September 1996
                                  HEXAZINONE

                        Drinking Water Health Advisory
                                Office of Water ,
                    O.  S. Environmental Protection Agency
     The Health Advisory. (HA) Program, sponsored by the Office of Water (OW),
provides information on the health effects, analytical methodology 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 percent of  an  individual's  lifetime),, and
 lifetime exposures based on data describing  noncarcinogenic endpoints  of
. toxicity.   For those substances that are known or probable human carcinogens,'
 according to the Agency classification scheme (Group A or 8), 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 lifelong
 exposure and the consumption of drinking water.  The cancer unit risk is
 usually derived from the linearized multistage model with 95 percent 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, logit 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  than another.  Because
 each  model  is based on differing assumptions,  the estimates  that are derived
 can differ by several  orders, of  magnitude.         .                         •

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Hexazinone
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                            September 1996
II.  GENERAL INFORMATION AND PROPERTIES
                                        I
CAS No.   8001-35-2


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

Svnonvms               '             ...                        .
        Velpar; Hexazinone  (Budavari et  al.,  1989; Sine et  al.,  1989;  U.S.
        EPA, 1994a)                                              .
Uses
     •  Broad spectrum, pre-  and post-emergence herbicide  effective against
        woody and herbaceous  weeds  (Budavari et al.,  1989).'
        i                         ,
     •  Used when plants  are  actively growing  for control  of  many annual,
        biennial and perennial weeds and woody plants on noncropland areas;
        gives contact and residual  control; rainfall  is needed  for soil
        activation; controls  woody  plants  in reforestation areas;  selective
        weed control in conifers, sugarcane, pineapple, rubber  trees and
        alfalfa  (Sine et  al., 1989).

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

     •  Neilsen and Lee (1987) estimated that  approximately 5,000 kg of.
        hexazinone (active  ingredient) was used per year for  agricultural
        purposes (Goodrich  et al.,  1991).

Properties  (Budavari et  al., 1989; CHEMLAB, 1985; Kennedy, 1984;  Sine et  al.,
            1989; U.S. EPA, 1982)
     Chemical Formula
     Molecular Weight
     Physical State  (25°C)
     Boiling Point
     Melting Point
     Density
     Vapor Pressure  (25°C)

     Specific Gravity  (25°C)
     Water Solubility  (25°C)
     Log Octanol/Water
       Partition Coefficient
     Taste Threshold (Water)
     Odor Threshold-(Water)
C12H:,,N,0:
252
White crystalline solid

115 ,to 117°C, or 113.5°C,  or 97 to 100.5°C

2 x 10"7 mm Hg  (extrapolated  from  6.4 x 10"
5  mm Hg at 86°C)
1.25
33,000 mg/L or 29,800 mg/L
-4.40 (calculated)
odorless

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Hexazinone
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September 1996
Occurrence
        Hexazinone has not been found in any surface water samples  (9  sampler
        taken at 2 locations) or groundwater samples analyzed  (6  samples  from
        6 locations), STORBT  (1988).

        Hexazinone has been detected in ground water of five states  including
        Maine (Yarborough et  al., 1995, 1996), North-Carolina, South Carolina
        (Vaught, 1995), Colorado (Austin, 1994).. The Maximum  concentration
        reported in ground water to date is 115 ppb in South Carolina,  these
        detections resulted from probable nonppint sources; additional
        detections in Hawaii  resulted from point source mechanisms.

        Jennings and Gould (1995, draft) reported extensive use of hexazinone
        for blueberry farming in the State of Maine. Low  levels of hexazinone
        were .detected in ground water near blueberry sites.  Water samples .  .
        from 20 sites had detectable .levels ranging from 0.093 to 5.97 ppb
        (/ug/L) for fifteen of these sites, and 5 sites non-detectable  levels.
        The Maine Cooperative,Extension has been conducting ground water  and,
        surface water monitoring studies in blueberry-growing  areas  for the
        past several years.   All 32 wells in these study  areas contained
        hexazinone residues sometime during the study period.  Concentratios
        in ground water from  thesewells ranged up to 29.0 ppb  In  addition,
        four ponds and three  streams contained.hexazinone residues up  to  9.2
        ppb (Hess, 1966, yarborough et al., 1995, 1996).  According  to the
        Maine Pesticide Board, another 27 wells .tested positive with
        relatively lower concentrations of hexazinone (McLaughlin, 1994a).
        In 1992, hexazinone residues were also detected in two wells that
        supplied the drinking water of a school in Maine.  Concentrations in
        these wells ranged from 3 to 10 ppb (McLauglin, 1994b).
Environmental Fate
        Hexazinone is generally resistant to hydrolysis and  loss by
        volatilization, but is subject to both microbial degradation and*
        photolysis.  Its environmental half-life can vary between  2 weeks and
        6'months, but frequently is less than 30 days  (Neary et al., 1993).

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

        In an aerobic metabolism soil' study, hexazinone was  added  to .a
        Fallsington sandy loam and a Flanagan silt  loam at 4 ppm.  In these
        media,  C-Hexazinone and'its residues had  a half-life  of about  25
        weeks.  Of the extractablc !'C residues, approximately  one-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)-
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Hexazinone
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September 1996
     •  A field soil leaching study indicated that ^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, "c residues were found at all depths evaluated one month
        after application of hexazinone, including the 8- to 12-inch depth,
        when .total rainfall equaled 8.43 inches.  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).

     •  A soil thin layer chromatography (TLC) test for Fallsington sandy
        loam and Flanagan silt loam gave R, 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).

     •  In a terrestrial field dissipation study in Delaware using a Keyport
        silt loam, 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).  In 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).

     •  Neary et al. (1993) have concluded that most peak pesticide  .
        (including hexazinone) residue concentrations in groundwater are
        associated with storm run-off, principally during the first one to
        four storm events after application.  However, these peak
        concentrations are not always associated with hydrograph peaks, and
        may not occur until weeks, months or even a year after application,
        and then may persist for only a month or more than a year.  Soil
        types, water table depth, storm event duration and intensity,
    :   distance of residues from stream channels, routing and mechanism of
        transport were all apparent factors in the appearance and timing of
        base flow and run-off concentration peaks.

     •  Based on the octanol/water coefficient, hexazinone is not expected to
        accumulate in fish.

III. PHARMACOKINETICS

Absorption

     •  Rapisarda (1982)' reported that a dose of 14 mg/kg HC-labeled
        hexazinone (>99% pure).was about 80% absorbed in 3 to 6 days (77%
        recovery  in urine, 20% in feces) when administered by gastric'
        intubation to male and female Charles River CD rats with,or without
        3 weeks of dietary preconditioning with unlabeled hexazinone.
        Similar results were observed in rats dosed with 1000 mg/kg without
        preconditioning.

     •  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) MC-labeled  hexazinone.  The
        hexazinone was rapidly absorbed within 72 hours, with 61% detected in

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Hexazinone
                              -5-
September 1996
         the  urine  and 32%  in the  feces.   Trace amounts  were  found in the
         gastrointestinal (GI)  tract  (0.6%,,tissues  not  specified)  and expired
         air  (0.08%).  >              '
Distribution
         Orally administered hexazinone has not  been demonstrated to
         accumulate  preferentially  in any tissue (Rhodes-et  al.,  1978;  Molt
         et  al.,  1979;  Rapisarda, 1982).             , ,                     . ,

         Studies in  rats  by Rapisarda (1982)  and Rhodes et al.  (1978)  showed
         that  only very low levels  of "c-hexazinone (about 0.2% .of the
         administered dose) were found in any body tissue-3-6 days after the
         animals were administered  >14 mg/kg hexazinone by gastric intubation
         with  or without  dietary preconditioning.   .

