EPA-540/1-86-028
Environmental
Agency
                                          ice of Emergency and
                                        ^medial Response
                                       Washington DC 20460
               Superfund
Off'ce of Research and Development
Office of Health and Environmental
Assessment
Environmental Criteria and
Assessment Office
Cincinnati OH 45268
                HEALTH  EFFECTS  ASSESSMENT
                FOR  METHYLENE  CHLORIDE

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                                           EPA/540/1-86-028
                                           September  1984
       HEALTH EFFECTS  ASSESSMENT
         FOR  METHYLENE CHLORIDE
    U.S. Environmental  Protection Agency
     Office of Research and  Development
Office of  Health and Environmental Assessment
Environmental Criteria  and Assessment Office
            Cincinnati, OH  45268
    U.S. Environmental  Protection Agency
  Office of  Emergency and Remedial Response
Office of Solid Waste  and  Emergency Response
            Washington, DC  20460

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                                  DISCLAIMER

    This  report  has  been  funded  wholly  or  In  part by  the  United  States
Environmental  Protection  Agency under  Contract  No.  68-03-3112  to  Syracuse
Research Corporation.  It has been  subject  to  the Agency's peer and adminis-
trative review, and  1t has  been  approved  for  publication as an EPA document.
Mention of  trade  names or  commercial  products  does  not  constitute  endorse-
ment or recommendation for use.
                                      11

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                                    PREFACE
    This report  summarizes  and evaluates Information relevant  to  a prelimi-
nary  Interim  assessment  of  adverse health effects  associated  with methylene
chloride.   All   estimates   of  acceptable  Intakes  and  carcinogenic  potency
presented  1n  this  document  should  be  considered as preliminary  and  reflect
limited  resources   allocated   to  this  project.    Pertinent  toxlcologlc  and
environmental data  were  located  through  on-Hne literature searches  of  the
Chemical   Abstracts,  TOXLINE,   CANCERLINE   and   the  CHEMFATE/OATALOG  data
bases.  The basic literature searched  supporting this  document 1s  current up
to September, 1984.   Secondary sources of Information have  also  been  relied
upon  1n the  preparation of  this  report  and  represent   large-scale  health
assessment  efforts   that entail   extensive   peer   and  Agency  review.   The
following  Office of Health  and Environmental Assessment  (OHEA)  sources  have
been extensively utilized:


    U.S. EPA.   1980b.  Ambient Water  Quality Criteria  for Halomethanes.
    Environmental Criteria  and Assessment Office,  Cincinnati,  OH.  EPA
    400/5-80-051.  NTIS PB 81-117624.

    U.S.  EPA.   1982.   Addenda   to Hazard   Profiles  on  Halomethanes.
    Environmental   Criteria  and   Assessment  Office,   Cincinnati,  OH.
    Internal draft.

    U.S.  EPA.   1983b.  Reportable  Quantity  for   Olchloromethane.   Pre-
    pared  by  the  Environmental Criteria and  Assessment  Office,  Cincin-
    nati,  OH,, for   the  Office of  Solid Waste  and  Emergency  Response,
    Washington,  DC.

    U.S. EPA.   1985a.   Health Assessment Document  for  Olchloromethane.
    Environmental  Criteria   and   Assessment   Office,  Research  Triangle
    Park, NC.  EPA  600/8-82-004F.  NTIS PB 85-191559.

    U.S.  EPA.   1985b  Addendum  to  the  Health  Assessment Document  for
    Dlchloromethane/Methylene  Chloride.   Updated  Carcinogen  Assessment
    of  Dlchloromethane   (Methylene  Chloride).   External   Review  Draft.
    OHEA, Washington, DC.  EPA 600/8-82-004FA.


    The Intent 1n these  assessments 1s  to suggest acceptable exposure  levels
whenever sufficient  data were  available.   Values were not derived or  larger
uncertainty  factors  were employed  when the  variable  data  were  limited  1n
scope tending to generate conservative (I.e., protective) estimates.   Never-
theless, the  Interim values  presented  reflect the  relative  degree of  hazard
associated with  exposure  or  risk  to the chemlcal(s) addressed.
                                      111

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    Whenever possible, two categories of values  have  been  estimated for sys-
temic toxicants (toxicants for which cancer  Is  not  the endpolnt of concern).
The  first,  the AIS  or  acceptable  Intake  subchronlc,  1s  an estimate  of  an
exposure  level  that  would not  be expected  to cause  adverse  effects  when
exposure occurs during  a  limited  time  Interval  (I.e., for  an  Interval that
does  not  constitute a  significant portion of  the  Hfespan).   This  type  of
exposure estimate  has not been  extensively used  or  rigorously  defined,  as
previous  risk  assessment  efforts  have  been  primarily   directed  towards
exposures from  toxicants  In  ambient air or water where lifetime exposure  1s
assumed.  Animal  data  used  for  AIS estimates  generally   Include  exposures
with  durations  of  30-90 days.   Subchronlc  human data  are  rarely available.
Reported exposures are  usually from chronic  occupational exposure situations
or from reports of acute accidental exposure.

    The  AIC,  acceptable  Intake  chronic,  1s  similar   1n concept to  the  ADI
(acceptable  dally  Intake).   It   1s  an   estimate  of  an exposure  level  that
would not  be expected  to  cause  adverse effects when exposure  occurs  for  a
significant portion  of  the Hfespan [see  U.S.  EPA (1980a)  for  a discussion
of  this  concept].    The  AIC  1s  route specific  and  estimates  acceptable
exposure  for  a given  route  with  the   Implicit  assumption that  exposure  by
other routes 1s Insignificant.

    Composite  scores  (CSs)  for  noncardnogens  have  also  been  calculated
where data  permitted.   These  values are used for ranking  reportable  quanti-
ties; the methodology for their development 1s  explained 1n U.S. EPA (1983a).

    For  compounds for which there  is sufficient  evidence of carc1nogen1dty,
AIS  and AIC  values  are not derived.   For a  discussion  of  risk assessment
methodology for  carcinogens  refer  to  U.S. EPA  (1980a).   Since  cancer  1s  a
process   that  1s  not characterized  by a threshold,  any exposure contributes
an increment  of risk.   Consequently,  derivation of AIS and  AIC values  would
be Inappropriate.   For  carcinogens, q-|*s  have been  computed based  on  oral
and inhalation data 1f available.
                                      1v

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                                   ABSTRACT
    In  order  to  place the  risk assessment  evaluation  1n  proper  context,
refer  to  the preface  of   this  document.   The  preface outlines  limitations
applicable to all documents of  this  series as well  as  the appropriate Inter-
pretation and use of the quantitative estimates  presented.

    The major Issue  of  concern  1s the amply demonstrated  cardnogenlcity  of
methylene chloride.  Human data  that rule out cardnogenlcity to  humans  are
not available  .   Animal experiments  have clearly demonstrated  the  cardno-
genlcity of methylene  chloride  In mice and strongly suggest  cardnogenlcity
1n  rats.   Methylene chloride has  been shown to  be mutagenlc In  Salmonella
and to  Increase  the number  of  chromosomal aberrations  1n cultured  Chinese
hamster ovary cells.   Negative  results were  obtained  for  mltotlc  recombina-
tion 1n yeast, 1n mutagenldty  tests  1n Drosophlla  and evaluations of sister
chromatld exchange  1n   cultured  Chinese  hamster  ovary cells.   A  human  q-|*
of  6.3xlO~4  (mg/kg/day)"1  has  been  estimated   for  Inhalation  exposure
from  a  rat  study  which   showed  an  Increased  Incidence  of  salivary  gland
sarcomas (U.S. EPA,  1985a).   An  evaluation of  the  draft results  of  the  NTP
(1985) bloassay  1s currnetly  1n  progress.

