follows:
          Rfd »   fNOAEL or LQAEL1
                 Uncertainty factor(s)
mg/kg bw/day
     Selection of the uncertainty factor to be employed in the calculation of
the RfD is based on professional judgment while considering the entire data
base of toxicological effects for the chemical.  To ensure that uncertainty
factors are selected and applied in a consistent manner, the Office of
Drinking Water (ODW) employs a modification to the guidelines proposed by the
National Academy of Sciences (NAS, 1977, 1980) as follows:

          An uncertainty factor of 10. is generally used when good chronic or
          subchronic human exposure data identifying a NOAEL are available and
                                     VIII-1

-------
          are supported by good chronic or subchronic  toxicity data  in other
          species.

     •    An uncertainty factor of 100 Is generally used when  good chronic
          toxicity data identifying a NOAEL are available  for  one or more
          animal  species (and human data are not available), or when good
          chronic or subchronic toxicity data identifying  a  LOAEL in humans
          are available.

     *    An uncertainty factor of 1,000 is generally  used when limited  or
          incomplete chronic or subchronic toxicity data are available,  or
          when good chronic or subchronic toxicity data identifying  a LOAEL,
          but not a NOAEL, for one or more animal  species  are  available.

     The uncertainty factor used for a specific risk assessment is  based prin-
cipally on scientific judgment rather than scientific fact and accounts for
possible intra- and interspedes differences.  Additional  considerations,
which may necessitate the use of an additional uncertainty factor of 1  to 10,
not incorporated  in the NAS/ODW guidelines for selection  of an uncertainty
factor include the use of a less-than-lifetime study for deriving an RfD,  the
significance of the adverse health effect, pharmacokinetics factors, and the
counterbalancing of beneficial effects.

     From the RfO, a Drinking Water Equivalent Level (OWEL)  can be  calculated.
The DWEL represents a medium-specific  (i.e., drinking water)  lifetime expo-
sure, at which adverse, noncarcinogenic  health effects are not anticipated to
occur.  The DWEL assumes  100% exposure from drinking water.    The DWEL provides
the noncarcinogenic health effects basis  for establishing a drinking water
standard.

For ingestion data, the DWEL is derived  as follows:

     DWEL =>    RfD x fbodv weight in kol    - 	mg/L  (	
              Drinking water volume in L/day
                                    VIII-2

-------
 where:
               Body weight -assumed to  be  70  kg  for an adult.
      Drinking water volume - assumed to be 2  L per day for an adult.

      In  addition  to the  RfO  and  the DUEL,  Health Advisories (HAs) for
 exposures of shorter  duration (One-day, Ten-day, and Longer-term) are
 determined.   The  HA values are used as  informal guidance to municipalities and
 other organizations when emergency spills  or  contamination situations occur.
 The  HAs  are  calculated using an  equation similar to the RfO and DWEL; however,
 the  NOAELs or LOAELs  are identified from acute or subchronic studies.  The HAs
 are  derived  as follows:
     HA
           fNOAEL or  LQAEL1 x  fbwl
                 X (.
L/day)
     Using the above equation, the following drinking water HAs are developed
for noncarcinogenic effects:

     1.  One-day HA for a 10-kg child ingesting 1 L water per day.
     2.  Ten-day HA for a 10-kg child ingesting 1 L water per day.
     3.  Longer-term HA for a 10-kg child ingesting 1 L water per day.
     4.  Longer-term HA for a 70-kg adult ingesting 2 L water per day.

     The One-day HA calculated for a 10-kg child assumes a single acute expo-
sure to the chemical and is generally derived from a study of less than 7 days
duration.  The Ten-day HA assumes a limited exposure period of 1 to 2 weeks
and is generally derived from a study of less than 30 days duration.  The
Longer-term HA is derived for both a 10-kg child and a 70-kg adult and assumes
an exposure period of approximately 7 years (or 10% of an individual's
lifetime).  The Longer-term HA is generally derived from a study of subchronic
duration (exposure for 10% of an animal's lifetime).
                                    VIII-3

-------
 2-    Carcinogenic  Effects  "

      The  EPA categorizes the carcinogenic potential of a chemical, based on
 the  overall weight of evidence,  according to  the following scheme:

      •  Group A:    Human Carcinogen.   Sufficient evidence exists  from epi-
                    demiology  studies  to support a  causal association between
                    exposure to the chemical and human cancer.

