820K88145
August, 1987
                                       HEXAZINONE

                                    Health Advisory
                                Office  of Drinking Water
                          U.S.  Environmental Protection Agency
I.  INTRODUCTION

        The  Health Advisory  (HA)  Program, sponsored by  the Office of  Drinking
   Water (ODW), provides  information  on  the health effects,  analytical  method-
   ology and treatment  technology that would be  useful  in dealing with  the
   contamination  of drinking water.   Health Advisories  describe  nonregulatory
   concentrations of  drinking water contaminants at which adverse health  effects
   would not be anticipated  to occur  over specific exposure  durations.  Health
   Advisories contain a margin of safety to protect sensitive  members of  the
   population.

        Health Advisories serve as informal technical guidance to assist  Federal,
   State and local officials responsible for protecting public health when
   emergency spills or  contamination  situations  occur.  They are not  to be
   construed as legally enforceable Federal standards.  The  HAs  are subject to
   change as new  information becomes  available.

        Health Advisories are developed  for one-day, ten-day,  longer-term
   (approximately 7 years, or 10% of  an  individual's lifetime) and  lifetime
   exposures based on data describing noncarcinogenic end points of toxicity.
   Health Advisories  do not  quantitatively incorporate  any potential  carcinogenic
   risk from such exposure.   For those substances that  are known or probable
   human carcinogens, according to the Agency  classification scheme  (Group A or
   B),  Lifetime HAs are not  recommended. The  chemical  concentration  values for
   Group A or B carcinogens  are correlated with  carcinogenic risk estimates by
   employing a cancer potency (unit risk) value  together with  assumptions for
   lifetime  exposure  and  the consumption of drinking water.  The cancer unit
   risk is usually derived from the linear multistage model  with 95%  upper
   confidence limits.   This  provides  a low-dose  estimate of  cancer risk to
   humans that is considered unlikely to pose  a  carcinogenic risk in  excess
   of the stated  values.   Excess  cancer  risk estimates  may also  be calculated
   using the One-hit, Weibull,  Logif or  Probit models.  There  is no current
   understanding  of the biological mechanisms  involved  in cancer to suggest that
   any one of these models is able to predict  risk more accurately thar another.
   Btcause each model is  based on differing assumptions, the estimates  that are
   derived can differ by  several  orders  of magnitude.

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    Hexazinone                                                  August,  1987

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II.  GENERAL INFORMATION  AND  PROPERTIES

    CAS No.:   51235-04-2
    Structural  Formula:
                          a
                                          • V
                                        .A
                                       CH,

       3-Cyclohexyl-6-(dimethylamino)-1  methyl-1,3,5-triazine-2, 4( 1H, 3H)-dione;

    Synonyms

         0  Velpar;  Hexazinone.

    Use

         0  Contact  and  residual  herbicide  (Meister,  1983).

         0  Usage  areas  include plantations of coniferous  trees,  railroad right-
           of-ways,  utilities, pipelines,  petroleum  tanks,  drainage ditches, and
           sugar  and alfalfa  (Kennedy,  1984).

    Properties   (Kennedy,  1984; CHEMLAB,  1985)

           Chemical Formula                 C11H20°2N3
           Molecular Weight                 226 (calculated)
           Physical State (25°C)            White  crystalline solid
           Boiling  Point                    —
           Melting  Point                    115-117°C
           Density
           Vapor  Pressure (86°C)            6.4 x  10~5 mm  Hg
           Specific Gravity
           Water  Solubility  (25°C)          33,000 mg/L
           Log Octanol/Water  Partition     -4.40  (calculated)
              Coefficient
           Taste  Threshold
           Odor Threshold                  odorless
           Conversion Factor

    Occurrence

         0  Hexazinone has been found  in none of  the  surface water samples
           or  ground water samples  analyzed from  13  samples taken at 6
           locations (STORET,  1987).

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     Hexazinone                                                 August,  1987

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     Environmental Fate

          0  Hexazinone did not hydrolyze in water within the pH range of  5.7  to  9
            during a period of 8 weeks (Rhodes, 1975a).

          0  In a soil aerobic metabolism study, hexazinone was added to a Fallsington
            sandy loam and a Flanagan silt loam at 4 ppm.  I4c-Hexazinone residues
            had a half-life of about 25 weeks.  Of the extractable 14c residues,
            half was present as parent compound and/or 3-cyclohexyl-l-methyl-6-
            methylamino-l,3,5-triazine-2,4-(lH,3H)-dione.  Also present were
            3-(4-hydroxycyclohexyl)-6-(dimethylamino)-l-methyl-l-(lH,3H)-dione
            and the triazine trione (Rhodes, 1975b).

          0  A soil column leaching study used 14c-hexazinone, half of which was
            aged for 30 days and applied to Flanagan silt loam and Fallsington
            sandy loam.  Leaching with a total of 20 inches of water showed that
            unaged hexazinone leached in the soils; however, leaching rates were
            slower for the aged samples, indicating that the degradation  products
            may have less potential for contaminating ground water (Rhodes, 1975b).