         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 tng/kg/day.  The investigators
         reported no detectable residues in milk, fat,  liver., kidney or lean
         muscle..        • '   .
 Metabolism
         Major urinary metabolites of hexazinone in rats identified by Rhodes
         et al.  (1978) were 3-(4-hydroxycyclohexyl)-6-(dimethylamino)l-methyl-
         l,3,5-triazine-2,4-(lH,3H)-dione (metabolite A); 3-cyclohexyl-6-
         (methylamino)-1-methyl-l,3,5-triazine-2,4-(1H,3H)-dione
         (metabolite B);  and 3-(4-hydrpxycyclohexyl)-6-(methylamino)-l-methyl-
         l,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
         "c-hexazinone and/or its metabolites occurs mostly in the urine  (61
         to 77%)  and in the feces (20 to 32%).  .
 IV.   HEALTH EFFECTS
 Humans.
         The Pesticide Incident Monitoring System database (U.S. EPA, 1981)
         indicated that 3 of 43,729 incident reports involved hexazinone.
         Only one report.cited exposure to hexazinone alone,  without other.

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Hexazinone
                              -6-
September 1996
        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.  Three
        additional cases of human incidents with haxazinone were reported
        since June 1992 to the "Incident Data System" of the Office of
        Pesticide Programs: one case involving a number of tree planters not
        wearing protective clothing, 30% developed skin-irritation that
        desappeared 3-4 days later; and* two other cases involving a backpack
        sprayer operator and a utility worker spraying this chemical, both
        sustained skin and eye irritation with .rapid* recovery from symptoms.
Animals
     Short-term Exposure

     •  Reported oral LD50 values  for technical-grade hexazinone in rats range
        from 1,690 to >7,SOO mg/kg  (DuPont, 1977a, 1980a; Kennedy, 1984).

     •  DuPont (1975d) and Kennedy  (1984) reported the oral LDs0 value of
        technical-grade hexazinone  in beagle dogs to be >3,400' mg/kg.

     *  Reported oral LD"10 values  for hexazinone  in guinea pigs range from 8OO
        to 860 mg/kg  (DuPont, 1973a; Kennedy, 1984)\

     *  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, 0 or 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 hexazinone.

     •  In an 8-week range-finding  study (Kennedy and Kaplan,  1984), Charles'
        River CD-I mice (10/sex/dose) 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 fbod
        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  livei: 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.

     Dermal Ocular Effects

     •  In an acute dermal toxicity test performed by DuPont  (1976a), 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.   Ho
        deaths were observed throughout a  14-day observation period.  No
        other symptoms were reported.

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Hexazinone
                              -7-
September 1996
     •  DuPont (1973b) 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.                                     ' ''     <
                                                   .
     *  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 alanine aminotransferase (ALT, formerly glutamic pyruvic-
        transamiriase or 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.                               /

     •  DuPont (1977b) applied 6,000 mg/kg hexazinone as a 63% solution
        occlusively to the shaved backs and trunks o'f male albino rabbits.
        All rabbits showed moderate skin irritation which cleared 7-days
        after cessation of treatment.  No treatment-related mortalities were
        reported after a 14-day observation period.              '

     •  DuPont (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 senaitizatiori, 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.    .

     *  Using a ,10% solution, DuPont (1976b) repeated the DuPont (1972) study
        with guinea pigs and observed no irritation or.sensitization.

     *  DuPont (1980a) reported that in albino rabbits,  a single dose of
        hexazinone applied as a 27% (vehicle not specified) solution to one
        eye per animal and left 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 25-day
        observation period in one of'the three eyes.  Eyes treated with lower
       . doses were normal within ,.3 days.

     Long-term Exposure

     •  In a 90-day feeding study, DuPont (1973c)  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 SAP
        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

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Hexazinone
                              -8-
September 1996
        (25 mg/kg/day) and a Lowest-Observed-Adverse-Effect Level (LOAEL) of
        5,000 ppm (125 mg/kg/day) were identified.

        In a 90-day feeding study (DuPont, 1973d), Crl-CD rats (10/eex/dose)
        received hexazinone (>98% pure) at dietary .levels of 0, 200, 3,000 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, SO 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).

        Groups of purebred beagle dogs (5/sex/group) were fed ad libitum 0,
        200, 1,500 or 6,000 ppm of hexazinone in their diet for 12 months
        (DuPont, 199la).  Based on monitored food consumption, these doses
        corresponded to 0, 5.00, 41.24 and 161.48 mg/kg/day in males,'and 0,
        4.97, 37.57 and 166.99 mg/kg/day in females.  Increased SAP, aerum
        globulin, and hepatocellular vacuolation, as well as decreased serum
        albumin were reported for males at the 41.24 mg/kg/day dose.
        Increased hepatocellular pigmentation and concentric membranous
        bodies, and decreased serum albumin were reported for females at the
        41.24 mg/kg/day dose.  Also at this dose, one male.appeared
        emancieted and one female had pale kidneys.  Additional effects were
        reported in the high-dose animals, including decreased body weight
        and food consumption that was perhaps due, at least in part, to poor
        palatability of the diet.  The high dose caused also in these animals
        moderate macrocytic anemia as evidenced by decreased erythrocyte
        counts, hematocrits andfhemoglobins in males, and by increased mean
        corpuscular volumes and mean corpuscular.hemoglobins in both sexes.
        Clinical chemistry parameters affected at the high dose included
        increased blood urea nitrogen (BUN), creatinine (females), serum
        alanine aminotransferase, serum aspartate aminotransferase, SAP and
        globulin, and decreased glucose, cholesterol, total protein
        (females), calcium and inorganic phosphate.  The lower cholesterol
        and phosphate were considered reflective of poor nutritional status
        in some high-dose animals, and the elevated BUN and creatinine of
        potential kidney damage.  In addition to the histological and
        enzymatic indications of liver damage, relative liver weights were
        significantly increased at the high dose.  No significant effects
        were observed at the low dose.  The study thus establishes a chronic
        oral NOAEL of 200 ppm, or 5.0 mg/kg/day, of hexazinone in the diet.
        The LOAEL was determined to be 1,500 ppm, or 41.24 mg/kg/day for
        males and 37.57 mg/kg/day for females.

        Six-week old CD-I mice  (SO/sex/group) were fed ad libitum either 0,
        200, 2,500 or 10,000 ppm of hexazinone in the diet for 2 years
        (DuPont, 1981)..  These doses correspond to approximately 0, 30, 375
        or 1,500 mg/kg/day using a conversion of 1 ppm in the diet equal to
        0.15 mg/kg/day  (Lehman, 1959).  No treatment-related changes in
        mortality, hematological parameters or gross lesions were reported.
        Corneal opacity, sloughing and discoloration of the distal tip of the
        tail were .noted as early as the fourth week of the study in some 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

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Hexazinone'
                              -9-
September 1996
        organ weight changes included increases in the liver at 10,000 ppm  *
        (males and females) and 2,500 ppm  (females), plus several judged by
      .  the authors not to be treatment-related:, lung increases (absolute and
        relative) in males at 200 and 2,500 ppm, kidney decreases in males at
        all doses, testicular increases at 2,500 and 10,000 ppm, relative
        brain increases in males at 10,000 ppm and females at 2,500 ppm, and
        thymus, kidney and heart decreases in females at 10,000 ppm.  Liver
        hypertrophy, hyperplastic nodules, cellular necrosis and inflammatory
        foci were reported in one or both  sexes at the mid and/or high doses.
       'The identified NOAEL and LOAEL for chronic oral exposure of mice to
        hexazinone were 200 ppm (30 mg/kg/day) and 2,500 ppm (375 mg/kg/day),
        respectively.   .    .

