DRAFT CRITERIA DOCUMENT
       FOR 1,2-DICHLOROETHANE
           FEBRUARY 1984
       HEALTH EFFECTS BRANCH
  CRITERIA AND STANDARDS DIVISION
      OFFICE OF DRINKING WATER
U.S. ENVIRONMENTAL PROTECTION AGENCY
      WASHINGTON, D.C.  20460

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                              TABLE OF CONTENTS
I -     Summary	

II.    General Information and Properties

III.   Pharmacokinetics 	,

IV.    Human Exposure	,
V.     Health Effects in Animals
                              v
VI.    Health Effects in Humans .
VII.   Mechanism of Toxicity	

VIII.  Quantification of Toxicological Effects,

IX.    References	

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                             1-1





I.   Summary



    1,2-Dichloroethane (ethylene dichloride, EDC,  1,2-DCE)



    is the largest volume chlorinated organic chemical in



    production, and thus has the potential for significiant



    environmental pollution.  Its use as an intermediate in



    the manufacture of vinyl chloride constitutes  the largest



    volume of usage, but the many dispersive uses  probably



    contribute more significantly to human exposure.  These



    dispersive uses include fumigating stored grain, extracting



    oil from seeds, manufacturing paints, coatings and adhesives,



    cleaning textiles, cleaning polyvinyl processing equipment



    and as a solvent for processing pharmaceutical products



    and animal fats.



        Despite its widespread use, little 1,2-DCE has been



    detected in air, food or water except near point emission



    sources.  Most authorities consider that air is the



    principal route of exposure, although environmental



    sampling indicates that average exposure is minimal.



    Fugitive emissions from industry and miscellaneous consumer



    applications of products containing 1,2-DCE are more likely



    to be the major sources of exposure to humans  in non-industrial



    settings.



        1,2-DCE exhibits a high degree of toxicity in animals



    and is a mutagen as well as an animal carcinogen.  Most



    studies reported in the literature are inhalation studies;



    very little has been reported on ingestion toxicity other

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                             1-2





than carcinogenicity.  Also, the exposure dose levels in the



inhalation studies have invariably been in a range not



normally encountered in the environment.  Virtually nothing



is known of the more subtle toxicology of very low chronic



exposure to 1,2-DCE.  Numerous instances of human toxicity



have been recorded, resulting from industrial exposures or



accidental or deliberate ingestion.



        No definitive studies have been reported on the nature



or the extent of 1,2-DCE metabolism in humans after exposure.



On the basis of limited studies on animals, metabolites which



have been identified in vivo in mice and rats or in liver and



kidney crude enzyme systems in vitro are (1) 2-chloroethanol,



(2) 2-chloroacetic acid, (3) S-carboxymethylcysteine, (4)



thiodiacetic acid, (5) glycolic acid, (6) oxalic acid, (7) carbon



dioxide and (8) S,S-ethylene-bis-cysteine.



        The National Academy of Sciences (NAS) Safe Drinking



Water Committee and EPA's Carcinogen Assessment Group (CAG)



have calculated projected incremental excess cancer risks



associated with the consumption of 1,2-DCE via drinking



water by mathematical extrapolation from high dose animal



studies using the linear, non-threshold multi-stage model



(NAS, 1979; Anderson, 1983). A range of 1,2-dichloroethane



concentrations was computed that would be estimated to increase



the risk of one excess cancer case per million (10^), per



hundred thousand (10^) or per ten thousand  (10^) people

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                             1-3



over a 70-year lifetime, assuming daily consumption at the



stated exposure level.  The Academy estimated, at the upper



95% confidence limit, that consuming two liters of 1,2-DCE



contaminated water per day over a lifetime having a 1,2-



dichloroethane concentration of 70 ug/1, 7ug/l or 0.7 ug/1



would result in one excess cancer per 10,000, 100,000 or



1,000,000 people exposed, respectively.  Using the CAG approach,



it can be estimated at the upper 95% confidence limit that



consuming two liters of contaminated water per day over a



lifetime having a 1,2-dichloroethane concentration of 95 ug/1,



9.5 ug/1, 9-*ag^l or 0.95 ug/1 would result in one excess



cancer per 10,000 100,000 or 1,000,000 people exposed, respectively



     Using methodology described in detail elsewhere, the EPA's



Carcinogen Assessment Group also has calculated estimated



excess cancer risk rates associated with 1,2-dichloroethane



in ambient water, extrapolating from data obtained in the



NTP bioassay in male rats { increased incidence of hemangio-



sarcomas)(U.S. EPA, 1980; NCI,1978). CAG employed the linear



non-threshold model to estimate the upper bound 95% confidence



limit of the excess cancer rate that would occur at a specific



exposure level for a 70 kg adult, ingesting 2 liters of water



and 6.5 g of fish and seafood/day ("fish factor"), over a 70-



year lifespan.



     These estimates are summarized in Table 1-1.

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                             1-4
                           TABLE 1-1

    Drinking Water Concentrations and Associated Cancer Risks

Excess Lifetime     Range of Concentrations (ug/la)
  Cancer Risk
             	CAGb	CAGC	NASq


10-4                    94.0            59.9           70.0
10-5                     9.4             6i0            7.0
10-6                     0.94            0.6            0.7
a Assumes the consumption of two liters of water per day, except
  for GAG*3 which also included "fish factor"; upper 95% confidence
  limit

b (U.S.EPA,1980)

c (Anderson, 1983)

d (NAS, 1977;1980)

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                            II-l
II-  General Information and Properties
     1,2-Dichloroethane, the first chlorinated hydrocarbon
described in the chemical literature, was produced initially
by Dutch chemists in 1795 (Hardie, 1964).  For more than a
century, little commercial use of the compound occurred.  By
1970, however, such strong demand existed that 1,2-dichloroethane
was manufactured in greater tonnage than any other chlorinated
organic compound (Rothon, 1972).  In 1975, 1,2-dichloroethane
was the sixteenth highest-volume chemical produced in the
United States (Hawley, 1977) .  Previously regarded by some
investigators as an irritating but relatively non-toxic
liquid (Rothon, 1972), 1,2-dichloroetha'ne is now recognized
as a highly toxic material and a potential human carcinogen
and mutagen (Fishbein, 1976).

     PHYSICAL PROPERTIES
     1,2-Dichloroethane  is a colorless, oily liquid that has
a sweet taste and an odor like chloroform (Hawley, 1977).  It
is appreciably volatile, evaporating at a rate which is 0.788
times that of carbon tetrachloride or gasoline (Whitney,
1961).  Air saturated with 1,2-dichloroethane contains 350
g/m3 at 20C and 537 g/m3 at 30C.  Its solubility in water
is 9 g/1 at 20C. (Irish, 1963).  1,2-Dichloroethane is
completely miscible with ethanol, chloroform, ethyl ether
and octanol (Windholtz,  1976).  The log of the partition co-
efficient (log P) of 1,2-dichloroethane between octanol and
water is 1.48 (Radding et al., 1977).

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                            II-2





     1,2-Dichloroethene forms an azeotrope with water which



distills at 71.9C under a pressure of 1 atm.  The binary azeotrope



contains 19.5% water.  Fourteen other binary azeotropes are



known (Mitten et al.r 1970).  A ternary azeotrope containing



78% 1,2-dichloroethane, 17% ethanol, and 5% water boils at 66.7C.



     1,2-Dichloroethane is a good solvent for fats, greases,



waxes, unvulcanized rubber, resins and many other organic



compounds (Bardie, 1964); however, its usefulness as a solvent



for cellulose ethers and esters is enhanced greatly by the



addition of methanol, ethanol or their acetates (Mitten et



al., 1970).



     Other physical properties are listed in Table II-l.





     CHEMICAL PROPERTIES



     Dry 1,2-dichloroethane is stable at ambient temperature



but decomposes slowly in the presence of air, moisture and



light, forming hydrochloric acid and other corrosive products.



The decomposing liquid, which becomes darker in color and



progressively acidic, can corrode iron or steel containers.



This deleterious reaction is completely inhibited by small



concentrations of alkylamines (Hardie, 1964) .

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                            II-3

                         TABLE II-l

          Physical Properties of 1,2-Dichloroethane
Molecular weight

Density at 20C

Melting pointt C

Boiling point, C

Index of refraction at 20C

Vapor pressure, torr

     At 10.0C
     At 29.4C


Solubility in water, ppm

     At 20C
     At 30C

Vapor density (air = 1)

Flash point, closed cup, C

Ignition temperature, C

Viscosity at 20C, cP

Conversion factors at 25C
and 760 torr
98.96

1.2351

-35.36

83.47

1.4448
40
100
8,690
9,200

3.42

 13

413

0.840

1 mg/liter = 1 g/m3
    = 247 ppm
1 ppm = 4.05 mg/m3 =
      405 ug/liter
Source:  Verschueren, 1977; Weast, 1977.

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                            II-4



     Both chlorine atoms in 1 , 2-dichloroethane are reactive



and can be replaced by other substituents.  This bifunctional



nature of 1 , 2-dichloroethane makes it useful in the manufacture



of condensation polymers (Rothon, 1972),  Hydrolysis, with



slightly acidulated water at 160C to 175C and 15 atm pressure



or with aqueous alkali at 140C to 250C and 40 atm pressure,



yields ethylene glycol, HOCH2CH2OH.  At 120C, addition of



ammonia under pressure yields ethylenediamine, H2NCH2CH2NH2 



1 ,1 ,2-Trichloroethane, CH2ClCHCl2r and other higher chloroethanes



are formed by chlorinating 1 , 2-dichloroethane at 50C in



light from a mercury vapor lamp.  1 ,2-Dichloroe thane reacts



with sodium polysulfide to form polyethylene tetrasulfide and



with fuming sulfuric acid to give 2-chloroethylsulfuryl



chloride, CH2C1CH2OSO2C1 .  With Friedel-Craf ts catalysis,



both chlorine atoms in 1,2-DCE can be replaced with aromatic



ring compounds; for example, with benzene, diphenylethane,



            , is formed (Bardie, 1964).
     CONTAMINANTS AND CHARACTERISTICS OF THE COMMERCIAL PRODUCT



     Commercial 1 , 2-dichloroethane is usually technical grade



material that is  97% to 99% pure.  Common commercial



specifications for this product include:  (1) free from



suspended matter  and sediment; (2) color, to pass test; (3)



distillation range, 82.5C to 84.5C at 760 torr; (4) specific



gravity at 20C,  1.253 to 1.257; and (5) maximum activity,



as HC1 , 0.005%.   Most commercial products contain about 0.1%

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                            II-5



by weight alkylamine to inhibit spontaneous decomposition



(Mitten et al., 1970). Uninhibited or impure 1,2-dichloroethane



may contain chlorine or hydrogren chloride that can corrode



iron or steel containers normally used to store or transport technical



grade material.  Technical grade 1,2-dichloroethane is a



severe fire hazard and a moderate explosion hazard, but



spontaneous heating is not a problem.  When subjected to



excessive heating, such as during a disaster, technical grade



1,2-dichloroethane may decompose, releasing hydrogen chloride



and phosgene, both of which are highly toxic (Sax, 1975).

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                            III-l



III.  PHARMACOKINETICS



     General



     Very little is known of the tissue distribution,



accumulation, metabolism or biological half-life of dichloro-



ethane in the human after acute or chronic vapor inhalation,



the most common form of exposure.  Few data are available on



metabolism after ingestion.  From the few quantitative studies



in mice after intraperitoneal administration, a major route



of excretion of unchanged dichloroethane is via the lungs,



but the compound is readily and extensively metabolized



principally by the liver and to an unknown extent by other



tissues.  Renal excretion is the important route of elimination



of end degradation products.  Detailed information on the



mammalian biotransformation intermediates is not available,



although some principal metabolites have been identified and



several pathways of metabolism proposed.  The importance of



greater knowledge of the biochemical mechanisms and pathways



of metabolism rest in the growing awareness that the intermediate



metabolites of dichloroethane probably are responsible for



the tissue and organ toxicities of the compound and also for



its carcinogenic potential.  1,2-Dichloroethane itself appears



to be only a weak mutagen, but at least four postulated



metabolites, namely, chloroacetaldehyde, chloroethanol,



S-chloroethylglutathione, S-chloroethylcysteine, have been



shown to be strong mutagens in bacterial test systems.  In



addition, direct covalent binding of as yet unidentified



highly reactive metabolites to DNA and microsomal protein

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                            III-2



has been noted.  Further research on the pharraacokinetics



and metabolism of dichloroethane is strongly indicated,



particularly with respect to low chronic exposures by inhalation



or ingestion, if rational and intelligent assessment of the



hazard potential of 1,2-DCE is to be made.



     ABSORPTION AND DISTRIBUTION



     Inhalation of 1,2-dichloroethane vapor in air is the



common route of exposure at work sites where this compound is



manufactured or used.  Accidental or intentional ingestion of



1,2-dichloroethane is considered to be uncommon.  Skin



absorption occurs but is negligible in most industrial vapor



exposure situations, although absorption may be significant



by this route with direct liquid contact (Irish, 1963).



     No systematic studies of absorption, distribution or



excretion of 1,2-dichloroethane by humans have been reported.



However, once inhaled or ingested, 1,2-dichloroethane can be



expected to be distributed into virtually all body tissues.



The compound is appreciably soluble in water and very soluble



in lipid with partition coefficients at 25C for olive oil/gas



and blood serum/gas of 164 and 30, respectively (Morgan et al.,



1972).  As expected from its general anesthetic properties in



animals, 1,2-dichloroethane readily passes the blood/brain



barrier.  Distribution is known to occur also into milk



(Urosov, 1953) and across the placental barrier into the



fetus (Vozovaya, 1975, 1976, 1977).

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                           III-3

     Pulmonary excretion of dichloroethane, as with other

halogenated hydrocarbons, is undoubtedly the major route of

elimination of unmetabolized dichloroethane following exposure,

Urosov (1953) reported that women exposed to about 15.5 ppm

demonstrated initial concentrations in exhaled air of 14.5

ppm.  The breath concentration declined to about 3 ppm 18

hours after exposure was terminated.  Similar observations

have been made in animals (monkey, dog, cat, rabbit, rat and

guinea pig) in early investigations of the anesthetic

properties and toxicity of dichloroethane (Kistler and

Luckhardt, 1929; Lehman and Schmidt-Kehl, 1936; Heppel et

al., 1945).  Yllner (1971a) found that up to 45 percent of an

intraperitoneal dose of 1,2-dichloroethane (0.17 mg/kg) was

recovered unchanged and excreted in the urine, indicating that

extensive biotransformation occurs in mice.  The percentage

recovered in exhaled air unchanged increased with the dose

suggesting a limited capacity for biotransformation (Table

III-l) .

                        TABLE III-l

Percent Distribution of Radioactivity Excreted (48-hr)
        by Mice Receiving 1,2-Dichloroethane-l^c*

14CO2 (exhaled air)
Dichloroethane
(exhaled air)
Urinary metabolites
0.05
13
11

73
Dose (g/kg)
0.10 0.14
8 4
21 46

70 48
0.17
5
45

50
*Adapted from Yllner (1971b)

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                           III-4

     The accumulation of 1,2-dichloroethane in the milk of

cows fed with fumigated grain was studied by Sykes and Klein

(1957).  These researchers administered the 1,2-dichloroethane

as a corn oil solution in sealed gelatin capsules.  Two cows

received the equivalent of 100 ppm in 7 kg of grain concentrate

daily.  Two other cows were fed the equivalent of 500 ppm for

the first 10 days , then 1000 ppm for an additional 12 days.

A fifth cow served as a control.  Seven milk samples were analyzed

between the 3rd and 22nd days of the experiment.  The concentra-

tion of 1,2-dichloroethane in the control sample varied from

0.0 to 0.10 ppm, with a mean of 0.06 ppm.  The milk of cows

receiving 100 ppm daily contained from 0.10 to 0.29 ppm 1,2-DCE,

reaching a peak on the 5th day, then declining to the minimum.

The milk of cows receiving the higher dose of 1,2-dichloroethane

contained from 0.18 to 0.45 ppm.  The highest concentration

was reached on the 9th day, after which a slow decline was

observed.  No reduction in appetite or milk production occurred

during the experiment.  Sykes and Klein (1957)  also considered

the possibility that 1,2-dichloroethane is metabolized by cows

to a non-volatile organic chloride, but they were unable to

verify the presence of chloride in milk from a cow fed 1000

ppm 1,2-dichloroethane for 12 days.


     METABOLISM AND DISPOSITION
     Until recently, almost all of the volatile haloalkanes,

particularly those used as anesthetics, were considered to be
                                                   /
biologically inert substances eliminated from the body via

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                           III-5



the lungs without significant alteration.  Considerable



evidence is now available to show that many of the volatile



industrial solvents as well as the most commonly used anesthetics



are metabolized appreciably in vivo (Van Dyke and Chenoweth,



1965; Cohen, 1971; Cascorbi et al., 1972).  Some of the most



significant questions to be answered deal with the possible



toxic effects produced by metabolites of the haloalkanes on



liver and kidney as well as their mutagenic, teratogenic and



carcinogenic potential.



     No definitive studies have been reported on the nature



or the extent of dichloroethane metabolism after human exposure.



Bryzkin (1945) reported that dichloroethane underwent rapid



transformation to an "organic chloride" in patients who subse-



quently died after ingesting 150 to 200 ml; dichloroethane



itself was not, however, found in tissues at autopsy.  Current



information on mammalian metabolism of 1,2-dichloroethane



derives from only a few animal studies.  Figure III-l shows



the probable mammalian biotransformation of this haloalkane



as determined from these studies.  Metabolites which have been



identified in vivo in mice and rats, or in liver and kidney



tissue crude enzyme systems in vitro are: (1) 1-chloroethanol,



(2) 2-chloroacetic acid, (3) S-carboxymethylcysteine, (4)



thiodiacetic acid, (5) glycolic acid, (6) oxalic acid, (7)



carbon dioxide, (8) S,S-ethylene-bis-cysteine.



     Main Pathway



     The principal pathway of metabolism as shown in Figure



III-l and determined by Yllner (1971a, b) in mice, involves

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 _,._  ^.A      '.^s-     '--	

Figure  3 .  Postulated Pathways of B ^transformation of Qlcnioroecndne
                  (based on a review of available studies;
(1)  C1CH2-CH2C1
                       glutathione S-alkyltransferase
   C1CH
       9 '
            hydrolytic
            dehalogenation
               (liver)
  SG
(12)
(2)* C1CH2-CH2OH
glutathionase
            alcohol
            dehydrogenase
GS-CH2-CH2-SG (ID).
                                       glutathionase
                                     ,,  (liver, kidney)
         H2C-S-CH2-CH(NH2)-COOH

         H2C-S-CH2-CH(NH2)-COOH
(3)  C1CH2-CHO
             C1CH2-CH2-S-CH2-CH(NH2)-COOH

                                   (13)
            aldehyde
            dehydrogenase
     C1CH2-COOH
                                      hydrolytic
            glutathione
            S-alkyltransferase
                                   dehalogenation
                                  (8)*

                            HOCH.  COOH - CO
 (5)  GS-CH2-COOH
             glutathionase
             (liver,  kidney)
                              (9)3
                     COOH
                     

                     COOH
 (5)*  HQOC-CH(NH2)-CH2-S-CH2-COOH

             deamination
             decarboxylation
 (7)* CH2-COOH


      S
      
      CH2-COOH
               1.  Dichloroethane
               2.  Chloroethanol
               3.  Chloroacataldehyde
               4.  Chloroacetic acid
               5.  S-carboxymethylglutathione
               6.  S-carboxymethylcysteine
               7.  Thiodiacetic acid
               8.  Glycolic acid
               9.  Oxalic acid
               10.  S-,S-ethylene-bis-g1utathione
               11.  S,S-ethylene-bis-cysteine
               12.  S-chloroethylglut3thione
               13.  S-cMoroethyl cysteine
                          -^alternative  pathway  (Johnson,
      *  metabolites  which  have  been  identified

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                           III-7



an initial hydrolytic dehalogenation to 2-chloroethanol,



conversion by alcohol and aldehyde dehydrogenases to



inonochloroacetic acid (a major urinary metabolite), with



further dehalogenation by enzymatic interaction of monochloro-



acetate with glutathione or cysteine to yield S-carboxymethyl-



cysteine and finally thiodiacetic acid.  Yllner administered



dichloroethane-l^c and chloroacetate-l^c intraperitoneally



to mice and determined the metabolites in urine and exhaled



air.  The results of his experiments are summarized in Table



III-l and III-2.  Some 11 to 46 percent (increasing with



dose; Table III-l) of the injected dichloroethane was excreted



via the lungs unchanged; 5 to 13 percent was metabolized to



carbon dioxide and water, and the remainder, 50 to 73 percent



of the dose, was excreted as urinary metabolites.  Table III-2



lists the metabolites identified in urine after dichloroethane



and chloroacetic acid administration.



     Yllner (1971a, b) proposed that the degradation of 1,2-



dichloroethane to 2-chloroacetic acid involves a primary



reacton in which chlorine is removed from one of the carbon



atoms (hydrolytic dehalogenation) to yield 2-chloroethanol.