          0  A field soil leaching study indicated that l^c-hexazinone residues
            were leached into the lower sampling depths with increasing rainfall.
            A Keyport silt loam (2.75% organic matter; pH 6.5) and a Flanagan
            silt loam (4.02% organic matter; pH 5.0) were used.  For the  Keyport
            silt loam, ^4C residues were found at all depths measured, including
            the 8- to 12-inch depth, when total rainfall equaled 8.43 inches,
            1 month after application of hexazinone.  For the Flanagan silt loam,
            14C residues were found at all depths sampled, including the  12- to
            15-inch depth, 1 month after application, when a total of 7.04 inches
            of rain had fallen (Rhodes, 1975c).

          0  A soil TLC test for Fallsington sandy loam and Flanagan silt  loam
            gave Rf values for hexazinone of 0.85 and 0.68, respectively.  This
            places hexazinone in Class 4, indicating it is very mobile  in these
            soils (Rhodes, 1975c).

          0  In a terrestrial field dissipation study using a Keyport silt loam
            in Delaware, hexazinone had a half-life of less than 1 month.  In a
            field study in Illinois ' (Flanagan silt loam), hexazinone had  a half-
            life of more than 1 month (62% of the parent compound remained at
            1 month)  (Rhodes, 1975b).  Tn a separate study with Keyport silt
            loam, some leaching of the parent compound to a depth of 12 to 18
            inches was observed (Holt, 1979).


III.  PHARMACOKINETICS

     Absorption

          0  Rapisarda (1982) reported that a dose of 14 mg/kg 14c-labeled
            hexazinone (>99% pure) was about 80% absorbed in 3 to 6 days
            (77% recovery in urine, 20% in feces) when administered by gastric

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Hexazinone                                              November 11, 1986

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        intubation to male and  female Charles River CD rats with or without
        3 weeks of dietary preconditioning with unlabeled hexazinone.

     0  Rhodes et al. (1978)  administered 2,500 ppm (125 mg/kg)  hexazinone in
        the diet to male rats for 17 days.  This was followed by a single dose
        of 18.3 mg/300 g (61  mg/kg)  14c-labeled hexazinone.   The hexazinone
        was rapidly absorbed  within  72 hours, with 61% detected  in the urine
        and 32% in the feces.  Trace amounts were found in the gastro-
        intestinal (GI) tract (0.6%, tissues not specified)  and  expired air
        (0.08%).

Distribution

     8  Orally administered hexazinone has not been demonstrated to accumulate
        preferentially in any tissue (Rhodes et al., 1978; Holt et al., 1979;
        Rapisarda, 1982).

     0  Studies in rats by Rapisarda (1982) and Rhodes et al. (1978) showed
        that no detectable levels of 1^C-hexazinone were found in any body
        tissues when the animals were administered >14 mg/kg hexazinone by
        gastric intubation with or without dietary preconditioning.

     0  In a study with dairy cows by Holt et al. (1979) hexazinone was given
        in the diet at 0, 1,  5 or 25 ppm for 30 days.  Assuming that 1 ppm in
        the diet of a cow equals 0.015 mg/kg (Lehman, 1959), these levels
        correspond to 0, 0.015, 0.075 or 0.37 mg/kg/day.  The investigators
        reported no detectable residues in milk, fat, liver, kidney or lean
        muscle.

Metabolism

     0  Major urinary metabolites of hexazinone in rats identified by Rhodes
        et al.  (1978) were 3-(4-hydrocyclohexyl)-6-(dimethylamino)1-methyl-
        1,3,5-triazine-2,4-(lH,3H)-dione  (metabolite A); 3-cyclohexyl-6-
        (methylamino)-1-methyl-1,3,5-triazine-2,4-(1H,  3H)-dione  (metabolite B);
        and 3-(4-hydrocyclohexyl)-6-(methylamino)-!-methyl-1,3,5-triazine-2,4-
        (lH,3H)-dione  (metabolite C).  The percentages  of these metabolites
        detected in  the urine were  46.8,  11.5 and 39.3%, respectively.
        The major fecal metabolites detected by Rhodes  et al. (1978) were
        A (26.3%) and C  (55.2%).  Less than  1% unchanged hexazinone was
        detected in  the urine or the feces.  Similar results were reported
        by Rapisarda  (1982).
 Excretion
        Rapisarda  (1982) and Rhodes et al.  (1978) reported that excretion of
        14c-hexazinone and/or its metabolites occurs mostly in the urine
        (61 to 77%) and in the feces  (20 to  32%).

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    Hexazinone                                                 August,  1987

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IV.  HEALTH EFFECTS
    Humans
            The Pesticide  Incident Monitoring  System data base (U.S.  EPA,  1981)
            indicated  that 3  of  43,729  incident reports  involved  hexazinone.
            Only one report cited exposure  to  hexazinone alone, without other
            compounds  involved.  A 26-year-old woman inhaled hexazinone dust
            (concentration not specified).   Vomiting occurred within  24 hours.
            No other effects  were reported  and no treatment was administered.
            The other  two  reports did not involve human  exposure.
    Animals
       Short-term Exposure

         0  Reported oral  LD^g values  for technical-grade hexazinone in rats range
            from 1,690 to  >7,500 mg/kg (Matarese,  1977;  Dashiell and Hinckle,
            1980; Kennedy,  1984).

         0  Henry (1975) and Kennedy  (1984)  reported the oral LD50 value of
            technical-grade hexazinone in beagle dogs to be >3,400 mg/kg.

         0  Reported oral  LD5Q values  for hexazinone in  guinea pigs range from
            800 to 860 mg/k9 (Dale,  1973; Kennedy, 1984).