     •  DuPoht (1977c) 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.  Kales fed ,2,500 ppm.and females fed either 1,000 or
        2,500 ppm had'significantly lower  body weights than controls (p
        <0.05).  Male rats fed 2,500 ppm had slightly elevated leukocyte
        counts with a greater proportion of eosinophils.  Hale rats fed
        either 1,000 or 2,500 ppm displayed decreased alkaline phosphatase
        activity.  Statistically significant effects on organ weights
        included elevated'  relative lung weights in males fed 1,000 ppm; lower
        kidney and lower relative liver and heart-weights in males fed
        2,500 ppm; increased liver and spleen weights in females fed 200 ppm;
        and elevated stomach and relative  brain weights in females fed
        2,500 ppm.  At necropsy,•gross pathologic findings were similar among
        all groups.  Changes attributed to hexazinone were not apparent in
        any of the tissues evaluated microscopically.  The authors identified
        200 ppm (10 mg/kg/day) as the NOAEL.  However, the increased liver
        and spleen weights- observed in females would indicate that 200 ppm
        might be more appropriately identified as a LOAEL.

     Reproductive Effects

     •  Two rat reproduction studies were  performed by DuPont that provided
        supplementary or minimum data as judged by EPA (DuPont, 1979c;
        Kennedy and Kaplan, 1984).  In the first, a one-generation
        reproduction study (Kennedy and Kaplan, 1984), Crl-CD rats
        (10/sex/dose) received hexazinone  (>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/risy.
        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).

     •  In a seperate, three-generation reproduction study that was part of a
       . larger, long-term study, (DuPont;  1979c; Kennedy and Kaplan, 1984),
        Crl-CD rats (20/sex/dose) received hexazinone (95.8% pure) at dietary
       . levels of 0, 200, 1,000 or 2,500 ppm for 90 days (approximately 0,
        10, 50 or 125 mg/kg/day, assuming  the above dietary assumptions for a

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Hexazinone
                             -10-
September 1996
        rat).  Following 90 days of feeding, 20 rats/sex/dose were selected
        to serve as the parental (F0)  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 nerve s.n parental
        rats for the second generation.  Similar procedures were used to
        produce a third generation; the same reproductive parameters were
        evaluated for the second and third generations. . There were no
        significant differences between the control and treated groups with
        respect to the various calculated indices  (fertility, gestation,
        viability and lactation), thus identifying a NOAEL of 2,500 ppra
        (125 mg/kg/day) for reproductive effects.  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, indicating a NOAEL
        of 1,000 ppm (.50 mg/kg/day) and a LOAEL of 2,500 ppm (125 mg/kg/day)
        for developmental growth effects.  Based upon all effects, the study
        supports an overall NOAEL of 1,000 ppm (50 mg/kg/day) and an overall
        LOAEL of 2,500 ppm (125 mg/kg/day).

     •  Groups of Sprague-Dawley rats (30/sex/group) were fed ad"libitum
        diets containing O, 200, 2,OOO or 5,OOO ppm of hexazinone during
        growth, mating, gestation and lactation in a 2—generation
        reproduction study (OuPont, 1991b).  pi rats were dosed for 73 days
        prior to mating, and Fl rats for 105 days prior their first mating  •
        for the F2A litters (longer for the F2B litters).  Maternal toxicity
        effects were noted at the mid- and high doses.  Based on reduced body
        weights and body-weight gains in Pi and Fl females, the NOAEL and the
        LOAEL for systemic effects were determined to be 200 and 2,000 ppm,
        respectively (14.3 and 143 mg/kg/day based on body weight and dietary
        consumption data for PI females during the premating period;
        corresponding.doses for Fl females were somewhat higher).  Kale
        fertility, female fertility, gestation, viability and lactation
        indices were not affected by treatment.  Increased absolute (PI) or
        relative (Fl) testes weight at 5,000 ppm'was .not deemed
        toxicologically significant.  The reproductive NOAEL was thus 5,000
        ppm or, based upon body weight and dietary consumption data during
        the premating periods, 294 mg/kg/day (PI males), 399 mg/kg/day (Fl
      •  males), 383 mg/kg/day (PI females), or 484 rag/kg/day "(Fl-females).
        Decreased Fl, F2A and F2B pup body weights were observed at 2,000 and
        5,000 ppm, as was decreased F2B pup survival at 5,000 ppm.  Based
        upon the decreased pup weights, the developmental NOAEL and LOAEL
        were 200 and 2,000 ppm, respectively.  Using body weight and dietary
        consumption data taken during the premating periods, the
        corresponding maternal doses were approximately 14.3 mg/kg/day (PI
        females) or 17.7 mg/kg/day (Fl females), and 143 mg/kg/day (PI
        females) or 180 mg/kg/day (Fl females).  Therefore, this study
        supports an overall NOAEL of 200 ppm (14.3 mg/kg/day) and an overall
        LOAEL of 2,000 ppm (143 mg/kg/day), and waj judged by EPA to be of
        guideline quality.

     Developmental Effects

     •  In a-developmental study in the rat that was conducted by DuPont
        .(DuPont, 1974) and later published  (Kennedy and Kaplan, 1984),
        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
        (approximately 0, 10, 50 or 250 mg/kg/day  following the previously
        stated dietary 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

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Hexazinone
                             -11-
September 1996
        sacrificed and ovaries and uterine horns were weighed arid examined.
        The number and location of live fetuses, dead fetuses and resorption
        sites were noted and were unaffected by treatment. •Fetuses from the
        0 and 5,000 ppm.dose groups were evaluated for developmental' effects
        (gross, soft tissue or skeletal abnormalities).  Maternal weight gain
        during the exposure period was depressed modestly at 1,000 ppm and
        substantially at 5,000• ppm.  At sacrifice, no adverse effects were
        observed for the dams... No malformations or adverse growth effects
        'were noted in the fetuses.  This study identified a NOAEL of
        1,000 ppm (50 mg/kg/day) and a LOAEL of 5,000 ppm (250 mg/kg/day) for
        maternal effects based on'substantially depressed maternal weight
        gain.  A NOAEL of 5,000 ppm  (250 mg/kg/day) was established for
       . developmental effects in the fetus.  '     .   '     •            .   •    .