      •  Group B:    Probable Human Carcinogen.   Sufficient evidence of car-
                    cinogenicity in animals with limited  (Group Bl) or inade-
                    quate (Group 82) evidence  in humans.

      •  Group C:    Possible Human Carcinogen.   Limited evidence of carcino-
                    genicity in animals in the absence of human data.

      •  Group 0:    Not Classified as  to Human Carcinoqenicitv.  Inadequate
                    human and  animal evidence  of careinogenicity or for which
                    no data are available.

          Group E:   Evidence of Noncarcinogenicitv  for Humans.  No evidence of
                    carcinogenicity in at least two adequate animal tests  in
                    different  species  or in both adequate epidemiologic and
                    animal  studies.

      If toxicological  evidence leads  to  the classification of the contaminant
as a  known, probable,  or possible human  carcinogen, mathematical models are
used  to calculate  the  estimated excess  cancer  risk associated with the inges-
tion  of the contaminant in drinking water.  The data used in these estimates
usually come from  lifetime exposure studies in animals.  To predict the risk
for humans from animal data, animal doses must be  converted to equivalent
human doses.  This  conversion  includes  correction  for noncontinuous exposure,
less-than-lifetime  studies, and for differences in size.  The factor that
compensates for the size difference is  the cube root of  the ratio of the
                                    VIII-4

-------
 animal and human body weights.   It is  assumed  that  the  average adult human
 body weight is 70 kg, and that  the average water consumption of an adult human
 is 2 liters of water per day.

      For contaminants with a carcinogenic potential, chemical levels are
 correlated with a carcinogenic  risk estimate by employing a cancer potency
 (unit risk) value together with the assumption for  lifetime exposure via
 ingestion of water.   The cancer unit risk is usually derived from a linearized
 multistage model  with a 95% upper confidence limit  providing a low-dose
 estimate; that is,  the true risk to humans, while not identifiable, is not
 likely to exceed  the upper-limit estimate and,  in fact, may be lower.  Excess
 cancer risk estimates may also  be calculated using  other models such as the
 one-hit,  Weibull,  logit,  and probit.   There is little basis in the current
 understanding of  the biological  mechanisms involved in  cancer to suggest that
 any one of these  models is able to predict risk more accurately than any
 others.   Because  each model  is  based on differing assumptions, the estimates
 that are derived  for each model  can differ by  several orders of magnitude.

     The  scientific  data  base used to  calculate  and support the setting of
 cancer risk rate  levels has  an  inherent uncertainty due to the systematic and
 random errors in  scientific  measurement.  In most cases, only studies using
 experimental  animals have been  performed.  Thus,  there  is uncertainty when the
 data are  extrapolated to  humans.   When developing cancer risk rate levels,
 several other areas  of uncertainty exist, such  as the incomplete knowledge
 concerning, the health effects of contaminants,  in drinking water; the impact of
 the  experimental  animal's age,  sex,  and species;  the nature of the target
 organ  system(s) examined;  and the actual rate  of exposure of the internal
 targets  in  experimental  animals  or humans.  Dose-response data usually are
 available only for high levels  of exposure, not  for the lower levels of
exposure closer to where  a standard may be set.   When there is exposure to
more than one  contaminant, additional  uncertainty results from a lack of
 information  about possible synergistic or antagonistic  effects.
                                    VIII-5

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B.   QUANTIFICATION OF NONCARCINOGENIC EFFECTS FOR ENOOTHALL

1.   One-dav Health Advisory

     The single oral LDSO values of endothall Ion  In various formulations
range from 31 to  138 rag/kg bw  (U.S. EPA, 1981a).  No studies were found that
Identified a NOAEL or LOAEL based on more sensitive endpoints (i.e., other
than mortality) suitable for derivation of the One-day HA value.  In the
absence of adequate data, it is recommended that the Ten-day HA of 800 »g
endothall ion/L be used as a conservative estimate of the One-day HA value.