         0  Kennedy (1984)  studied  the response of male  rats to repeated oral
            doses of hexazinone (89 or 98% active ingredient).  Groups of six
            rats were intubated with  hexazinone, 300 mg/kg, as a 5% suspension
            in corn oil.   Animals were dosed 5 days/week for 2 weeks (10 total
            doses).  Clinical signs and body weights were monitored daily.  At
            4 hours to 14  days after  exposure to the last dose, microscopic
            evaluation of  lung, trachea,  liver, kidney,  heart, testes, thymus,
            spleen, thyroid, GI tract, brain, and bone marrow was conducted.  No
            gross or histological changes were noted in  animals exposed to either
            active ingredient percentage of hexazinone.

         0  In an 8-week range-finding study (Kennedy and Kaplan, 1984), Charles
            River CD-1 mice (10/sex/ddse) received hexazinone (>98% pure) in the
            diet for 8 consecutive  weeks at concentrations of 0, 250, 500, 1,250,
            2,500 or 10,000 ppm. Assuming 1 ppm in the  diet of mice equals
            0.15 mg/kg (Lehman, 1959), these dietary concentrations correspond to
            doses of about 0, 37.5,  75.0, 187.5, 375.0 or 1,500 mg/kg/day.  No
            differences were observed  in general behavior and appearance, mortality,
            body weights,  food consumption or calculated food efficiency between
            control and exposed groups.  No gross pathologic lesions were detected
            at necropsy.   The only  dose-related effects  observed were increases
            in both absolute and relative liver weights  in mice fed 10,000 ppm.  A
            No-Observed-Adverse-Effect-Level (NOAEL) of  2,500 ppm (375.0 mg/kg/day)
            was identified by the authors.

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Hexazinone                                                  August,  1987

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   Dermal/Ocular  Effects

     0  In  an acute dermal toxicity test performed by MeAlack (1976),  up to
        7,500 mg/kg of a  24% aqueous solution of hexazinone (reported  to be
        1,875 mg/kg of active ingredient)  was applied occlusively for  24
        hours to  the shaved backs and trunks  of male albino rabbits.   No
        deaths were observed throughout a 14-day observation period.

     0  Morrow (1973) reported an acute dermal toxicity test in which  60 mL
        of  a 24%  aqueous  solution of hexazinone (reported as 5,278 mg/kg) was
        applied occlusively to the shaved trunks of male albino rabbits for 24
        hours. No mortalities were observed  through an unspecified observation
        period.  One animal exhibited a mild, transient skin irritation.

     0  In a 10-day study conducted by Kennedy (1984), semiocclusive dermal
        application of hexazinone for 6 hours/day for 10 days to male  rabbits
        at 70 or  680 mg/kg/day resulted in no signs of skin irritation or
        toxicity.  A trend toward elevated serum alkaline phosphatase  (SAP)
        and serum glutamic pyruvic-transaminase (SGPT) activities was  observed,
        but no hepatic damage was seen by microscopic evaluation.  In  a
        second 10-day study using 35, 150 or 770 mg/kg/day, the highest dose
        again resulted in elevated SAP and SGPT activities, but they returned
        to normal after 53 days of recovery.   Histopathological evaluations
        were not  performed in the second study.

     0  Edwards (1977) applied 6,000 mg/kg hexazinone as a 63% solution occlu-
        sively to the shaved backs and trunks of male albino rabbits.   No
        treatment-related mortalities were reported after a 14-day observation
        period.

      0  Morrow (1972) reported the results of dermal irritation tests in which
        a single  dose of  25 or 50% hexazinone was applied to the shaved, intact
        shoulder  skin of  each of 10 male guinea pigs.  To test for sensitization,
        four sacral intradermal injections of 0.1 mL of a 15% solution were first
        given over a  3-week period.  After a 2-week rest period, the guinea
        pigs were challenged with 25 or 50% hexazinone applied to the shaved,
        intact shoulder skin.  The test material was found to be nonirritating
        and nonsensitizing at 48 hours post-application.

      0  Using a  10% solution, Goodman  (1976) repeated the Morrow study with
        guinea pigs and observed no irritation or sensitization.

      0  Dashiell and  Henry  (1980) reported that in  albino rabbits, a single
        dose of hexazinone applied as  27%  (vehicle  not specified) solution to
        one  eye per animal and unwashed was  a severe ocular irritant.   When
        applied at  27% (vehicle not specified) and  washed or at  4% (aqueous
        solution) unwashed, mild to moderate corneal cloudiness, iritis
        and/or conjunctivitis resulted.  By  21 days post-treatment with  the
        higher dose,  two  of the three  rabbit eyes had returned to normal; a
        small area  of mild corneal cloudiness persisted through  the 35-day
        observation period in one of the three eyes.  Eyes treated with  lower
        doses were  normal within 3 days.