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                               ACKNOWLEDGEMENTS
    The  Initial  draft  of  this  report  was  prepared  by Syracuse  Research
Corporation under  Contract No.  68-03-3112  for EPA's  Environmental  Criteria
and  Assessment  Office,  Cincinnati,  OH.   Dr.  Christopher  DeRosa and  Karen
Blackburn were the Technical  Project Monitors  and  Helen Ball  was',the Project
Officer.  The final documents  1n  this  series  were  prepared for the Office of
Emergency and Remedial Response, Washington, DC.

    Scientists from  the  following U.S. EPA offices  provided  review comments
for this document series:

         Environmental Criteria and Assessment Office, Cincinnati, OH
         Carcinogen Assessment Group
         Office of A1r Quality Planning and Standards
         Office of Solid Waste
         Office of Toxic Substances
         Office of Drinking Water

Editorial review for the document series was provided by:

    Judith Olsen and Erma Durden
    Environmental Criteria and Assessment Office
    Cincinnati, OH

Technical support services for the document series  was provided by:

    Bette Zwayer, Pat Daunt, Karen Mann and Jacky Bohanon
    Environmental Criteria and Assessment Office
    Cincinnati, OH
                                      v1

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                               TABLE  OF  CONTENTS

1.
2.


3.










4.






5.
6.





7.

ENVIRONMENTAL CHEMISTRY AND FATE 	
ABSORPTION FACTORS IN HUMANS AND EXPERIMENTAL ANIMALS ,
2.1. ORAL 	
2.2. INHALATION 	
TOXICITY IN HUMANS AND EXPERIMENTAL ANIMALS 	
3.1. SUBCHRONIC 	
3.1.1. Oral 	
3.1.2. Inhalation 	
3.2. CHRONIC 	
3.2.1. Oral 	
3.2.2. Inhalation 	
3.3. TERATOGENICITY AND OTHER REPRODUCTIVE EFFECTS. . . .
3.3.1. Oral 	
3.3.2. Inhalation 	
3.4. TOXICANT INTERACTIONS 	
CARCINOGENICITY 	
4.1. HUMAN DATA 	
4.2. BIOASSAYS 	
4.2.1. Oral 	
4.2.2. Inhalation 	
4.3. OTHER RELEVANT DATA 	
4.4. WEIGHT OF EVIDENCE 	
REGULATORY STANDARDS AND CRITERIA 	
RISK ASSESSMENT 	
6.1. ACCEPTABLE INTAKE SUBCHRONIC (AIS) 	
6.2. ACCEPTABLE INTAKE CHRONIC (AIC) 	
6.3. CARCINOGENIC POTENCY (q-j*) 	
6.3.1. Oral 	
6.3.2. Inhalation 	
REFERENCES 	
Page
1
3
... 3
3
... 7
7
... 7
7
9
... 9
... 10
. , . 14
. . . 14
. . . 15
. . . 16
. . . 18
. . . 18
18
. . . 18
. . . 19
... 22
... 27
... 29
... 32
... 32
... 32
... 32
... 32
... 32
... 34
APPENDIX: Summary Table for Methylene Chloride ............   48

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                               LIST OF TABLES



No.                               Title                                Page
2-1
4-1
4-2
4-3
4-4
5-1
Absorption of Methylene Chloride by Human Subjects
(Sedentary Conditions) 	
Summary of Salivary Gland Region Sarcoma Incidence In Male
Rats 1n a 2-Year Inhalation Study with Dlchloromethane. . . .
Tumor Incidence In Rats Treated with Methylene Chloride . . .
Tumor Incidence In Mice Treated with Methylene Chloride . . .
Mutagenldty and Genotoxlclty of Methylene Chloride .....
Regulatory Standards and Criteria for Methylene Chloride. . .
4
20
23
24
25
30

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                             LIST  OF  ABBREVIATIONS

ADI                     Acceptable dally Intake
AIC                     Acceptable Intake chronic
AIS                     Acceptable Intake subchronlc
BCF                     B1oconcentrat1on factor
bw                      Body weight
CS                      Composite score
EKG                     Electrocardiograph
LOAEL                   Lowest-observed-adverse-effect level
NOEL                    No-observed-effect level
ppm                     Parts per million
SCE                     Sister chromatld exchange
STEL                    Short-term exposure limit
TLV                     Threshold limit value
TWA                     Time-weighted average
                                      1x

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                     1.   ENVIRONMENTAL CHEMISTRY AND FATE

    The relevant  physical  and  chemical properties and  environmental  fate of
methylene chloride (CAS No. 75-09-2),  also  known  as  methylene  dlchlorlde and
dlchloromethane, are shown below.
    Chemical class:
    Molecular weight:
    Vapor pressure:
    Solubility 1n water:
    Log octanol/water
    partition coefficient:
    Soil mobility:
      (predicted as retardation
       factor for a soil depth
       of 140 cm and organic
       carbon content of 0.087%)
    BCF:
    Half-life In air:
    Half-life 1n water:
halogenated aliphatic hydrocarbon
(purgeable halocarbon)
84.93
362.4 mm Hg at 20°C
(Callahan et a!., 1979)
13,030 mg/!t at 25°C
(Horvath, 1982)
1.25 (Callahan et al., 1979)
<1.2 (estimated)
2.3 (estimated)
53-127 days (Singh et al., 1981;
Maklde and Rowland, 1981)
1-6 days (estimated)
30-40 days 1n lake water
(Zoeteman et al., 1980)
    The  soil  mobility  value  has  been  estimated  from  a  comparison  of  the
octanol/water partition  coefficient  values  and the solubilities (Callahan et
al.,  1979)  of  this  compound with  those for  chloroform and  the retardation
factor for chloroform given by Wilson et al. (1981).
    The  estimated  half-life value for  methylene  chloride  in water  Is based
on  the  reaeratlon  rate  ratio  of   0.650   and  oxygen  reaeratlon  rate  of
0.19-0.96  day'1   (Mabey  et  al.,   1981).    The   difference  between  this
                                      -1-

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estimated half-life value and  the value given by  Zoeteman  et  al.  (1980)  for
lake water 1s probably due  to  the retardation  of  volatility due to suspended
and  sedlmentated  particulated  matter  1n  the  lake  water,  a factor  not  con-
sidered In estimating the half-life by the first  method.
    The BCF for methylene chloride has  been  estimated  from  Us octanol/water
partition coefficient value  and the equation  given by Velth  et  al.  (1979).
    The half-life of  methylene  chloride 1n soil  could not  be  located  1n  the
literature searched.  However, evaporation Is  expected to be  the predominant
loss mechanism from the  soil surface.   In  subsurface soil,  blodegradatlon  of
a chlorinated  aliphatic  hydrocarbon  such  as  methylene  chloride may be  slow
(Wilson  et  al.,  1983).   Therefore,  In  subsurface  soil,  the  nondegraded
methylene chloride 1s expected to leach Into  groundwater.
                                      -2-

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           2.  ABSORPTION  FACTORS  IN HUMANS AND  EXPERIMENTAL MAMMALS
2.1.   ORAL
    Pertinent data regarding the  absorption of  methylene  chloride  after  oral
exposure  could  not  be located  1n the  available  literature.   Roberts  and
Marshall  (1976)   Indicated  that  absorption  through  the  Intestinal  mucosa
appeared  to  be fairly  rapid  and  complete.   A number  of  reports of  severe
toxldty  following  1ngest1on   (Llewellyn,  1966;   Stewart  and  Hake,  1976;
FMedlander  et  al.,  1978)  also  Imply that  absorption following  1ngest1on
occurs.
2.2.   INHALATION
    The majority of  data  regarding absorption  of  methylene  chloride  pertains
to  Inhalation exposure because that  route  1s  most likely to be  Involved  1n
cases  of  occupational  exposure.   Several studies  1n  both  man and  experi-
mental animals have,  been  performed.   These data are summarized  from  U.S.  EPA
(1981a).
    R1ley  et  al.  (1966)  described the  kinetics of absorption  and  excretion
1n a 70 kg man exposed for  2  hours to 100 ppm methylene chloride 1n  air.   As
absorption progressed,  the  concentration  In alveolar  air  Increased,  Indicat-
ing decreased absorption  as a  steady-state condition was achieved.   In  this
study,  equilibrium had not been  reached  at   the  end  of  2  hours.   At  this
time,  exposure was  discontinued  and  methylene chloride  1n  exhaled  air  was
measured.  The decline  In concentration of methylene  chloride  1n  exhaled  air
appeared  to  be  exponential  and  roughly  proportional  to the amount  absorbed
during the exposure  period.  The  retention factors  expressed as a  percentage
of Inhaled dose 1n this and related studies are summarized 1n Table 2-1.
                                      -3-