As evidence for this reaction, he found chloroethanol to be a



metabolite (minor) in the urine (Table III-2) .  Kokarovtseva



and Kiseleva (1978) also have identified chloroethanol in



the blood and in liver tissue of rats within one hour and



four 24-48 hours after oral administration of dichloroethane



(750 mg/kg).  Heppel and Porterfield (1948) obtained an



enzyme preparation from rat liver capable of hydrolyzing the

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                            III-8

                         TABLE III-2

        Percent Distribution of Radioactivity Excreted
       (48-hr) as Urinary Metabolites by Mice Receiving
                 1,2-Dichloroethane-14c*
                              After             After
                          dichloroethane    chloroacetate
   Metabolite               (0.17 g/kg)        (0.10 g/kg)

Chloroacetic acid             16                  13

2-chloroethanol               0.3

S-carboxymethylcysteine       45                  39

Conjugated S-carboxymethyl-    3                   3
cysteine

Thiodiacetic acid             33                  37

S,S-ethylene-bis-cysteine     0.9                 

Glycolic acid                                    4

Oxalic acid                                      0.2


*Adapted from Yllner (1971a, b)

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                           III-9



carbon-halogen bonds of chloro-derivatives of methane and



ethane.  Dichloroethane was a substrate for this enzyme,



although the reaction product was not specifically identified



as chloroethanol.  Furthermore, from a quantum chemical study



of the metabolism of a series of chlorinated ethane anesthetics,



Loew et al. (1973) concluded on theoretical grounds that the



initial metabolic reaction is a hydrolytic fission of a carbon-



chlorine bond with the formation of alcohols.  The enzyme



or enzyme system for this primary reaction has not been



isolated or identified.  There is little evidence that the



P-450 mixed-function oxidase system is followed.  Van Dyke



and Wineman (1971) found that the enzyme system was similar



in function to a microsomal mixed-function oxidase system



requiring oxygen and NADPH and small amounts of cytosol.



This system slowly dechlorinated 1,2-di-36ci-ethane, but



was more active with 1,1-dichloroethane, 1,1,2-trichloro-



ethane and 1,1,2,2-tetrachloroethane.  Cox et al. (1976)



studied the aerobic binding to microsomal P-450 of a series



of chloroalkanes.  Whereas most of these compounds interacted



to give a Type 1 difference spectra associated with metabolism



of these substrates by direct C-hydroxylation, 1,2-dichloroethane



failed to give an observable interaction.



     Following 2-chloroethanol formation, Yllner (1971a, b)



proposed that this alcohol was enzymatically converted to 2-



chloroacetic acid via 2-chloroacetaldehyde.  Chloroacetic



acid was found as a major urinary metabolite of mice (Table



III-2).

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                           111-10



      Johnson (1967) had observed that chloroethanol was



readily dehydrogenated to chloroacetaldehyde by purified



alcohol dehydrogenases from yeast or horse liver.  Williams



(1959) previously had suggested that chloroacetic acid appeared



in vivo via chloroacetaldehyde.  After dichloroethane adminis-



tration (0.17 mg/kg), Yllner found that chloroacetic acid



appeared in mouse urine in significant amounts within 24



hours where chloroethanol was only a minor metabolite (Table



III-2).  In addition, Kokarovtseva and Kiseleva (1978)



observed that after oral administration of dichloroethane



(750 mg/kg) or 2-chloroethanol (80 mg/kg) to rats, the blood



level of 2-chloroethanol at 4 hours was 67.8 or 15.8 ug/ml,



respectively, and declined in accordance with first-order



kinetics with a half-life of about 9 hours.  While chloro-



acetaldehyde and chloroacetic acid were not measured, these



investigators suggested that a conversion of chloroethanol to



chloroacetic acid occurred.  The relatively low blood concen-



trations found after the large amounts of dichloroethane



ingested and the first-order kinetics of chloroethanol



metabolism were postulated to be due to initial sequestration



of dichloroethane in adipose and other tissues, with a gradual



diffusion redistribution as liver metabolism of dichloroethane



to chloroethanol and chloroethanol to chloroacetic acid



proceeded.  Significant blood and liver tissue levels of



chloroethanol were found even 48 hours after dosing.



     The urinary metabolites found in largest amount after



administration of 1,2-dichl.oroethane or 2-chloroacetic acid to

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                           III-ll
mice (Yllner, 1971a, b) are S-carboxymethylcysteine (ca.
40 percent) and thiodiacetic acid (ca. 35 percent) (Table
III-2).  Yllner suggests that these metabolites arise from
enzymatic conjugation  (S-alkyltransferase) of chloroacetic
acid with glutathione  forming S-carboxymethylglutathione with
chloride excision.  S-carboxymethylglutathione is converted by
glutathionase to S-carboxymethylcysteine, part of which is
further metabolized to thiodiacetic acid (Figure III-l).
Johnson (1966, 1967) has shown that S-carboxymethylglutathione
is rapidly degraded by rat kidney homogenate to yield glycine,
glutamic acid and S-carboxymethylcysteine.  However, an
alternative scheme with chloroacetaldehyde conjugation has
been proposed by Johnson (1967).  In his study of the metabolism
of orally administered 2-chloroethanol in the rat, Johnson
found  that chloroethanol caused a rapid depletion of liver
glutathione with a concomitant formation of S-carboxymethyl-
glutathione.  In vitro, the reaction with a rat liver cytosol
fraction required stoichiometric amounts of glutathione (1
mole)  and NAD (2 moles).  Since pyruvate was also required
for reaction, Johnson  (1967) postulated that chloroethanol
was converted by alcohol dehydrogenase to chloroacetaldehyde
which  then conjugated  with glutathione to give S-formylmethyl-
                                  i.
glutathione, and thence by an NAD-requiring dehydrogenation
to S-carboxymethylglutathione.  Johnson (1966) also has
reported that chloroacetaldehyde is rapidly conjugated with
glutathione in vitro by a non-enzymatic reaction at pH 7.0.
Thus,  Johnson concluded that this was probably the principal

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                           111-12



in vivo reaction in mammals.  However, based on Yllner's



results with the metabolism of chloroacetic acid (Table III-2),



it appears likely that in vivo dehydrogenation of 2-chloroethanol



in mammals proceeds through chloroacetaldehyde to chloroacetate



before conjugation with glutathione occurs.



     Recently, it also has been suggested by Rannug and Beije



(1979) that there are some similarities in the biotransformation



pathways of 1,2-chloroethane and vinyl chloride (Figure III-2).






     Secondary Pathways



     Yllner (1971a, b) observed that after dichloroethane



administration to mice some 5 to 15 percent (depending on dose)



was metabolized completely to C02 and water, and also that



after chloroacetate administration small amounts of glycolic



and oxalic acids appeared in urine (Tables III-l, III-2).



Since these acids are known to be metabolized with C$2'



Yllner (1971 a,b) proposed that chloroacetate is enzymatically



hydrolyzed to glycoiate by hydrolytic dehalogenation, a



portion of which is further oxidized to oxalic acid.



     Yllner (1971a, b) found small amounts of S,S'-ethylene-



bis-cysteine in urine of mice injected with dichloroethane



(Table III-2) .  This metabolite was believed to occur in



vivo from a reaction between dichloroethane and glutathione



catalyzed by the glutathione S-alkyltransferase previously



demonstrated in rat liver by Johnson (1966).  The S,S'-ethy-



lene-bis-glutathione was presumed to be further degraded to

-------
 HjC-CHCI - H^-CHCJ - OCH2-CHO^
   Gly-C
                             aCH-j-CHjOH
            K3SH
      ^CH-CH2-S-CH2-CHO
                 :xn:
                    Gly -C
                  :      XCH-CH2-S-CH2OH
                               Tv"1
                  7-Glu - N       -IXl
                        H
                                              Gly-C
                                                                 +GSH
                                                    CH - CH2-S-CH2 -CH2C1
       ^
       ^ CM - CH2-S-CH2-COOH
COOH
 \
  CH - CH2-S-CHj - COOH

 '            fxiy^
NH,
                      COOH
                       s
                        CH -
                       /
                      NH,
                                       -CH2 - CH2OH
                      COOH
                       \
                        CH - CH2 -S-CH2 -CHjOH

                      NHCOCH,  -     '	'
                                                       COOH
                                                        \
                                                        CH -
                                                       COOH
                                                        \
                                                                   Ivuj
                                                        CH - CH2-S-CH2
                                                      NHCOCH,
HOOC -
               -S-CH2 -COOH
                    ;xv;
Figure  - Suggested metabolic main pathways of vinyl chlor-
ide  (I) and DCE (V) showing similarities and differences.
The  illustrated pathways are in  accordance with mutagenicity
data and  data from metabolic studies (identified urinary
metabolites and depression of non-proteins sulfhydryl content
in vivo).   The following symbols have been used: I, vinyl
chloride,  II, chloroethylene oxide: III, chloroacetaldehyde;
IV,  2-chloroethanol; V, DCS; VI, -(2-chloroethyl) gluta-
thione; VII,  S-(2-chloroethyl) cysteine? VIII, N-acetyl-S-
(2-chloroethyl)  cysteine; IX, -(2-hydroxyethylT glutathione;
X, S^-(2-hydroxyethyl) cysteine;  XI,  N-acetyl-S-(2-hydroxy-
ethyl) cysteine;  XII, -(2-oxoethyl)  glutathione; XIII, -
(carboxymethyl)  glutathione; XIV,  S_-(carboxymethyl) cysteine;
XV, thiodiglycolic acid.  (Rannug,  V.,  and B. Beije.  The
Mutagenic Effect of 1,2-Dichloroethane on Salmonella typhi-
murium.   II.  Activation by the isolated perfused rat liver.
Chem. Biol. Interaction 24:265-285,  1979).

-------
                            111-14



S,S'-ethylene-bis-cysteine.  Nachtomi et al. (1966, 1970)



also found that an enzyme system from the soluble supernatent



fraction of rat liver catalyzed a reaction between dichloro-



ethane and glutathione to a small extent.  The products were



S-betahydroxyethyl-glythione and S,S'-ethylene-bis-gluta-



thione.  Earlier, Bray et al. (1952) had studied the dehaloge-



nation of dichloroethane and other halogenated hydrocarbons



by rabbit liver extracts.  These workers found no evidence



for enzymatic dehalogenation of dichloroethane or chloroetha-



nol but suggested non-enzymatic dechlorination by direct



interaction with sulfhydryl groups (glutathione, cysteine),



a reaction which occurred with many compounds without the



liver extract.  Morrison and Munro (1956) showed that such a



reaction occurs in vitro with cysteine to form S,S'-ethylene-



bis-cysteine.  The tendency of 1,2-dichloroethane to injure



kidney tubules and cause pulmonary edema suggests that the



chlorinated compound is indeed capable of reacting with



sulfhydryl groups in vivo (Winteringham and Barnes, 1955).



The quantitative studies by Yllner (1971a, b) show that this



pathway involving direct reaction of dichloroethane with



glutathione or cysteine could only be a minor pathway.

-------
                            .IV-1




IV.  HUMAN EXPOSURE

-------
                             V-l



V.   HEALTH EFFECTS IN ANIMALS



     General



     The acute and chronic toxicity of 1,2-dichloroethane



exposure is not, in general, different from that observed



with other halogenated aliphatic hydrocarbons.  Whereas high-



dose exposure to 1,2-dichloroethane causes immediate central



nervous system effects leading to unconsciousness, coma,



circulatory collapse and death, lower single or repeated



exposures result in abnormalities of the liver, kidneys, lungs,



heart, adrenals and gastrointestinal tract.  These organ



systems show both morphological and functional abnormalities.



In part, the pathologic changes in the tissue can be ascribed



to the lipophilic and electrophilic nature of the compound,



but these adverse effects probably are related also to toxic



metabolic products since 1,2-dichloroethane is readily and



extensively metabolized.  Most toxicities resulting from 1,2-



dichloroethane exposure are similar for different species



of animals, although there are a few manifestations which



are species specific.  In the animal studies which have been



carried out to date, the exposure dose levels (over both



acute and chronic duration) have invariably been in a range



not normally encountered in the natural environment.  Virtually



nothing is known of the subtle toxicology of low level chronic



exposures to 1,2-dichloroethane.  Almost all toxicity studies



reported in the literature are based on  inhalation exposures;



few studies have been made on toxicity resulting from ingestion,



particularly via drinking water.

-------
                             V-2



     The narcotic properties of 1,2-dichloroethane have been



known for over 100 years, but its toxicity precludes its use



as an anesthetic agent.  The central nervous system depression



observed in a variety of species of animals is characteristic



of compounds of the chloroethane series and of related



halogenated aliphatic hydrocarbon compounds.  In addition to



central nervous system effects, other documented toxicity



associated with 1,2-dichloroethane exposure in laboratory



animals include damage to the liver, kidney, adrenal glands



and skin, as well as pathological changes in the cardiovascular,



hematological and immunological systems.  A summary of these



effects as well as dose data appear in the text below and in



Tables V-l through V-3.  Effects on reproduction and teratogenic



effects as well as mutagenicity and carcinogenicity are



discussed separately below.






     Acute Toxicity



     The principal acute effect of 1,2-dichloroethane in



mammals is central nervous system depression with unconsciousness



and coma resulting from exposure to high concentrations.



Visible signs of 1,2-dichloroethane poisoning include



restlessness, handling intolerance, abnormal weakness,



intoxication, dizziness, muscle incoordination, irregular



respiration and loss of consciousness.  Deaths occurring



within a few hours after recovery from narcosis are usually



the result of shock or cardiovascular collapse; deaths



delayed by several days most often result from renal damage

-------
                             V-3

                          TABLE V-l

              Correlation of Symptoms,  Exposure
              Time, and Concentration for Guinea
               Pigs Inhaling 1,2-Dichloroethane
Average period necessary to produce symptom
at various concentrations (min)
Symptom


Nose and
eye irri-
tation
Unsteadi-
ness
Inability
to walk
Retching
Jerky, rapid
respiration
Uncon-
sciousness

2000 4000-
ppm 4500 ppm
6* 3-10 Z


20-45 8-18

a 30

a b
a b

a 30-40


10,000-
17,000 ppm
1-2


2-3

4-10

7-15
10-30

10-20


25,000- 60,000-
35,000 ppm 70,000 pp:
1-2 1


1-2 1-2

3-5 2-4

5-13 2-4
5-13 4-8

4-7 3-7

   is symptom was not observed even after 480 min of exposure

   is symptom was not observed even after 360 min of exposure,

Source:  Adapted from Sayers et al., 1930.

-------
Mortality after single acute exposure to 1,2-dlchloroethane by inhalation
Animal

Mice

Rats


Guinea pig*
Rabbits
Raccoons
Cats
Hogs

Mice

Rats

Guinea pigs
Sources:
Number

22
19
20
16
IS
14
16
2
3
2

20
23
20
13
12
Adapted
Height
(8)



146
177
257
685
3.940

3,240
27,300



170
257
321
from Heppel
Tine Mortality
(he) ratio

1
2
7
3
1
7
7
7
 7
7

7
2
7
4
7
et al.,

Exposure
22/22
19/19
20/20
1/2 15/16
1/2 0/15
14/14
12/16
0/2
0/3
2/2
Exposures
20/20
1/23
4/20
0/13
6/12
1945, Table 1, p.
0
to 3000 ppra
22
0
0
0

0
0


Q
to 1500 ppn
4
0
0

0
55. Reprinted by permission of
Cumulative mortaltiy
lat
day

19
19
1

11
7


0

20
0
2

1
2nd 3rd 4th
day day day


20
3 5 13

13 14
11 12


2


0 1
2 4

436
the publisher.

-------
                             V-5

                          TABLE V-3

              Lethal Doses of 1,2-Dichloroethane
                     to Nonhuman Mammals
Species
Mouse



Rat


Guinea pig

Rabbit


Dog

Pig
aLCLo - lowest
LDLo - lowest
Category3
LCLo
LDLo
LDLo
LDLo
LDLo
LDLO
LD50
LCLo
LDLo
LCLo
LDLo
LD50
LDLo
LDLO
LCLO
published lethal
reported lethal
Dosage
5000 mg/m3
600 mg/kg
380 mg/kg
250 mg/kg
1000 ppm/4 hr
500 mg/kg
680 mg/kg
1500 ppm/7 hr
600 mg/kg
3000 ppm/7 hr
1200 mg/kg
860 mg/kg
2000 mg/kg
175 mg/kg
3000 ppm/7 hr
concentration in
dose by any route
Route
Inhalation
Oral
Subcutaneous
Intraperitoneal
Inhalation
Subcutaneous
Oral
Inhalation
Intraperitoneal
Inhalation
Subcutaneous
Oral
Oral
Intravenous
Inhalation
air;
other than
        inhalation; LDso - median lethal dose by any route other
        than inhalation.

Source:  Adapted from NIOSH, 1977, p. 388.

-------
                             V-6
                                                               

(Spencer et al., 1951; Irish, 1963).  Despite these qualitative


statements, the manner in which 1,2-dichloroethane exerts its


lethal effects in mammals cannot always be easily identified


or characterized.  For example, Heppel et al. (1946) stated,


"In spite of the fact that this important compound has been


extensively studied in this laboratory for nearly three years,


it must be admitted that the exact mechanism of death remains


obscure."  Since that time, it has become generally accepted


that 1,2-DCE causes death by direct effects on the central


nervous system (CNS).


     Weakness, disordered, vertiginous movement, persistent


thirst, eye and nasal irritation, static and motor ataxia,


retching movements and marked changes in respiration are


common signs of acute 1,2-dichloroethane poisoning in non-


human animals.  Sayers et al. (1930) observed all of these


signs in guinea pigs after less than 10 minutes' exposure to


60,000 ppm 1,2-dichloroethane and in 25 minutes to 10,000 ppm


(Table V-l).  However, no signs of poisoning were apparent


following exposure at 1200 ppm for 8 hours.  Death occurred


in less than 30 minutes with animals exposed to 60,000 ppm


and usually after about a day following a 25-minute exposure


to 10,000 ppm.  Congestion and edema of the lungs and genera-


lized passive congestion throughout the visceral organs were


commonly observed in animals that died during exposure.


Renal hyperemia and pulmonary congestion and edema were


typical conditions in animals that died one to eight days


following exposure.  Similar histopathological lesions, as

-------
                             V-7



well as fatty degeneration of the myocardium and renal tubular



epithelium, also were reported by other observers who exposed



mice, rats, guinea pigs, rabbits, cats and dogs sufficiently



long to air containing 1000 to 3000 ppm 1,2-dichloroethane



(Heppel et al.r 1945, 1946; Spencer, et al., 1951).



     The acute toxicity of 1,2-dichloroethane varies with



species and route of exposure.  In general, it appears to be



more toxic to mammals than is carbon tetrachloride (Hofmann,



et al., 1971).  Table V-2 summarizes mortality in seven species



of animals due to a single acute exposure by inhalation that



varied in duration from 1.5 to 7 hours.  Few animals survived



exposure at 3000 or 1500 ppm for 7 hours, but death was



frequently delayed for days in some species.  Congestion of



the viscera and degeneration of the liver and kidneys were



common findings among these animals (Heppel et al., 1945).



     Data published by the National Institute for Occupational



Safety and Health (NIOSH, 1978) indicate that, for exposure



by inhalation, the lowest doses that are lethal for a variety



of common mammalian species range from about 1000 ppm for 4



hours to about 3000 ppm for 7 hours.  In contrast, a dose of



175 mg/kg administered intravenously is lethal in the dog



(NIOSH, 1977).  Other minimum lethal doses are indicated in



Table V-3.

-------
                            V-8



     The effects of acute exposure to 1,2-dichloroethane are



also strongly dependent on the concentration of the toxi-



cant.  For example, when rats were exposed to air containing



1000 ppm 1,2-dichloroethane, 7.20 hours elapsed before half



the population died; however, with concentrations of 3000 and



12,000 ppm, the median lethal response times decreased to



2.75 and 0.53 hours, respectively (Spencer et al., 1951).



Similarly, when male guinea pigs were injected intraperi-



toneally with 150 or 300 mg/kg 1,2-dichloroethane in corn



oil, no noticeable hepatotoxic effects occurred; when 600



mg/kg was injected, a low order of damage occurred, as measured



by increased serum concentrations of ornithine carbamyl



transferase (DiVincenzo and Krasavage, 1974).  1,2-Dichloroethane



also exhibits concentration-dependent nephrotoxic characteristics



when it is injected intraperitoneally into male Swiss mice.



Plaa and Larson (1965) observed a progressive increase in the



number of mice (10%, 30% and 56%) having excessive urinary



protein, but not excessive urinary glucose, following



injection of 0.075, 0.2 and 0.4 ml of 1,2-dichloroethane per



kilogram of body weight.  It should be noted, however, that



the last cited dose is well above the minimum lethal dose for



mice -



     Duprat, et al. (1976) studied the irritant property of



1,2-dichloroethane and other simple chlorinated hydrocarbons



by making a single application or installation of the solvents



to the skin or eye of rabbits and then following the course of



the resulting lesions macroscopically and histologically.

-------
                             V-9



1,2-Dichloroethane was rated a primary irritant in both



applications but was considered less potent as a skin irritant



than perchloroethylene, chloroform, 1, 1, 2-trichloroethane,



trichloroethylene and methylene chloride-  As an eye irritant,



1,2-dichloroethane was classified less potent than chloroform,



methylene chloride, dichloroethylene, trichloroethylene and



trichloroethane.



     Although acute exposures to 1,2-dichloroethane produce



roughly similar responses in many mammalian species, the



systemic administration of this compound to dogs produces



one effect not ordinarily seen in other mammalian species:



clouding of the cornea.  Typically, there is a necrosis of



the endothelium beginning in the basal portions of the cells,



followed by secondary swelling of the stroma, formation of



excess basement membrane and thickening of Descemet's layer.