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Hexazinone                                                 August,  1987

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   Long-term Exposure

     0  In a 90-day  feeding  study,  Sherman et al.  (1973)  fed beagle dogs
        (four/sex/dose)  hexazinone  (97.5% active  ingredient) in the diet
        at levels  of 0,  200,  1,000  or 5,000 ppm.   Assuming 1 ppm in the diet
        of a dog equals  0.025 mg/kg/day (Lehman,  1959),  these levels correspond
        to about 0,  5,  25 or 125 mg/kg/day.   At  the  highest dose level tested,
        decreased  food  consumption, weight loss,  elevated alkaline phosphatase
        activity,  lowered albumin/globulin ratios  and  slightly elevated liver
        weights  were noted.   No gross or microscopic lesions were observed
        at necropsy.  Based  on the  results of this study  a NOAEL of 1,000 ppm
        (25 mg/kg/day)  and a Lowest-Observed-Adverse-Effect-Level (LOAEL) of
        5,000 ppm  (125  mg/kg/day) were identified.

     0  In a 90-day  feeding  study (Kennedy and Kaplan,  1984), Crl-CD rats
        (16/sex/dose) received hexazinone (>98% pure)  at  dietary levels of
        0, 200,  1,000 or 5,000 ppm.  Assuming 1 ppm  in the diet of rats
        equals 0.05  mg/kg/day (Lehman, 1959), these  levels correspond to
        about 0, 10,  50 or 250 mg/kg/day.  Hematological  and biochemical
        tests and  urinalyses were conducted on subgroups  of animals after 1,
        2  or 3 months of feeding.  Following 94 to 96  days of feeding, the
        rats were  sacrificed and necropsied.  The  only statistically significant
        effect reported was  a decrease in body weight  in  both males and
        females  receiving 5,000 ppm.   No differences in food consumption were
        reported.  Results of histopathological examinations from the control
        and high-dose groups were unremarkable.   The authors identified a
        NOAEL of 1,000  ppm (50 mg/kg/day).

     0  In a 1-year  feeding  study (Kaplan et al.,  1975) weanling Charles River
        CD rats  (36/sex/dose) received hexazinone  (94  to  96% pure)  at dietary
        levels of  0, 200, 1,000 or  2,500 ppm (which, according to the authors,
        corresponds  to  0, 11, 60 or 160 mg/kg/day  for  males and 0,  14, 74 or
        191 mg/kg/day for females).  Results of  this study indicated a decrease
        in weight  gain  by both sexes at 2,500 ppm and  by  females at 1,000 ppm.
        The authors  indicated that  various unspecified clinical, hematological
        and biochemical  parameters  revealed no evidence of adverse effects.
        No significant  gross or histopathological  changes attributable to
        hexazinone were noted.  From the information presented in the study,
        a  NOAEL  of 200  ppm (11 mg/kg/day for males and 14 mg/kg/day for
        females) can be identified.

     0  In a 2-year  study, Goldenthal and Trumball (1981) fed hexazinone
        (95 to 98% pure) to  Charles River CD-1 mice  (80/sex/dose) at dietary
        levels of  0, 200, 2,500 or  10,000 ppm.  Assuming  that 1 ppm in the
        diet of  a  mouse equals 0.15 mg/kg/day (Lehman,  1959), these levels
        correspond to 0, 30,  375 or 1,500 mg/kg/day.  Corneal opacity sloughing
        and discoloration of the distal tip of the tail were noted as early
        as the fourth week of the study in mice  receiving 2,500 or 10,000 ppm.
        A  statistically significant decrease in body weight was observed in
        male mice  receiving  10,000  ppm and in female mice receiving 2,500 or
        10,000 ppm.   Statistically  significant increases  in liver weight were
        noted in male mice receiving 10,000 ppm; male  and female mice in the
        10,000-ppm dose  group also  displayed statistically significant increases

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Hexazinone                                                 August,  1987

                                     -8-
        in relative liver weight.   Sporadic occurrence of  statistically
        significant changes in  hematological effects  were  considered by
        the authors to be unrelated to hexazinone treatment.   Histologically,
        a number  of liver changes  were observed among mice fed 2,500 or
        10,000 ppm.  The most characteristic finding  was hypertrophy of
        centrilobular parenchymal  cells.   Other histological  changes included
        an increased incidence  of  hyperplastic liver  nodules  and an increased
        incidence and severity  of  liver cell necrosis.  Mice  fed 200 ppm
        showed no compound-related histopathological  changes.   A NOAEL of
        200 ppm (30 mg/kg/day)  was identified by the  authors.

     0  Kennedy and Kaplan (1984)  presented the results of a  2-year feeding
        study in  which Crl-CD rats (36/sex/dose) received  hexazinone (94 to
        96% pure) at dietary levels of 0 (two groups), 200, 1,000 or 2,500 ppm
        (approximately 0, 10, 50 or 125 mg/kg/day assuming that 1 ppm in the
        diet of a rat equals 0.05  mg/kg/day)(Lehman,  1959).  After 2 years
        of continuous feeding,  all rats in all groups were sacrificed and
        examined.  Males fed 2,500 ppm and females fed either 1,000 or 2,500
        ppm had significantly lower body weights than controls (p 98% pure) for
        approximately 90 days at dietary levels of 0, 200, 1,000 or 5,000 ppm.
        Assuming  that 1 ppm in  the diet of rats equals 0.05 mg/kg/day  (Lehman,
         1959), this corresponds to approximately 0, 10, 50 and 250 mg/kg/day.
        Following  the 90-day feeding period, six rats/sex/dose were selected
        to serve as the parental generation.  The authors concluded that the
        rats had normal fertility.  The young were delivered in normal numbers,
        and survival during the lactation period was unaffected.  In the
        5,000 ppm  group, weights of pups at weaning (21 days) were significantly
         (p  <0.01)  lower than controls or other  test groups.  The results of
         this study identify a NOAEL of 1,000 ppm  (50 mg/kg/day)  (no decrease
        in weanling weight).