2.   Ten-dav Health Advisory

     Table VIII-1 summarizes studies considered for calculation of the Ten-day
HA for endothall.  The study by Brieger (1953c) defined a LOAEL of 40 mg
endothall ion/kg  bw/day based  on gross necropsy and histopathology (slight
liver degeneration and focal hemorrhagic areas in kidneys of rats).  However,
the study of Brieger (1953c) defined no NOAEL because no experiments with
doses lower than  the LOAEL were performed.

     The teratogenicity study  in rats (Science Applications, Inc., 1982)
defines NOAELs of 10 and 30 mg endothall technical/kg bw/day for maternal
toxicity and teratogenicity, respectively.  The teratogenicity study in mice
(IROC, 1981) defines NOAELs of 5 and 20 mg endothall technical/kg bw/day for
maternal toxicity and teratogenicity, respectively.

     The higher NOAELs of 20 and 30 mg endothall/kg bw/day for teratogenicity
in mice and rats, respectively, are not considered in calculating the Ten-day
HA, because they  are equal to  or greater than the LOAEL of 20 mg endothall/kg
bw/day for maternal toxicity in mice (IRDC, 1981) and in rats (Science Ap-
plications, Inc., 1982).
                                    VIII-6

-------
    

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-------
      The NOAEL of 10 mg endothall  technical  (89.5% acid equivalent)/kg bw/day
 for maternal toxlclty in rats (Science Applications,  Inc.,  1982)  is therefore
 selected for calculation of the Ten-day HA.   The selected  value  is higher  than
 the NOAEL of 5 ing endothall/kg bw/day for maternal toxicity in mice (IRDC,
 1981),  and is without significant  fetotoxicity or teratogenicity.  Although
 10 mg/kg/day was not tested in mice,  the similarity of maternal  toxic effects
 in the  mice and rats at 20 mg/kg/day  (deaths of 2/25  rats  and 2/25 mice)
 supports the use of the higher NOAEL  between these studies.

      Using a NOAEL of 10 mg endothall/kg bw/day,  the  Ten-day HA  for a 10-kg
 child is calculated as follows:

      Ten-day HA » flO mQ/ko/davmO ko)  • 1.0  mg/L =  0.8 mg endothall
                        (100)(1 L/day)                 ion/L (800  ,.g/L)
      where:
          10 mg/kg/day


                10 kg
                  100
NOAEL,based on absence of maternal  or fetal  toxicity
in mice exposed to endothall technical (89.5% acid
equivalent), adjusted for purity to 10 mg/kg/day, via
gavage during days 6 to 16 of gestation.
assumed weight of a child.
uncertainty factor, chosen in accordance with NAS/ODW
guidelines for use with a NOAEL from an animal study.
               1 L/day = assumed water consumption by a 10-kg child.

     3.   Longer-term Health Advisory

     The DUEL adjusted for a 10  kg child  (200 »g/L)  is proposed for use  as  a
Longer-term HA.  The proposed  Longer-term HA for a 70-kg  adult is  the  DWEL
(700 ng/l).  The studies  summarized  in Table VIII-2  that  are considered  for
derivation of the DWEL can also  be considered for calculation of the Longer-
term HA because the duration of  both  studies is  well  below  the lifespans of
the species tested.  On this basis, the 2-year feeding study in dogs by  Keller
(1965) is preferred over  the reproduction study  in rats by  Scientific
                                     VIII-8

-------
 Associates (1965)  which although each generation was on study for 100 .days  as
 compared with the  longer duration of 2 years  for the dogs,  has a somewhat
 higher NOAEL and LOAEL.

      Similarly,  the 2-year study In  dogs by Keller  (1965) is  preferred over
 the study of Greenough et al.  (1987) because  of the longer  duration  and  the
 slightly lower LOAEL and NOAEL.                           >

      No existing guidelines or standards were located for longer term (sub-
 chronic) exposure  to endothall.