This response also occurs in cats and rabbits when 1,2-



dichloroethane is injected directly into the anterior chamber



of the eye but not with systemic administration of the



compound.  The unique response of the dog eye appears to



result from a greater amount of 1,2-dichloroethane coming in



contact with the dog endothelium rather than from any unusual



susceptibility of the eye itself (Heppel et al., 1944;



Kuwabara, et al., 1968).








     Longer Term Exposures



     Longer-term exposures of rats and guinea pigs to air



containing 100 ppm 1,2-dichloroethane for 7 hours per day.-

-------
                             V-10



five days per week for several months generally produced no



deaths and no evidence of adverse effects as judged by general



appearance, behavior, mortality, growth, organ function or



blood chemical chemistry (Heppel, et al., 1946; Spencer, et



al., 1951; Hofmann, et al., 1971 ).  However, similar exposures



of rats, guinea pigs, rabbits and monkeys to air containing



400 or 500 ppm 1,2-dichloroethane usually resulted in high



mortality and a limited number of varying pathological findings,



including pulmonary congestion, diffuse myocarditis,



slight to moderate fatty degeneration of the liver, kidney,



adrenal and heart, and prolonged plasma prothrombin time



(Heppel, et al., 1946; Spencer, et al., 1951; Hofmann, et al.,



1971).  Different effects were observed in rabbits exposed to



high concentrations of 1,2-dichloroethane for a few hours/day



over extended periods of time.  After inhaling 3000 ppm



1,2-dichloroethane for 2 hours per day, five days per week for 90



days, rabbits exhibited varying degrees of anemia accompanied



by leukopenia and thromobocytopenia.  In addition, there was



frequent hypoplasia of the granuloblastic and erythroblastic



parenchyma in the bone marrow.  The cellular concentration of



leukolipids was reduced, but no change occurred in polysaccha-



rides, peroxidase, or ribonucleic acid.  In view of these



findings, the authors suggested that 1,2-dichloroethane



might exert a direct poisoning effect on bone marrow  (Lioia



and Elmino, 1959; Lioia, et al., 1959).

-------
                             V-ll



     Reproduction and Teratology



     In a series of studies, Vozovaya (1971, 1974, 1975,



1976) exposed female white rats (strain not stated) to air



containing 57 mg/m3 (14 ppm) 1,2-dichloroethane for 4 hours



per day, six days per week for six to nine months to determine



the effects of this compound on reproductive function of



these animals and on the development of progeny.  Fertility



of the treated rats decreased and the number of still births



increased relative to controls.  Viability of first generation



offspring decreased.  First generation females exhibited



prolonged estrus and a high perinatal mortality rate.  These



effects were augmented and others were observed when rats



were exposed in similar experiments to mixtures of 1,2-



dichloroethane (30 +_ 10 mg/m3) and gasoline (1210 + 70 mg/m3).



In particular, a decrease in the incidence of conception



occurred which was not seen during similar exposures to the



separate compounds.  In addition, there was a significant



decrease in the viability of first generation offspring.  For



example, at the end of the sixth month, mortality in the



group exposed to 1,2-dichloroethane alone was 25.0 +_ 6.92% as



compared with 5.4 + 3.75% in the controls (P < 0.05).  However,



for the group exposed to the combination of 1,2-dichloroethane



and gasoline, mortality (P < 0.05) was 28.0 +_ 9.16% (Vozovaya,



1975) .  In a later study in which 108 random-bred female white



rats were exposed to gasoline (31.0 +_ 33 mg/m3) and 1,2-dichloro-



ethane (15+3 mg/m3) separately and in combination 4 hours

-------
                              V-12



per day, six days per week for four months, Vozovaya (1976)



found increased numbers of degenerative follicles in the ovaries



of rats exposed to the mixture of compounds but not in ovaries



of rats exposed to the compounds separately.  In the affected



rats, a high total embryonic mortality was caused by a high



rate of preimplantation deaths and also by a high rate of



resorptions of embryos at an early stage of development.



     In other studies, Alumot and co-workers (1976)  added



250 or 500 ppm 1,2-dichloroethane, with appropriate precaution



to avoid losses by volatilization, to the food of rats for two



years.  No significant differences were found between these



animals and controls with respect to growth, feed consumption



or feed efficiency.  At the levels tested, the added 1,2-



dichloroethane had no effect on male fertility or reproductive



activity of rats of either sex.  Based on the results of this



study, the authors recommended an acceptable daily intake and



tolerance of 1,2-dichloroethane in human food of 0.07 mg/kg of



body weight and 10 ppm, respectively.



     Inhaled 1,2-dichloroethane is transported into the uterus



and ovaries of non-pregnant rats.  During pregnancy it passes



through the placental barrier of rats and is accumulated in



fetal tissues, especially the liver (Vozovaya and Malyarova, 1975)



     Rao, et al. (1980) studied the effect of inhaled 1,2-



dichloroethane on embryonal and fetal development in rats and



rabbits and on the reproductive capacity of rats.  For the



teratology studies, 16-30 pregnant Sprague-Dawley rats were

-------
                              V-13



exposed to 0, 100 or 300 ppm 7 hours/day on Days 6-15 of



gestation.  Rabbits (19-21 per group) were exposed to the



same concentrations of dichloroethane on Days 6-18 of pregnancy.



Rats were sacrificed on Day 21, rabbits on Day 29 of gestation.



     Ten of the 16 rats exposed to 300 ppm died.  Animals in



this high dose group exhibited lethargy, ataxia, decreased body



weight and food consumption and vaginal bleeding prior to death.



No deaths occurred in the low dose group or the controls.  Only



one rat in the high dose group exhibited implantation sites;



all implantations were resorbed.  Exposure to 100 ppm did not



effect mean litter size, numbers of resorptions or fetal body



measurements.  The number of litters/group was decreased (15/30



as compared with 22/30 in the control group).  No teratological



changes were observed at any dose.



     Three of 19 rabbits in the high dose group died, as did 4



of 21 in the low dose group.  The incidence of pregnancy was



not affected, as it had been in the rat.  There was no effect



on mean litter size, incidence of resorptions, fetal body



measurements or maternal body weights.  In addition, no alteration



in the incidence of major malformations was observed at either



dose.



     In the reproductive study, 20 Sprague-Dawley rats/sex/group



were exposed at levels of 0, 25, 75 or 150 ppm 1,2-dichloroethane.



During 60-day prebreeding period, the animals were exposed for



6 hours/day, 5 days/week. During the breeding period and gestation,



they were exposed 6 hours/day, 7 days/week.  Females who delivered



litters were not exposed from Day 21 of gestation through the

-------
                             V-14



fourth day post-parturition so as to allow for delivery and



rearing of the offspring.




     No significant changes in body weight occurred during the



prebreeding periods. Female body weights during gestation and



rearing of both F/la and F/lb litters were unaffected. Food



consumption by males in the 150 ppm dose group increased



significantly in the latter part of the study. In the females,



a decrease in food consumption occurred in the high and middle



dose groups during the first week, but returned to normal



afterwards. Of all the indices measured, only the average number



of pups per litter (both live and dead) at birth was significantly



lower in the 75 ppm group. Kidney weights of F/lb male in the



75 ppm group were significantly higher when measured at sacrifice



on Day 21 of age.  No histological changes accompanied this change.



     The only teratology/reproductive function study to date



which the test animals were exposed to 1,2-dichloroethane in



their drinking water was reported by Lane, et al, (1982).  The



authors conducted a modified multigeneration reproduction study



which included screening for dominant lethal and teratogenic



effects.  Male and female ICR Swiss mice received 1,2-dichloro-



ethane at concentrations of 0, 0.03, 0.09 or 0.29 mg/1 in



drinking solution (1% Emulphor in deionized water, v/v).



These concentrations were designed to correspond to daily



doses of 0,5,15 or 50 mg/kg bw.  Two control groups were



used:  1) untreated, and 2) 1% Emulphor vehicle.

-------
                             V-15



     The F/O mice were randomized into test groups of 10 males



and 30 females, acclimated for 2 weeks and then placed upon the



appropriate testing regimen.  After 35 days on the test regimen,



the now 14-week olds were randomly mated to produce the F/1A



litters.  Two weeks after weaning of the F/1A litters, the



F/O adults were rerandomized and remated to produce the



F/1B litters.  Parental stock for the second generation was



drawn from these F/1B offspring.  F/O females were rested



for 2 weeks following weaning of the F/1B pups.  The offspring



from the F/1C mating were used in the dominant lethal and



teratology screening.  By the end of the experiment, the F/O



adults had been exposed to 1,2-DCE in their drinking water



for a total of 25 weeks.



     At weaning, the F/1B litters were culled to 30 females



and 10 males/group.  Matings between siblings were avoided.



The F/1B weanings were placed on the testing regimen and



when reaching 14 weeks of age, were randomly mated to produce



the F/2A litters.  Two weeks after these offspring were



weaned, the F/1B adults were remated randomly to produce the



F/2B offspring which were used in the dominant lethal and



teratology screening.  By the end of the experiment, the



F/1B adults had been exposed to the drinking water solutions



for a total of 24 weeks.



     Weekly body weight and twice-weekly fluid consumption



data were collected for the F/O and F/1B adult mice throughout



the study.  The authors stated that there were no statistically



significant differences seen in either of these parameters.

-------
                            V-16

However, no data were presented in the paper so the reader

could not make a judgment about the validity of that conclu-

sion.  Mortality rates in the same two adult groups also

were monitored.  These are summarized in Table V-4.  Significant

numbers of the animals in the low dose group of F/O adults

died (20% of the males, 13.3% of the females compared with

no male controls and only 3.3% of the female controls).  How-

ever, this death rate appeared not to be dose-related, as it

did not increase at the higher two doses.  Among the F/1B

adults, more controls died than did treated animals.

                          TABLE V-4

         Percentage Mortality Among Males and Females
                 Ingesting 1,2-Dichloroethane
               Mofified from Lane et. al, 1982
Concentration
Compound (mg/ml)
1 ,2-Dichloroethane 0.00C
(1,2-DCE) 0.00d
0.03
0.09
0.29
F/10 percentage
Mortality3
Males
0.0
0.0
20.0
0.0
0.0
Females
3.3
3.3
13.3
6.7
0.0
F/1B percentage
Mortality13
Males Females
20.0
0.0
0.0
0.0
0.0
7.4
0.0
3.3
3.3
0.0
A After 25 weeks of dosing.
b After 24 weeks of dosing.
c Naive control.
d 1% Emulphor vehicle control.

     Adult reproductive performance was monitored in the F/O

and F/1B adults, as they produced the F/1A and F/1B generations

(F/O) and the F/2A generation (F/1B).  The fertility and gesta-

tion indices (Fl and Gl, respectively) are shown in Table V-5.

No significant dose-related differences were seen in any

treatment group when compared with the controls.

-------
                                TABLE V-5

                       Reproductive Performance of
                 Adult Mice Ingesting 1,2-Dichloroethane
                    (Modified from Lane,  et al, 1982)
Litter
Concentration
(mg/ml)
O.OOC
O.OOd
0.03
0.09
0.29
F/1A
Fia
90.0
93.3
89.3
82.8
90.0

GIb
92.6
82.1
92.0
83.3
85.2
F/1B
FI
70.0
76.7
89.3
62.1
70. a
F/2A
GI
71.4
78.2
84.0
94.4
90.5
FI
76.2
86.2
93.1
82.8
85.2
GI
100.0
96.0
81.5
100.0
78.3
3 FI (Fertility Index) = (No. females pregnant/no, females mated)  X 100.
b GI (Gestation Index) = (No. females with live litters/no, females pregnant)  X 100
c Naive control.
d Emulphor vehicle control.

-------
                            V-18



     Twenty-one day litter survival studies were conducted on



litters of the F/1A, F/1B and F/2A generations.  Litter size



was recorded on Days 0, 4, 7, 14 and 21.  Offspring were



weighed collectively on Days 7 and 14 and individually on



Day 21.  Viability and lactation indices (VI and LI, respectively)



also were calculated.  1,2-Dichloroethane, at the doses



administered, did not cause any significant adverse inter-



generational or transgenerational effects on mean litter



size at birth (Table V-6), mean postnatal body weights (Table



V-7) and survival indices (Table V-8).  Values of the F/2A



postnatal body weights (Table V-7) and survival indices (Table



V-8) were decreased from  the F/1A and F/1B values with few



exceptions.  The decrease occurred in all groups, including



both controls, and thus was believed not to be treatment-related.



Necropsies of weanlings from these groups yielded no evidence



of dose-dependent gross pathology or congenital malformation.



     Findings from the dominant lethal screening are presented



in Table V-9.  Statistically significant effects in the



ratio of dead to live fetuses (DF/LF) were observed in both



generations.  However, these effects did not appear to be



dose-related, since there were both increases and decreases



as observed when compared with the controls.  The frequency



(F%) of dominant lethal factors in both generations was



minimal (-7 to +8).

-------
                              V-19
                            TABLE V-6

                  Mean Litter Size At Birth3 of
                        Mice Ingesting
                      1,2-Dichloroethane
                (Modified from Lane, et al., 1982)
Litter
Concentration
Compound
1




, 2-Dichloroethane
(1,2-DCE)



0
0
0
0
0
(mg/ml)
.00b
.00C
.03
.09
.29
F/1A
13
12
13
12
11
.1 +
.0 +
.2 +
.9 +
.4 +
3.2
2.3
3.2
2.7
2.7
F/1B
13.1
12.1
12.5
10.5
10.4
+ 4.5
+ 3.0
+ 4.1
+ 4.4
+ 4.8
F/2A
11.8
12.2
11.3
12.3
12.6
+

Jf
+
+
2.
2.
3.t
2.
1.
a Mean pups per litter _+ SD.
b Naive control.
c 1% Emulphor vehicle control

-------
                                                   V-20
                                                  TABLE V-7

                                Mean Postnatal Body Weights3 of Offspring Of
                                   Mice Ingesting 1,2-Dichloroethane
                                   (Modified fron Lane, et alf  1982)




1,2-DCE concen-
tration
(mg/hil)
O.OQb
O.OQC
0.03
0.09
0.29
a Mean pup body
b Naive control


Day 7



4.8 + 1.0
4.8 + 0.5
4.8 -l- 0.5
4.7 + 0.7
5.1 + 0.6
weight (g)


F/1A
Day 14



7.1 + 1.3
7.5 + 0.7
7.1 + 0.8
7.4 + 1.1
7.1 + 0.9
+ SD.
l
Litter
F/1B F/2A
Day 21 Day 7 Day 14 Day 21 Day 7 Day 14 Day 21



11.0 + 2.4 4.8 + 0.8 7.7 + 1.5 12.0 + 1.5 3.7 -1- 1.2 5.2 + 2.2 7.1 + 3,
11.5 + 1.5 5.0 + 0.5 8.0 + 0.7 12.7 + 4.1 4.0 + 0.6 5.7 + 1.5 7.6 + 2,
10.5 + 1.8 5.0 -l- 0.4 7.9 + 0.7 12.2 + 1.3 4.7 + 0.9 7.0 + 1.6 9.7 + 2.
10.9 + 1.8 5.0 + 0.8 7.6 + 1.0 11.0 + 2.2 3.7 + 1.1 5.3 + 2.0 7.1 + 2,
10.7 + 1.7 4.9 + 0.7 7.8 + 1.4 11.0 -I- 2.3 4.4 + 0.5 6.6 + 0.9 8.9 + 1,


1% Emulphor vehicle control.

-------
                                   -45-
                                TAHLE /'

              Survival Indices for Litters of Mice Ingesting
                           1,2-Dichloroethanea
                       (Modified from Lane, et al, 1982)
Litter
F/1A
Compound
1 , 2-Dichloroethane
(1,2-DCE)
Concentration
(mg/ml)
0.00d
0.00
0.03
0.09
0.29
VIb
97.2
97.5
98.1
94.3
93.0
LIC
94
98
97
97
97
.8
.2
.8
.5
.2
F/1B
VI
96
94
96
97
93

.9
.0
.7
.0
.1
LI
90
94
96
99
97

.4
.4
.4
.0
.7
F/2A
VI
88.5
89.6
91.8
89.6
92.3
LI
86
81
95
86
89

.3
.3
.0
.8
.6
a The F/1C and F/2B pregnancies were interrupted for dominant lethal  and
  teratology studies.
b VI (viability index) =
                                  4 litter size) i
                                  0 litter size)
                                            ize if itA.*/-
                                            ize)i-j//  A
c LI (lactation index) =1 < p(Day 21 litter size)i~]/A/S '
                        f~ L(pups kept at Day 4)iJ'  J]
                        U-l
d Naive control.
e 1% Emulphor vehicle control.
                                                                          **;
                                                                           '

-------
                            V-21
                         TABLE V-8

       Survival Indices for Litters of Mice Ingesting
                    1,2-Dichloroethanea
              (Modified from Lanef et al, 1982)
Litter
F/1A
Concentration
(mg/ml)
0.00d
O.OQC
0.03
0.09
0.29

VI b
97.2
97.5
98.1
94.3
93.0

Lie
94.8
98.2
97.8
97.5
97.2
F/1B

VI
96.9
94.0
96.7
97.0
93.1

LI
90.4
94.4
96.4
99.0
97.7
F/2A

VI
88.5
89.6
91.8
89.6
92.3

LI
86.3
81.3
95.0
86.8
89.6
a The F/1C and F/2B pregnancies were interrupted  for  dominant  lethal  am
  teratology studies.
b VI (viability index)
(Day 4  litter  size)i
(Day 0  litter  size)i
N = No. litters
c LI (lactation index)
(Day 21  litter  size)i
(pups kept at Day  4)i
d Naive control.
e 1% Emulphor vehicle control.
N = No.litters. P
  kept at Day 4 =

-------
                                                       V-22

                                                     TABLE V-9
                                   Results of Dominant Lethal Screening in Females
                                    Mated to Males Ingesting 1,2-Dichloroethane
                                        (Modifified from Lane, et al., 1982)
Concentration
(mg/ml)
F/1C
Mating



F/2B
Mating



O.OQC
O.OQd
0.03
0.09
0.29
O.OQC
0.00d
0.03
0.09
0.29
Nunber
pregnant
17
19
16
23
17
15
25
27
24
16
Fertility
Index9
56.7
63.3
66.6
76.7
56.7
62.5
83.3
90.0
80.0
63.3
Resorp- Live
Implants^ tions" fetuses*5
14.1
14.0
14.0
14.5
13.2
12.2
11.6
12.3
12.0
10.9
1.4
0.7
1.6
0.9
0.6
1.0
0.8
0.9
1.7
0.1
12.7
13.3
12.4
13.6
12.5
11.2
10.8
11.4
. 10.3
10.8
DF/LF
23/216
13/252*
26/198*
21/312
11/213
15/168
19/271
23/309
40/247*
2/172*
DF > 1
9/8
11/8
8/8
16/7
7/10
3/12
9/16
14/13
12/12
2/14
DF > 2
6/11
2/17
1/15
5/18
2/15
1/14
3/22
5/22
5/19
0/16
FL%

-1.89
2.60
-6.77
1.42

3.21
-2.14
8.13
4.02
alndices defined:
           Fertility index=  number of females pregnant    x 100
                             number of females available

                   DF/LF  =  total number of dead fetuses
                             total number of live fetuses

                   DF >_ 1 = total number of females with one or more dead fetuses
                            total number of females with zero dead fetuses
                              - continued next page -

-------
                                            V-23


                   DF ^ 2 = total number of females with two or more dead fetuses
                            total number of females with less than two dead fetuses

FL% (frequency of dominant lethal factors)= II - mean live fetuses, treatmentlx 100 (Ehling et al., 1978)
                                            L_    mean live fetuses, naiveJ
b Mean value per dam.
c Naive control.
d 1% Etnulphor vehicle control.
* Significantly different from control at p <0.05.
  Vehicle controls were compared to naive controls;
  treatment groups were compared with their vehicle controls.

-------
                            V-24



     Maternal ingestion of 1,2-dichloroethane did not produce



any apparent adverse reproductive effects (Table V-10) or



increased incidences of fetal visceral or skeletal abnormalities



(Table V-ll).  The authors concluded, therefore, that, at the



doses tested, 1,2-dichloroethane did not present a hazard to



reproduction and development.






     CARCINOGENICITY



     Because of its structure, 1,2-dichcloroethane has been



classified as a substance having limited suspicion of carcino-



genicity (U.S. EPA, 1977c); nonetheless, several studies



have addressed the carcinogenic potential of this compound.



     In an inhalation study lasting 212 days, Spencer et al.



(1951) found no evidence of carcinogenic activity when Wistar



rats were exposed 151 times to 200 ppm 1,2-dichloroethane



for 7 hours per day.  More recently, in an inhalation study



at the Montedison Research Institute in Bologna, Maltoni (as



cited in Albert, 1978) separately exposed 90 male and 90



female Swiss mice and Sprague-Dawley rats 7 hours daily, five



times weekly, to 0, 5, 10, 50, or 150 ppm 1,2-dichloroethane.