      0   In a three-generation reproduction study  (DuPont,  1979), Crl-CD rats
         (36/sex/dose) received hexazinone  (98% pure) at dietary levels of 0,
         200,  1,000 or 2,500 ppm for 90 days  (approximately 0, 10, 50 or  125

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Hexazinone                                                 August,  1987

                                     -9-
        "ig/kg/day,  assuming the above  assumptions for a rat).   Following
        90 days  of  feeding,  20 rats/sex/dose were selected to serve as the
        parental (Fg)  generation.   Reproductive  parameters tested included
        the number  of  matings,  number  of  pregnancies and number of pups per
        litter.   Pups  were  weighed  at  weaning, and one male and female were
        selected from  each  litter  to serve  as parental rats for the second
        generation.  Similar  procedures were used to produce a third generation;
        the same reproductive parameters  were collected for the second and
        third  generations.   The authors stated that there were no significant
        differences  between the control and treated groups with respect to
        the various  calculated indices (fertility, gestation,  viability and
        lactation).  However, body  weights  at weaning of pups  in the 2,500 ppm
        dose group  were  significantly  (p  <0.05)  lower than those of controls
        for the  F2  and F3  litters.   The results  of this study identify a
        NOAEL  of 1,000 ppm  (50 mg/kg/day).

   Developmental Effects

     8  Kennedy  and  Kaplan  (1984)  presented the  results of a study in which
        Charles  River  Crl-CD rats  (25  to  27/dose) received hexazinone (97.5%
        pure)  at dietary concentrations of  0, 200, 1,000 or 5,000 ppm (approxi-
        mately 0,  10,  50 or 250 mg/kg/day following the previously stated
        assumptions  for  the rat) on days  6 through 15 of gestation.  Rats
        were observed  daily for clinical  signs and were weighed on gestation
        days 6,  16  and 21.   On day 21, all  rats  were sacrificed and ovaries
        and uterine  horns  were weighed and  examined.  The number and location
        of live  fetuses, dead fetuses  and resorption sites were noted.
        Fetuses  from the 0  and 5,000 ppm  dose groups were evaluated for
        developmental  effects (gross,  soft  tissue or skeletal abnormalities).
        At sacrifice,  no adverse effects  were observed for the dams.  No
        malformations  were  noted in the fetuses.  However, pup weights in the
        high-dose group  were significantly  lower than in the controls.  This
        study  identified a  NOAEL of 1,000 ppm (50 mg/kg/day).

     0  Kennedy  and  Kaplan  (1984)  presented the  results of a study in which
        New Zealand  white  rabbits  (17/dose) received hexazinone suspended in
        a 0.5% aqueous methyl cellulose vehicle  by oral intubation on days 6
        through  19  of  gestation at levels of 0,  20, 50 or 125 mg/kg/day.
        Rabbits  were observed daily and body weights were recorded throughout
        gestation.   On day  29 of gestation, all  rabbits were sacrificed, uteri
        were excised and weighed,  and  the number of live, dead and resorbed
        fetuses  was  recorded.  Each fetus was examined externally and internally
        for gross,  soft  tissue and  skeletal abnormalities.  No clinical signs
        of maternal  or fetal toxicity  were  observed.  Pregnancy rates among
        all groups  compared favorably. The numbers of corpora lutea and
        implantations  per  group were not  significantly different.  Resorptions
        and fetal viability,  weight and length were also similar among all
        groups.   Based on  the information presented in this study, a minimum
        NOAEL  of 125 mg/kg/day for maternal toxicity, fetal toxicity, and
        teratogenicity can  be identified.

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  Hexazinone                                                 August,  1987

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     Mutagenicity

        0  The  ability of hexazinone to induce unscheduled DNA synthesis  was
          assayed by Ford  (1983) in freshly isolated hepatocytes from the  livers
          of 8-week-old male Charles River/Sprague-Dawley rats.  Hexazinone
          was  tested at half-log concentrations  from  1 x 10~5 to 10.0 mM and  at
          30.0 mM.  No unscheduled DNA synthesis  was observed.

        0  Valachos et al.  (1982) conducted an in  vitro assay for chromosomal
          aberrations in Chinese hamster  ovary cells.  Hexazinone  was found  to
          be clastogenic without S-9 activation  at  concentrations  of  15.85 mM
          (4.0 mg/mL) or 19.82 mM (5.0 mg/mL); no significant increases  in
          clastogenic activity were seen  at 1.58, 3.94 and  7.93 mM (0.4,  1.0
          and  2.0 mg/mL).  With S-9 activation,  significant increases in aber-
          rations were noted only at a concentration of 15.85 mM (4.0 mg/mL).

        0  In a study designed to evaluate the clastogenic potential  of hexazinone
          in rat bone marrow cells (Farrow et al.,  1982), Sprague-Dawley CD  rats
          (12/sex/dose) were given a single dose  of 0, 100, 300 or 1,000 mg/kg
          of the hexazinone by gavage  (vehicle not  reported).  No  statistically
          significant increases in the frequency  of chromosomal aberrations  were
          observed at any  of the dose levels  tested.  The authors  concluded  that,
          under the conditions of this study, hexazinone was not clastogenic.