     •  Mated Sprague-Dawley rats were administered single oral daily doses
        of hexazinone by gavage during gestation days 7 through 16 (DuPont,
        1987).  The following dose levels were tested:  0, 40, 100, '400 and
        900 mg/kg/day.  Treatment-related effects, observed only in dams from
        the 400 mg/kg/day and 900 mg/kg/day groups, included alopecia, and
       •stained chin and nose; decreased body weight gain and food
        consumption during and after dosing, until the termination of the
        study; and increased relative liver weight (liver weight/body weight
        ratio).  Treatment-related developmental effects, observed only in  - _.
        the 400 mg/kg/day and 900 mg/kg/day groups, included decreased fetal
        body weights;, and increased  incidence of fetuses with no kidney
        papilla and with unoaai'fied  sternebrae.  Maternal and developmental
        toxic effects observed the 9OO mg/kg/day group were, in most
        .instances, statistically significant (p •_' 0.05) when compared with
        those observed in the control group.-  Maternal and developmental
        toxic effects observed in the 400 mg/kg/day group were minimal and,,
        only occasionally statistically significant (p i 0.05) when compared
        with those noted in the controls.  .Based on the above findings,
        maternal NOEL and LOEL were  100 mg/kg/day and 400 mg/kg/day,
        respectively.  The developmental NOEL and LOEL were also
        100 mg/kg/day and 400 mg/kg/day, respectively,

     •  Artificially inseminated New Zealand .white rabbits (17/group) were
        exposed to 0; 20, 50 or 125 mg/kg/day hexazinone by gavage for
        gestation days 6-19  (DuPont, 1980).  Significant changes in maternal'
        toxic effects were observed only in the high-dose group and included
        increased incidence of depression and discharge from the eyes;
        decreased body weight gain;, and increased resorptions.  Treatment-
        related developmental effects were observed also only in the high-
        dose group and included decreased fetal body weight gain and delayed
        ossification of extremities.  Based on these findings, the NOEL and
        LOEL for maternal toxicity were TO mg/kg/day and 125 mg/kg/day,
        respectively.  The NOEL and LOEL for davelopmental toxi.city were a) BO
        50 mg/kg/day and 125 mg/kg/day, respectively.          .          ,
                    A                 '                   '
     Mutaoenicity                           ,

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

     •  DuPont (1982b) 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

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Hexazinone
                             -12-
                                                   September 1996
         (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
        aberrations were noted only at a concentration of  15.85 mM
         (4.0 mg/mL).  Concentrations above  thsae yielded no  analyzable
        metaphase cells due to cytotoxicity.

        In a study designed to evaluate the clastogenic-potential of
        hexazinone in rat bone marrow cells (OuPont, 1982c), Sprague-Dawley
        CD rats (12/sex/dose) were given a  single dose of  0, 100, 300  or
        1,000 mg/kg of 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.

        Hexazinone was tested for mutagenicity in Salmonella typhimurium
        strains TA1535, TA1537, TA1538, TA98 and TA100 at  concentrations up
        to 2,OOO ^g/plate.  The compound was not found to  be mutagenic, with
        or without S-9 activation {DuPont,  1977d).

        Hexazinone was tested in Chinese hamster ovary  (CHO)/hypoxanthine-
        guanine-phosphoribosyltransferase assay (HGPRT), both withand  without
        activation.  The compound was not found negative in  both tests
         (DuPont, 1992).                         .
     CarcJ-nogenieity

     *  DuPont  (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 mg/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 parehchymal
        cells,  increased incidence of hyperplastic liver nodules and liver
        cell necrosis.  The authors concluded that hexazinone was  not
        carcinogenic to mice.                       . .          .        ,

     •  No carcinogenic effects were  observed in Crl-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 {DuPont, 1977c? ,
        Kennedy and .Kaplan, 1984).  The authors concluded that none of the
        tumors were attributable to hexazinone.

V.',   QUANTIFICATION OF TOXICOLOGICRL  EFFECTS

     Health Advisories (HAs) are gor.arally tieiarmined loi: one-day, ten-day,
longer-term 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:
        HA
(NOAEL or LOAEL)  x fBW)
   (UP) x  (	 L/day)
mg/L (round
                                                       ed to
where:
    NOAEL or LOAEL  =
          No- or Lowest'-Observed-Adverse-Ef feet-Level
          mg/kg bw/day.
                                                                   in

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Hexazinone
                             -13-
                                                                • September 1996
                BW  =• assumed body-weight 'of a child (10 kg)  or an adult
                       (70'kg).

                UF  =  ,uncertainty factor (10, 100,  1,000 or 10,000), in
                       accordance with EPA or National Academy of
                       Sciences/Office of Water (NAS/OW)  guidelines.

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

One-day Health Advisory

     No suitable information was found in the available literature for  >
determining the One-day HA for hexazinpne.  The Ten-day HA of 2,000 ^g/L>,
calculated below, is recommended for use as a conservative estimate for a
1-day exposure.                               •                           •

Ten-day Health Advisory        ,  '      •

     The developmental study in rabbits conducted by DuPont (1980c) has been
selected to serve as the primary basis for the Ten-day HA because it examined,
an exposure of the appropriate duration,  and because it established both a
NOAEL and a LOAEL.  In this study, artificially inseminated New Zealand white
rabbits (17/group) were exposed to 0, 20, 50 or 125 mg/kg/day hexazinone by
gavage during gestation days 6-19 .  Significant changes in maternal toxic
effects were observed only in" the high-dose group and included increased'
incidence of depression and .discharge from the eyes, decreased body weight
gain1, and increased resorptions.  Treatment-related developmental effects were
also observed only in the high-dose group, and included decreased fetal body
weight gain and delayed ossification of extremities.  Based on these findings/
the NOAEL and LOAEL for both maternal arid developmental toxicity were 50
mg/kg/day and 125 mg/kg/day, respectively.  These effect levels are generally
supported by two rat 'teratology 'studies.   In rats fed 0, 200, 1,000 or 5,000
ppm of hexazinone (approximately 0, "10, 50 or 250 mg/kg/day) from gestation
days 6 through IS, no significant adverse maternal or fetal effects were
observed, except that, during treatment maternal weight gain was substantially
depressed at 5,000 ppm (Dupont, 1974).  This study's NOAEL and LOAEL were thus
1,000 ppm (50 mg/kg/day) and 5,000 ppm;(25Q mg/kg/day),.respectively.  The
second -study, in which rats were fed 6, 40, 100, 400 or 900 mg/kg/day of
hexazinone during gestation days 7 through 16, established both maternal and
developmental NOAELs and LOAELs of 100 mg/kg/day.and 400 mg/kg/day,
respectively. , In light of these three studies, the rabbit study (DuPont,
1980c) NOAEL of 50 mg'/kg/day has been selected as the basis of the Ten-day HA.
However, because- rabbit appears tobe more sensisitive than the, rat in these
developmental studies.  However, a 90-day dietary exposure study in the dog
suggests that the rat and rabbit may not be the most sensitive test species
for the effects of hexazinone  (DuPont, 1973c).  Therefore, an extra.
uncertainty factor of three has been incorporated into the derivation of the
Ten-day HA to account for the lack of short-term toxicity data in the dog.
     The Ten-day HA for the 10-kg child is calculated as follows:

                  (50 mQ/ko/davi 110 kg) _      mg/L '

                                           rounded to 2,000 ug/L
     fen-day HA =


where:
      50 mg/kg/day
                       .NOAEL,  based on absence of maternal systemic'and pup
                       developmental effects that were observed in rabbits
                       •after maternal exposure to hexazinone at "higher doses

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Hexazinone
                             -14-
                                         September 1996
                       (125 mg/kg/day) via the diet for 10 days {gestation
                       days 6 through 155 .       .

             10 kg  =  assumed weight of child.

              • 300  =  uncertainty factor; this uncertainty factor was chosen
                       in accordance with EPA or NAS/OW guidelines in which a
                       NOAEL from an animal study is employed (a factor of 100
                       to account for interspecies extrapolation and
                       variability in human sensitivity,  and a factor of 3 to
                       account for the lack of short-term toxicity data in the
                       dog, which appears to be the most sensitive test
                       species for hexazinone). ,

           -1 L/dayv =  assumed water consumption by a 10-kg child.