Initially, the highest exposure was 250 ppm, but this was



reduced after ten weeks to 150 ppm because the animals could



not tolerate the higher concentration.  After exposure of 1



1/2 years' duration, surviving animals were to be held until



the end of their natural lives.  In an interim report after



78 weeks of exposure and 26 weeks of observation, Maltoni

-------
                                                          V-24A

                                                      TABLE  V-10

                       Results of Teratology Screening in Females  Ingesting 1,2-Dichloroethane

                                          (Modified from Lane, et  al., 1982)
Concentration
(mg/fail)
No. of
liters
Fecundity
Index3
Implants^
Resorp-
tions"
Live
fetuses^
DF/LF a
DF I3
DF 2a M:Fa
 Fl/C
  mating
 F/2B
  mating
0.03
0.09
0.29

0.00C
                0.03
                0.09
                0.29
 9
 8
10
 6
 8

 9
 6
 4
 9
 6
 90.0
100.0
100.0
100.0
 80.0

100.0
100.0
100.0
100.0
 85.7
12.0
12.1
14.9
13.8
13.4

14.1
14.5
16.0
13.1
13.0
1.8
5.6
2.5
5.3
1.0

1.0
2.7
0.8
2.7
0.7
10.2
 6.5
12.4
 8.5
12.4

13.1
11.8
15.2
10.5
12.3
16/92
47/51*
25/121*
32/51
8/99*
4/5
6/2
6/4
5/1
3/5
1/8
6/2*
5/5
3/3
2/6
49:51
59:41
48:52
48:52
43:57
9/118
17/71*
3/61*
24/94
5/74*
7/2
3/3
2/2
5/4
5/1
2/7
2/4
1/3
2/7
0/6
47:53
39:61
57:43
46:54
49:51
     AIndices defined:   Fecundity index = percentage of  copulation plug-positive females bearing  live  fetus(es) at
sacrifice.  DF/LF=  ratio of  dead fetuses to live  fetuses.  M:F = ratio of  live male to
female  fetuses  expressed as  a percentage of the total  number of live  fetuses.

bMean value per dam.

cl% Naive control.

dl% Fjnulphor vehicle control.


     *Significantly different from control at p  0.05.  Vehicle controls were compared  to  naive controls;  treatment
groups were compared with their vehicle controls.

-------
                                                        V-25

                                                      TABLE V-ll

                     Distribution of Visceral and Skeletal  Malformations Among Fetuses/Litters
                                            of Females Ingesting 1,2-DCE

                                          (Modified fron Lane, et al., 1982)
F/1C litters
Cone. (mg/fal)i
Total No. fetuses/total No.
litters:
O.OOa
92/9
O.OOQb 0.03
51/8
121/10
0.09
51/6
0.29
99/8
O.OOa
118/9
F/2B litters
0.00b
71/6
0.03
61/9
0.09
94/9
0.29
74/6
Visceral malformations
Total number examined
Hydrocephalus
Cleft palate
33/8
0/0
0/0
19/7
0/0
0/0
 46/9
1/1
0/0
18/4
0/0
0/0
29/7
0/0
0/0
38/9
0/0
0/0
24/5
0/0
0/0
20/4
0/0
0/0
29/8
Q/o
0/0
24/6
0/0
0/0
Atrial, ventricular, or cardiac
hypertrophy
Malrotation of the heart
Hydronephros is
Dilated renal pelvis
Dilated bladder
Cryptorchidism/hialpositioned
testis
0/0
0/0
1/1
0/0
0/0

1/1
0/0
0/0
0/0
1/1
0/0

0/0
1/1
0/0
0/0
0/0
0/0

0/0
0/0
0/0
0/0
2/1
0/0

0/0
0/0
0/0
0/0
1/1
0/0

0/0
0/0
0/0
0/0
1/1
0/0

0/0
1/1
0/0
0/0
0/0
0/0

0/0
0/0
0/0
0/0
0/0
1/1

0/0
1/1
0/0
0/0
0/0
0/0

0/0
0/0
0/0
0/0
0/0
0/0

0/0
                                      Skeletal malformations
Total number examined
Dyplastic skull
Dysplastic supraoccipital
region
Microagnathia
Asymetric stenebrae
Bifid sternebrae
Hypoplastic sternebrae
Extra ribs
Wavy ribs
(c) 80/9
0/0

3/2
0/0
24/6
8/3
3/1
2/2
0/0
47/5
0/0

3/2
0/0
9/4
1/1
0/0
1/1
0/0
41/4
0/0

0/0
o/o 
2/2
7/2
0/0
0/0
0/0
65/8
0/0

2/2
0/0
9/5
4/3
0/0
2/2
1/1
50/6
1/1

1/1
0/0
16/6
5/3
1/1
2/2
0/0
aNavie control.
bi* Fimilnhor vehicle control.

-------
                            V-26





indicated that he "has found no evidence of any exceptional



tumors in rats or mice" (Albert, 1978).  This conclusion was



qualified as "almost conclusive."  The animals were allowed



to live until spontaneous death.



     After more than 60,000 pathologic slides were examined,



the authors concluded the 1,2-DCE did not show carcinogenic



effects under the experimental conditions (Maltoni, et al.,



1980).  The negative results may be explained by the fact



that Maltoni, et al. did not follow NCI guidelines in the



conduct of their study.  On the other hand, Maltoni, et al.,



(1980) noted several factors which could be involved:  the



route of administration of 1,2-DCE; the purity of the compound



used; the possibility of laboratory pollution; the size of



both treated and control animal groups; the professionality



of the study team, the different strains of animals used;



and the possible differences in pathological interpretation.



     In 1977, Theiss et al. reported on an investigation of



the carcinogenic potential of 1,2-dichloroethane and other



organic contaminants of U.S. drinking water by injecting the



compounds intraperitoneally into six- to eight-week-old strain



A/St male.  Each dose of reagent grade 1,2-dichloroethane



was injected into groups of 20 mice three times a week for 24



injections.  Three dose levels were used:  20, 40, and 100



mg/kg in each injection; 100 mg/kg was the maximum tolerated dose.



Tricaprylin was used as the vehicle.  Twenty-four weeks after



the first injection, the mice were sacrified and their lungs

-------
                             V-27
  % -*-*.

were placed in Tellyesniczky1s fluid.  After 48 hours the


lungs were examined microscopically for surface adenomas.


The frequency of lung tumors in each group was compared


with that in a vehicle-treated control group by means of the


Student's "t" test.  The incidence of lung tumor increased


with dose, but none of the groups had pulmonary adenoma


responses that that were significantly greater (P < 0.05)


than that of the vehicle-treated control mice.


     NCI Bioassay


     Two studies of the carcinogenicity of 1,2-dichloroethane


were performed for the National Cancer Institute (NCI) by the


Hazleton Laboratories, Inc., Vienna, Virginia.  The results


of both were released by NCI on September 26, 1978.  In one


of these studies, 200 8-week-old Osborne-Mendel rats were


exposed to technical grade 1,2-dichloroethane delivered by


oral intubation.  Fifty rats of each sex separately received


either the maximum tolerated dose (95 mg/kg daily, time-


weighted average dosage over a 78-week period) or one-half of


this dose.  Twenty rats of each sex served as untreated


controls, and an equal number were given the vehicle (corn


oil) by intubation.  Survival of male rats exposed to the


high dose was low: 50% (25/50) were alive by week 55, but


only 16% (8/50) lived to week 75.  None survived the study.


Male rats in other groups fared better:  in the low dose


group, 52% (26/50) survived at least 82 weeks, and, in the


untreated control group, 50% (10/50) survived at least 87


weeks.  The survival rate of female rats exposed to the high

-------
                        V-28
dose was 50% (25/50) by week 57 and 20%  (10/50) by week 75.

Half (25/50) of the female rats in the low-dose group survived

at least 85 weeks.  Terminal survival times for all

groups are shown in Table V-12.

      Gross necropsies were performed on animals dying during

the experiment or killed at the end.  Twenty-eight organs,

as well as all tissues containing visible lesions, were

fixed in 10% buffered formalin, embedded in paraplast and

sectioned for microscopic examination.  Diagnoses of any

tumors and other lesions were coded according to the Systema-

tized Nomenclature of Pathology of the College of American

Pathologists, 1965.  Squamous-cell carcinomas of the fore-stomach

occurred in 18% of the high-dose males and in 6% of the low-dose

males but were not found in the controls.  The Cochran-Armitage

test included a significant positive association between dosage

and the incidence of squamous-cell carcinomas in these animals.

The Fisher exact test also confirmed the significance of these

results (P = 0.001) when comparison was made between the

high-dose group and the pooled vehicle control group.  Only

one squamous-cell carcinoma of the fore-stomach occurred in

the exposed female rats and none were found in the controls

(Table V-13).

-------
                             V-29
                          TABLE V-12

                 Terminal Survival of Rats in
               Experimental and Control Groups
                 Involved in Carcinogenicity
               Studies with 1,2-Dichloroethane
MALES FEMALES
Animals
Group Weeks in alive at Weeks in
study end of study study
Untreated
controls* 106 4/20 (20%) 106
Vehicle 110 4/20 (20%) - 110
controls
Low-dose 110 1/50 (2%) 101
group
High-dose 101 0/50 (0%) 93
group*5
Animals
alive at
end of study
13/20 (65%)
8/20 (40%)
1/50 (2%)
0/50 (0%)
a Five male and female rats were sacrificed at 75 weeks of
  study.

b All animals in this group died before the bioassay was
  terminated.

Source:  Adapted from Albert, 1978, Table I, p. 15.

-------
                             V-30

                          TABLE V-13

            Squamous-cell Carcinomas of the Forestomach
                 in 1,2-Dichloroethane-treated Rats
                                   Rats with squamous-cell
Group          '                    carcinoma of forestomach
                         Males

Untreated controls                    0/20 (0%)
Vehicle controls                      0/20 (0%)
Low-dose group                        3/50 (6%)
High-dose group                       9/50* (18%)

                      Females

Untreated controls                    0/20 (0%)
Vehicle controls                      0/20 (0%)
Low-dose group                        1/49 (2%)
High-dose group                       0/50 (0%)
a A squamous-cell carcinoma of forestomach metastasized
  in one male of high-dose group.

Source:  Adapted from National Cancer Institute, 1978.

-------
                            V-31



     Hemagiosarcomas also occurred in exposed male and female



rats but not in the control animals (Table V-14).  They were



seen in the spleen, liver, adrenals, pancreas, large intestine



and abdominal cavity.  Low-dose animals had higher incidences



of hemangiosarcoma than high-dose animals.  The Cochran-



Armitage test indicated a significant (P = 0.021) positive



association between dosage and the incidence of circulatory



system hemangiosarcoma in males, but not females, when dosed



groups were compared with the pooled vehicle control group.



The Fisher exact test confirmed these findings with statistically



significant probability values as follows:  P = 0.016 for



high-dose males versus pooled control and P = 0.003 for low-



dose males versus pooled control.



     The NCI rat study also showed significant increases in



the incidence of mammary adenocarcinomas in treated female



rats.  In the high-dose group, tumors were noticed as early



as 20 weeks after treatment.  Eventually 36% (18/50)  of this



group developed lesions (Table V-15).  The Cochran-Armitage



test indicated significant (P = 0.001) positive association



between the dosage and the incidence of mammary carcinomas



when results were compared with either control group.  The



Fisher exact tests were significant when compared with the



high-dose group and either the matched vehicle group (P =



0.001) or the pooled vehicle control group (P = 0.002).



Historically, adenocarcinomas of the mammary gland occur in



2% (4/200) of the vehicle control females.

-------
                           V-32

                        TABLE V-14

     Hemangiosarcomas in 1,2-Dichloroethane-treated Ratsa



         Males                       Females
Low-dose      High-dose*3     Low-dosec    High-dose
11/50 (22%)   5/50 (10%)     5/50 (10%)   4/50 (8%)
a No hemangiosarcomas were found in male or female controls,

b Only 49 animals were examined for hemangiosarcomas of the
  spleen and adrenals and 48 for hemangiosarcomas of the
  pancreas.

c Only 48 animals were examined for hemangiosarcomas of the
  large intestine.
Source:  Adapted from National Cancer Institute, 1978

-------
                             V-33

                          TABLE V-15

            Adenocarcinomas of the Mammary Gland
          in 1r2-Dichloroethane-treated Female Rats
Untreated
controls
Vehicle
controls
1,2-Dichloroethane-
    treated rats
                                  Low-dose
                                 High-dose
2/20 (10%)
0/20 (0%)
 1/50 (2%)
18/50 (36%)
Source:  Adapted from NCI, 1978.
     In summary, the NCI study indicates a positive association

between exposure to 1,2-dichloroethane and the incidence

in male, but not female, rats of squamous-cell carcinomas of

the forestomach and hemangiosarcomas of the circulatory

system.  The study also statistically links an incrased

incidence of adenocarcinomas of the mammary gland in female

rats with exposure to technical grade 1,2-dichloroethane.

Analysis of purity performed by NIOSH after completion of the

bioassay showed that there was about 99% 1,2-DCE, along with

chloroform as the major contaminant as well as 12 other

minor contaminants (Hooper, et al., 1980).

     The second NCI carcinogenic study of 1,2-dichloroethane

used 200 5-week-old B6C3F1 mice instead of rats.  Fifty male

and female mice were administered technical grade 1,2-dichloro-

ethane in maximum tolerated doses or in half of the maximum

tolerated dose by oral intubation.  For male mice this dose

-------
                            V-34



was 195 or 97 mg/kg/day, but for female mice it was 299 or



149 mg/kg/day (time-weighted average dose over a 78-week



period).  Twenty mice of each sex were used as untreated



controls, and an equal number were given the vehicle (corn



oil) by oral intubation.  As in the NCI rat study, gross



necropsy was performed on each animal that died or was killed



at the end, and similar histopathologic examinations were



made.



     Hepatocellular carcinomas occurred in all male mice



(Table V-16), but only two were seen in females.  The number



of hepatocellular carcinomas in the high-dose male group were



significantly greater than those in the control groups.  The



Cochran-Armitage test indicated a positive dose-response



association with either the matched (P = 0.025) or the pooled



(P = 0.006) controls.  The Fisher exact test also yielded a



significant (P = 0.009) comparison of the high-dose to the



pooled control group.



     A large number of alveolar/bronchiolar adenomas were



also observed in the mouse study.  They were present in 31%



of the male (15/48) and female (15/48) high-dose mice.  None



occurred in the untreated or vehicle control males, and only



one appeared in each female control group (Table V-17).  The



Cochran-Armitage test showed a significant (P = 0.005) positive



dose-response association when either high-dose male or female



groups were compared with appropriate untreated or vehicle



control groups.  The Fisher exact test also indicated that

-------
                             V-35

                         TABLE V-16

                 Hepatocellular Carcinomas in
               1,2-Dichloroethane Treated Mice
Group                               Mice with hepatocellular
                                           carcinomas
                            Male

Untreated controls                      2/17 (12%)
Vehicle controls                        1/19 (5%)
Low-dose group                          6/47 (13%)
High-dose group                        12/48 (25%)

                          Female

Untreated controls                    -  0/19 (0%)
Vehicle controls                        1/20 (5%)
Low-dose group                          0/50 (0%)
High-dose group                         1/47 (2%)
Source:  Adapted from NCI, 1978.

-------
                             V-36

                         TABLE V-17

            Alveolar/Bronchiolar Adenomas in Mice
               Treated with 1,2-Dichloroethane
                                     Mice with
Group                           alveolar/bronchiolar
                                      adenomas
                        Male

Untreated controls                         0/17 (0%)
Vehicle controls                           0/19 (0%)
Low-dose group                             1/47 (2%)
High-dose group                           15/48 (31%)

                        Females

Untreated controls                         1/19 (5%)
Vehicle controls                           1/20 (5%)
Low-dose group                             7/50 (14%)
High-dose group                           15/48 (31%)
Source:  Adapted from NCI 1978.

-------
                             V-37

both high-dose groups had a significantly (p = 0.016) higher

incidence rate than either of the control groups, but this

test attributed no statistical significance to the incidence

of alveolar/bronchiolar adenomas in the low-dose female mice,

     Squamous-cell carcinomas of the forestomach occurred in

ten of the mice treated with 1,2-dichloroethane and in two

of the controls (Table V-18).  The Cochran-Armitage test

indicated a significant (P = 0.035) positive association

between dosage and the incidence of these lesions when dosed

female groups were compared with the pooled vehicle control,

but the Fisher exact tests did not confirm this association.

                           TABLE V-18

        Squamous Cell Carcinomas of the Forestomach in
                1,2-Dichloroethane Treated Mice
Group                           Mice with squamous-cell
                                carcinoma of forestomach
                         Male

Untreated controls                      0/17 (0%)
Vehicle controls                        1/19 (5%)
Low-dose group                          1/46 (2%)
High-dose group                         2/46 (4%)

                       Female

Untreated controls                      0/19 (0%)
Vehicle controls                        1/20 (5%)
Low-dose group                          2/50 (4%)

High-dose group                         5/48 (10%)
Source:  Adapted from NCI, 1978.

-------
                             V-38



     A statistically significant positive association between



dosage and the incidence of mammary adenocarcinomas in female



mice was also reported.  These malignancies occurred in 18%



(9/50) of the low-dose mice (P = 0.001, Cochran-Armitage



test; P = 0.039, Fisher exact test) and 15% (7/48) of the



high-dose mice (P = 0.003, Cochran-Armitage test).  No



adenocarcinomas of the mammary gland occurred in either the



pooled vehicle controls (0/60) or the matched vehicle controls



(0/20) (NCI, 1978).



     To summarize, the NCI study indicated statistically



significant association between oral intubation exposure to



1,2-dichloroethane and the incidence of alveolar/bronchiolar



adenomas in both male and female mice.  The study also



established a statistically significant relationship between



oral intubation exposure and the occurrence of hepatocellular



carinomas in male mice.  No such relationship was found for



female mice, nor was an unequivocal association found between



oral intubation exposure to 1,2-dichloroethane and the



occurrence of squamous-cell carcinomas of the forestomach in



either male or female mice.



     The NCI bioassay had some major experimental design



flaws.  The rats treated with 1,2-dichloroethane and the



vehicle control rats were housed in the same room as other



rats intubated with 1,1-dichloroethane, dibromochloropropane,



trichloroethylene and carbon disulfide.  Untreated control



rats were housed in a different room along with other rats

-------
                            V-39



intubated with 1,1,2-trichloroethane and tetrachloroethylene



(NCI, 1978) .




     All mice used in the 1,2-dichloroethene study were housed



in the same room as other mice intubated with 1,1,2,2-



tetrachloroethane, chloroform, allyl chloride, chloropicrin,



dibromochloropropane, 1,2-dibromoethane, 1,1-dichloroethane,



trichloroethylene, 3-sulfolene, iodoform, methylchloroform,



1,1,2-trichloroethane, tetrachloroethylene, hexachloroethane,



carbon disulfide, trichlorofluoromethane and carbon tetrachloride



(NCI, 1978).



     The high dose rats showed a significant dose-related



increase in mortality (P < 0.001).  The results were skewed



particularly because the vehicle control had a greater



mortality than low dose males early in the study.  High dose



male rat survival was low, 50% dead by week 55 and 89% dead



by week 75 (Table V-12).



     The rats, in general, appeared to suffer from chronic



murine pneumonia ranging from 70% in high dose females to 95%



in vehicle control females.  Male rats appeared to have some



hematopoietic system effects as observed primarily in the



spleen:  16%  and 12% in low and high-dose male rats, respectively,



vs. 5% in vehicle controls.  The female rats had 12% and 40%



in the low and high-dose, respectively, vs. 10% in vehicle



controls.  In males, 12% of the low-dose and 16% of the



high-dose vs. 0% in the vehicle controls had adverse circula-



tory system effects.  The females had 6% and 16% adverse

-------
                             V-40
effects in the low and high-dose, respectively.  In the liver,
excluding fatty metamorphosis, there were 8% and 14% adverse
effects in the high and low dose, respectively, vs. 0% in the
vehicle controls for males and 8% and 16% in the high and low-
dose, respectively, vs. 5% in the vehicle controls for females.
     There were reported endocrine effects in the male rat of
14% and 16% in the low and high dose respectively vs. 0% in
the vehicle controls.
     The mice also suffered from chronic murine pneumonia.
The untreated and vehicle controls, even though housed in the
same room, did not suffer from pneumonia.
     In the female mouse, the integumentary system, 14% and
6% with low and high dose, respectively, was affected.  At
the high dose, the urinary bladder (10%) was affected.
     A carcinogenic bioassay of 1,2-DCE by inhalation was
carried out by Maltoni, et al. (1980).  Four groups of 180
Sprague-Dawley rats and four groups of Swiss mice of both
sexes were exposed to four 1,2-DCE concentrations:  250-150
ppm, 50 ppm, 10 ppm, 5 ppm or 0 ppm respectively, for 7 hours
daily, 5 days a week, for 78 weeks.  The 250 ppm exposure had
to be reduced to 150 ppm after several days because of severe
toxic effects on the animals, particularly the mice.  Two
groups of 180 rats and one group of 249 mice served as
controls.  At the end of the exposure period,  the animals
were allowed to live until spontaneous death.  No specific
types of tumors were found in treated animals  of either
species.  No relevant changes in the incidences of  tumors

-------
                            V-41



normally occurring in the Sprague-Dawley rats, apart from a



non dose-correlated increase in mammary tumors when compared



with the controls.  This was due to enhanced numbers of



fibromas and fibroadenomas as opposed to malignant tumor types,



     On the basis of data gathered to date, it appears that



1,2-dichloroethane is an animal carcinogen when administered



by the oral route.  No significant increase in the incidence



of tumors has been observed in animals exposed via inhalation.