        0  Hexazinone was tested for mutagenicity  in Salmonella typhimurium
          strains TA1535,  TA1537, TA1538, TA98 and  TA10O at concentrations up
          to 7,000 ug/plate.  The compound was not  found to be mutagenic,  with
          or without S-9 activation  (DuPont,  1979).

     Carcinogenicity

        0  Goldenthal and Trumball  (1981)  fed  hexazinone (98% pure) for 2 years
          to mice  (80/sex/dose) in the diet at 0, 200, 2,500, or 10,000  ppm
           (0,  30,  375 or 1,500 lag/kg/day, based  on  Lehman  [1959]).  A number
          of  liver changes were observed  histologically at  the 2,500- and
           10,000-ppm level.  These included hypertrophy of  the centrilobular
          parenchymal cells, increased incidence  of hyperplastic liver nodules
          and  liver cell necrosis.   The authors  concluded that hexazinone  was
          not  carcinogenic to mice.

        0  No carcinogenic  effects were observed  in  C.:1-CD rats  (36/sex/dose)
          given hexazinone (94 to  96% pure) in the  diet at  0,  200, 1,000,  or
           2,500 ppm  (0,  10,  50, or  125 mg/kg/day) for  2 years  (Kennedy and
           Kaplan,  1984).   The authors  concluded  that none of the tumors  were
          attributable  to  hexazinone.
V.   QUANTIFICATION OF TOXICOLOGICAL EFFECTS

        Health Advisories (HAs)  are generally determined  for one-day,  ten-day,
   longer-term (approximately 7  years) and lifetime exposures if adequate data
   are available that identify a sensitive noncarcinogenic end point of toxicity.
   The HAs for noncarcinogenic toxicants are derived using the following formula:

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Hexazinone                                                 August, 1987

                                     -1 1-
              HA = (NOAEL or LOAEL) X (BW) , 	   /L (	 u /L)
                     (UF) x (	 L/day)

where:

        NOAEL or LOAEL = No- or Lowest-Observed-Adverse-Effect-Level
                         in mg/kg bw/day.

                    BW = assumed body weight of a child (10 kg) or
                         an adult (70 kg).

                    UF = uncertainty factor (10, 100 or 1,000), in
                         accordance with NAS/ODW guidelines.

             	 L/day = assumed daily water consumption of a child
                         (1 L/day) or an adult  (2 L/day).

One-day Health Advisory

     No information was found in the available  literature that was suitable
for determination of the One-day HA for hexazinone.  It is, therefore,
recommended that the Longer-term HA value of 2.5 mg/L (2,500 ug/L, calculated
below) for a 10-kg child be used at this time as a conservative estimate of
the One-day HA value.

Ten-day Health Advisory

     The study reported by Kennedy and Kaplan (1984) in which pregnant rabbits
(17/dose) received hexazinone by oral intubation at levels of 0, 20, 50 or
125 mg/kg/day on days 6 through 19 of gestation was considered to serve as
the basis for deriving the Ten-day HA for a 10-kg child.  Since no signs of
maternal or fetal toxicity were observed in this study, a NOAEL of 125 mg/kg/day
(the highest dose tested) was identified.  The NOAEL from this study is
greater than that identified in a 90-day rat feeding study (50 mg/kg; Kennedy
and Kaplan, 1984).  The LOAEL from the one-generation rat reproduction study
was 250 mg/kg based on decreased weanling weight.  Effects at doses between
50 and 250 mg/kg have not been reported for the rat.  However, in a 90-day
dog study, a LOAEL of 125 mg/kg was identified  (Sherman et al., 1973).
Therefore, the rabbit study was hot selected to derive a Ten-day value.
It is, therefore, recommended that the Longer-term HA value of 2.5 mg/L
(2,500 ug/L) for the 10-kg child be used at this time as a conservative
estimate of the Ten-day HA value.

Longer-term Health Advisory

     The 90-day feeding study in dogs (Sherman et al., 1973) has been selected
to serve as the basis for determination of the Longer-term HA for hexazinone.
In this study, dogs received hexazinone in the diet at levels of 0, 200,
1,000 or 5,000 ppm (0, 5, 25, or 125 mg/kg/day) for 90 days.  Decreased food
consumption and body weight gain, elevated alkaline phosphatase activity,
lowered albumin/globulin ratios and elevated liver weights were observed at
the highest dose.  A NOAEL of 1,000 ppm (25 mg/kg/day) and a LOAEL of 5,000 ppm
(125 mg/kg/day) were identified.  This NOAEL is generally supported by a 90-day

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Hexazinone                                                 August, 1987

                                     -12-
rat feeding study that reported a NOAEL of 50 mg/kg/day (Kennedy and Kaplan,
1984).  Effects in dogs exposed to hexazinone at 50 mg/kg/day have not been
reported.

     Using a NOAEL of 25 mg/kg/day, the Longer-term HA for a 10-kg child
is calculated as follows:

       Longer-term HA = (25 mg/kg/day) (10 kg) = 2.5 mg/L (2,500 ug/L)
                           (100) (1 L/day)

where:

   25 mg/kg/day = NOAEL, based on absence of hepatic effects or weight loss
                  in dogs exposed to hexazinone via the diet for 90 days.