 4.    Reference Dose and Drinking Hater Equivalent Leel-
     Table VIII-2 summarizes studies considered for derivation of the RfD and
DWEL for endothall.  The study by Keller (1965) identified a LOAEL of 6 mg
endothall ion/kg bw/day and a NOAEL of 2 mg endothall  ion/kg bw/day based on
increased organ weights and organ-to-body weight ratios for the stomach and
small  intestine.  Although no significant histopathological changes were
observed in association with the increased organ weights and organ-to-body
weight ratios, the effect appeared to be dose dependent.  In addition, in a
1-year dog study by Greenough et al. (1987), dose-related histologic changes
in the stomach and small intestine ranging from marginal hyperplasia
(4.8 mg/kg/day) to reactive hyperplasia and necrosis (28.6 mg/kg/day) were
observed.  However, the NOAEL and LOAEL were higher than in the Keller (1965)
study.  Thus, the study of Keller (1965) has been selected as the basis for
derivation of the RfD and DWEL.  Similarly, the study  by Scientific Associates
(1965), a three-generation study (100 days/generation), with a higher NOAEL of
4 mg/kg/day and a shorter duration, is not used to calculate the RfD and DWEL
values.

     Using the study of Keller (1965),  the DWEL is derived as follows:

Step 1:  Determination of the Reference Dose (RfD)
           f? mq/kq/day) „ 0 02 mg endothall/kg/day
               (100)
                                    VIII-9

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                                                           VIII-IO

-------
 where:
       2 mg/kg/day - NOAEL for endothal.l  ion,  based on  absence  of Increased
                     organ weight and  organ-to-body weight  ratios for the
                     stomach  and  small  Intestine of dogs  exposed  to d1sodium
                     endothall  via the diet  for  2 years.
           100      » uncertainty  factor,  chosen  In  accordance with
                     NAS/ODW  guidelines for  use  with a  NOAEL from an
                     animal study.
Step  2:   Determination  of the Drinking Water  Equivalent Level  (DUEL)
DWEL . (0.2 mg/kg/day) (70 kg)
          z I/day
                                               endothall/L  (700 «g/L)
where:
      0.02 mg/kg/day  - RfD.
               70 kg  » assumed weight of an adult.
             2 L/day  » assumed water consumption of a 70-kg adult.

     The DWEL assumes 100% Intake from drinking water.  The DWEL may be
reduced when relative source contribution is taken into account.

     No existing guidelines or exposure standards were found that relate
directly to human exposure.  Several residue tolerances have been established
for crops.  These range from 0.05 ppm (negligible residues) for rice, grain,
and straw to 0.1 ppm  for cottonseed, hops, and potatoes (U.S. EPA, 1986).

     An interim tolerance of 200 #g/L has been published for residues of
endothall, used to control aquatic plants, in potable water (U.S. FDA, 1986).

C.   QUANTIFICATION OF CARCINOGENIC EFFECTS FOR ENDOTHALL

1.   Categorization of Carcinogenic Potential
                                    VIII-11

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                •
      The  International  Agency for Research on  Cancer  (IARC) and the U.S.
 Environmental  Protection  Agency have  not  evaluated  the carcinogenic potential
 of  endothall  (WHO,  1982).   Available  toxicity  data  do not  show endothall as
 carcinogenic.   Endothall  can  be placed  in Group  D  (inadequate evidence  in
 humans  and  animals)  by  the  EPA's guidelines  for  carcinogenic risk  assessment
 (U.S. EPA,  1986).

 2.   Quantitative Carcinogenic  Risk Estimates

     No quantitative assessment  of excess cancer risk has been reported.

D.   SUMMARY   .

     Table VII1-3 summarizes HA  and DUEL values calculated on the basis of
noncarcinogenic endpoints.  No  estimations of  excess cancer risk were
performed.
                                   VIII-12

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 Gzhegotskii  MI,  Martynyuk VZ.   1966.   Toxicology  of  the  combined herbicide
 "murbetol."   Hyg.  Sanit.  31:225-229.

 Heidelberger C,  Freeman AE,  Prenta  RJ, Sivak A, Bertram  JS,  Casto  BC,  Dunkel
 VC,  Francis  MW,  Kakunaga  T,  Little  JB, Schechtman LM.  1983.   Cell  transforma-
 tion by chemical agents - A  review  and analysis of the literature.  A  Report
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 114:283-385.

 IRDC.   International  Research  and Development Corporation.   1981.   Teratology
 study in mice.   Study No.  470-006.  EPA Accession No. 070277.