Several explanations have been proposed to reconcile these



apparent discrepancies, such as a difference in responsiveness



by the strains of test animals studied .and the route of



exposure affecting the carcinogenicity of the substance.



     There are several studies reported in the literature



which demonstrate covalent binding of 1,2-dichloroethane to



macromolecules, including DNA (Banerjee and Van Duuren, 1979;



Guengerich, et al., 1980; DiRenzo, et al., 1982).  The work



of Banerjee and Van Duuren was designed to determine if



1) 1,2-DCE interacts with microsomal proteins of the liver,



its principal target organ in the mouse, 2) if it binds to



DNA in the absence or presence of microsomes and 3) if a



correlation can be shown between binding and carcinogenicity.



Microsomal protein preparations were obtained from young



B6C3F1 mice.  DNA was isolated from salmon sperm.  Each



preparation was incubated individually with [14C] 1,2-DCE in



the presence of native or denatured hepatic microsomes (2 mg



protein) from male B6C3F1 mice.  No detectable radioactivity



was measured in preparations utilizing denatured microsomes,

-------
                            V-42



but considerably binding was observed to both liver microsomal



proteins (19,000 + 2,300 dpm/mg protein) and to sperm DNA



(570 + 2 dpm/mg protein) in the presence of the native



microsomal preparation.



      Banerjee and Van Duuren (1979) also did comparative in



vitro studies with hepatic microsomal protein preparations



from B6C3F1 mice and Osborne-Mendel rats.  The results can be



seen in Table V-19.  Hepatic microsomal protein from mice bound



eight and six times more 1,2-DCE than did microsomal protein



from male and female rats, respectively.  This result is



statistically significant for both the males and females of



these species (P < 0.001).  The covalent binding of [14c] 1,2-



DCE was five times greater to DNA in the presence of microsomes



from male B6C3F1 mice ,than in the presence of microsomes from



male Osborne-Mendel rats, whereas 1,2-DCE was bound 2.5 times



greater to DNA in the presence of microsomes from female mice



than from female rats.  This result was also statistically



significant:  P < 0.001 for males and P < 0.02 for females.



These observations are similar to those reported earlier by



the same authors for trichloroethylene  (Banerjee and Van



Duuren, 1978).  In both studies, significantly greater binding



of 14C-compound was noted in the target organ proteins of



mice which are susceptible to compound-induced hepatocellular



carcinoma than for Osborn-Mendel rats which are resistant to



liver carcinoma by TCE or 1,2-DCE.  These observations lend



support to the hypothesis that a correlation exists between



binding to DNA and the compound-induced carcinogenicity.

-------
                            V-43

                         TABLE V-19

  In vitro Binding of EDC to Hepatic Microsomal Protein from
 B6C3Fi mice and Osborne-Mendel Rats and to Salmon Sperm DNA
                            [I4c]EDC bound to macromolecules3

Species                      nmole/mg protein      nmole/mg DNA

                               male    female       male  female
B6C3F1 mice                 1.75+0.15   1.23+0.17  0.05+0    0.05+0
Osborne-Mendel rats         0.22+0.04   0.21+0.03  0.01+0    0.02+0
a The results for mice are the average +SD of 3 males and 3 females;
  the results for rats are the average +_SD of 7 males and 5 females.
  Three analyses were performed for each animal.

(Modified from Banerjee and Van Duuren, 1979).

-------
                            V-44

     Similar studies have been conducted by Guengerich, et al.

(1981) in Sprague-Dawley rats. Microsomal and cytosolic

fractions of liver homogenates were prepared from phenobarbi-

tal-treated males. Little irreversible binding of 1,2-DCE to the

microsomal preparations was observed in the absence of NADPH;

irreversible binding was linear with respect to time over the 90

minute testing period in the presence of NADPH. Liver micro-

somes catalyzed the NADPH dependent metabolism of 1,2-dichloro-
                                                ^
ethane to metabolites irreversibly bound to calf thymus

DNA.  Cytosolic fractions also catalyzed binding of the

compound to DNA in a reaction enhanced by GSH.  Both reactions

were linear with respect to time for 150 minutes of incubation.

Pretreatment of rats with phenobarbital increased microsomal

rates of total non-volatile product formation two-fold and

irreversible binding to protein four-fold, but did not

significantly affect covalently binding to DNA.

     DiRenzo, et al. (1982) also showed that in vitro covalent

binding to calf thymus DNA by 1,2-dichloroethane occurred

following activation by hepatic microsomes isolated from

phenobarbital-treated rats (strain not named).  The degree

of binding to form a DBA-adduct was considerably lower for

1,2-DCE than for most of the other compounds tested (see

Table V-20).  This could be due, in part, to the fact that

only a relatively small fraction of 1,2-DCE is metabolized

to active metabolites by the  microsomal fraction.  The

greater conversion occurs in the presence of the cytosolic

-------
                                       V-45

                                    TABLE V-20

            Microsonal Bioactivation and Covalent Binding of Aliphatic
                              Halides  to Calf Thymus DMA


                Aliphatic halides                  Binding to ENA
1 , 2-Dibromoethane
Bronotrichlorone thane
Chloroform
Carbon tetrachloride
Trichloroethylene
1,1, 2-Trichloroethane
Di chlorone thane
Halothane
1 ,2-Dichloroethane
1,1, 1-Tr ichloroe thane
0.52+0.14(6)
0.51+0.18(6)
0.46+0.13(6)
0.39+0.08(6)
0.36+0.14(7)
0.35+0.07(7)
0.11+0.05(6)
0.08+0.01(6)
0.06+0.02(6)
0.05+0.01(3)
*nnol bound/fag DNA/h.  Values are the mean +_ standard deviation for the
 number of experiments in parentheses.

 (Modified from DiRenzo,  et al.f  1982)

-------
                            V-46



fraction.  Thus, proportoinately less active metabolite



would have been available with which adducts with DNA



would be formed.



     MUTAGENICITY



     There are a number of studies which demonstrate a positive



correlation between mutagenicity and carcinogenicity (Ames,



1979).  In addition, there is evidence accumulated in mammals



that most environmental carcinogens require bioactivation.



Therefore, the identification of carcinogens by mutagenicity



tests may be largely dependent upon the particular test system



which is used.  Table V-21 shows the results obtained with



1,2-dichloroethane in a number of short-term test systems.



     1,2-Dichloroethane was shown to inhibit the growth of



DNA polymerase-deficient Escherichia coli (P01A~) (Brem,



et al., 1974). E_. Coli bacteria which are deficient in the



enzyme DNA polymerase are sensitive to the inhibitory



actions of chemicals which attack cellular DNA because



they are unable to repair damage to their DNA.



     In the bacterium Salmonella typhimurium, 1,2-dichloroethane



produced a dose-dependent, although relatively weak, direct



mutagenic effect in standard mutagenicity tests (Brem, et al.,



1974; Simmon, et al., 1978).  However, when further studies



were undertaken, 1,2-dichloroethane was found in most of



them to be activated to a highly mutagenic metabolite, when



metabolized by enzymes in the soluble fraction (S-9) of the



rat liver cell. (Kanada and Uyeta, 1978; Rannug, et al.,



1978; Rannug and Beije, 1979).  In addition, the mutagenic

-------
                                                      TABLE V-21

                                  Results of 1,2-Dichloroethane in Short-term Assys
Assay System

A. Prokaryotic Mutagenesis:

     Salmonella
                                      Effect*
                                     Measured
          n
          n
          n
          n
          n
          ii
     E. Coli, PolA+/PolA-
          M

              .Lysis K39(a)
B. Drosophila
     sex-linked recessive
     lethal test (larvae and
        adults)
              Results
              Weakly +
              highly + (activated)
              + (with S-9)
              + (TA 100)
              -i- (with activation)
              - (with induced S-9)
              + (with S-9)
              +  (with S-9  + GSH)

              - (no S-9)
              - (with/without S-9)
              + (lethal mutation)
              + (eye-color marker)
References
Brem, et al., 1974
Rannug and Beije, 1979
(Canada and Uyeta, 1978
Simmon, et al., 1978
Guengerich, et al., 1980
King, et al., 1979
McCann, et al., 1975
Rannug, et al., 1978

Brem, et al., 1974
Brem, et al., 1974
Kristofferson, 1974
(abstract - no details
available)
Rapoport, 1960
Shakarnis, 1969
Nylander, et al., 1978
King, et al., 1979
* G = genotoxic;

+ = positive;
NG = non-genotoxic

- = negative

-------
(Table V-21 continued)

Assay System

C.  DNA  Binding
D. Barley kernels




E. Saccharomyces cerevisiae


F. Mouse micronucleus test

G. Allium root tip
H. Pulmonary tumor induction
   in Strain A mice
 Effect*
Measured
   NG?


   NG

   NG
 Results*
                                                  + (In vitro, naked
                                                    Calf thyraus DNA,
                                                    with NADPH + S-9)
                                                  + (In vitro, naked
                                                    with calf thymus DNA,
                                                    NADPH + cytosolic
                                                    fraction)

                                                  + (minor covalent
                                                    binding to naked
                                                    calf thymus DNA
                                                    with S-9)

                                                  + (Covalent binding
                                                    to DNA)
+(increased t's of
  recessive lethal
  mutations)

Weakly +
References
                                      Guengerich,  et al.,
                                      1980
                                      DiRenzo,  et al.,  1982
                                      Banerjee and
                                      VanDuuren,  1979
                                      Ehrenberg,  et al.,
                                      1974
Simmon, unpublished
(cited in Simmon, 1980)

King, et al., 1979

Kristofferson, 1974
(abst.) (no details
available)

Theiss, et al., 1977
                                                                          f
                                                                          03

-------
                            V-49




metabolite was assumed to be a glutathione conjugate, which



when synthesized and tested was highly mutagenic (Rannug



and Beije, 1979; Guengerich, et al. 1980).  This was surprising



because compounds which are conjugated with glutathione are



usually considered to be rendered less reactive and quickly



and harmlessly excreted from the body.  However, in this



case, displacement of one reactive chlorine group by glutathione



actually causes the other chlorine to become more reactive,



and the compound formed is highly mutagenic.  Also, a synthetic



glutathione conjugate of this type was demonstrated to be



directly mutagenic.



     In other investigations of its mutagenic activity, 1,2-



dichloroethane produced single-strand breaks in DNA of hamster



cells and chromosomal aberrations in barley kernels (Ehrenberg,



et al., 1974).  The mutagenic effectiveness of 1,2-dichloro-



ethane was reported to be 100 times greater than expected



from the frequency of initial reactions with DNA.  Displacement



of a chlorine is thought to result in this amplification of



effectiveness.



     These findings concur with those indicating that displacement



of one chlorine by glutathione, as shown by Rannug and co-workers



51978) leads to a more reactive derivative.



     1,2-Dichloroethane has also been shown to be mutagenic



in  Drosophila melanogaster (Rapoport, 1960; Nylander, et al.



1978; King et al., 1979).  Nondisjunction and recessive sex-



linked lethal mutations were induced in Drosophila treated

-------
                             V-50



with 1t2-dichloroethane through their food supply (Shakarnis,



1969).  A high frequency of mutations was also produced in a



sex-linked genetaically unstable Drosophila system (Nylander,



et al, 1978).  Mutation was measured by the frequency of somatic



mutations for eye pigment.  Metabolic activity in Drosophila was



suggested.



     The synthetic reaction product of 1,2-dichloroethane and



cysteine is a relatively strong mutagen in Drosophila and in



Arabidopsis, as well as in Salmonella typhimurium (Rannug et



al., 1978).



     Other possible metabolites of 1,2-dichloroethane,



chloroethanol and chloracetaldehyde, are highly mutagenic.



Chloracetaldeyde is a direct-acting mutagen in Salmonella



(McCann et al. ,M975) .
         \

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                            VI-1



VI. HEALTH EFFECTS IN HUMANS



     General



     1,2-Dichloroethane is toxic to humans when it is ingested,



inhaled or absorbed through skin or mucous membranes (Sax,



1975).  The primary effects of acute or chronic exposure to



1,2-dichloroethane are central nervous system depression,



gastrointestinal upset and injury to the liver, kidneys,



lungs, and adrenals (Irish, 1963).



     Acute Toxicity



     Oral ingestion of 1 or 2 ounces, about 400 to 800 mg/kg



body weight, of 1,2-dichloroethane by an adult male is fatal



(NIOSH, 1978).  Clinical symptoms of acute 1,2-dichloroethane



poisoning by ingestion usually appear within 2 hours after



exposure.  Typically, they include headache, dizziness,



general weakness, nausea, vomiting of blood and bile, dilated



pupils, heart pains and constriction, pain in the epigastric



region, diarrhea and unconsciousness.  Pulmonary edema and



increasing cyanosis often are observed.  If exposure is



sufficiently brief, these symptoms may disappear when the



individual is no longer exposed (Wirtschafter and Schwartz,



1939; McNally and Fostvedt, 1941).  However, persistent



effects occur with sufficient exposure.  Autopsies frequently



reveal hyperemia and hemorrhagic lesions of vital organs,



especially the stomach, intestines, heart, brain, liver and



kidney.  Not all instances of 1,2-dichloroethane ingestion



are fatal, but death has resulted in the majority of reported

-------
                            VI-2



cases.  Most often these deaths were attributed to circulatory



and respiratory failure (Budanova, 1965; Yodaiken and Bancock,



1973; Luzhnikov et al.f 1976; Zhizhonkov, 1976).  Hypermia



and hemorrhaging into the tissues of the visceral organs and



lungs is often revealed at autopsy (Martin et al, 1969;



Yodaiken and Babcock, 1973; Bryzhin, 1975).  The symptoms



described here observed in humans, including a prolonged latent



period in certain of the clinical manifestations and delayed



death, as well as the autopsy findings, are supported by



animal data.



     Exposure to 4000 ppm of 1,2-dichloroethane vapor for 1



hour produces serious illness in humans (Association of the



Pesticide Control Officials, Inc., 1966).  However, two men



exposed experimentally in 1930 to 1200 ppm of 1,2-dichloroethane



for 2 minutes apparently suffered little discomfort, except



that the odor of 1,2-dichloroethane was extremely noticeable



(Sayers et al., 1930).  The effects of acute exposure by



inhalation are similar to those described for ingestion,



but the primary target appears to be the central nervous



system (Patterson et al., 1975).  Neural depression increases



with the amount of 1,2-dichloroethane absorbed  (Stewart,



1967).  Damage to the liver, kidneys and lungs also occurs;



reports of leukocytosis and elevated serum bilirubin are



common.



     The absorption of 1,2-dichloroethane through skin



produces effects similar to those reported for  inhalation,

-------
                            VI-3



but large doses are required to cause serious systemic



poisoning.



     Brief contact of 1,2-dichloroethane with skin



seldom causes serious difficulties; however, repeated or



prolonged contact results in extraction of normal skin oils



and can cause cracking (Wirtschafter and Schwartz, 1939;



Duprat, et al., 1976).  Although pain, irritation and



lacrimation normally occur when 1,2-dichloroethane contacts



eye tissue, significant damage usually occurs only if



the compound is not promptly removed by washing (Irish, 1963).



     Chronic Toxicity



     Few reports of chronic ingestion of 1,2-dichloroethane



were found, but a few. reports of repeated exposures to low



concentrations of 1,2-dichloroethane by inhalation or skin



absorption have been published.  Chronic exposures to 1,2-



dichloroethane by inhalation or absorption usually result



in progressive effects that closely resemble the effects



described for acute exposure, especially neurological



changes, loss of appetite, gastrointestinal problems,



irritation of the mucous membranes and liver and kidney



impairment.  The concentrations and exposure times associated



with the onset of chronic symptoms in humans are difficult



to deduce from the existing literature.  In general, low level



exposures of 10 to 100 ppm for durations of a few days to a



few months appear to be characteristic of most reports.



Fatalities may occur following such exposures, but they are

-------
                            VI-4



more frequently associated with acute rather than chronic



poisonings (Irish, 1963).



     In addition to the above, information concerning



biochemical changes and microscopic lesions resulting from



exposure to 1,2-dichloroethane is increasing (Yodaiken and



Babcock, 1963; Bonitenko, 1974). Unfortunately, the available



information concerning the toxicology of 1,2-dichloroethane



in humans is concerned with poisoning at higher concentrations



or doses (NIOSH, 1978).  The more subtle toxic effects



which may result from chronic low level environmental



exposure have not been reported.  Of particular interest is



the accumulation of 1,2-dichloroethane in the body with chronic



low level exposure, which is suggested from the water/air,



blood/air, olive oil/air, olive oil/water, and olive/oil



blood partition coefficients (Morgan, et al, 1972; Sato and



Nakajima, 1979).  1,2-Dichloroethane does concentrate in milk



(Urosova, 1953; Sykes and Klein, 1957).  More studies are



required to gather information related to chronic low



level exposures.



     Sice 1,2-dichloroethane is both water soluble and



lipid soluble, disposition after lung absorption of 1,2-



dichloroethane in the body is widespread, and hence the



toxic effects are related to virtually every organ system.



The toxic consequences which have been seen in human subjects



exposed to 1,2-dichloroethane vapors are similar to those



seen following ingestion and include: cardiovascular disorders

-------
                            VI-5



with increased heart rate, fluctuations in blood pressure,



changes in blood components and damage to the myocardium, a



characteristic narcotic effect on the central nervous system



with nausea, vomiting, headache, dizziness, unsteady gait,



dilated pupils, pathological reflexes, unconsciousness and



coma, changes in the gastrointestinal tract with gastroenteritis,



chest and stomach pains, cyanosis and pulmonary edema,



damage to kidney function and signs of liver damage



(Wirtschafter and Schwartz, 1939; Gaurino, et al, 1959).



      Autopsy findings in fatal cases following acute



poisoning include extensive bleeding into the tissues of



all organs, inflammation, congestion, degeneration and



necrosis in the liver, hemorrhaging of respiratory mucosa,



hemorrhaging, swelling and inflammation of the lungs,



degeneration of the myocardium, and hemorrhaging, inflamation



and swelling of the kidney (Brass, 1949; Troisi and Cavallazi,



1961).



     Odor is not a dependable guide for avoiding dangerous



chronic exposures to 1,2-dichloroethane.  Although some



individuals can detect as little as 3 ppm under laboratory



conditions, others consider it barely detectable at 50 or



100 ppm (Hoyle, 1961; Verschueren, 1977),  The odor of



1,2-dichloroethane is generally considered unmistakable at



180 ppm, but even at this concentration, it may not be



considered unpleasant.  In addition, it is easy to become



adapted to odor at low concentrations (Irish, 1963).

-------
                            VI-6




     Poisoning Incidents and Case Histories - More than 100



cases histories of fatal and non-fatal 1,2-dichloroethane



poisonings have been reported in some detail in the literature,



In almost all cases involving ingestion of 1,2-dichloroethane



(approximately 30), death resulted.  The amounts of 1,2-



dichloroethane consumed by the victims varied from "one



sip" to 100 ml or more.  Age varied from 1.5 years to



about 80.  Signs and symptoms included: violent vomiting,



nausea, collapse and unconsciousness.  Death usually occurred



within two days of exposure, but, in a few instances, it was



delayed up to six days.



     More than 70 cases of acute inhalation exposures to



1,2-dichloroethane are described in the literature (see



Table VI-1); only a small fraction of these, about 13%,



resulted in fatalities.  In general, acute inhalation



exposures have been work-related and associated with the



use of end products containing 1,2-dichloroethane.  Most



fatalities have been adult males.  Symptoms and signs



associated with acute inhalation exposures are generally



similar to those previously described.  In lethal exposures



by inhalation, death does not occur as rapidly as in lethal



exposures by ingestion.  However, most victims succumb




within two weeks.