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                                  TABLE 2-1

             Absorption of Methylene Chloride by Human Subjects*
                            (Sedentary  Conditions)
Inhalation
Concentration
(ppm)
50
100
150
200
662
806
1152
1181
44-680
100
100
200
250
500
750
Exposure
(hours)
7.5
7.5
7.5
7.5
0.30
0.50
0.50
0.50
2.00
2.00
4.00
2.00
0.50
0.50
1.00
Retention
(X)
70
60
63
60
74
75
72
70
31
53
41
51
55
55
34
Reference
DIVIncenzo and Kaplan, 1981



Lehmann and Schm1dt-Kehl, 1936



RHey et al., 1966
DIVIncenzo et al.. 1972


Astrand et al., 1975

Engstrom and Bjurstrom, 1977
*Source:  U.S.  EPA,  1981a
                                      -4-

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    The theoretical  absorption  of methylene chloride  during  short exposures
should be  related directly  to  the concentration  In  Inhaled  air.   Although
the protocol that generated  these  data  was  not  reported by U.S. EPA (1981a),
the data of Lehmann and Schmidt-Kehl (1936)  confirm this hypothesis.
    D1V1ncenzo and  Kaplan  (1981)  exposed  groups  of  4-6  volunteers  to  50,
100, 150 or  200  ppm methylene chloride for  7.5  hours.  Serial breath excre-
tion curves were  obtained.   Pulmonary absorption was  rapid during the first
hour,  then  began  to  decline as  steady-state  was  approached.   Postexposure
methylene chloride  exposures 1n  exhaled air  dropped  rapidly.   By  7  hours
after treatment was terminated, expired air  from those volunteers  exposed to
50, 100 or 150 ppm  contained <0.1  ppm methylene chloride.   The concentration
In expired air from those exposed to 200 ppm  declined to 1 ppm by 16 hours
post-treatment.   Respiratory elimination consistently accounted  for  <5% of
the total amount  of methylene chloride absorbed.
    Astrand  et  al.  (1975)  stated  that  the amount  absorbed   Increased  with
duration of  exposure  and  physical activity  (resulting in Increased  venti-
lation  and   cardiac  output).   Astrand  et  al.  (1975)  found   that  physical
activity for 0.5  hours during exposure to  250  or  500  ppm methylene chloride
doubled  absorption but  decreased  retention from  55  to  40%  because of  a
3-fold (6.9-22 8./m1nute) Increase 1n ventilation rate.
    Engstrom  and  Bjurstrom  (1977)  demonstrated  that  methylene  chloride
absorption  was  related  directly   to  degree of  obesity  1n  human  subjects.
Obese subjects (fat =  25% bw) absorbed  30%  more  methylene  chloride than  lean
subjects  (fat  =  8% bw)  when exposed  to 750  ppm  for  1  hour.   Biopsy  and
analysis of  subcutaneous  fat revealed a substantial (10.2 and  8.4 mg/kg  wet
                                      -5-

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tissue) concentration  1n  adlposa  after 1 and  4 hours postexposure,  respec-
tively.  Although  the concentrations  1n  fat  were  somewhat  lower  1n  obese
than  1n  lean subjects,  the total  amount  of  body  fat  resulted  In  greater
total methylene  chloride  absorption  1n  obese  subjects.
    Savolalnen et al.  (1977) exposed' rats  to air containing  200  ppm  methyl-
ene chloride 6 hours/day for 5 days.   Tissue concentrations were  measured  In
brain, blood, liver and peMrenal fat  on the 5th  day  of  exposure  after  0  (18
hours after  exposure  on  day 4),  2,   3,  4 and 6 hours of exposure.  Although
no  absorption  factors  were  discussed, the  persistence  In  peMrenal  fat
before exposure  on the fifth day Indicated considerable  retention In  adlposa
relative to other tissues.
                                     -6-

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                3.   TOXICITY  IN  HUMANS  AND  EXPERIMENTAL  ANIMALS
3.1.   SUBCHRONIC
3.1.1.   Oral.  No  reports of  subchronlc  oral exposure of  humans  to methyl-
ene chloride  have  been  located  1n the available  literature.   Only one study
of  subchronlc oral  toxldty of  methylene  chloride  1n  animals  was  found.
Bornmann and  Loeser (1967)  exposed 30 male  and  30 female  Wlstar  rats  for  3
months   to   drinking   water   containing  0.125   g  methylene   chloride/1.
Although actual  water   Intake,  hence  amount   of  methylene chloride, was  not
reported 1n  the secondary  source (U.S.  EPA,  1983b),  an  Intake  of 12.5  mg
methylene  chlor1de/kg/day  was  estimated  assuming rats  weigh 0.35 kg  and
drink  35 ml  of water/day.   No  difference  1n   behavior,  appearance,  body
weight or survival  of  treatment animals  was  observed compared  with an equal
number  of   control  animals.   No  significant  differences  In  hematologlc
values, urlnalysls  or  plasma  levels  of nonesterlfled fatty adds  were found
In 8-10 male  rats  from  each  group.   Blood  glucose levels  1n 10 treated males
were  slightly  elevated  compared with  10 control  males,  but all  values  fell
within the normal  range.  Estrous cycles,  as  evaluated  by microscopic  exami-
nation of  vaginal  smears,  Indicated no  changes  that were  due  to  treatment.
Necropsy and  histopathologlcal  examination  of  -20 animals of  each sex  and
group  revealed  no  lesions  1n  any  Internal organ  examined.   This  study
defined  a  free-standing NOEL of  12.5 mg  methylene chlorlde/kg/day In  rats
whose exposure was  from drinking water.
3.1.2.   Inhalation.   Inhalation  exposure  of  humans  to  methylene  chloride
1s  likely  to  be a  result  of occupational  exposure;  consequently,  long-term
exposure can  be expected.  Therefore,  studies  of  repeated exposure of  humans
to  methylene  chloride   are discussed  1n  Section  3.2.2.   Subchronlc  exposure
can  be expected  in the  case  of  the use of  consumer  products  containing
                                      -7-

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methylene  chloride,  such  as  paint  stripping products  and various  aerosol
cans containing  the  chemical.   Historically,  subchronlc  Inhalation  exposure
of  humans   to  methylene  chloride has  been  a concern  In  one  particularly
high-risk  occupation,  astronauts  exposed to  vapors  emanating  from materials
used 1n  the Interiors  of  spacecrafts.  Consequently,  several  Investigators
(Thomas  et al.,  1972;  Haun  et  a!.,  1971,  1972;   We1nste1n  et  al.,  1972;
MacEwen  et al.,  1972)  exposed laboratory  animals   to  atmospheric methylene
chloride for up  to 14  weeks.   The U.S. EPA (1983b)  summarized the results of
these  studies  as follows.   Mice  exposed to  25 or  100 ppm  (87  or  348 mg/m3)
methylene  chloride continuously  for  14 weeks  had an Increase  1n spontaneous
activity at  the  lower  concentration  but not  at  the  higher  one.   No  gross or
hlstologlcal lesions  were  found  at  autopsy,  except  that livers  of  the mice
exposed  to 100  ppm  stained  positive  for  fat.  HexobarbHal sleep  time was
unaffected,  but  hepatic levels of  cytochromes were  somewhat  altered.   Rats
subjected  to the same  exposure  regimens  had nonspecific renal  tubular degen-
eration  and  regeneration,  and  hepatic  cytoplasmlc  vacuollzatlon and positive
fat  staining  at both  exposure  levels.  Rats  appeared  to be  the more sensi-
tive species.   No  specific macro- or microscopic  organ changes  or changes 1n
hematologlc  or  clinical chemistry values  were noted  In  the  small number of
monkeys  In this  study.   Carboxyhemoglobln levels,   the  result  of metabolism
of  methylene  chloride  to carbon monoxide  and  subsequent  action  on  hemo-
globin,  were elevated  In monkeys  at  both exposure levels and 1n dogs only at
the  higher exposure,  but  there  was no  cumulative  Increase  1n carboxyhemo-
globln  over  the period  of exposure.  No overt  signs  of  toxldty or changes
1n body  weights  relative to controls were noted 1n any of these four species.
     Higher  levels  of  continuous  exposure  were  also Investigated.  Exposure
of   the  same  four  species  to   1000  or  5000  ppm  (3480  or   17,400  mg/m3)
                                      -8-