Longer-term Health Advisory

     The two-generation rat study by DuPont  (1991b) has been selected to serve
as the basis for the Longer-term HA because it was well conducted, provides
both a NOAEL and LOAEL, and results in the most conservative  (lowest) Longer-
term HA.  Groups of Sprague-Dawley rats (30/sex/group) were fed ad libitum
diets containing 0,,200, 2,000 or 5,000 ppm of hexazinone during growth,
mating, gestation and lactation in a 2-generation reproduction study .  PI
rats were dosed for "73 days prior to mating, and Fl rats for 105 days prior
their first mating for theiF2A litters (longer for the F2B litters).  Maternal
toxicity-effects were noted at the mid and high doses.  Based on reduced body
weights and body-weight gains in PI and Fl females, the NOAEL and the LOAEL
for systemic effects were determined to be 200 and 2,000 ppm, respectively
(14.3 and 143 mg/kg/day, based on actual body weight and dietary consumption
data for PI females during the premating period.  The respective values
calculated from data for Fl females were 17.7 and 180 mg/kg/day).. Male
fertility, female fertility, gestation, viability and lactation indices were
not affected by treatment.  Increased absolute (PI) or relative (Fl) testes
weight at 5,000 ppm was not deemed toxicologically significant.  Based upon
decreased pup weights observed at 2,000 and 5,000 ppm, the reproductive NOAEL
and LOAEL'were also determined to be 200 and 2,000 ppm (14.3 and 143
mg/kg/day), respectively.  The 90-day feeding study in dogs conducted by
DuPont  (1973c) was also strongly considered as a basis for deriving the
Longer-term 'HA.   Based on altered food consumption, body weight gain/ -liver
weight, alkaline phosphatase activity and albumin/globulin ratios, this' study
established a NOAEL and LOAEL of 1,000 ppm  (25 mg/kg/day) and 5,000 ppm (125
mg/kg/day), respectively.  Because the true lowest-effect level cannot be
adequately identified in either study and because 73 to 105+ days more closely
approximates 10 percent of a rat's life than does 90 days for a dog  (i.e., in
terms of duration, there was a relatively more appropriate longer-term
exposure for rats than for dogs), the rat reproduction study was selected as
the basis for the 'Longer-term HA determination.  The dog study provides good
support for this level:
      Longer-term HA
(14.3  mg/kg/day)  .(10  kg)

    (100)  (1  L/day)
1.43
(Rounded to 1, 000 ug/L)
whe re:
    14.3 mg/kg/day  =  NOAEL,  based on absence of reduced maternal weight gain
                    •:   and absence of reduced pup weight in rats exposed to

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 Hexazinone
                              -15-
                                          Septeraber 1996
                        hexazinone via  the diet'for 73 to 105+ days prior to
                        mating  and during gestation.'

              10 kg  =  assumed body weight-of child.

                100  =  uncertainty factor; this  uncertainty factor was chosen
                        in accordance with EPA or NAS/OW guidelines in which a
                        NOAEL from an animal  study is  employed.

            1 L/day  =  assumed water consumption by a 10-kg child.
      The Longer-term HA for the 70-kg adult is calculated as follows:
             Longer-term HA =(14.3 mg/kg/day)  (70  kg)
                               (100)  (2 L/day)
 where:
                               = 5.25 mg/L

                          (Rounded  to  5,0,00  ug/LJ
     14.3 mg/kg/day
              70 kg

                100
NOAEL, based on absence of reduced maternal weight -gain
and absence of reduced pup weight in rats exposed to
hexazinone via the diet for 73 to 105+ days prior to
mating and during,gestation.

assumed weight of adult.
i
uncertainty factor, chosen in accordance with EPA or
NAS/OW guidelines for use with a NOAEL from an animal
'study.
            2 L/day  =  assumed water consumption by a 70-kg 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
 noncarcinogenic 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
 estimate 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^1003
 exposure from that' medium,  at 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.   The 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, i'f
 data is not available,  a value of 20% .is assumed.  If the contaminant is
•classified as a known,  probable or possible carcinogen,, according to the
 Agency's classification scheme of carcinogenic potential (U.S.  EPA,  1986),
 then caution must be exercised in making a decision on how to deal with
 possible lifetime exposure to this substance.   For human (A) or probable human
 (B)  carcinogens,' a Lifetime HA is not recommended.   For possible human
 carcinogens (,C),  an additional 10-fold safety factor is used to-calculate the

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Hexazinone
                             '-16-
                                     September 1996
Lifetime HA.  The-risk manager must balance this assessment of carcinogenic
potential and the quality of the data against the likelihood of occurrence and
significance of health effects related to noncarcinogenic end points of
toxicity.  To assist the risk manager in this process, drinking water
concentrations associated with estimated excess lifetime cancer risks over the
range of 1 in 10,000 to 1 in 1,000,000 for the 70-kg adult drinking 2 L of
water/day are provided in the Evaluation of Carcinogenic Potential section.

     The one-year dog-feeding study by DuPont (1991a> has been selected to
serve as the basis for the RfD because it was a well conducted study that
established both a NOAEL and a-LOAEL^for relatively less severe effects, and
because the dog may be more sensitive than .rodent species to the toxic effects
of hexazinone.  In this study, groups of purebred beagle dogs  (5/sex/group)  .
were fed ad libitum 0, 200, 1,500 or'6,000 ppm of hexazinone .in their diet for
12 months (DuPont, 1991a).  Based on monitored food consumption, these doses
corresponded to 0, 5.00, 41.24 and 161.48 mg/kg/day in males, and 0, 4.9"7,
37.57 and 166.99 mg/kg/day in females.  Increased SAP, serum.globulin and
hepatocellular vacuolation, as well as decreased serum albumin were reported
for males at the mid dose.  Increased hepatocellular pigmentation and
concentric membranous bodies, and decreased serum albumin were reported for
females at the mid dose.  Also at this high dose level, one male appeared
emanciated and one female had ale kidneys.  Additional gross, histological,
hematological and enzymatic effects were reported in the. high-dose animals,
while no significant effects were "observed at the low dose.  The study thus
establishes a chronic oral NOAEL of 200 ppm, or 5.0 mg/kg/day, of hexazinone
in the diet.  The LOAEL was determined to be 1,500 ppm, or 41.24 rag/kg/day, for
males and 37.57 mg/kg/day for females.                                  ,      '

Step 1:  Determination of Reference Dose  (RfD)

     Based upon the DuPont  (1991a) one-year dog-feeding study described above,
and using a 100-fold uncertainty factor to account for intra- and inter-
species variation, an RfD of O.05 mg/kg/day can be established for hexazinone.
     RfD*  = 5 mg/kg/day
                 100
0.05 mg/kg/day
*This RfD was peer, reviewed by 'both the Office of Pesticide Programs Peer
Review Committee and the Office of Water Toxicology Review Panel.  Further
external peer review of 'the RfD was performed by two external  reviewers.
However, due to the 'Agency's revision of the IRIS operational  procedures,
the RfD calculated above for this chemical  is not on IRIS.

Step 2:  Determination of  the Drinking Water Equivalent  Level  (DWEt,)
          -  (0.05 mg/kg/day)  (70  kg) _
          - -•	 <2  L/day)	  ~  1'?
                                       (Rounded  to  2,000  ug/L)
where:                               .

    0.05 mg/kg/day   =   RfD         '               .    -

              70  kg   *   assumed weight of adult.

           2  L/day   = ,  assumed water consumption by 70-kg adult.

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Hexaizihone
                             -17-
September 1996
Step 3:  Determination of the Lifetime HA

     .  Lifetime HA = (1.75 mg/L)  (20%)  = 0.35 mg/L (rounded to 400 ug/L)

where:                                          -        .
                                    •                             , i
         1.75 mg/L  =  Lifetime HA at 1004 contribution from ingestion of
                       drinking water.