     Among recorded case histories, most victims of acute



inhalation poisoning recovered and were released as clinically



normal a few days after exposure.  Only a few follow-up

-------
                                       VI-7

                                     TABLE VI-1


                   Cases of Fatal 1,2-Dichloroethane Ingestion
Patient
 Anount of Chemical
taken into the body
      (if known)
    Onset and
 Progression
 of symptoms
                                                                Reference
63-year-
old man
    2 onces
1-1/2-year-
old boy
1-1/2-year-
4 males 20-29
years old
53-year-
old man
    1 sip



    Unknown


    150-200 ml
    Unknown; maybe
    on several
    occasions
2 hours
Nausea; faintness;
vomiting; dazed;
cyanotic: dilated
pupils; coarse rales;
weak, rapid pulse;
dark brown liquid
stools; increased
cyanosis; pulse and
heart sounds absent;
dypspnea; death 22 hours
after ingestion

Extreme weakness;
comatose; vomiting;
death the next day

Coma; anuria;
pneumonia

3-4 hours
Symptoms not reported;
death 10, 15,33, and
35 hours after ingestion

Inattentive; sleepy;
excitement; uncon-
sciousness; rapid,
irregular breathing;
cyanosis; completely
dilated pupils; light
pulse; heart and
respiratory failure;
lung edema; death at
least 10 hours after
ingestion.
Hueper and
  Smith,
  1945
     Keyzer,
        1944
     Meurs,
       1944

     Bryzhin,
         1945
     Bloch,
       1046

-------
                                      VI-8

                              TABLE VI-1 (Continued)
Patient
Amount of Chemical
taken into the body
     (if known)
     Onset and
    Progression
    of symptoms
                                                                   Reference
43 -year-
old man
alcoholic

43-year-
old man,
alcoholic
55-year-
old man,
asthmatic
 4 drinks diluted
with orange juice
4 drinks diluted
with orange juice
20 ml
Unconsciousness;
death 8 hours after
ingestion

Confusion; deep
sleepiness; uncon-
sciousness; vomiting
with blood; death 24
hours after ingestion

Epigastric pain;
extreme dizziness;
sleepnessness; vomit-
ing; slow pulse; death
24 hours after ingestion
Hulst,
   1946
Hulst,
   1946
Roubal,
   1947
16-year-
old man
50 ml
Vomiting; epigastric pain;
fourth day:  muscle spasms,
hiccups, pulse 108, no eye-
lid response to light; death
91 hours after ingestion
Stuhlert,
    1949
Man
Unknown
Violent vomiting;
painful visceral
cramps; extreme
weakness; pale,
cyanotic; weak,
rapid pulse; weak
heart sounds; rales;
dyspnea; increased
cyanosis and dyspnea,
and weakening pulse;
death 20 hours after
ingestion
Stuhlert,
    1949

-------
                                    VI-9

                            TABLE VT-1 (Continued)
Patient
Amount of Chemical
taken into the body
      (if none)
 Onset and
Progression
of Symptoms
Reference
Man
Unknown
50-year-
old man
30 ml
Man
About 20 ml
Man
30-year-
old man
About 20 ml


40 ml
 Violent vomiting;
 circulatory failure
 and death 39 hours
 after ingestion

 30 minutes                 Lochlead
 Unconsciousness;           and Close,
 vomiting, cyanosis;        1951
 dilated, fixed pupils;
 pulmocary edema, extreme
dyspnea; death 10 hours
 after ingestion

 1 hour                     Flotow
 Collapse; repeated         1952
 vomiting; after 12
 hours blue lips, diffi-
 culty breathing; death
 13 hours after ingestion

 Death within 12 hours of
 ingestion

 Slight cough;              Garrison
 reddened conjuctivae;         and
 shock; weak, rapid         Leadingham
 pulse (100); regained      1954
 consciousness after 3
 hours; hyperactivity
 alternating with semi-
 comatose condition; death
 28 hours after ingestion

-------
                                     VI-10

                             TABLE VI-1 (Continued)
Patient
Anount of Chemical
taken into the body
     (if known)
  Onset and
  Progression
  of symptoms
                                                                           Reference
Nan
2-year-
old boy
79-year-
old man
  1 sip
2-year-
old boy
   1 sip
23-year-
   1 sip
2 hours
Violentely ill; shock
cyanosis; pulmonary
edema; light coma;
vomiting and diarrhea;
low blood pressure; severe
albuminuria; death at 19
hours after ingestion

2 hours
Violently vomiting; 20
hours after ingestion;
restlessness, cramps;
death occurred approxi-
mately 21 hours after
ingestion during convulsions

Void ting; weakness;
pale, cyanotic;
scarcely conscious;
vagueness; rapid, regular
pulse (136); blood pressure
not measureable; died 40 hours
after ingestion with heart and
circulatory failure

Vomiting; diarrhea;
tonic spasms; increasing
loss of consciousness;
dyspnea; impaired circu-
lation; death 20 hours after
ingestion

1 hour
Dizziness; nausea;
unconsciousness;
vomiting; cyanosis;
no pupil reaction; no
corneal reflex; difficult
breathing; strong motor
unrest; death after 8
hours due to respiratory
and circulatory failure
                                                            Hubbs and
                                                              Prusmack,
                                                                1955
                                                             Durwald,
                                                                1955
Weiss,
   1957
Reinfried,
   1958

-------
                                      VI-11

                              TABLE VI-1 (Continued)
Patient
Amount of Chemical
taken into the body
     (if known)
    Onset and
   Progression
   of symptoms
Reference
63-year-
old man
  1 or 2 sips
3 men, 19-27
years old
70, 80 and 100 ml
32-year-
old man,
8 ml
27-year-
old man
Half a glass
Shortly after inges-          Freundt
tion; unconsciousness;         et al.
soon regained conscious-        1963
ness, strong vomiting;
period of improvement;
10.5 hours after ingestion
unconscious; blood pressure
falling; 14 hours after
ingestion death resulting from
circulatory failure

Few minutes                   Kaira,
Vomiting; weakness;
dizziness; lost can-
sciousness; deaths
occurred 5-8 hours
after ingestion

Immediate                     Bogoyav-
Burning sensation in           lenski,
mouth throat, stomach;        et al.
drank milk and vomited;          1968
weakness; speach retar-
dation; lethargic; asthenic;
cold sweat; heart sounds
muffled; weak and rapid
pulse; 22 hours after inges-
tion excitation, restlessness,
delirium, face flushed, coarse,
systolic murmur, respiratory
depression, circulatory weak-
ness , anuria, then death 56
hours after ingestion

2.5 hours
unconsciousness; vomiting
of dark vomitus; regained
consciousness after 12 hours,
burning sensation in digestive
tract; dyspnea; nausea; cynosis;
respiratory rate 32/minute; moist
rales in lungs; heart sounds muf-
fled; pulse 102, extrasystoles;
anuria; death 19 hours after
ingestion

-------
                                      VI-12

                              TABLE VI-1 (Continued)
Patient
Amount of Chemical
taken into the body
     (if known)
  Onset and
  Progression
  of symptoms
Reference
80-year-
old man
      50 ml
57-year-
old man
      40 ml
18-year-
old man
      50 ml
14-year-
old boy
      15 ml
Elevated serum              Secchi et
enzymes-LDH, SCOT            al. 1968
SGPT, alkaline phos-
phatease, glutamic
dehydrogenase, RNAase;
death a few hours after
ingestion

Somnolence; vomiting;       Martin et
sinus tachycardia (100);     al. 1969
ventricular extrasystoles;
return of consciousness
14 hours after ingestion
dyspnea; loss of blood
pressure; cardiac arrest;
death 24 hours after ingestion

1 hour                      Schoenborn
Somnolent; cyanotic;           et al.
4 hours later foul              1970
smelling diarrhea;
5.5 hours later shock
of circulatory system;
death after 17 hours in
irreversible shock

Within 2 hours severe       Yodaiken
headache; staggering;          and
lethargy; periodic          Babcock,
vomiting; blood pres-          1973
sure drop; oliguric;
increasingly dyspenic,
somnolent and oliguric;
ecchymoses; sinus brady-
cardia; cardiac arrest;
pulmonary edema; refractory
hypotension; death on 6th day

-------
                            VI-13



case studies have been made to determine if long-term effects



develop from acute inhalation exposure to 1,2-dichloroethane.



In a few poorly documented instances, chronic changes in



the central nervous system appear to have persisted 1 to 18



years following exposure (Smirnova and Granik, 1970).  In



the most serious case, illness was accompanied by encephalitis



and injury to the subcortical region that improved only



slowly during 14 years.  It is uncertain, however, that



exposures were only to 1,2-dichloroethane.  Further studies



of delayed effects of acute inhalation exposures to



1,2-dichloroethane are needed.



     Recent Studies



     Since 1970, several comprehensive studies have been



published which detailed the human toxicity of 1,2-



dichloroethane in the acute as well as the chronic forms.



     Summarized in Table VI-2 are the symptoms of acute



1,2-dichloroethane poisoning from ingestion in 118 patients



and the clinical findings in these patients reported by



Akimov et al. (1976, 1978).  The amount of compound swallowed



ranged from 20 to 200 ml.  The patients were divided into



three groupsmild, moderate, and severethe severity of



the symptoms do not necessarily correlate with the amount




ingested.

-------
                                    VI-14

                                  TABLE VI-2

                  Symptoms and Clinical Findings of Acute
                   Peroral 1,2-Dichloroethane Poisoining

                (translated from Akimov et al., 1976, 1978)
Simp tons
Degree of severity of
	Poisoning	
Mild   Moderate   Severe
                   Total Nunber
                   of Patients,
                   absolute (%)
Dichloroethane odor
in mouth

Dry skin

Mucosal cyanosis

Respiratory disorders

Tachycardia

Arterial hypotension

Loss of consciousness

Mydriasis

Horizontal nystagmus

Speech disorders

Muscular hypotonia

Decrease in tendon
reflexes

Presence of pathologic-
reflexes
17
10
81
108 (91)
15
2
3
12
3
-
6
8
4
2
2
10
2
4
5
4
1
10
4
6
4
5
64
76
63
57
81
49
69
16
15
52
48
89 (75)
80 (67)
70 (59)
74 (62)
88 (74)
50 (42)
85 (72)
28 (23)
25 (21)
58 (46)
55 (46)
                                 8 (6)
Convulsions
                                 9  (7)

-------
                                    VI-15

                            TABLE VI-2 (Continued)
Symptoms
Degree of severity of
	poisoining	
Mild   Moderate   Severe
            Total Number
            of patients,
            absolute (%)
Cerebellar disorders:

     Ataxia               8
     Romberg's sign       9
     Intention tremor    13
     Adnodochokinesis     7
     Dysmetria            5

Extrapyramidal disorders:

     Pare nictation       2
     Hypomimia            4
     Bradykinesia         3

Delirious hallucina-      1
tions
          7-
          9
          9
          7
          4
          2
          5
          4
18
21
29
16
11
 9
19
11
33 (27)
39 (33)
51 (43)
30 (25)
20 (16)
13 (11)
28 (23)
18 (15)

 4 (3)

-------
                            VI-16



     The most common effects in mild to severe 1,2-



dichloroethane poisoning were a pronounced odor on the



patient's breath, cyanosis, difficulty in breathing,



tachycardia, hypotension, mydriasis, loss of muscle tone



and a decrease in tendon reflexes.  Neurological syndromes



involving disturbances in consciousness, mental disorders,



cerebellar and extrapyramidal abnormalities were often



noted (Table VI-3).



     The neurological symptoms in mild poisoning disappeared



4 to 5 days after the onset.  These disorders were more



prolonged in moderate poisoning, and a cerebellar syndrome



was observed for up to two weeks in some patients from



this group.  The neurological disorders in the group of



patients who were severely poisoned were characterized by



loss of consciousness, muscle hypotonia, a decrease in tendon



and periosteal reflexes, the onset of pathological reflexes



in the feet and convulsions.  The cerebellar and extrapyramidal



disorders, which lasted for 2 to 3 weeks, were more pronounced.



     Shchepotin and Bondarenko (1978) described acute



toxicity to 1,2-dichloroethane in 248 patients, males and



females between the ages of 15 and 72.  The majority of



these patients (85 percent) suffered harmful effects resulting



from oral ingestion of the liquid chemical, while toxicity



followed inhalation of vapors in 15 percent.  The length



of inhalation of 1,2-dichloroethane was, on the average,



20 to 30 minutes.  However, concentrations of the inhaled



1,2-dichloroethane vapors were not reported.

-------
                                   VI-17

                                TABLE VI-3

                Characteristics of the Basic Forms of Damage
          to the Nervous System in Acute Dichloroethane Poisoning

                   (translated from Akimov et al., 1978)
                               Severity of damage
     Mild
     Medium
   Severe
Euphoria

Hallucinations


Mild nystagmus
Reduction of
   abdominal
   and sole
   reflexes
Moderate atactic
   symptoms
Deafness

Hallucinations
Psychomotor excitation

Mydriasis
Persistent nystagmus
                            Muscular hypotonia
Reduction of abdominal
   and sole reflexes
                            Reduction of reflexes
                              of extremities
Pronounced atactic
    symptoms

Hypomimia
Bradykinesia
Stupor, coma
Mydriasis
Persistent
  nystagmus
Reduction of
  corneal
  reflexes

Muscular
  hypotonia

Reduction of
  abdominal
  and sole
  reflexes

  Reduction of
  reflexes of
  extremities

Toxic convulsions

Pronounced atc-
  tic symptoms

Hypomimia
Bradykinesia
                            Dysarthria
                                Dysarthria

-------
                           VI-18



     Four main clinical syndromes were identified with 1,2-



dicloroethane poisoning in these patients.  The hepatic and



cardiovascular systems were affected most often following



central nervous system disorders.  Renal dysfunction was



also observed.  Neurological disorders were noted in all



patients.  These included unconsciousness (narcotic effect)



and respiratory inhibition via depression of the medullary



center of the brain.  A syndrome of acute cardiovascular



insufficiency developed in 60 percent of the patients



including arrhythmias and a fall in both systolic and



diastolic blood pressure, with reduction of cardiac output



and decreased peripheral resistance.  In 35 percent of the



patients, a syndrome of liver dysfunction was evident.  The



liver was enlarged, hyperbilirubinemia was severe, and



serum albumin and asparagine transaminase activities were



increased.



     With inhalation poisoning, in particular, the kidneys



were affected.  This is explained by the relatively high



arterial blood flow (20 percent of cardiac output) perfusing



the kidneys.  Nephropathology in these patients was manifested



by oliguria, proteinuria, azotemia and acute renal failure



with disturbances of acid base balance.



     Of interest was a common syndrome of gastroenteritis



not only in the patients poisoned by ingestion, but also



in the patients poisoned by inhalation, although the degree



of gastroenteritis was milder in those patients poisoned by




inhalation.

-------
                            VI-19



     Shchepotin and Bondarenko (1978) attempted to correlate



the severity of 1r2-dichloroethane poisoning with the



concentrations of 1,2-dichloroethane in blood and urine as



determined by gas chromatography.  While a severe clinical



course of poisoning was sometimes noted with high concentrations



in blood and urine, no correlation between severity and DCE



levels in body fluids was established.  Similarly, no direct



correlation between severity of poisoning and the amount of



1,2-dichloroethane inhaled was evident.



     Bonitenko (1974, 1977), in a description of 1,2-



dichloroethane toxicity in 32 patients, compared the severity



of clinical symptoms of poisoning with concentrations of



the chemical in the blood.  Coma was associated with blood



concentrations of 15-30 mg percent, and the level at which



consciousness returned corresponded to levels below 8-10 mg



percent.  The method of measurement was not described.



These investigators determined at autopsy that the level in



adipose tissue was 68 mg per 100 gm of tissue while the



corresponding level in blood was only 1.2 mg percent.



     Luzhnikov et al. (1970), in a study of a series of 110



patients, observed clinical symptoms similar to those reported



by Akimov et al.  Within the first hours following exposure,



77 percent of these patients demonstrated acute gastritis



with vomiting, neurological disorders including coma (81



percent), acute cardiovascular insufficiency (57 percent),



hepatitis (56 percent) with liver enlargement and functional

-------
                           VI-20



abnormalities (abnormal bromosulfonphthalein clearance,



plasma bilirubin and plasma glutamine-asparagine transaminase



levels).  Clinical symptoms of poisoning were observed with



only minimal concentrations of 1,2-dichloroethane in the



blood (0.5 mg percent).  Coma developed at a blood concen-



tration as low as 5 to 7 mg percent and higher.  Gas-liquid



chromatography was utilized to measure the concentration



of 1,2-dichloroethane.  Differences in analytical methodology



may help to explain the apparent discrepancy in the values



associated with development of coma given by Bonitenko and



those reported by Luzknikov et al.  Time of sampling may



also affect the resulting concentration measurement.



     Luzhnikov and co-workers (1974, 1976) also investigated



the toxic effects of 1,2-dichloroethane on the myocardium in



at least 160 patients.  These workers developed a concept



of "exotoxic shock," that is, hemodynamic shock due to the



toxic effects of a chemical on the myocardium.  During the



compensatory phase of shock, total peripheral resistance



was 15 to 25 percent higher than normal, arterial blood



pressure was normal or increased slightly, while cardiac



output and blood volume were decreased significantly.  In



decompensated shock, pronounced and progressive hypotension



was observed, cardiac output was decreased 30 to 70 percent



and peripheral resistance was either unchanged or slightly



decreased.  Electrocardiographic (ECG) changes including



arrhythmias were observed in both compensated and decompensated



shock.

-------
                           VI-21



     In analyzing the myocardial function, definite changes



in the cardiac cycle were found in the compensated shock



phase: isometric contraction was decreased, expulsion time



(ventricular emptying period) was increased, intraventricular



pressure was increased and asynchronous contractions



occurred.  In the decompensated exotoxic shock phase,



myocardial contractile force was markedly decreased during



ventricular systole and prolonged periods of asynchronous



contractions were observed.  The authors noted that a 25-30



percent increase in peripheral resistance for a prolonged



period will produce the observed left sided heart failure,



especially after the observed kidney lesions appear as an



additional contributing factor (Luzhnikov et al., 1974, 1975).



     Morphological examination of the myocardium at autopsy



showed significant edema in the cells of the capillary



endothelium and stenosis of the capillary lumina.  The



micro-circulatory vessel changes also were accompanied by



pronounced edema of the myocardial interstices with



accumulation of polymorphonuclear leucocytes and microfocal



hemorrhages.  Histological examination showed a diminished



presence of glycogen and degenerative changes of varying



degrees in the cardiac muscle.  Mitochondrial damage was



indicated by a decrease in enzyme activities.



     Toxicity in Infants and Children



     1,2-Dichloroethane poisoning in children presents a



clinical syndrome similar to that seen in adults.  Hinkel

-------
from an exposure to a "nerve balsalm" medicine which was 75
percent 1,2-dichloroethane.  The features of clinical
toxicity are summarized in Table VI-4.  Within an hour after
exposure, severe and persistent vomiting occurred.  Immediately,
or even after an interval of 10 to 12 hours, various degrees
of narcotic effects were present.  The symptoms ranged from
somnolence to coma; less frequently, motor unrest, reflex
increases and convulsions occurred.  Indications of circulatory
failure were also present.  The manifestations of toxicoses
in the child thus correspond to those observed in adults.
The disturbances in kidney and liver function which are
observed in the adult were less frequent in the children
poisoned from the "nerve balsalm."  However, corresponding
investigations have not been undertaken in all instances.
Tachycardia indicated that the effect of 1,2-dichloroethane
on the heart was similar to that of chloroform, although
no ventricular fibrillation was recorded.  The blood changes
were not exceptional.  In particular, there was no leukocytosis
or erythrocyte and hemoglobin increase which have been
described by others.  Electroencephalograms were not routinely
performed; however, in the patients for which they were
recorded, the EEC's proved to be normal.  The gross and
histopathological findings were the same as those described
for 1,2-dichloroethane poisoning elsewhere in the literature.

-------
                                                      TABLE VI-4
4.
5.
6.
                                 SUMMARIZATION OF THE CLINICAL SYMPTOMS IN CHILDHOOD
                                            (adapted from Hinkel, 1965)
Appearance of the Gastrointestinal Circulatory Clinical
Cases clinical symptoms symptoms CNS symptoms symptoms interval
1 . immediately
2. 1 hour
3. 1/2 hour
severe vomiting
severe vomiting
Severe vomiting
later diarrhea,
incon-
spicuous
unrest,
slugglish
pupil react-
tion
soporose to
comatose
circulatory
insufficiency
circulatory
insufficiency
circulatory
insufficiency
not pre-
sent
not pre-
sent
not pre-
sent
Blood Liver & Kid-
picture ney findings
no find-
ings
no find-
ings
	
urine no
findings
urine no
findings
	
Details
easy
course
easy
course
exitus
 2 hours
immediately
1 hour
                              pressure pain in
                              abdomen, liver
                              swelling
severe vomiting
severe uninter-
rupted vomiting
somnolent,    circulatory    not pre-  no find-  urine, no  survived
reflex and     insufficiency   sent     ings      findings
tonus increase
somnolent to  circulatory     12 hours  no find-
 soporose      insufficiency            ings
                                   albumi-
                                   nuria,
                                   leukocyturia,
                                   retention of
                                   substances
                                   normally in
                                   urine
                             survived
                  somnolent to   circulatory    12 hours
                    soporose     to sufficiency
                                                              exitus
7.
1/4 hour
severe vomiting
staggered
gait, somno-
lence
circulatory
insufficiency
8 hours  leukocy-   no find-
         tosis with   ings
         left dis-
         placement
survi-
ved

-------
                           VI-2 4



In spite of the fact that some of the characteristic changes



of 1,2-dichloroethane poisoning were not present, the



diagnosis of oral hydrocarbon intoxication was indicated.



     The toxic lethal dose in children is less than for



adults, ranging from 0.03 to 0.9 gm/kg.  However, this oral



dose level did not always cause death.



     Infant exposure to 1,2-dichloroethane with subsequent



toxic effects can occur via the milk of nursing mothers who



heve been exposed to the compound.  Urusova (1953) demonstrated



the presence of 1,2-dichloroethane in the milk of nursing



mothers who were exposed to the chemical by inhalation or



cutaneous absorption in an industrial setting.  Samples of



breast milk and exhaled air from the lungs usually were



taken immediately after work and at periods up to 2 1/2 hours



after work exposure.  1,2-Dichloroetahne was found in the



breast milk within 5 minutes after the ending of the work



period, peaking 1 hour post work exposure.  A similar pattern



was found for breath analysis.  A concentration of 1,2-



dichloroethane in the work atmosphere was determined to be



0.063 mg/liter (0.016 ppm).  After exposure to this atmos-



pheric concentration for one hour, 0.58 mg/liter (0.014 ppm)



was found in the expired air, and 0.54 to 0.64 mg percent



was found in the breast milk.  In many cases, 1,2-dichloro-



ethane was detected in the mothers' milk 18 hours after work had



ended.  The concentration ranged between 0.2 to 0.63 mg



percent, whereas the breath concentration of 1,2-dichloroethane

-------
                           VI-2 5



was 0.009 to 0.017 mg/liter (0.002 to 0.004 ppra).  1,2-Dichloro-



ethane was blown out of the milk by an air stream at the rate



of 1 liter/hour with heating in a water bath to  50 and was



concentrated in alcohol.  The amount of dichloroethane was



determined by Ginzburg's method.  The exhaled air was collected



through the exhalation valve of a gas mask.  The dichloroethane



was absorbed and concentrated in alcohol and determined by



the same method.