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resulted 1n  signs  of severe  toxldty  at the higher dose:   narcosis  for the
first  24  hours and  pronounced  lethargy for the  remainder  of  the  exposure
period, reduced food  consumption,  and  high rates  of mortality  1n mice, dogs
and  monkeys.   Rats  were  somewhat  less sensitive;  none died.   Liver  and
kidney  damage  were common  findings  1n  all  species.   At  the  lower  exposure
level  (1000  ppm),  only the  dogs  were  severely affected and died.   Mice and
rats did not show  overt  signs  of  toxlclty,  but  body weight gain was  slightly
depressed 1n the  rats.   Less severe hlstopathologlcal changes  than  had been
seen at  5000 ppm  were  noted  1n  the livers of all  four species and  1n the
kidneys of rats exposed  to 1000 ppm.  Monkeys  had no  significant changes 1n
hematologlc or  clinical chemistry values.
    Taken  collectively,   these  studies   seem   to   Indicate  that  subchronlc
exposure to  methylene chloride  causes  effects on  the Hver and  kidneys of
exposed  animals.    Lesions  In rats  exposed  to  25   or   100  ppm  methylene
chloride appear to be more  severe  than  lesions 1n mice exposed  to  the same
concentrations.  Monkeys and 'dogs  seem to  be  the  species least affected.  At
higher exposure concentrations  (1000 ppm),  dogs appear  to be  most  sensitive
and  to  experience  treatment-related  mortality.   A  level  of   25  ppm  (87
mg/m3)  1n  air  seems  to  define  a  LOAEL In rats  when  the  data from  these
studies are considered collectively.
3.2.   CHRONIC
3.2.1.   Oral.   No  reports of chronic oral  exposure  of humans  to  methylene
chloride have  been found  1n  the  available literature.  The National  Cancer
Institute has  completed  a 2-year  study with  rats  and mice,  In which  the
animals were treated with  methylene  chloride by gavage.   As  of May 1985, the
study had been  withdrawn pending further  review.
                                      -9-

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3.2.2.   Inhalation.  In humans mild  Intoxication  by methylene  chloride  re-
sults 1n  somnolence,  lassitude,  anorexia and mild  Ughtheadedness,  followed
by greater degrees  of  disturbed  central  nervous system  function  and  depres-
sion.   Permanent  disability has  not  been  reported.   When  fatalities  occur
the  cause has  been attributed  to cardiac  Injury and  heart failure  (NAS,
1978).
    Further reports  of  human Intoxication from methylene  chloride were pre-
sented by  NIOSH  (1976).  Most  of  the case  reports  were  concerned with  acute
exposure  and  are  not  discussed  here.    Most  of  the epidemlologic  studies
lack data  on  the  concentration  of  methylene chloride  In  breathing  space  air
or they are complicated  by exposure to other chemicals;  therefore,  they  are
not suitable for risk assessment.
    Weiss  (1967)  reported  a  case  of toxic encephalosls  1n  a chemist  exposed
for several hours  per  day  for  5 years to methylene chloride used In  a  salt-
recrystalUzatlon   operation.    Measurements   revealed   concentrations   of
660-3600  ppm  methylene  chloride  In workroom  air  with a  mean of 900 ppm In
the breathing zone.  This  worker  had  physical  contact with  liquid  methylene
chloride.
    Recent  ep1dem1olog1cal  studies  have  not  revealed   adverse  effects  1n
humans  occupatlonally-exposed  to  methylene  chloride.    FMedlander  et  al.
(1978)  reported  an ep1dem1olog1cal study  of male  workers  at Eastman  Kodak
exposed primarily  to methylene chloride.   The  workers  had  been exposed  to
TWA concentrations of 30-125 ppm methylene  chloride  (estimated both  from  air
monitoring  and   blood  carboxyhemoglobln  levels)   for ojp to  30  years.    A
proportionate mortality  study,  using death  certificates  from   334  exposed
workers who  died from 1956-1976,  was performed.   A  cohort  mortality  study
Involving  all   751  workers  employed  1n  the exposure  area in   1964 and  a
                                     -10-

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separate analysis of  a  subgroup  of 252 of these workers  exposed  for  a mini-
mum of  20  years by 1964 were  also performed.   Data from  this  subgroup were
analysed separately to  discuss effects requiring long  latency  periods.   The
follow-up period 1n the cohort mortality  study  was  13  years.   Control groups
consisted of  other  Eastman  Kodak  male employees working In production  but
not  exposed  to  methylene  chloride,   New  York  State   male  cause- and  age-
specific  mortality   rates   and  United States  male  age-specific  mortality
rates.   Follow-up of  workers  aged  >25 years  was >97%  as of 1964.   None  of
these studies revealed any  Indication  of  Increased  risk of death  from circu-
latory disease Including 1schem1c heart disease, cancer or other causes.
    More  recently,  Ott  et  al.   (1983)  Investigated  mortality and  current
cardiac  health  In  workers   from  a  fiber  production  plant  In  which methylene
chloride was  used  as a  solvent.  Reasoning   that  metabolism  of  methylene
chloride to carbon monoxide  results 1n an  Increase  1n  percentage  of carboxy-
hemoglobln  with  a  commensurate  decrease  1n  the oxygen-carrying  capacity  of
the  blood,  these  authors  (Ott   et  al.,   1983) suggested  that exposure  to
methylene  chloride  may  lead  to  an  Increase   1n the  Incidence of  1schem1c
cardiac  disease.  Data  on  mortality  were  obtained  from  a  cohort  of  workers
1n a  fiber  manufacturing plant exposed for at  least 3  months between  January
1,  1954 and  January  1, 1977  to a TWA  of -140  ppm methylene chloride.   A
control  cohort  was  composed of  workers  In  another  part  of  the plant  not
exposed  to  methylene  chloride.  Another  cohort was the  expected  death data
for 5-year  Intervals  matched by  race  (white and nonwhHe)  and  sex.   Mortal-
ity data Indicated  no Increase 1n deaths  In either  men or  women  from circu-
latory  system diseases,  Ischemlc  heart  disease as  a   separate category,  or
malignant neoplasms  associated with exposure  to methylene chloride.
                                     -11-