               20%  =  assumed percentage of daily exposure, contributed by,
                       ingestion of drinking water.
Evaluation of Carcinogenic Potential
                                                               V
     •  A reassessment  of the available carcinogenicity  studies  in  two  rodent
    ""   species, a two-year mouse  study by DuPont  (1981), and  a two-year rat
        study by Kennedy and Kaplan  (1984), did  not provide' evidence  that
        hexazinone demonstrate either the presence or absence of a
        carcinogenic  effect.  Therefore", applying the criteria described in
        EPA's guidelines for assessment of carcinogenic  risk  (U.S.  EPA,
        1986), hexazinone may be classified in Group D:  not  classified.
        This category is for agents with inadequate animal  evidence of
        carcinogenicity."    ,

     •  The -International Agency' for Research on Cancer  has not  evaluated  the
        carcinogenic  potential of  hexazinone.    '           •     • _  -

VI.  OTHER CRITERIA,  GUIDANCE AND  STANDARDS                              '  ,

     •  The tolerances  listed in 40 CFR §180.396 for the combined residues of
        hexazinone and  its metabolites in or on  plant and animal commodities .
        range from 0.1  to 10 ppm  (U.S. EPA, 1994a, 1987).

     •  Hexazinone meets the triggers for classification as a restricted-use
        chemical for .groundwater concerns  (U.S.  EPA, 1996).'

     •  Under the Worker Protection Standard  (WPS), the  interim  restricted.
      • entry level for all registered uses of hexazinone is  currently
        24 hours  (U.S.  EPA, 1994a) .                         •'

     •  There are ..no  special toxicological concerns that warrant the
        establishment of active-ingredient-based personal protective
        equipment  (PPE) requirements'for hexazinone handlers.  The  PPE
        required for  entry when concentrations of the chemical require
        restricted entry is:  coveralls, chemical-resistant gloves, shoes
        plus socks, and protective eyewear (U.S. EPA, 1994a).

VII..ANALYTICAL METHODS                '

     •  Hexazinone. can  be analyzed by EPA Method 507..

        Determination of'hexazinone using Method 507 —  sample'is extracted
        with methylene  chloride.   The methylene  chloride extract is dried,  and
        concentrated  during a solvent exchange to methyl tert-butyl ether.
        The analytes "in, the extract are separated and identified by a
        capillary column gas chromatograph equipped 'with a  nitrogen-

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Hexazinone                                                      September 1996
                             -18-


        phosphorus detector.  Confirmation of the compounds may be obtained
        using a dissimilar column or by the use of GC-MS (U.S. EPA, 1991).

VIII. TREATMENT TECHNOLOGIES

     ». A pilot-scale treatability study for the removal of pesticides
        including hexazinone was conducted on production wastewaters at
        •DuPont in Laporte, Texas.  The plant consisted o.f a 100 L aeration
        basin, clarifier and sarid filter, and the treatment process included
     . >  the addition of'powdered activated carbon to the activated sludge.
        Operating conditions reported were:  hydraulic retention time of 2.1
        days, solids retention time of 10 days, and carbon dose of 1,480
        mg/L.  A 96.2% removal was achieved for hexazinone with an influent
        concentration of approximately 658 ^g/L  (Meidl and Dietrich, 1989) .

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

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 Hexazinone
                              -19-
                                                                 September 1996
 IX.   REFERENCES                 ,                                     ,       .
                                      .•                i
 Austin Bradford,  1994.  Ground Water Monitoring Activities, South Platte River
 Alluvial .aquafier,  1992-1993,  Report to the Commissioner of Agriculture,
 Colorado Department of Agriculture,  Colorado department, of Health.
 Budavari,  S.,  M.J.  O/Neil,  A.  Smith and P.E. Heckleman,  eds.  1989.
.index,  eleventh ed.   Rahway,  NJ:   Merck and Co.,  Inc.,  p. 742.
                                                                      The Merck
 CHEMLAB.   1985.   The- Chemical Information System, CIS, Inc.  Baltimore, MD.

 DuPont.   1992.   E.I. du Pont de Nemours and Company.  Mutagenicity Study in
.Chinese Hamster Ovaries (CHO) /Hypoxanthine-Guanine-.Phosphoribosyltransferase
 Assay (HGPRT)  with and without Acivation.  MRID % 00076956.

 DuPont.   1991a.   E.I. du Pont de Nemours and Company,  chronic toxicology
 study with hexazinone in dogs.  MRID No. 421623-01; HED/OPP Doc. No. 009575. c"

 DuPont.   1991b.   E.I. du Pont.de Nemours and Company.  Reproductive and
 fertility effects with IN-A3674-207; multigeneration reproduction study in
 rats..  MRID No.  ,420665-01; HED/OPP. Doc .  No. 009574. Ul

 DuPont.   1987.  E.I. du Pont de Nemours and Company.  Developmental toxicity
 'study in the rat.  MRID No. 403975-01; 'HED/OPP Doc. No. 007205. "'

 DuPont.   1983.  E.I. du Poht de Nemours an'd Company.  Unscheduled DNA
 synthesis/rat hepatocytes in vitro.   (INA-3674-112) . ' Haskell Laboratory
 report no. 766-82  (study authored by Ford, L. )   MRID 00130708.'"

 DuPont.   1982a.   E.I. du Pont de Nemours and Company.  Metabolism of JIC- -
•labeled hexazinone in the rat  (study authored by Rapisarda, C.).  Document no.
 AMR-79-82.  Accession No. 247847.".'

 DuPont.   1982b.   In vitro assay for chromosome aberrations in Chinese  Hamster
 Ovary (CHO) cells.  Haskell Laboratory  report no. 768-82  (study  authored by
 Vlachos, D., J.  Mart'enis and A. HorstJ .  MRID 00130709. U)

 DuPont.   1982c.   E.I. du Pont de Nemours and Company.  In vivo bone marrow
 cytogenetic assay in rats. . HLA Project rib: ,201-573 .  Final report  (study
 authored by Farrow, M., T. Cartina, M.  Zito et al.).  MRID 0013155. M.
 ()  This study was submitted to the U.S. EPA Office of,Pesticide Programs  and
     is subject to Section 10 (Protection of Trade Secrets and Other
     Information) of the U.S'. Federal Insecticide, Fungicide and Rodenticide
     Act (FIFRA).  Section 10 prohibits public disclosure of confidential
     business information.        ,                       .    .

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Hexazinone
                             -20-
                                                                 September 1996
DuPont.  1981.  E.I. du  Pont de Nemours and Company.  Two-year  feeding study
in mice  (study authored  by Goldenthal, E.I. and  R.R.  Trumbull;  study published
in 1984 by Kennedy, Jr., G.L and A.M. Kaplan as:  Chronic  toxicity,
reproductive, x and teratogenic studies of hexazinone.  Fund. Appl. Toxicol.  -
4:960-971).  IRDC No.  125-026.  MRIDNo. OO79203, 413593-01,  425093-01;
HED/OPP Doc. No. 001355, 007205, 008659, 008658 .'".
" i                                                                           4

DuPont.  1981.  E.I. du  Pont de Nemours and Company.  Two-year  feeding study
in mice  (study authored  by Goldenthal, E.I. and  R.R.  Trumbull;  study published
in 1984 by Kennedy, Jr., G.L and A.M. Kaplan as:  Chronic  toxicity,
reproductive, and teratogenic studies of hexazinone.  Fund. Appl. Toxicol.
4:960-971).  IRDC No.  125-026.  MRIDNo. OO79203, 413593-01,  425093-01;
HED/OPP Doc. No. 001355, 007205, 008659, 008658. tbl

DuPont.  1980a.  E.I.  du Pont de Nemours and Company.   Eye irritation  tests in
rabbits — United Kingdom  Procedure.  Haskell Laboratory  report no. 839-80
(study authored by Dashiell, O.L. and J.E. Henry).  MRID 00076958.'"