          10 kg = assumed body weight of a child.

            100 = uncertainty factor, chosen in accordance with  NAS/ODW
                  guidelines for use with a NOAEL from an animal study.

         1 L/day = assumed daily water consumption of a child.

      The Longer-term HA for a 70-kg adult is calculated as follows:

       Longer-term HA =  (25 mg/kg/day) (70 kg) , 8<75   /L (8,75o Ug/L)
                           (100)  (2 L/day)

where:

   25 mg/kg/day = NOAEL, based on  absence of hepatic effects or weight
                  loss in dogs exposed to hexazinone via the diet for
                  90 days.

           70 kg = assumed body weight of  an  adult.

             100 = uncertainty  factor, chosen  in  accordance with NAS/ODW
                  guidelines for  use  with a  NOAEL from an animal study.

         2  L/day = assumed daily water consumption of an adult.

 Lifetime Health Advisory

      The Lifetime HA represents that  portion of  an  individual's total  exposure
 that is  attributed  to  drinking water  and  is  considered protective of  noncar-
 cinogenic  adverse health effects  over a lifetime exposure.   The Lifetime  HA
 is derived in  a three  step process.   Step 1  determines the Reference  Dose
 (RfD),  formerly called the Acceptable Daily  Intake  (ADI).  The  RfD  is  an  esti-
 mate of  a  daily exposure to the human population that is  likely to  be  without
 appreciable risk  of deleterious  effects over a lifetime,  and is derived  from
 the  NOAEL (or  LOAEL),  identified  from a chronic  (or subchronic) study, divided
 by an uncertainty factor(s).   From the RfD,  a Drinking Water Equivalent  Level
 (DWEL)  can be  determined (Step 2).  A DWEL  is  a  medium-specific  (i.e., drinking
 water)  lifetime exposure level,  assuming  100% exposure from  that  medium,  at

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Hexazinone                                                 August, 1987

                                     -13-
which adverse, noncarcinogenic health effects would not be expected to occur.
The DWEL is derived from the multiplication of the RfD by the assumed body
weight of an adult and divided by the assumed daily water consumption of an
adult.  Itie Lifetime HA is determined in Step 3 by factoring in other sources
of exposure, the relative source contribution (RSC).  The RSC from drinking
water is based on actual exposure data or, if data are not available, a
value of 20% is assumed for synthetic organic chemicals and a value of 10%
is assumed for inorganic chemicals.  If the contaminant is classified as a
Group A or B carcinogen, according to the Agency's classification scheme of
carcinogenic potential  (U.S. EPA, 1986), then caution should be exercised in
assessing the risks associated with lifetime exposure to this chemical.

     A 2-year rat feeding/oncogenicity study (Kennedy and Kaplan, 1984) was
selected as the basis for determination of the Lifetime HA for hexazinone.
Crl-CD rats (36/sex/dose) received 0, 200, 1,000, or 2,500 ppm hexazinone (0,
10, 50, or 125 mg/kg/day) for 2 years.  Body weight gain in males and females
in the 2,500-ppm group, and females in the 1,000-ppm group, was significantly
lower than that in controls.  No clinical, hematological or urinary evidence
of toxicity was reported.  Based on decreased body weight gain, a NOAEL of
200 ppm (10 mg/kg/day) and LOAEL of 1,000 ppm (50 mg/kg/day) were identified.

     Using a NOAEL of 10 mg/kg/day, the Lifetime HA is calculated as follows:

Step 1:  Determination of the Reference Dose (RfD)

                    RfD = (10 mg/kg/day) = 0.03 mg/kg/day
                            (100) (3)

where:

        10 mg/kg/day = NOAEL, based on absence of body weight effects in rats
                       exposed to hexazinone 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.

                   3 = modifying factor; to account for data gaps (chronic
                       dog-feeding study) in the total data base for hexazinone.

Step 2:  Determination of the Drinking Water Equivalent Level (DWEL)

          DWEL = (0.03 mg/kg/day) (70 kg) . 1<05 mg/day (1,050 ug/L)
                         (2 L/day)

where:

      0.03 mg/kg/day = RfD.

               70 kg = assumed body weight of an adult.

             2 L/day = assumed daily water consumption of an adult.

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      Hexazinone                                                  August,  1987

                                           -1 4-


      Step 3:   Determination of Lifetime  Health  Advisory

                  Lifetime HA = (1.05 mg/L)  (20%)  =  0.21  mg/L (210 ug/L)

    where:

                 1.05 mg/L = DWEL.

                       20% = assumed relative  source contribution from  water.

      Evaluation  of Carcinogenic  Potential

           0   No  evidence of carcinogenicity  in  rats or mice  has  been observed.

           0   The International Agency  for  Research  on Cancer has not evaluated
              the carcinogenic potential  of hexazinone.

           0   The criteria described in EPA's  guidelines  for  assessment of car-
              cinogenic  risk (U.S.  EPA, 1986), place hexazinone in Group D:  not
              classified.  This category  is for  substances  with inadequate animal
              evidence  of carcinogenicity.


  VI.  OTHER CRITERIA, GUIDANCE AND  STANDARDS

           0   Residue tolerances  range  from 0.5  to 5.0 ppm  for the combined residues
              of  hexazinone and its metabolites  in or on  the  raw  agricultural
              commodities pineapple, pineapple fodder and forage  (U.S.  EPA, 1985a).