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    In another  study  of cardiac function,  these  Investigators (Ott  et  al.,
1983} collected  24-hour EKG data  from 50  workers  from two  fiber  producing
plants.    Data  regarding  24 workers  from  the  plant where  exposure to  TWA
concentrations of 60-475  ppm methylene chloride occurred were  compared  with
data from 26  workers  from a similar plant  not  using methylene  chloride.   No
significant  changes 1n  ventricular  or  supraventrlcular  ectoplc  activity,  nor
episodic  ST  segment  depression  were associated with exposure to  methylene
chloride.
    Burek et  al.  (1980) briefly discussed  other epldemlologlc  studies   (Ott
et  al.,  1980a,b;   Skory,   1980;  Skory  et  al.,  1980a,b)   that   apparently
revealed  no adverse health effects  attributable to  methylene  chloride.   The
titles of some  of   these  papers  Indicated  that more  sensitive  parameters  of
toxldty  were  evaluated  than  those studied  by FMedlander  et al.  (1978).
Exposure data from  these  studies  were  not  available  1n  the  secondary source
from which this  discussion was  taken (Burek et al.-,  1980).
    Cherry et  al.   (1981)  reported  that   a  group  of  46 men  occupationally
exposed  to 75-100  ppm methylene chloride  for  an unspecified  length  of  time
complained of excessive neurological symptoms.   Clinical  examinations,  motor
conduction velocity measurements, EKGs  and a battery of  psychological  tests
"designed to  detect  minimal  brain   damage"  were administered  to  29 of  the
exposed  men  and an equal  number  of age-matched  unexposed  men employed  at
similar  jobs.  The  results  revealed no evidence of  cardiac  abnormalities  or
neurological  or  behavioral  Impairment  associated with  exposure to  methylene
chloride.
    Burek et  al.  (1980,  1984)  and   Dow Chemical  Co. (1980)  studied  chronic
Inhalation exposure  of  animals  to  methylene chloride.  Sprague-Dawley  rats
(SPF-der1ved,   129/sex/exposure  concentration)  and   Golden  Syrian  hamsters
                                     -12-

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(~108/sex/exposure concentration) were  exposed  to 0,  500,  1500 or  3500  ppm
(0, 1740,  5220  or 12,180  mg/m3) methylene  chloride  of >99%  purity.   Expo-
sures  were  for  6  hours/day,  5  days/week  (excepting  holidays)  for  up to  2
years.  Rats were  subjected  to Interim kills at  6,  12, 15 or  18  months  for
cytogenetlc or  general chemical and  histopathologlcal  studies.
    During  the  first  week of  exposure, rats 1n  the  high group exhibited  a
slight  decrease 1n  physical   activity, but  appeared  to return  to  normal
activity for the remainder of  the trial.   During  the  first 2 months, rats in
all groups  suffered  a  disease believed to  be  sialodacryoadenitls, a  tran-
sient  viral  Involvement  of  the salivary glands.  No  increased mortality  was
associated  with the  disease.    None  of the  exposure  levels   affected  body
weights, clinical  chemistries,  or  hematologic or urlnalysis values  in  rats.
Carboxyhemoglobln  levels ranged  from  0-5.3%  1n controls  and  8.9-20.4% 1n
exposed rats but  did not  appear  to be dose-related  nor  related  to  time of
exposure.    Mortality  was   unaffected  by   treatment  except   that  high-dose
females had a   significantly  elevated  mortality  rate  starting at  the  13th
month of exposure.
    Mean  Hver  weights   were  increased  in  both male  and  female rats  1n  the
high-dose  group,   which  was  first   noticed  at  the  18-month   Interim  kill.
Histopathologically  significant alterations  related  to  methylene  chloride
were  found  only  1n   the liver.  An increased  incidence of  hepatocellular
vacuolization  indicative  of   fatty  degeneration was   noted  In all  exposed
groups  of  rats.   Incidence and severity appeared  to be dose-related.  Multi-
nucleated  hepatocytes,  a spontaneous geriatric  change in female  rats,  were
observed after  12  months in exposed  and treated groups alike.   A significant
Increase  in the number  of  fod  of altered  hepatocytes  was  observed in high-
dose  females.   Males  exposed  to 1500 or 3500 ppm had an  Increased incidence
                                     -13-

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of  hepatocellular  necrosis and  coagulation  necrosis.  Some  females  exposed
to  500  ppm for 12 months  appeared to have slightly  Increased  hepatic  hemo-
slderln.   High-dose  group  female  rats and middle- and high-dose  male  rats
had a  decreased  Incidence or severity of  chronic  progressive glomeruloneph-
ropathy, another normal  geriatric  change,  compared with controls.   High-dose
male  rats,  consequently,   exhibited  less  severe   nonrenal   lesions  (uremlc
pneumonHls,  mineralization  of  organs  and  blood  vessels,  brain  malaria,
myocardlal  degeneration,  etc.)  associated with  chronic  progressive  renal
disease.
    In  this  study  hamsters  appeared  to  be  less   sensitive  to  methylene
chloride  than  did rats.   Although carboxyhemoglobin  levels  were  higher  In
hamsters  (0.3-4.0%  1n control groups,  22.2-34.6%  1n  treatment  groups)  than
In  rats,  no clear  evidence of toxldty was observed  In hamsters.   Methylene
chloride-exposed  hamsters   exhibited  a decreased  Incidence  or  severity  of
amyloid deposition In  their tissues,  a normal  geriatric change  In hamsters,
compared with controls.
    In  rats,  this   study  appeared   to  define  a   LOAEL   of  500  ppm  (1740
mg/m3), associated with  mild  hepatomegaly and mild  hepatocellular  vacuoll-
zatlon Indicative of  fatty  Infiltration.   Assuming a  body  weight for  rats  of
0.35 kg and an Inhalation  rate  of 0.26  mVday, exposure  for 6  hours/day,  5
days/week  resulted 1n an Intake of 230.8 mg/kg/day.
3.3.   TERATOGENICITY AND OTHER REPRODUCTIVE EFFECTS
3.3.1.   Oral.   Pertinent  data   associating   oral  exposure  of  humans   to
methylene  chloride with  terata or  reproductive effects could not  be  located
1n  the available  literature.   The  estrous cycle In  female rats  was reported
to  be  unaffected  by  exposure  to  0.125 g  methylene chloride/1  1n  their
drinking water for 3  months (Bornmann and  Loeser, 1967).
                                     -14-

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3.3.2.   Inhalation.   Pertinent  data  regarding  teratogenldty or  reproduc-
tive dysfunction In humans exposed by  Inhalation  to  methylene chloride could
not be  located  1n  the available  literature.   Schwetz et  al.  (1975)  exposed
Swiss-Webster  mice  and  Sprague-Dawley  rats  to  1250  ppm  (-4350  mg/m3)
methylene chloride for 7 hours/day on  days  6-15  of gestation.  House fetuses
were  collected  and examined  on  day  18 and  rat  fetuses  were  collected  and
examined  on  day   21  of  gestation.    Dams  of  both   species  were  minimally
affected; slightly  Increased  carboxyhemoglobln  formation  was  the  only effect
reported.   Delayed development  (manifestations  unspecified)  was  the  only
effect  noted  1n  rat fetuses;  1n  mouse fetuses,  slightly  advanced  ossifica-
tion of the sternebrae were noted, suggesting accelerated development.
    The  teratogenic effect  of methylene  chloride 1n rats was  also Investi-
gated by  Hardin  and Manson  (1980).   Groups of 26-28  Long-Evans  hooded  rats
were  exposed  to 4500  ppm  (-15,600  mg/m3) methylene  chloride for 6 hours/
day (group  one  before -and  during  gestation,  group  two- before  gestation  and
group  three  during  gestation).    "Before  gestation"  exposures  were the  3
weeks Immediately  preceding  mating and "during gestation" exposures Included
the first 17  days  of  gestation.   Gravlda  from 16-18  dams/group were examined
on day 20 of gestation.
    A  slight but  significant decrease  1n  fetal  body  weight  occurred  1n
groups exposed during  gestation compared  with controls  and the group  exposed
only  before gestation.   No  other  abnormalities  were  reported.  Bornscheln et
al.  (1980)  reported on  the  behavioral effects on the  pups  of 10  dams  from
each  group  allowed to deliver.  No  statistically significant differences 1n
body  weight  were  noted  In  any  of   the  treatment  groups  compared  with
controls, up  to  400 days of  age.   Treatment  appeared to  have  no  effects on
food and water consumption, wheel  running activity or avoidance learning.
                                     -15-