     1,2-Dichloroethane also has been found in cows' milk which



provides another source for exposure in infants  and young



children (Sykes and Klein, 1957).



     Microscopic Pathology and Cellular Toxicity



     Within the last few years, increasing interest has



been expressed in the toxic manifestations of 1,2-dichloroethane



exposure at the cellular and biochemical levels.  As noted



above, Luzhnikov et al. have described the histological



changes in myocardial tissue (1974, 1976).  Yodaiken



and Babcock (1973) described clinical features and pathologic



findings in detail for a case of fatal poisoning.  The



significant abnormalities related to the liver, kidneys and



adrenal glands.  Microscopically, extensive liver parenchymal



cell necrosis was found with only scattered vacuolated



cells and occasional islets of surviving cells located near



or around central veins and portal triads.  Fat  stains



confirmed the presence of lipid in the vacuoles.  The



kidneys were yellow and swollen.  The glomerulae were intact

-------
                           VI-26



although focal epithelial cell necrosis was observed.  Marked



degenerative changes were found in the descending proximal



limb and the thick ascending limb of the nephrons.  Lipid



staining showed extensive fat droplet accumulation most



marked in cortical areas but present throughout the tubular



structure.  The adrenals microscopically showed vascular



congestion and well-marked focal degenerative cell damage



in all zones of the cortex.  The prominent clinical chemistry



before death was hypoglycemia and hypercalcemia (Yodaiken



and Bancock, 1973).



     Schoenborn et al. (1970) found disseminated intravascular



coagulation in a single acute fatality of 1,2-dichloroethane



poisoning.  But, unlike Martin's observations in 1968, this



patient did not show an increased tendency to bleed.



     Luzhnikov et al. (1974) studied the coagulability



of blood in 30 patients.  In 1,2-dichloroethane poisoning,



they found an increased amount of heparin in the blood.



Also observed was an increase in fibrinolytic activity, a



prolonged clotting time and an increased prothrombin index,



all of which are in accord with hemorrhaging or increased



tendency toward hypocoagulation.



     Bonitenko et al. (1974, 1977) have shown that the



leucocyte count in the blood of patients poisoned with 1,2-



dichloroethane increases as a function of severity of



poisoning (see Table VI-5).  In addition, increases in serum



aminotransferase enzyme activities correlates with severity



of poisoning (Table VI-6).  These latter effects are related

-------
                           VI-27

                        TABLE VI-5
      Mean Number of Leukocytes in the Blood as a Function
      of the Severity of the 1,2-Dichloroethane Poisoining

                    (Bonitenko et al., 1977)
Degree of               Me_an                 Std. Dev,
poisoning               x                      m
Mild                    6800                    240

Moderate                9200                    330

Severe                 12000                    360

-------
                           VI-28

                        TABLE VI-6

   Mean Serum Aminotransferase Values in the Early Stages
        of 1,2-Dichloroethane Poisoning (U per ml)

                  (Bonitenko et al.f 1977)
Degree of
poisoning
Alanine-aminotrans-
ferase (SCOT)
               Aspartate-amino-
               transferase (SGPT)
                     mean
                       x
           Std dev
             m
Mild

Moderate

Severe
     39

     62

    117
 4.9

 7.1

12.5
                mean
                  x
       Std. Dev.
           m
 32.7      5.2

 50.2      7.3

107       13.2

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                           VI-2 9



to organ damage, particularly to damage in the liver.  The



blood leucocyte and serum enzyme activity provide a means



of early evaluation of the degree of 1,2-dichloroethane



poisoning and institution of appropriate therapy.



     Epidemiology - The earlier available reports of chronic



exposure to 1,2-dichloroethane are complicated by concurrent



exposure of the subjects to other organic chemicals.  Hence



the description of observed toxic effects encountered in



these reports cannot be ascribed entirely to 1,1-dichloroethane,



These reports may, however, have certain value in suggesting



the synergistic toxicities which may occur with simultaneous



multi-chemical exposure, and are, therefore, summarized below.



     Forty-eight cases of poisoning in Italy by a fumigant



mixture of 75 percent 1,2-dichloroethane and 25 pecent



carbon tetrachloride were reported by DiPorto and Padellaro



(1959).  Mild, moderate and severe pathological syndromes



were described.  Central nervous system effects and



gastrointestinal disorders were seen commonly in these patients.



The effects were mild for 28, moderate to severe for 16 and



fatal for 4 persons.  Clinical findings included acute



hepatorenal insufficiency with the implications associated



with this syndrome.  In addition, necrotic and hemorrhagic



lesions in the liver, primarily in the centrolobular cells,



necrosis of the tubular epithelium in the kidneys, as well



as proliferative changes in the glomeruli including



multinucleated cells, were found in the fatal cases.

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                           VI-30



     In the same year, Cetnarowicz (1959) published a study



of Polish workers employed by an oil refinery that used a



4:1 mixture of 1,2-dichloroethane and benzene as a processing



fluid.  After a two- to eight-month exposure to 10 to 200



ppm 1,2-dichloroethane in the work site air, 16 workers on



one shift experienced a general reduction in body weight



of 2 to 10 kg; four had tender, slightly enlarged livers,



seven had tenderness of the epigastrium and most had



elevated urobilinogen levels in the urine.  Thirteen of



the workers had normal levels of erythrocytes and hemoglobin,



but only nine showed a normal distribution of white blood



cells.  Other workers had abnormal levels of serum bilirubin,



albumin, globulin, fibrin and blood non-protein nitrogen.



In general, about half of the workers had some loss of



liver function, and nearly one-third experienced changes



in the gastrointestinal tract, sinus bradycardia or hemato-



poietic system.  It should be noted, however, that some of



the reported blood changes could reflect benzene poisoning



rather than 1,2-dichloroethane poisoning.



     Khubutiya (1964) studied hematologic changes in an



unspecified number of 1,2-dichloroethane workers.  Blood



cell morphology, color index, red blood cell count and



hemoglobin content were recorded.  Samples from about one-



third of the workers contained hyperchromic erythrocytes



without megaloblasts.  Nearly half of the blood samples



showed moderate to high sedimentation rates induced by an

-------
aosoiute neutropniiia ana aosojiuce xyiupnopeaia was

Moderate or marked monocytosis was frequently observed.
                                                   \
Turk's cells occurred in the peripheral blood of one worker

in five.  The number of platelets was frequently reduced.

Khubutiya attributed both the monocytosis and the Turk's

cells to stimulation of the reticuloendothelial system by

long, unspecified exposures to 1,2-dichloroethane.

     Brzozowski et al. (1954) reviewed the health status

and work practices of Polish agricultural workers who used

1,2-dichloroethane as an insecticide.  The liquid was

brought to the field in barrels and was then poured by

hand into a series of holes.  Skin absorption, which

resulted from spillage on clothes and shoes, was probably

as significant a contribution to exposure as inhalation.

Air concentrations of 1,2-dichloroethane were estimated at

15 to 60 ppm.  Signs and symptoms of exposure were reported

in 90 of 118 workers.  The most common subjective complaints

were conjunctival congestion, reddening of the pharynx,

bronchial symptoms, metallic taste in the mouth, headache,

weakness, nausea, abdominal and epigastric pains, tachycardia,

dyspnea after effort and burning and reddening of skin.

Liver function tests were significantly abnormal in 70

percent of those tested.

     No changes were found in the blood or functions of

internal organs of 100 factory workers exposed to 1,2-

dichloroethane for six months to five years at concentrations

-------
                           VI-3 2



of 25 ppm or less (Rozenbaum, 1947).  However, functional



disturbances of the nervous system occurred in several



workers, including heightened lability of the autonomic



nervous system, diffuse red dermatographism, muscular



swelling, bradycardia and increased sweating.



     Kozik (1975) reported a study of a group of workers in



a Russian aircraft industry chemically exposed to 1,2-dichloro-



ethane during the manufacture of soft rubber tanks.  He



compared findings in this group to those for the workers in



the entire factory.  He looked at morbidity and temporary



loss of ability to work for the two groups.



     Concentrations of 1,2-dichloroethane varied from 5 to



40 ppm and persisted for 70% to 75% of the working time of



the exposed group.  Total morbidity, acute gastrointestinal



disorders, neuritis, radiculitis and other diseases were



generally more pronounced among workers exposed to 1,2-



dichloroethane than among other workers in the factory.



Among 83 exposed workers, 19 were found to have diseases



of the liver and bile ducts, 13 had neurotic conditions,



11 experienced autonomic dystonia, 10 had goiter or hyper-



thyroidism and 5 reported asthenic conditions.



     No epidemiological studies of 1,2-DCE other than in



industrial exposures have been reported.

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                           VI I-1



VII. MECHANISMS OF TOXICITY




     The cellular mechanisms of toxicity of 1,2-dichloroethane



remain to be investigated.  However, a few generalizations



may be made.  1,2-DCE causes acute toxicity via direct



effects on the central nervous system (CNS).  The morphological



evidence shows that 1,2-DCE produces adverse effects on



the lungs, liver, heart, adrenals and kidneys.



     The signs and symptoms of acute toxicity of 1,2-DCE



vary depending on the species, route of administration and



concentration or dose.  Depending upon the intensity of the



exposure and the species of the animal, the liver may show



fatty degeneration or slight congestion with slight



parenchymal degeneration.  The kidney often shows signs of



moderate inflammatory irritation with moderate exposure,



but with more severe poisoning, tubular damage ranges from



slight parenchymal degeneration to complete necrosis with



interstitial edema, congestion and hemorrhage.  Plaa and Larson



(1965) observed an increase in urinary protein due to the



nephrotoxic effect of 1,2-DCE.



     When administered perorally, 1,2-DCE produces direct



irritation of the gastrointestinal tract with cellular



mucosal damage, probably due in part to the solubility



properties of the chemical (Parker, et al., 1979).  Kistler



and Luckhardt (1929) found hemorrhages in the mesentery and



in the intestinal mucosa.  Pre-neoplastic and malignant



lesions of the gastrointestinal tract were observed in

-------
                           VI I-2



rodents exposed to 1,2-DCE by gavage in the NCI bioassays



(NCI, 1978) .



     Pulmonary congestion and edema are very frequent



findings whether the exposure to 1,2-DCE is by inhalation



or orally (Parker, 1979).  Like chloroform, 1,2-DCE may



have direct effects on the functional properties of the



heart.  Heppel, et al. (1945, 1946) and Hofmann, et al.



(1971) observed fatty degenerative changes in the myocardium



of the guinea pig after inhalation exposure.



     Metabolite Toxicity and Protection



     The 1,2-dichloroethane metabolites, chloroacetaldehyde,



chloroethanol (oral LD$Q for rats - 95 mg/kg), and chloroacetic



acid (oral LDso for rats - 76 mg/kg) are several times more



toxic than dichloroethane itself (oral LD$Q for rats - 770 mg/kg)



(Woodward et al., 1941; Heppel et al., 1945, 1946; Ambrose,



1950; Hayes et al., 1973).  Johnson (1967) suggests that chloro-



acetaldehyde may be the toxic metabolite, since this very



reactive compound is capable of both enzymatic and non-enzymatic



interaction with cellular sulfhydryl groups.  However,



Yllner (1971a, b) found that chloroacetic acid also reacted



extensively with sulfhydryl compounds in vivo.  Heppel, et



al. (1945, 1946) found a high mortality (35 percent) in



rats given 1.3 g/kg of 1,2-DCE orally.  Mortality was



reduced by pre- or post-administration of methionine,



cysteine, cystine and other sulfhydryl compounds.  Sulfur-



containing amino acids, cystine and methionine, also protected

-------
                           VI I-3



young rats from inhalation exposure.  This protective



effect of sulfhydryl compounds is clearly related to the



marked depletion of glutathione levels that occurs in the



livers of rats given 1, 2-dichloroethane, chloroethanol or



chloroacetaldehyde (Johnson, 1965, 1967).



     Johnson (1965, 1966, 1967) observed that, within 2



hours, a single oral dose of 1,2-dichloroethane (4 millimoles/kg)



reduced the level of liver glutathione in rats to 52% of



that in controls.  2-Chloroethanol (0.67 millimole/kg)



similarly lowered glutathione  levels to 17% of control



values with formation of S-carboxymethylglutathione.



Reduction of liver glutathione may have serious toxicological



consequences because the liver is more susceptible to



injury in the absence of this  compound (Hayes, 1975) .



     Johnson (1965, 1967) also noted that the morbidity and



mortality of young rats given  chloroethanol orally was



reduced by concomitant administration of ethanol.  He



postulated that the protective effect of ethanol was due to



simple substrate competition for alcohol dehydrogenase



which catalyzes the conversion of chloroethanol to



chloroacetaldehyde.  Ethanol also inhibited early effects



of chloroethanol on liver glutathione depletion in these



animals.  This author suggests also that the minimal toxicity



observed with chronic low inhalation doses of dichloroethane



in different animal species by Heppel et al. 1946) may be



explained simply by the rapid  replenishment of tissue



glutathione.

-------
                           VI I-4



     Over the past several decades, scientists have conducted



a great deal of research in an effort to establish the



mechanism(s) by which chemical substances exert their



carcinogenicity-  The somatic cell mutation theory of



carcinogenicity suggests that for a carcinogenic response



to occur, an irreversible change must occur in the cell



which results in proliferation of a neoplasm.  This change



reflects a mutational event in the DNA of that cell, suggesting



that the chemical carcinogen must interact directly with or



otherwise alter the DNA to initiate the change.  In recent



years, however, some substances have been shown to be carcino-



genic, but by mechanisms in which there apparently is no



direct interaction with or alteration of the DNA of the cell



by the substance.  Presumably, these compounds are not capable



of initiating the alteration of a normal cell to a neoplastic



one, but can facilitate expression of a neoplastic response



in latent cells.  On the basis of these purported differences



in mechanisms, carcinogens now are often classified into two



broad categories: genotoxic and epigenetic or non-genotoxic.



     The mechanisms by which a compound exerts its



carcinogenicity rarely can be determined by the chronic



testing of whole animals such as is done in the NTP bioassay.



Thus, a large number of short-term in vitro and in vivo



assay systems have been developed for the purpose of



elucidating mechanisms.  Since most of the in vitro testing



systems measure mutational events, and many carcinogens are

-------
                           VI I-5



mutagens, it is becoming accepted that positive results in



these test systems may  indicate genotoxicity.  The decision



as to whether a substance  is genotoxic can be made qualitatively



on the basis of several criteria: 1) a reliable, positive



demonstration of genotoxicity  in appropriate prokaryotic



and eukaryotic systems  in  vitro; 2) studies on binding to



DNA and 3) evidence of  biochemical or biologic consequences



of DNA damage (Weisburger  and Williams, 1981).



     No single test system appears capable of detecting all



carcinogens that are genotoxic.  Therefore, a number of



scientists have proposed testing batteries such that results



from each test within the  battery, when evaluated as a



whole, may allow one to make a conclusion about the mechanism



of carcinogenicity of a particular compound.  1,2-Dichloro-



ethane has not been systematically studied in any specific



battery of tests, but has  been evaluated in a number of



test systems that have  been proposed for inclusion in one



or more batteries.  Table  V-21 lists the results obtained



with 1,2-dicloroethane  in  a number of these short-term



test systems.  Each test system is designated as measuring



genotoxic or nongenotoxic  events.  In addition, there is



recorded a positive or  negative result for 1,2-dichloroethane



in the test system as well as  the reference citation.  Most



of the studies have appeared in the peer-reviewed literature.



     When considering the  body of data as a whole, it



becomes evident that 1,2-dichloroethane probably exerts its



carcinogenicity primarily  via  genotoxic mechanism(s).

-------
                            VIII-1


VIII. Quantification of Toxicological Effects


     The quantification of toxicological effects of a chemical

consists of an assessment of the non-carcinogenic and carcino-

genic effects.  In the quantification of non-carcinogenic

effects, an Adjusted Acceptable Daily Intake (AADI) for the

chemical is determined.  For ingestion data, this approach

is illustrated as follows:

     Adjusted ADI -    (NOAEL or MEL in mg/kg)(70 kg)
                     (Uncertainty factor)(2 liters/day)

The 70 kg adult consuming 2 liters of water per day is used

as the basis for the calculations.  A "no-observed-adverse-effect-

level" or a "minimal-effect-level" is determined from animal

toxicity data or human effects data.  This level is divided

by an uncertainty factor because, for these numbers which are

derived from animal studies, there is no universally acceptable

quantitative method to extrapolate from animals to humans,

and the possibility must be considered that humans are more

sensitive to the toxic effects of chemicals than are animals.

For human toxicity data, an uncertainty factor is used to

account for the heterogeneity of the human population in

which persons exhibit differing sensitivity to toxins.  The

guidelines set forth by the National Academy of Sciences

(Drinking Water and Health, Vol. 1, 1977) are used in estab-

lishing uncertainty factors.  These guidelines are as follows:

an uncertainty factor of 10 is used if there exist valid

experimental results on ingestion by humans, an uncertainty

factor of 100 is used if there exist valid results on long-

-------
                            VII1-2





term feeding studies on experimental animals, and an uncertainty



factor of 1000 is used if only limited data are available.



     In the quantification of carcinogenic effects, mathematical



models are used to calculate the estimated excess cancer



risks associated with the consumption of a chemical through



the drinking water.  EPA's Carcinogen Assessment Group has



used the multistage model, which is linear at low doses and



does not exhibit a threshold, to extrapolate from high dose



anjlmal studies to low doses of the chemical expected in the



environment.  This model estimates the upper bound (95%



confidence limit) of the incremental excess cancer rate that



would be projected at a specific exposure level for a 70 kg



adult, consuming 2 liters of water per day, over a 70 year



lifespan.  Excess cancer risk rates also can be estimated



using other models such as the one-hit model, the Weibull



model, the logit model and the probit model.  Current



understanding of the biological mechanisms involved in cancer



do not allow for choosing among the models.  The estimates



of incremental risks associated with exposure to low doses



of potential carcinogens can differ by several orders of



magnitude when these models are applied. The linear, non-



threshold multi-stage model often gives one of the highest



risk estimates per dose and thus would usually be the one



most consistent with a regulatory philosophy which would



avoid underestimating potential risk.



     The scientific data base, which is used to support the



estimating of risk rate levels as well as other scientific

-------
                            VIII-3



endeavors, has an inherent uncertainty.  In addition, in



many areas, there exists only limited knowledge concerning



the health effects of contaminants at levels found in drinking



water. Thus, the dose-response data gathered at high levels of



exposure are used for extrapolation to estimate responses at



levels of exposure nearer to the range in which a standard



might be set. In most cases, data exist only for animals; thus,



uncertainty exists when the data are extrapolated to humans.



When estimating risk rate levels, several other areas of



uncertainty exist such as the effect of age, sex, species



and target organ of the test animals used in the experiment,



as well as the exposure mode and dosing rates.  Additional



uncertainty exists when there is exposure to more than one



contaminant due to the lack of information about possible



additive, synergistic or antagonistic interactions.



Non-carcinogenic Effects



     The non-carcinogenic toxic effects of 1,2-dichloroethane



(1,2-DCE) in humans and other animals from both acute and



longer-term exposures at relatively high levels include



central nervous system (CNS) depression, liver and kidney



damage, gastrointestinal distress, adrenal and pulmonary



effects and circulatory disturbances.  The appearance and



intensity of these effects are dependent upon dose and duration



of exposure.  Death following high level acute exposures



usually results from respiratory or circulatory failure.



Delayed fatalities usually are due to renal damage. Fatty



degeneration in the liver, heart and adrenals also have been



observed.

-------
                            VIII-4





    - No information is available on the existence of any sub-



group of the human population which is likely to be more



susceptible to the toxicity of 1,2-dichloroethane, nor is



there any information on the nature of interaction between



1,2-DCE and other chemicals during multiple chemical exposure.



     Reported minimum acute lethal doses in non-human mammals



range from 600 to 2000 mg/kg (see Table VIII-1). Humans, however,



may be more sensitive to the acute effects of this substance



as there exists a case report describing the death of an



adolescent male following ingestion of about 350 mg/kg of



the solvent (Yodaiken and Babcock, 1973).



     Some of the effects occurring after extended exposure in



animals to 1,2-dichloroethane are described below in the



section on Quantification of Non-carcinogenic Effects. Different



effects were noted in rabbits exposed to 3000 ppm 1,2-DCE for



2 hr/day, 5 days/week for 90 days( Lioia and Elmino, 1959;



Lioia, et al, 1959). These authors reported that the animals



exhibited varying degrees of leukopenia and thrombocytopenia. In



addition, there was frequent hypoplasia of the granuloblastic



and erythroblastic parenchyma in the bone marrow. The cellular



concentration of leukolipids was reduced, but no changes occurred



in polysaccharides, peroxidase or RNA. The investigators suggested



that 1,2-DCE might exert a direct poisoning effect on bone



marrow.