DuPont.  1980b.  E.I.  du Ront de Nemours and Company.   Oral LD5(1 test in
rats — EPA proposed guidelines.  Haskell Laboratory  report  no. 943-80 (study
authored by Dashiell,  O.L. and L. Hinckle) . MRID 00062980. ul

DuPont.  1980c.  E.I.  du Pont de Nemours- and Company.   Developmental toxicity
study in the rabbit  (study published in 1984 by  Kennedy, Jr., G.L and  A.M.
Kaplan as:  Chronic toxicity, reproductive, and  teratogenic studies  of
.hexazinone.  Fund. Appl. Toxicol. 4:960-971).  MRIDNo. 0.0028863;  HED/OPP
Doc. No. 00230, 007205.               ,                                    '   -

DuPont.  1979a.  E.I.  du Pont de Nemours and Company.   Residues resulting from
application of DPX-3674  to soil  (study authored  by  Holt, R.F.).  Wilmington,
DE:  E.I. du Pont de Nemours and "Company,  Inc. •
          /'
DuPont.  197 9b.  E.I.  du Pont de Nemours and Company.   Hexazinone livestock
feeding studies; milk  and meat  (study authored by Holt, R.F.. , F.J. Baude  and
D.W. Moore.  MRID 00028657.""

DuPont.  1979c.  E.I.  du Pont de Nemours and Company.   Three-generation
reproduction study in  the rat.  Haskell Laboratory  Report  No. 35377  (study
published in 1984 by" Kennedy, Jr., G.L and A.M.  Kaplan  as:  chronic  toxicity,
reproductive, and teratogenic studies of hexazinone.  Fund. Appl. Toxicol.
4:960-971) . ~ Accession No. 097323; HEP/OPP Doc.  No. 002321, 007205.'*'

DuPont.  1978.  E.I. du  Pont de Nemours and Company.  Metabolism of  Velpar®
weed killer in the rat (study authored by  Rhodes, R., R.A.  Jewel.! and  H.
Sherman).  Wilmington, DE:  E.I. du Pont de Memours and Company, Inc.   MRID
00028864. ul            *                                        .  .
 DuPont.   1977a.   E.I.  du Pont de Nemours and Company.   Oral LD5() test.
 Haskell  Laboratory report no.  1037-77  (study authored by Matarese,  C.).
' 0011477. Ul
                                                                          MRID
 {)  This study was  submitted to the U.S.  EPA Office  of  Pesticide  Programs and
  • . La subject to Section  10  (Protection  of Trade  Secrets  and  Other
    information) of the U.-S. Federal  Insecticide,  Fungicide and Rodenticide
    Act  (FIFRA).  Section  10 prohibits public disclosure of confidential
   - business information.                     .     •                  •    .

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Hexazihone
                              -21-
         September 1996
DuPont.  1977b.  E.I. du  Pont de Nemours  and  Company.   Acute  skin absorption
test on rabbits LD5|j.  Haskell Laboratory  report.no.  841-77 (study authored by
Edwards, D.F.).  MRID 00091140.U)                                      •

DuPont.  1977c.  E.I. du  Pont de Nemours  and  Company.   Long-term feeding study
in rats with hexazinone:  Haskell -Laboratory  Report  No:  353-77  (study authored
by Kaplan, A.M., C.V. Frazier,  L.L. Adams,  et al.; study published in 1984 by
Kennedy, Jr., G.L and A.M.  Kaplan  as:   Chronic toxicity/  reproductive, and
teratogenic studies of hexazinone.  Fund. Appl.  Toxicol.  4:960-971).   MRID No.
00078045, 00108686-38; HED/OPP  DOC. No. 002331,  007205."'.
DuPont.  1977d.  E.I. du  Pont de Nemours  and  Company.
the Ames Test., Haskell Laboratory Report.,No.  588-77.
Gene mutation assay in
MRID No. 00098982,u>
DuPont,  1976a.  E.I. du  Pont  de Nemours  and  Company.   Skin  absorption'LD50.
Haskell Laboratory  report no.  353-76  (study authored  by McAlack,  J.W.).   MRID
00063971. U)
                                                    i

DuPont.  1976b.  E.I. du  Pont  de Nemours  and  Company.   Primary skin irritation
and sensitization tests on guinea  pigs.   Haskell  Laboratory  Report no.  434-76
(study authored by  Goodman,  N).  MRID 00104433.'"        " '    ,
        \                      .                         ^
DuPont.-  1975a.  E.I. du  Pont  de Nemours  and  Company.  'Studies with'"Velpar"-
weed killer  in water  (study authored  by Rhodes, R'.C.).   Biochemicals
Department Experimental Station, Wilmin'gton,  DE:   E.I.  du Pont de Nemours and
•Company, Inc."1

DuPont.  1975b., E.I. du  Pont  de Nemours  and  Company.   Decomposition of
"Velpar" weed killer  in soil (study authored'by Rhodes,  R.C.).   Biochemicals
Department Experimental Station, Wilmington,  DE:   E.I.  du Pont de Nemours and
Company, Inc.                -••"•'•

DuPont.  1975c.  E.I. du  Pont  de Nemours,  and  Company.   Mobility and adsorption
studies with-"Velpar" weed, killer  on  soils  (study authored by Rhodes,  R.C.). .
Biochemicals Department Experimental  Station, Wilmington,  DE:  ,E.I. du Pont de
Nemours and  Company,  Inc.  ...                          •

DuPont.  19"75d.  E.I. du  Pont  de Nemours  and  Company.   Acute oral test (dogs).
Haskell Laboratory  report no.  617-75  (study authored  by-Henry,  J.E.).   MRID
00076957. <•"       .   .
 (a) 'This  study was  submitted to the USEPA Office of Pesticide Programs and.is
 is subject  to Sen 10 (Protection of Trade Secrets and Other Information) of
 the, U.S.  Federal  Insecticide, Fungicide and Rodent.icide Act (FIFRA).  Section
 10 prohibits public disclosure of confidential business information.