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    The minor and reversible effects on  fetal  development  1n  mice exposed to
1250  ppm  (-4350 mg/m3)  methylene  chloride  reported  by  Schwetz  et  al.
(1975) appeared  to  be  a LOAEL  1n  this  study.   Exposure  for 7  hours/day,
assuming mice  Inhale  0.05 mVday  and  weigh 0.03  kg,  resulted 1n  an  Intake
of  2114.6  mg methylene chlor1de/kg/day.  This  Intake  1s more  than  50  times
greater  than  the Intake (26.6 mg/kg/day)  1n  humans associated with  occupa-
tional exposure  to  261  mg/m3 (10 m3  Inhaled/day,  human  body weight  of  70
kg) 1n the study by Cherry et  al.  (1981).   Hence,  these data  will not Impact
risk assessment.
3.4.   TOXICANT INTERACTIONS
    No studies of toxic Interactions of methylene  chloride with  other  xeno-
blotlcs  have  been found 1n  the available literature.   Some  Interesting case
histories  1n  humans,  however,  suggest  that  Interactions  with  other compounds
may occur.   Functional  circulatory disorders 1n  workers  exposed for >3  years
to  methylene chloride  and  other  organochlqrlne compounds at  "permlssable"
levels have  been reported (Dunavsk11,  1972).  The  symptoms,  Including  chest
pain,  EK6 Irregularities,  bradycardla,  decreased  myocardlal  contractility
and altered  adaptation  to physical stress,  were not attributed to methylene
chloride alone.
    The  metabolism of methylene  chloride to carbon monoxide  forms  the  basis
for concern  about combined  exposure  to methylene chloride and carbon monox-
ide.   Fodor  and  Roscovanu (1976)  reported  that exposure of human subjects to
500  ppm of  methylene  chloride  (for  an unspecified  duration)  resulted  In
levels of  carboxyhemoglobln  1n blood  comparable with  those  produced by the
TLV  for   carbon  monoxide,  50 ppm.   Mixed  exposures  could  pose  a  serious
threat   to  the  well  being  of  occupatlonally-exposed  workers,  smokers  or
cardloresplratory patients.
                                     -16-

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    Savolalnen et  al.  (1977) expressed  concern  about  exposure to  methylene
choMde and other lypophHlc solvents resulting  1n enhanced danger  of  marked
central nervous system and metabolic  effects.
    Chrlstenson and Hu1z1nga (1971)  reported  the case  of a 17-year-old  male
found  dead  1n a  turret where  he  had been  using a  mixture of 80%  methylene
chloride and  14.9% methanol to  remove  paint.   Barbiturate derivatives  were
found  1n  the  blood,  brain,  urine  and  stomach contents.  Death was  ascribed
to the combination of methylene chloride and  barbiturates.  This  report  sug-
gested the  ability  of barbiturates  to  potentiate the  toxldty of  methylene
chloride.
    Finally,  two reports  of  phosgene poisoning  related  to  methylene chloride
(GerrHsen  and  Buschmann, 1960;  English,  1964)  point  out  that   phosgene,  a
combustion  product  of  methylene  chloride,  is  highly  toxic.   Both  cases
Involved  the  use  of  methylene chloride as  a paint remover  In   an  enclosed
area  heated  with  a  portable  kerosene  heater.  One  case  (GerrHsen  and
Buschmann,  1960) Involved a  woman  who was  exposed for  a 3-hour period during
1 day  when  she was 7 months pregnant;  that  evening, she  expectorated blood-
tinged sputum and  felt  a tightness  1n  her  chest.  The  next day  she was  hos-
pitalized  with  dyspnea,   cyanosis, and  elevated pulse  and  body  temperature.
She  was  treated  and  discharged  8 days   later.   She  gave  birth to  a healthy
infant 2 months later.
    The   second   case  (English,  1964)   Involved   a   67-year-old   Interior
decorator  exposed  for  8  hours  to  methylene chloride 1n  a  small  unventilated
room  heated with a  portable kerosene heater.   He experienced  breathlessness,
headache,  giddiness  and  a tightness across the  chest.   Upon  hospitaHzatlon
the  next  day  he  was  cyanotic,  sweating, and tachypneic  with extensive coarse
rales  in  both lungs.   He  was discharged after 5 weeks  but experienced lassi-
tude,  weakness and hypochondriosis for an additional  3  months.

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                             4.  CARCINOGENICITY
4.1.   HUMAN DATA
    Pertinent data  regarding  the carc1nogen1dty  In humans associated  with
methylene chloride could not be located 1n the available literature.
4.2.   BIOASSAYS
4.2.1.   Oral.  An NCI  bloassay  of  methylene chloride has  been  conducted  on
rats  and  mice,  exposed by  gavage,  but as of  May,  1985,  the study  had  been
withdrawn pending further review.
    The  National  Coffee  Association  performed  a  24-month   toxldty   and
cardnogenldty bloassay  In F344 rats  (NCA,  1982a,b)  and  B6C3F1 mice  (NCA,
1983).   In  the  rat study,  groups  of 85  males  and  85 females were  adminis-
tered  drinking  water   that  provided  methylene chloride at  0,  5, 50, 125  or
250 mg/kg bw/day  for  24  months.  A  second control  group of 50  rats/sex and a
high  dose group  (250 mg/kg bw/day)  of  25  rats/sex were  added to  undergo
treatment  for 78  weeks  followed  by  a  26-week recovery  period.   The  only
tumor  that  occurred  at Increased Incidences was combined  neoplastlc  nodules
and  hepatocellular  carcinoma  1n  female  rats  (p>0.05).   These  Incidences
(0/134,  1/85, 4/83, 1/85,  6/85 1n combined control,  5,  50, 125  and  250 mg/kg
bw/day  groups,  respectively),  however, were  within those  observed  1n  theo-
retical  controls  and  the U.S.  EPA (1985a) concluded  that  methylene  chloride
showed  "borderline" cardnogenldty In F344 rats.
    In  the  mouse  experiment,  groups  of  50  females and  60-200 males  were
treated  with drinking water that provided 0,  60, 125,  185 or  250 mg methyl-
ene  chloride/kg  bw/day  for 24  months.   A  marginally significant  (p<0.05)
Increase  1n the  combined  Incidence  of hepatocellular adenoma and  carcinoma
was  recorded  1n  male  mice (24/125,  51/200,  30/100,  31/99  and  35/125  In
combined  control,  60, 125, 185 and  250 mg/kg  bw/day groups,  respectively).
                                     -18-

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The  U.S.  EPA  (1985a)  considered  the  evidence  for  the  cardnogenldty  of
methylene chloride 1n mice to be "borderline".
4.2.2.   Inhalation.   Burek  et  al.  (1980,  1984)  and Dow  Chemical  Co.  (1980)
studied  the  cardnogenldty of  methylene  chloride  from  chronic  (2-year)
Inhalation  exposure.   Sprague-Dawley  rats  and golden  Syrian hamsters  were
exposed to methylene chloride at 0,  500,  1500  or  3500 ppm for 6  hours/day, 5
days/week for  up  to  2 years.   As  was  mentioned  previously,  hamsters  seemed
to  be less  sensitive  to  the  systemic toxic  effects  of methylene  chloride
than were rats.  No  exposure-related  differences  1n  the  Incidences of  benign
or  malignant  tumors  were observed  1n  male  hamsters.  There  was  a statisti-
cally  significant  Increase  1n  the  Incidence  of  benign  tumors  In  female
hamsters  exposed   to 3500   ppm  methylene  choMde,   but  this  Increase  was
attributed  to  Increased  longevity  enjoyed by  that  group as  a result  of
delayed diseases of aging.
    In  female  rats,  an  Increase 1n  the number of benign mammary  tumors  per
tumor-bearing rat  (but not 1n the  number  of tumor-bearing rats)  was  observed
at  all  dose levels.   An  Increase  1n the  number  of  benign  mammary tumors  1n
tumor-bearing  rats was  also noted  In males  1n  the high-dose  group.   More
Importantly,  a dose-related Increase 1n  sarcomas   Involving  the  salivary
gland  became statistically  significant at   the  high-dose exposure  level  In
male  rats   (Table  4-1).    These  tumors appeared  to  arise  from  mesenchymal
rather  than  epithelial  tissue.  Interpretation  of  these findings  Is  diffi-
cult,  according to  the  Investigators (Burek  et  al.,   1984).    Studies  of
chronic  methylene  chloride  exposure  at  high  levels  1n a  wide  variety  of
laboratory  spedes have  established  the liver  as the  primary target organ.
                                     -19-

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                                  TABLE 4-1

          Summary of Salivary Gland  Region Sarcoma Incidence 1n Male
           Rats  1n  a 2-Year  Inhalation Study with  D1chloromethanea
Dose
(ppm)
0
500
1500
3500
Incidence^
1/93
0/94
5/91
11/88
(15)
(0%)
(5.5%)
(12.5%)
Fisher's Exact Test
NA
NA
(p=0.10, NS)
(p=0.002)
aSource: Burek et al., 1980, 1984; Dow Chemical Co., 1980

bCochran-Arm1tage test for linear trend, p<0.0001.