 VII.  ANALYTICAL  METHODS

           0   Analysis  of hexazinone is by  a  gas chromatographic  method applicable
              to  the determination  of certain organonitrogen  pesticides in water
              samples (U.S. EPA,  1985b).  This method requires a  solvent extraction
              of  approximately 1  liter  of sample with methylene chloride using a
              separatory funnel.  The methylene  chloride  extract  is dried and
              exchanged  to acetone  during concentration to  a  volume of  10 mL or
              less.  The compounds  in the extract are separated by gas  chromatography,
              and measurement is  made with  a  thermionic bead  detector.   The method
              detection limit for hexazinone  is  0.72 ug/L.


VIII.  TREATMENT TECHNOLOGIES

           0   No  information was  found  in the available literature on treatment
              technologies used to  remove hexazinone from contaminated  water.

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    Hexazinone
August, 1987
                                         -15-
IX.  REFERENCES

    CHEMLAB.   1985.   The  Chemical  Information System,  CIS,  Inc.   Baltimore, MD.

    Dale,  N. *   1973.   Oral  LD50  test (guinea  pigs).   Haskell Laboratory Report
         No.  400-73,  unpublished study.   MRID 00104973.

    Dashiell,  O.L., and J.E.  Henry.*  1980.   Eye irritation tests in rabbits—United
         Kingdom  Procedure.   Haskell Laboratory Report No.  839-80, unpublished
         study.   MRID 00076958.

    Dashiell,  O.L., and L.  Hinckle.*  1980.   Oral LD5Q test in rats—EPA proposed
         guidelines.   Haskell Laboratory Report No.  943-80, unpublished study.
         MRID 00062980.
    DuPont.*  1979.   E.I.  duPont de Nemours & Co.  Supplement to Haskell Laboratory
         Report.   No. 352-77.   Reproduction study in rats with sym-triazine-2,4(1H,
         3H)-dione,  3-cyclohexyl-1 -methyl-6-dimethylamino (INA 3674, hexazinone).
         Accession No.  97323.

    Edwards, D.F.*  1977.   Acute skin absorption test on rabbits LD50.  Haskell
         Laboratory Report No.  841-77,  unpublished study.  MRID 00091140.

    Farrow,  M,  T.  Cartina,  M.  Zito et.  al.*  1982.  In vivo bone marrow cytogenetic
         assay  in  rats.   HLA Project No. 201-573.  Final Report.  (Unpublished
         study  received  July 11, 1983 under 352-378.)  Submitted by E.I. duPont
         de  Nemours S Co.,  Inc., Wilmington, DE.  MRID 0013155.

    Ford, L.*  1983.    Unscheduled DNA synthesis/rat hepatocytes in vitro.
         (INA-3674-11 2).   Haskell Laboratory Report No. 766-82, unpublished
         Study.  MRID 00130708.

    Goldenthal, E.I.  and R.R.  Trumball.*  1981.  E.I. duPont de Nemours & Co.,
         Inc.  Two-year  feeding study in mice.  IRDC No. 125-026, unpublished
         study.  Submitted to the Office of Pesticide Programs.  MRID No. 0079203.

    Goodman, N.*   1976.   Primary skin irritation and sensitization tests on guinea
         pigs.   Report No.  434-76,  unpublished study.  Submitted to the Office of
         Pesticide Programs.  MRID  00104433.

    Henry, J.E.*   1975.   Acute oral test (dogs).  Haskell Laboratory Report No.
         617-75,  unpublished study.  MRID 00076957.

    Holt, R.F., F.J.  Baude and D.W. Moore.*  1979.  Hexazinone livestock feeding
         studies;  milk  and  meat.  Unpublished study.  Submitted to the Office of
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    Holt, R.F.   1979.  Residues  resulting from application of DPX-3674 to soil.
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    Kaplan,  A.M.,  Z.A.  Zapp, Jr.,  C.F.  Reinhardt et al.*  1975.  Long-term
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         Laboratory Report No.  585-75.   MRID 00078045.

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Hexazinone                                                 August, 1987

                                     -16-
Kennedy, G.L.  1984.  Acute environmental toxicity studies with hexazinone.
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Kennedy, G.L., and A.M. Kaplan.  1984.  Chronic toxicity, reproductive, and
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Lehman, A.J.  1959.  Appraisal of the safety of chemicals in foods, drugs, and
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Matarese, C.*  1977.  Oral LD50 test.  Haskell Laboratory Report No.  1037-77,
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McAlack, J.W.*  1976.  Skin absorption LD50.  Haskell Laboratory Report No.
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Morrow, R.*  1973.  Skin absorption toxicity ALD and skin irritancy test.
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Rhodes, Robert C.   1975a.  Studies with "Velpar" weed killer in water.
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Rhodes, Robert C.   1975b.  Decomposition of "Velpar" weed killer in soil.
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Rhodes, Robert C.   1975c.  Mobility and adsorption studies with  "Velpar"
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Sherman,  H, N.  Dale and L. Adams et al.*   1973.   Three month feeding  study  in
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     February.

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Hexazinone                                                 August,  1987

                                     -17-
U.S. EPA.  1982.  U.S. Environmental Protection Agency.  Toxicology Chapter.
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Confidential Business Information submitted to the Office of Pesticide
 Programs.

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