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Hexazinone
                              -22-
                                              September 1996
DuPont.  1974.  E.I. du  Pont  de  Nemours  and Company.   Developmental toxicity
study in the rat  (study  published  in  1984  by Kennedy,  Jr.,  G.L and A.M.  Kaplan
as:  Chronic toxicity, reproductive,  and teratogenic  studies of hexazinone.
Fund. Appl. Toxicol. 4:960-971).   Accession No.  64258;  HED/OPP Doc No..002321,
007205.                     '           •

DuPont.  1973a.   E.I. du Pont de Nemours and Company.   Oral LD5() test (guinea
pigs) .'  Haskell Laboratory  report  no.  400-73 (study authored by N.  Dale) .
MRID 00104973.w      .  •             ,

DuPont.  1973b.   E.I. du Pont de Nemours and Company.   Skin-absorption
toxicity ALD and  skin irritancy  test.  Haskell  Laboratory report no.  503r73
 (study authored by Morrow,  R.).  MRID 00104974.'"
                                                 i
DuPont.  1973c.   E..I. du Pont de Nemours and Company.   Three month feeding
study in dogs  with sym-triazine-2,4{1H,3H)dione,  3-cyclohexyl-l-methyl(-6-
dimethylamino)  (INA-3674).  Haskell Laboratory  Report No.  408-73 (study
authored by Sherman, H.,  N. Dale,  L.  Adams,  et  al.').   MRID No. 00114484;
HED/OPP Doc. No.  002320,  007205.Sherman, H.,  N.  Dale  and L. Adams,  et al.
1973.u>    .                    >                                       .      '

DuPont.  1973d.   E.I; du Pont de Nemours and Company.   Three month-feeding
study in the rat  (study  published  in  1984  by Kennedy,  Jr.,  G.L and A.M.  Kaplan
as:  Chronic toxicity, reproductive,  and teratogenic  studies of hexazinone.
Fund. Appl. Toxicol. 4:960-971).   MRID No.  00104977;  HED/OPP Doc. No. 002321,
007205.<"              .                    . _

DuPont.  1972.  E.I. du  Pont  de  Nemours  and Company.   Primary skin, irritation
and sensitization tests  on  guinea  pigs.,  • Haskell Laboratory report no.  489-72
 (study authored by Morrow,  R.).  MRID 0.0104978 . Ul

Goodrich,  J.A., B.W. Lykins,- Jr. and  R.M.  Clark.  1991.  Drinking water from
agriculturally contaminated groundwater.  J.  Environ.  Qual. 20(41:707-717.
 Greenhalgh,  Tom.
'1994.
1994.   Data sent to Estella Waldman (OPP/EFED), March 3,
 Hess,  Timothy.   1996.   Personal Communication,  University of Maine,
 Cooperative  Extention.                                    '    .  >- .

 Jennings,  H.S.  and T.L.  Gould.   1995.   1994 Pesticides and Ground Water
 Monitoring Program.  "Board of Pesticides Control,  Augusta,  Maine (Draft, June,
 1995) .                  .. •                                 .            •

 Kennedy,  G.L.   1984.  Acute and environmental toxicity studies with .
 hexazinone.   Fund.  Appl.  Toxicol.   4:603-611.

 Kennedy,  G.L.  and A.M.  Kaplan.   1984.   Chronic toxicity, reproductive, and
 teratogenic.studies of  hexazinone.   Fund.  Appl. Toxicol.  4:960-971.
 (a)  This study was submitted to the USEPA Office of Pesticide Programs and is
 is subject to Sen 10 {Protection of Trade Secrets and Other Information) of
 the U.S. Federal Insecticide, Fungicide and Rodenticide Act (FIFRA).  Section
 10-prohibits public disclosure of confidential business information.

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 Hexazinone
                              -23-
                                              September 1996
 Lehman,  A.J.   1959.   Appraisal of the safety of chemicals in foods, drugs and
 cosmetics.   Assoc.  Food Drug Off. of the U.S.    •  '               "'

 Meidl,  J.A.  and M.J.  Dietrich.  1989.  "Treatment of pesticide production
 wastewater using the  PACT system."  Zimpro Passavant Report No. TA-56,
.Rothschild,  WI (April 1989).    .   '

 McLaughlin,  Edward.   1994a.   Information provided to Esbella Waldman
 (OPP/EFED)entitled "Velpar'in Maine - Summary", Maine Bluberry Commission,
 October 1994.                                    :         .

 McLaughlin,  Edward.   1994b,   Personal communication to Estelle Waldman
 (OPP/EFED),  Maine Blueberry Commission.

 Neary,  D.G.,  P.B. Bush and J.L. Michael.  1993.  Fate, dissipation and
 environmental effects of pesticides in southern forests:  a review of a decades
 of research progress.  Environ. Toxicol. chem.  12:411-428.              .   .

 Nielsen, E.G.  and L.K. Lee.   1987.  The magnitude and costs of groundwater '
 contamination from agricultural chemicals.  Agric. Econ. Rep. No. 576.  U..S.
 Dept'.  of-Agric.,  Resources and Technology Div., Economic Research Service.
 Reviewed in Goodrich, J.A.,  B.W. Lykins, Jr. and R.M. Clark.  1991.  Drinking
 water  from agriculturally contaminated1 groundwater.  J. Environ. Qual.
 20(4):707-717.
                          /
 Sine,  C.,  J.  Poplyk,  N. Fisher, E.D. Weil and W.A. Rigo, Jr., eds.  1989.
 Farm chemicals handbook, '89.  Willoughby, OH:   Meister Publishing Company, p.
 C-156.        .                 -' '  '                     .
 STORET.   1988.   STORET Water Quality File.  Computer printout.  Retrieved May,
 1988.   Washington,  DC: • U.  S. Environmental Protection.Agency, Office of
 Water.                '                 .            •  , '

 U.S.  EPA.   1996.  Justification for- Classifying Hexazinone as a restricted Use
 Chemical for Ground Water Concerns,  Office of Pesticide Programs, January 18,-
 1996.            '                '  •                          .  '

 U.S.  EPA.   1994a.   U.S. Environmental Protection Agency. - Reregistration
 eligibility decision,  hexazinone,  list A,  case 0266.  Red team review and
 concurrence copy,  August 17, 1994. .  Washington, DC:  U.S. Environmental
 Protection Agency,  Office of Pesticide Programs,  Special Review and
 Reregistration Division.

 U.S.  EPA.   1994b.   U.S. Environmental Protection Agency.  Carcinogenicity peer
 review, of hexazinone •  (2nd).   Carcinogenicity Peer Review Committee memorandum
 (July'27,  1994) concerning a May 11, 1994 meeting.  Washington DC:  U.S.
 Environmental Protection. Agency, Office of Prevention,  Pesticides and Toxic
 substances.
 U.S.  EPA.  1991.
 drinking water.""
"Methods for the determination of organic .compounds in
December 1988, revised July 1991.  NTIS PB91-231480.
 U.S.  EPA.   1987.   U. S. Environmental' Protection Agency.
 Regulations.   40 CFR 180.396.
                                        Code'of Federal
 U.S.  EPA.   1986.  U.  S. Environmental Protection Agency.  Guidelines for
 carcinogen risk assessment.  Fed. Reg. 51(185):33992-34003.  September 24,

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Hexazinone
                             -24-
Saptember 1996
U.S. EPA.. 1985^  U. S. Environmental Protection Agency.  U.S. EPA Method 633-
Organonitrogen pesticides.  Fed. Reg. 50:40701.  October 4.

U.S. EPA.  1982.  U.. S. Environmental Protection Agency.  Registration
standard for hexazinone.  Washington, DC:  U. S. Environmental Protection
Agency, Office of Pesticide Programs.

U.S. EPA.  1981.  U. S. Environmental Protection Agency.-  Computer printout:
pesticide incident monito'ring system.  'Washington, DC:  U. S. Environmental
Protection Agency, Office of Pesticide Programs.  Retrieved February, 1981.

Vaudht, Richard H.  1995.  Letter to Andrew Ertman from DuPont, May 24, 1995.

Yarborough, D.E., Timothy Hess, and Brian Perkins.  1996.  Evaluation of
Hexazinone Formulation on Soil Movement and Weed Control, University of Maine,
Cooperative Extension.

Yarborough, D.E.  1995.  Blueberry Reasearch advisory Committee Report,
Cooperative Extension, State of Maine, January 995.

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