NS = Not significant; NA = not applicable
                                     -20-

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The  present   Indication  of  an   apparent   relationship  between  methylene
chloride and the  salivary  gland  was unusual and  appeared  to be Inconsistent
with previously reported data.  Early  1n  the course  of  treatment, these rats
had  apparently  contracted  a  viral   disease,  s1alodacryoaden1t1s,  1n  the
salivary glands.   It was suggested  that the  combination  of the  virus  with
methylene  chloride  may have  Increased  the  Incidence  of  salivary  gland
neoplasla.   The fact  that  these  sarcomas appeared to arise  from mesenchymal
tissue  rather  than from epithelial  (glandular)   tissue  added to  the  confu-
sion.   The  authors  (Burek  et  al., 1984)  expected  primary salivary  gland
neoplasms to arise from epithelial cells.
    More recently,  Dow  Chemical   Co.  (1982)   conducted  a  2-year  Inhalation
toxldty and oncogenldty study  1n rats exposed  to 0, 50, 200  or 500  ppm,  6
hours/day,   5   days/week  for  20   (males)  or  24   months  (females).   Interim
necropsies  were performed at  6,  13, 15 and 18 months.   No treatment-related
Increase 1n  tumor Incidence was  observed.   This  study  has  been criticized
for  using  doses   too  low  to elicit  a  positive response.  Consequently,  the
National Toxicology  Program has  performed  another Inhalation study  1n  rats
and mice (NTP, 1985).  The  board  draft of  this study has been released 1n an
unaudited form.   In  this experiment,  50 male  and  50  female  F344/N rats  were
exposed  to  air containing  0  (chamber  controls),   1000,  2000 or  4000  ppm,  6
hours/day,  5 days/week  for  102 weeks.   Concurrently,  50 male and 50  female
B6C3F1 mice were  exposed  by the  same  schedule to air containing  0,  2000 or
4000 ppm methylene chloride.  During week 3 of treatment,  rats  of both sexes
1n the 1000 ppm group were  exposed to  2000  ppm and rats  of both sexes  1n the
2000 ppm group were exposed  to 1000 ppm.
    In  rats,   a   significant  positive  trend   (p<0.001)  for  mammary  tumors
(fIbroadenoma,  adenoma,  fibroma:   combined  Incidence)  was  observed in  both
                                     -21-

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sexes (Table  4-2).   The Incidence  1n  high group males and  females  was  sig-
nificantly greater than  in control  rats  (p<0.001).   Similarly,  the Incidence
of  subcutaneous  fibroma or  sarcoma  (combined)  1n male  rats  was higher  In
high group males  than controls  (p<0.05)  and  a positive  trend  (p=0.008)  was
observed.  The  Incidence  of  these  tumors  was  combined  because they  all
occurred  1n  the  mammary chain  and  were considered to  be of the  same  etio-
loglc origin.  Other  tumor  types also  occurred with a  significant  positive
trend  by  life  table  analysis,  but were  not  significant in  treated  vs.
control  groups.  These  included  the  combined  incidence  of neoplastlc nodules
and hepatocellular carcinomas  in  female  rats,  adrenal  gland pheochromocytoma
and interstitial  cell  tumors  1n males,  squamous cell metaplasia  in  females,
pituitary gland adenoma  or  carcinoma and mononuclear cell  leukemlas  in  both
sexes.   In male rats,  the  incidence of mesothelioma derived from the tunica
vaglnalls was  found  to  be significantly  higher 1n both  the high  and inter-
mediate  groups  than  1n  controls,   but  the  incidence  in  controls   In  this
experiment was unusually low compared to'hlstorical controls.
    The  most  striking  observation   1n  the mice  was the incidence   of  lung
tumors   (p=0.0001)  1n treated  mice  (Table 4-3).   The  period of  latency  was
significantly reduced  in treated mice  and lung  tumors  were believed  to  be
responsible for the  reduced  survival observed  1n  high-dose group males  and
females.  Also  noteworthy was  the  Incidence  of liver  tumors in treated mice
(see Table 4-3).
4.3.   OTHER RELEVANT DATA
    The  available  literature  contains  sufficient  information  on the  muta-
genldty  of methylene  chloride; several experiments are  summarized  in  Table
4-4.  Simmon et al.  (1977) reported  that  methylene chloride was mutagenic  to
Salmonella typhimurium strain  TA100 when  assayed  1n  a  desslcator  whose  atmo-
sphere  contained the  test compound.   Metabolic  activation was  not required.

                                     -22-

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                                   TABLE  4-2

           Tumor Incidence 1n Rats Treated with Methylene Chloride3
       Tumor Type
Control     1000 ppm     2000 ppm     4000 ppm
MALES

Fibroadenoma, adenoma,         0/50
fibroma of mammary gland

Subcutaneous (combined)        1/50
tumors of mammary area
              0/50
              1/50
 2/50
 4/50
 5/50b
 9/50c
FEMALES

Fibroadenoma, adenoma,         7/50
fibroma of mammary gland
             13/50
14/50
23/50b
aSource: NTP, 1985

bp<0.001

cp=0.002
                                     -23-

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                                  TABLE 4-3



           Tumor Incidence In Mice Treated with Methylene Chloride3
Tumor Type
MALES
Alveolar/bronchlolar adenomas
Alveolar/bronchlolar carcinomas
Multiple lung tumors
Hepatocellular adenoma and carcinoma
Hepatocellular carcinoma
Multiple liver tumors
FEMALES
Alveolar/bronchlolar adenomas
Alveolar/bronchlolar carcinomas
Multiple lung tumors
Hepatocellular adenoma and carcinoma
Hepatocellular carcinoma
Multiple liver tumors
Control

3/50
2/50
0/50
22/50
13/50
2/50

2/50
1/50
0/50
2/50
1/50
0/50
2000 ppm

19/50
10/50
10/50
24/49
15/49
11/49

23/48
13/48
11/48
6/48
11/48
3/48
4000 ppm

24/50b
28/50b
28/50
33/49c
26/49d
16/46

28/48b
29/48b
29/48
22/48e
32/48e
28/48
aSource NTP, 1985



bp=0.0001



cp=0.016



dp=0.005
                                     -24-

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                      TABLE  4  4



Nutagenlclty and Genotoxlclty of Methylene Chloride*














1
INJ

-------
                                                                      TABLE 4-4 (cont.)
Assay
Rec assay
Nilotic
recombination
Nltotlc
recombination
Sex-linked
recessive
lethal
Sex-linked
recessive
lethal
Sex-linked
• recessive
o? lethal
i
Nutations In
cell-culture
Chromosomal
aberration
Chromosomal
abberatlon
Chromosomal
aberration
Slster-
chromatld
exchange
Slster-
chromatld
exchange
Indicator
Organism
Bacillus
subtllls
Saccharomyces
cerevlstae 07
S. cerevlslae
03
Drosophlla
Drosophlla
Panagrelus
redlvlvus
CHO and V79
cells
rat bone
marrow cells
CHO cells
NMRI mice/bone
marrow
SCE/V79 cells