-------
                            VIII-5
                         Table VIII-1

     Acute Lethal Doses of 1,2-Dichloroethane in Animals
Species Category3
Mouse
Rat
Guinea pig
Rabbit
Dog
Pig
LCLQ
LDL0
LDL0
LDL0
LCL0
LDL0
LD50
LCL0 . -
LDL0
LCL0
LDL0
LD50
LDL0
LDL0
LCL0
Dosage
5000 mg/m3
600 mg/kg
380 mg/kg
250 mg/kg
1000 ppm/4 hr
500 mg/kg
680 mg/kg
1500 ppm/7 hr
600 mg/kg
3000 ppm/7 hr
1200 mg/kg
860 mg/kg
2000 mg/kg
175 mg/kg
3000 ppm/7 hr
Route
Inhalation
Oral
Subcutaneous
Intraperitoneal
Inhalation
Subcutaneous
Oral
Inhalation
Intraperitoneal
Inhalation
Subcutaneous
Oral
Oral
Intravenous
Inhalation
aLCLQ:lowest published lethal concentration in air; LDLQ: lowest
reported lethal dose by any route other than inhalation;
median lethal dose by any route other than inhalation.

Source: NIOSH, 1977, p.388

-------
                            VIII-6

Quantification of Non-carcinogenic Effecfts

     The only toxicological study published to date in which

the test animals were exposed to 1,2-dichloroethane in their

drinking water was reported by Lane, et al. (1982).  The

duration of dosing varied from 5 to 25 weeks, depending upon

the particular protocol used.  The authors conducted a multi-

generation reproductive study which included screening for

dominant lethal and teratogenic effects.  Male and female

ICR Swiss mice received the test substance at concentrations

of 0, 0.03, 0.09 or 0.29 mg/1 (0, 5, 15, or 50 mg/kg/day).

Under the conditions of this study,  there appeared to be no

dose-dependent effects upon fertility, gestation, viability

or lactation indices.  Weight gain and pup survival were not

affected adversely.  No significant dominant lethal or tera-

togenic effects occurred in either of the two generations

tested.  The no-effect level of 50 mg/kg may not be the

highest no-effect level since no higher doses were given.

If one were to use the results of this study to derive an

acceptable daily intake (ADI) for non-carcinogenic toxicity,

it might be developed as follows:

  ADI:    50 mg/kg/day X 100%  =0.05 mg/kg/day(or 3.5 mg/day
                100 X 10                        for a 70 kg adult)


     Where:    50 mg/kg/day = No-observed adverse effect level (NOAEL)
                              for reproductive and teratogenic effects

               70 kg = weight of protected individual

-------
                            VIII-7


               100% = percentage of dose absorbed

               100 = uncertainty factor, appropriate for use with
                     NOAEL from animal data, and no equivalent
                     human data

               10 = uncertainty factor, for less than lifetime
                    exposure

     The study by Alumot, et al. (1976), in which 250 or 500

ppm 1,2-dichloroethane was added to the feed of rats for up

to two years, yielded no significant differences between

treated and control animals.  Even though the authors

recommended an acceptable daily intake (ADI) of 25 mg/kg,

inadequacies in the conduct and reporting of the study exist,

rendering this, experiment inappropriate for use in the deriva-

tion of an ADI.

     Longer-term inhalation exposures (up to eight months)  to

100 ppm 1,2-dichloroethane for 6 to 7 hours/day, 5 days/week

in a variety of animal species yielded no adverse effects as

measured by general appearance, behavior, mortality rates,

growth rates, organ function and blood clinical chemistry in

separate studies reported by Heppel, et al., 1946,  Spencer,

et al., 1951 and Hofmann, et al., 1971.  Exposures at higher

levels (400-500 ppm)  for the same duration did result in

increased mortality and some pathological findings, including

pulmonary congestion,  diffused myocarditis,  slight to moderate

fatty degeneration of  the liver, kidney,  adrenal and heart as

well as increased prothrombin time.  If one were to use the

NOEL of 100 ppm identified in these three studies to derive an

ADI for non-carcinogenic effects, the ADI might be developed

-------
                            VIII-8

as follows:

     ADI:  405 mg/m3 X 1 m3/hr X6hrX0.3X5 = 0.00745 mg/kg/day
                100  X    10       X          7   (or 0.521 mg/day
                                                  for a 70 kg adult)

Where:   405 mg/m3  = NOAEL of 100 ppm (1 ppm = 4.05 mg/m3)

         1 m3/hr = respiratory rate of adult human (pulmonary rate/
                   body weight ratio assumed to be the same for
                   humans and test animals)

         6 hours  exposure duration/day

         5/7 = conversion of 5 day/week dosing to daily for
               7 day/week

         0.3 = fraction of test substance absorbed (assumed)

         100 = uncertainty factor, appropriate for use with NOAEL
               from animal data and no equivalent human data

         10 = uncertainty factor, for less than lifetime exposure


     From the data presented above, it is obvious that alter-

ations in reproductive function do not represent the most sensitive

end point of toxicity to this substance.  The end-points

identified in the inhalation studies are,for now, more appropriate

indicators of 1,2-dichloroethane's noncarcinogenic toxicity.

Therefore, the ADI derived from this series of studies will

be used to develop an Adjusted ADI for noncarcinogenic

effects for 1,2-dichloroethane.  Assuming that there is no

exposure to 1,2-dichloroethane from other sources, the

Adjusted ADI would be derived thusly:

       7.45 ug/kg/day x 70 kg x 100%   = 0.260 mg/1
                   2 1


Where: 7.45 ug/kg/day * ADI for 70 kg adult

-------
                            VIII-9



       70 kg = body weight of protected individual

       100% = assumed percentage contribution to total
              exposure by drinking water

       21= volume of drinking water imbibed/day by
             70 kg adult

     The Adjusted ADI is derived to reflect allowable daily

exposure of a 70 kg adult drinking two liters of water

per day, and whose sole source of exposure to 1,2-dichloro-

ethane is via that drinking water. This calculation does not

reflect the associated carcinogenic risk.

Carcinogenic Effects

     Near lifetime exposure to 1,2-dichloroethane has been shown

to significantly increase tumor incidences at several sites

in both rats and mice when administered by gavage, but not

following inhalation exposures in these species (different

strains) or thrice weekly intraperitoneal injections as

measured by observing the incidence of lung adenomas in

Strain Amice (NCI, 1978; Maltoni, et al., 1980;  Theiss, et

al., 1977).  Negative results in the Strain A mouse system,

however, are not considered to be sufficient evidence that a

compound is not a carcinogen.

     1,2-DCE at doses of 47 or 95 mg/kg/day was administered

in corn oil by gavage five times weekly to 50 Osborne-Mendel

rats of each sex per group for 78 weeks followed by an

observation period of 23 weeks for males and 15 weeks for

females.  A statistically significant increase in the incidence

of squamous cell carcinoma of the forestomach and hemangiosarcoma

of the circulatory system was observed in male but not  female

-------
rats (P < 0.04).  The female rats had a significantly increased
incidence of adenocarcinoma of the mammary glands (P < 0.002)
(NCI, 1978).
     In a complementary gavage study, 50 hybrid B6C3F1 mice
of each sex per group were dosed five times weekly for 78
weeks with 195 or 97 mg/kg/day in corn oil for male mice and
299 or 149 mg/kg/day in corn oil for female mice.  The mice
were observed for 12 to 13 weeks following cessation of the
treatment.  A statistically significant increase in the
incidence of mammary adenocarcinoma (P < 0.04) and endometrial
stromal polyps or sarcomas (P < 0.016) was seen in the female
mice; the incidence of alveolar/bronchiolar adenomas was
increased in both sexes (P < 0.028) (NCI, 1978).
     In an inhalation study, Swiss mice or Sprague-Dawley rats
of each sex were exposed to 607.5, 202.5, 40.5, or 20.3 mg/m3
of 1,2-DCE for 7 hours daily, 5 days per week for 78 weeks
(Maltoni, et al., 1980).  At the end of exposure period, the
animals were allowed to live out their natural lives.  In no
case did the incidence of a particular type of tumor appear
to be dose-related.  In this interim report, the authors
concluded that 1,2-DCE was not carcinogenic under the conditions
of their experiment.
     Several explanations have been proposed to reconcile the
differences in the results of the gavage and inhalation
studies.  These are presented in some detail in Chapter V.

-------
     In spite of the purported inadequacies of the bioassay,



NCI did conclude that under the conditions of the study, 1,2-



dichloroethane was carcinogenic to Osborne-Mendel rats and to



B6C3F1 mice (NCI, 1978). The National Academy of Sciences Safe



Drinking Water Committee, in its updated assessment of the



toxicity of 1,2-dichloroethane, recommended that additional



long-term oral ingestion studies employing several species



of animals be conducted to determine if 1,2-DCE is a carcinogen,



and, if so, which organs are involved in different species,



the nature of uptake, metabolism and accumulation of DCE and



its metabolites, and minimum times and doses of DCE required



to induce tumors (NAS, 1980).



     On the basis of the results of the NCI bioassay, the



International Agency for Research on Cancer (IARC) concluded



that there was sufficient evidence for 1,2-dichloroethane's



carcinogenicity in test animals.  For compounds classified



as having sufficient evidence of carcinogenicity in animals,



but lacking adequate data in humans (which would be the case



for 1,2-dichloroethane), IARC states that "it is reasonable,



for practical purposes, to regard such chemicals as if they



presented a carcinogenic risk to humans" (IARC, 1979).



     1,2-Dichloroethane was shown to be carcinogenic by the



oral route, the same route by which individuals would be



exposed to 1,2-dichloroethane when it is present in their



drinking water.  Therefore, one must determine whether or not



a carcinogenic risk exists and, if so, estimate the magnitude



of that risk to individuals drinking water which contains

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                            VIII-12





measurable levels of this substance.



     1,2-DCE has been studied in a variety of short-term



test systems which evaluate the mutagenic potential of the



compound and/or its potential for interaction with DNA.



The results of these studies are summarized in Table V-21.



Positive results in certain of these test systems are considered



to be predictive of carcinogenic potential.



     When considering the body of data as a whole, it becomes



evident that 1,2-dichloroethane possesses the potential to



exert its carcinogenicity via genotoxic mechanism(s).



Quantification of Carcinogenic Effects



     Using methodology described in detail elsewhere, the



EPA's Carcinogen Assessment Group (CAG) has calculated estimated



incremental excess cancer risks associated with exposure to



1,2-dichloroethane in ambient water, extrapolating from



data obtained  in the NTP Bioassay in male rats with this



compound (increased incidence of hemangiosarcomas) ( U.S.



EPA, 1980; NCI, 1978). CAG employed a linear, non-threshold



multistage model to estimate the upper bound 95% confidence



limit of the excess cancer rate that would occur at a specific



exposure level for a 70 kg adult, ingesting 2 liters of



water and 6.5 g of fish and seafood/day ("fish factor"),



every day over a 70-year lifespan.



     The National Academy of Sciences (NAS, 1980) and



EPA's CAG (Anderson, 1983) have estimated upper 95%



confidence limit excess cancer risk rates associated with



consumption of 1,2-dichloroethane via drinking water alone.

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                           VIII-13







Each group used the linearized, non-threshold multistage



model. HAS derived its estimates using data from the NCI



bioassay showing an increased incidence of squamous cell



carcinomas of the forestomach in male rats, mammary tumors



in female rats and mice, endometrial tumors in female mice



and lung adenomas in mice of both sexes.  CAG generated its



estimates based upon 1) mammary adenocarcinomas in female



mice, 2) mammary adenocarcinomas in female rats, 3) squamous



cell carcinomas in the forestomach of male rats, and 4) a



combined risk incorporating the above three as well as the



heraangiosarcomas in male rats. It is this combined risk



( 4)) that the ODW has chosen to represent CAG's extrapolation



for drinking water.



     In all three instances, a range of 1,2-dichloroethane



concentrations were computed that would be estimated to



increase the risk by one excess cancer per million (10^),



per one hundred thousand (105) and per ten thousand (104) in the



population over a 70-year lifetime assuming daily consumption



of 2 liters of water by a 70 kg adult at  the stated exposure



level. The ranges of concentrations and associated estimated



risks are summarized in Table VIII-2.

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                           VIII-14


                         Table VIII-2


Drinking Water Concentrations and Estimated Excess Cancer Risks

                         Range of Concentrations (ug/l)a
Excess Lifetime
Cancer Risk
10-4
10-5
10-6
0
CAGb
94
9.4
0.94
0.00
CAGC
59.9
6.0
0.6
0.00
NASd
70
7
0.7
0.00

a Assumes the consumption of two liters of water per day by 70
  kg adult over a lifetime; number represents 95% upper bound
  confidence limit

b (U.S. EPA, 1980)

c (Anderson, 1983)

d (NAS, 1980)

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                           IX-1

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                             IX-4

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                            IX-5

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 1978. "Mutagenic  Effects of Petrol in Drosophila  Melano-
 gaster;  I.  Effects of Benzene and 1,2-Dichloroethane.
 Mutat. Res.  17:163-167.

 Page, B.D., e_t a^_. , 1975.  Determination of Methylene
 Ethylene Dichloride and Trichloroethylene as Solvent Residues
 in Spice Oleoresins.  58(5):1062-1068.

 Patterson, R.M.,  M.I. Bornstein and E. Garshick, 1975.
 "Assessment of  Ethylene Dichloride as a Potential Air
tPollution Problem."  Vol. Ill, Report No. GCA-TR-75-32-GC3)
 GCA Corp., Bedford, Massachusetts.

 Pelizzari, E.D.,  1978.  "Quantification of Chlorinated
 Hydrocarbons in Previously Collected Air Samples."  U.S.
 EPA, RTP, N.C.  EPA 450/3-78-112.

 PEDco, 1979.  Monitoring of ambient levels of EDC near
 production and  user facilities.  Prepared for Office of
 Research and Development, U.S. Environmental Protection
 Agency.  Contract No. 68-02-2722.   Research Triangle Park,
 N.C. EMSL, U.S. EPA 600/4-79-029

 Pervier, J.W.,  R.C. Barley,  D.E. Fiels, B.M. Friedman,  R.B.
 Morris and W.A. Schwartz, 1974.  "Survey Reports on
 Atmospheric Emissions from the Petrochemical Industry."
 Vol. II. EPA 450/3-73-005b.   EPA,  Research Triangle Park,
 North Carolina.

 Plaa, G. and R. Larson,  1965.   "Relative Nephrotoxic Properties
 of Chlorinated  Methane,  Ethane and Ethylene Derivatives in Mice.
 Toxicol. Appl.  Pharmacol.  7:37-44.

 Radding, S.,  D.H. Liu, H.L.  Johnson and T. Mill, 1977.
 "Review of the  Environmental Fate  of Selected Chemicals."
 SRI International.  EPA 560/5-77-003,  OTS , EPA.
n

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                           1A-IU

Rannug, U. and B. Beije, 1979.  "The Mutagenic Effect of
1,2-Dichloroethane on Salmonella Typhimurium.  n.  Activa-
tion by the Isolated Perfused Rat Liver."  Chem.-Biol
Interactions. 24(1979)265-285.

Rannug, U., A. Sundvall and C. Ramel, 1978.  "Mutagenic
Effect of Dichloroethane on Salmonella Typhimurium."  I.
Activation Through Conjugation with Glutathione in vitro.
Chem.-Biol. Interactions.  20:1-16.

Rao, K.S., J.S. Murray, M.M. Deacon, J.A. John, L.L. Calhoun
and J.T. Young, 1980.  Teratogenicity and Reproduction Studies
in Animals Inhaling Ethylene Bichloride.  In:  The Banbury
Report No. 5.  Ethylene Bichloride:  A Potential Health Risk?
Ames, B.f P. Infante and R. Reitz, eds.  Cold Spring Harbor,
N.Y.  Cold Spring Harbor Laboratory.  pp. 149-161.

Rapoport, I.A.  1960.  The Reaction of Genie Proteins with
1,2-Dichloroethane.  Dokl.  Biol. Sci.  134:745.

Reinfried, H., 1958.  "On Lethal Poisonings Due to Ingestion
of 1,2-Dichloroethane Containing Rubbing Compounds."
Dtsch. Gesundheitswes.  13:778-779.

Rothon, R.N. 1972.  "Petroleum and Organic Chemicals."
Chemical Technology:  An Encyclopedic Treatment."   Vol.  4,
Barnes and Noble, New York, pp. 201-209.

Rozenbaum, N.D., 1947.  "Ethylene Dichloride as an Industrial
Poison."  Gig. Sanit. 12:17-21.

Roubal, J., 1947.  "Two Fatal Cases of Intoxication with
Symmetric Dichloroethane Ingestion."  Cas Lek Cesk 86:203-
206.

Sato, A. and T., Nakajima, 1979.  "A Structure-Activity
Relationship of Some Chlorinated Hydrocarbons."  Arch.
Environ. Health 34(2)69-75.

Sax, N.I., 1975.  "Ethylene Dichloride."  In: Dangerous
Properties of Industrial Materials, 4th Ed.,  Van Nostrand
Reinhold Co.,  New York,  p. 736.

Sayers, R.R.,  W.P. Yant, C.P.  Waite and F.A.  Patty,  1930.  "Acute
Response of Guinea Pigs to Vapors of Some New Commercial Organic
Compounds:  I. Ethylene Dichloride-"  Public  Health Reports
45:5 225-235.

Schoenborn, H.,  W. Prellwitz and P. Baum, 1970.   "Consumption
Coagulation Pathology of 1,2-Dichloroethane Poisoining."
Klin.  Wochenschr.  48:822

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                            IX-11

Schwartz, W.-A.f  F.G.  Higgins, Jr., J.A.  Lee,  R.  Newirth and
J.W. Pervier,  1974.   "Engineering and Cost Study of Air Pollution
Control  for the  Petrochemical Industry."  Vol. 3,  Ethylene
Bichloride Manufacture by Oxychlorination.  EPA  450/3-73-
006c.  EPA, Research  Triangle Park, NC.

Secchi,  G.C.,  G. Chiappino, A. Lotto, and N.  Zurio, 1968,
"Actual  Chemical Composition of the Commercial Trieline and Their
Hepatotoxic Effect -  Clinical and Enzymological  Studies."
Med. Lav. 59:486-497.

Shakarnis, V., 1969.  Induction of X Chromosome  Nondisjunctions
and Recessive  Sex Linked Lethal Mutations in  Females of Drosophila
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Shchepotin, B.M. and  Y.D. Bodarenko, 1978.  "Clinical Syndromes
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Simmon,  V.F.   Unpublished.  Cited in Simmon, V.F.  1980.
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Simmon,  V.F.,  J. Kauhanen, K. Mortelmans and R.G. Tardiff.
1978.  Mutagenic Activity of Chemicals Identified in
Drinking Water.  Mutat. Res. 53:262 (ABSTf"   "

Smirnova, N.A. and H.P. Granik, 1970.   "On the Remote Effects
of Acute Occupational Poisoning with Some Carbohydrates and Their
Derivatives."  Gig. Tr. Prof. Zabol 14(S);50-51.

Spencer, B.C., V.K. Rowe, E.M. Adams,  D.D. McCollister and
D.D. Irish, 1951.  "Vapor Toxicity of Ethylene Dichloride
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Stewart, R.D., 1967,  "Poisoning  from Chlorinated Hydrocarbon
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Storey,  C.L., L.D. Kirks and G.C. Mustaker,  1972.  "Fate  of
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Entomol.  65(4) :1126-1129 .

Stuhlert, H.,  1949.   "Fatal Poisoning from Ethylene Chloride-"
Detsch. Med. Wochenschr. 74:1542-1543.

Sykes,  J.F. and A.K. Klein, 1957.  "Chloro-Organic Residues
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Assoc.  Off. Agricul. Chem. 40(1):203-209 .

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                           IA-.L f.

Symons, J.M., T.A. Bellar, J.K. Carswell, J. DeMarco, K.L.
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Urosova, T.P., 1953.  "The Possible Presence of Dichloroethane
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U.S. EPA, 1975a.  "Standard Support on Environmental Impact
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U.S. EPA, 1977a.  Survey of Operating and Financial
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U.S. EPA, 1977b.  National Organics Monitoring Survey.
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U.S. EPA, 1978.  Personal communication citing Stanford
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U.S. EPA, 1979.  Formulations of a Preliminary Assessment
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U.S. EPA, 1980a.  Survey of EPA Regional Drinking Water
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U.S. EPA, 1980b.  Level I Materials Balance, 1 ,2-Dichloroethane
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U.S. EPA, 1980c.  The Occurrence of Volatile Organics in
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Environmental Protection Agency, Washington, D.C.

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                            IX-13

 U.S. EPA Carcinogen Assessment Group, 1980e.  Memo to J.A.
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 U.S. EPA,  1980f.  Carbon Tetrachloride;  Pesticide Programs;
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 U.S. EPA,  1981a.  Community Water Supply Survey (Office  of
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 Vozovaya,  M.A., 1971.  "Changes in the Estral  Cycle of White
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 Vozovaya,  M.A., 1975.  "The Effect of Low Concentrations  of
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 Vozovaya,  M.A., 1976.  "Effects of Low Concentrations of
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 Animals."   Gig. Saint. 6:94-96.

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                            IX-14

Weast,  R.  1977.   "Handbook  of  Chemistry and Physics."  59th
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