 Isensee AR.   1976.  Variability of  aquatic model  ecosystem-derived  data.
 Internat. J.  Environ. Studies  10:35-41.

 Johnston P,  Letkiewicz F,  Borum D,  Gambal N, Gerner  G, et al.  1984.
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 Keller  J.  1965.   Two-year chronic  feeding study  of  disodium endothall to
 beagle  dogs.  EPA  Pesticide  Petition 6G0503.  EPA Accession  No. 090586,
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 Maestri  M, Currier HB.  1966.   Toxic effects of endothall.   Plant  Physio!.,
 Proc. Ann. Meeting.   Abstract  VII.

 Mann JD, Pu M.   1968.  Inhibition of lipid synthesis by  certain herbicides.
 Weed Sci. 16:197-198.

 NAS.  1977.   National Academy  of Sciences.  Drinking Water and Health.
 Volume  I.  Washington, DC:   National Academy Press,  pp.  19-66.

 NAS.  1980.   National Academy  of Sciences.  Drinking Water and Health.
 Volume  III.   Washington,  DC:   National Academy Press, pp. 25-67.

 Rundell  JO, Matthews  EJ.   1981.  Evaluation of Aquathol  K« in  the In vitro
 transformation of  BALB/3T3 cells with  and without  metabolic activation assay.
 Report  to Metro, Seattle, WA;  EPA Accession No. 245680.

 Sandier L, Hamilton-Byrd  EL.   1981.  The induction of sex-linked recessive
 lethal  mutations in Drosoohila  melanooaster by Aquathol  K«, as measured by the
 Muller-5 test.  Report to Municipality of Metropolitan Seattle, Seattle, WA.

 Schechtman LM, Cumen RD,  Parmar AS, Sinsky PM.  1980a.   Activity of T1604 in
 the Salmonel1 a/miocrosomal assay for bacterial mutagenicity.   Report to
 Pennwalt Corp., Tacoma, WA;  EPA Accession No. 244126.

 Schechtman LM, Beard SF, Sinsky PM.  1980b.  Activity of T1604 in the ia vitro
mammalian cell point mutation assay in the absence of exogenous metabolic
 activation.   Report to Pennwalt Corp., Tacoma, WA; EPA Accession No. 244126.


                                     IX-2

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U.S. EPA.  1987.  U.S. Environmental Protection Agency.  Endothall health
advisory.  Washington, DC:  U.S. EPA, Office of Drinking Water.

U.S. FDA.  1986.  U.S. Food and Drug Administration.  Code of Federal
Regulations.  21 CFR 193.180; April 1.

Vigfusson NV.  1981.  Evaluation of the mutagenic potential of Aquathol K* by
the induction of sister chromatid exchanges in human lymphocytes in vitro.
Report to Municipality of Metropolitan Seattle, Seattle, WA; EPA Accession No.
245680.

Weil CS, Condra N, Haun C, Striegel JA.  1963.  Experimental carcinogenic!ty
and acute toxicity of representative epoxides.  Am. Indust. Hyg. Assoc. J.
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WHO.  1982.  World Health Organization.  IARC monographs on the evaluation of
the carcinogenic risk of chemicals to humans.  Chemicals, Industry processes,
and industries associated with cancer in humans.  International Agency for
Research on Cancer Monographs, Vols. 1-29.  Supplement 4.  Geneva:  World
Health Organization.

Wilson SM, Daniel A, Wilson GB.  1956.  Cytological and genetical effects of
the defoliant endothall.  J. Heredity 47:151-155.

Windholz K, Budavari S, Blumetti RF, Otterbein ES.  1983.  The Merck Index.
10th Ed.  Rahway, NJ:  Merck and Co., Inc., p. 516.

Wurgler FE, Sobels FH, Vogel E.  1977.  Drosophila as assay system for
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Handbook of Mutagenicity Test Procedures.  Amsterdam, New York, Oxford:
Elsevier Scientific Publishing Co., pp. 335-373.

Yeo RR.  1970.  Dissipation of endothall and effects on aquatic weeds and
fish.  Weed Sci. 18:282-284.
                                     IX-4

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