CHO cells
Application
NR
NR
NR
fed or
Injected
fed
NR
cell culture
Inhalation
cell culture
l.p.
Injection
cell culture

cell culture
Concentration
or Dose
NR
0-209 mN
NR
NR
0-620 mN
10"» to 10«
mol/l
0-SX
0-3500 ppra
0-10 pi/ml
0-3400 mg/kg bw
0-4. OX

0-10 tit/ml
Activating
System
NR
NA
NR
NA
NA
NA
NA
NA
NA
NA
NA

NA
Response Comments 1
Data available only In abstract form
* D7 strain metabolizes methylene
chloride to active Intermediates
Minimal data presented
Votallzatton not prevented
«- Conclusion; methylene chloride Is
mutagenlc to sperm
* Equivocal positive results
Equivocal negative results
NC
f Similar results In three replications
v Results equivocal
4- Positive dose-response

* Marginal but not significant response
Reference
Kanada and
Uyeta, 1978
Callen et al.,
1980
Simmon et al..
1977
Abrahamson and
Valencia, 1980
Gocke et al.,
1981
Samolloff
et al.. 1980
Jongen et al . ,
1981
Dow Chemical
Co.. 1980
Thllagar and
Kumar oo, 1983
Gocke et al.,
1981
Jongen et al..
1981

Thllagar and
Kumar oo, 1983
*Compound and/or purity not reported



NR = Not reported; NA = not applicable; NC - no comment

-------
The response was  strongly  dose-related.   This is typical  of  the response of
many strains of £. typhimurium  to methylene  chloride  (see Table 4-4).  In S.
cerevisiae D3, however, mitotic recombination was not  increased by methylene
chloride (Simmon et a!., 1977)  although  positive  results  were obtained in S.
cerevisiae 07  (Callen  et  al.,  1980).  Additionally, Filippova  et  al. (1967)
reported  that  methylene  chloride  was  negative when  tested  for  sex-linked
recessive lethals  in  Drosophlla melanogaster although  positive results  were
obtained by Gocke et  al. (1981).
    Thilagar and  Kumaroo  (1983) investigated the ability  of  methylene chlo-
ride to  induce SCE and chromosomal  aberrations  in cultured  Chinese  hamster
ovary cells.   They observed  extensive  chromosomal aberrations,  both with and
without   Aroclor   1242- and  !254-1nduced   rat   S-9   fraction  activation.
Negative results  were  reported  1n the  SCE  assay.  These  authors  discovered
that running   the  tests  in  plastic  rather   than  glass  markedly reduced  the
magnitude  of   the  positive  response,   indicating  the  likely  adsorption  of
methylene chloride to the plastic.
4.4.   WEIGHT  OF EVIDENCE
    Pertinent  data  regarding  carcinogenicity  1n   humans  associated  with
methylene  chloride  could  not   be  located  in  the  available, literature.
Although  an  NCI bloassay  has  been  conducted  In  rats  and mice  using gavage
administration, the  data  are not yet  available.   Burek  et  al.  (1980, 1984)
demonstrated that  sarcomas of the salivary  gland  In  male  rats are  associated
with inhalation  exposure to  high  levels (3500  ppm)  of  methylene  chloride.
Interpretation  of  the  biological significance  of these  results is rendered
difficult for  the reasons  discussed in  Section  4.2.   Another  NCI bloassay
involving inhalation exposure  has  recently  been performed  (NTP, 1985).   The
results  Indicate  that  methylene  chloride  1s  probably  carcinogenic  to  rats
(mammary tumors)  and clearly carcinogenic to mice (lung  and  liver  tumors).

                                     -27-

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Applying  the  criteria  for  evaluating  the  overall  weight  of  evidence  of
carc1nogen1c1ty to humans proposed by  the  Carcinogen  Assessment  Group of the
U.S. EPA  (Federal  Register,  1984), methylene chloride  1s  most appropriately
classified a B2 - Probable Human Carcinogen.
                                     -28-

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                     5.   REGULATORY STANDARDS AND  CRITERIA
    Pertinent  regulatory  standards and  criteria  for methylene  chloride are
summarized  1n  Table 5-1.   According  to  the ACGIH (1981)  the  TLV committee
adopted a  criteria  of  500 ppm In  the  Industrial  workplace.  Subsequent dis-
coveries that  exposures approaching this magnitude resulted 1n substantially
elevated blood  levels  of  carboxyhemoglobln led to a  modification  of the TLV
to 100  ppm;  a  STEL  of 500 ppm has  been  proposed.   In 1983, the ACGIH (1983)
had recommended reducing the STEL to 350 ppm.
    The NIOSH  (1976)  criteria  for methylene chloride was  set  at a TWA of 75
ppm for  a  10-hour  workday,  40-hour workweek.  Recognizing the  relationship
between methylene chloride  and carbon monoxide,  a formula has  been derived
to deal with methylene chloride  when  carbon monoxide concentrations  are >9
ppm.   The formula 1s [C(CO)  * L(CO)] + [C(DCM) * L(DCM)]  <1 where:
       C(CO)  = TWA concentration of carbon monoxide ppm
       L(CO)  = 35 ppm, the  recommended TWA limit  for carbon monoxide
       C(DCM) = TWA concentration of methylene chloride,  ppm
       L(DCM) = 75 ppm, the  recommended TWA limit  for methylene chloride.
    As an  oil  and  fat  solvent, methylene  chloride  Is allowed  In  spice oleo-
reslns  at  concentrations  up  to  30  mg/kg  and  1n  decaffeinated  coffee  at
concentrations up to 10 mg/kg,  according to  NIOSH (1976).
    OSHA (1976)  has established  occupational exposure standards as  follows:
8-hour  TWA,  1737  mg/m3;  acceptable  celling  concentration,  3474  mg/m3;
acceptable maximum peak > celling (5 minutes In any 3 hours),  6948  mg/m3.
    The U.S.  EPA (1980b) has  set the ambient  water  quality criterion  at  6
vg/l   on the  basis  of  qualitative  but  not  quantitative  data  concerning
the carclnogenldty  of  methylene chloride.  They  felt  that the median  con-
centration  found In  ambient  water should not be exceeded  until more defini-
tive  data  quantifying cancer risk to oral exposure have been generated.

                                     -29-

-------
                                   TABLE  5-1

            Regulatory  Standards  or  Criteria  for  Methylene  Chloride




 Standard or Criteria                  Value                     Reference
TLV
STEL
TWA*
TLV
STEL
100
500
75
100
350
ppm
ppm
ppm
ppm
ppm
(-360 mg/m3)
(-1700 mg/m3)



ACGIH,

NIOSH,
ACGIH,

1981

1976
1983

Level In spice oleo-             30 mg/kg                     NIOSH, 1976
resins

Level 1n decaffeinated           10 mg/kg
coffee

8-hour TWA                     1737 mg/m3                     OSHA, 1976
Acceptable celling             3474 mg/m3
Maximum peak                   6948 mg/m3

Ambient water quality             6 jag/a                      U.S. EPA, 1980
criterion

1-Day SNARL                      13 mg/a                      U.S. EPA, 1981b
10-Day SNARL                      1.3 mg/a
Longer SNARL                      0.15 mg/a


*See discussion In text for concurrent exposure to carbon monoxide.
                                     -30-

-------
    Based on  data from  acute  and subacute  toxldty studies,  the  Office of
Drinking Water Advisory  Opinion for methylene  chloride  (U.S.  EPA,  1981b) has
made Suggested No Adverse  Response Level  (SNARL)  recommendations for methyl-
ene  chloride  as  follows:    1-day  exposure,  13  mg/fc;  10-day  exposure,  1.3
mg/8,; and for longer exposures, 0.15  mg/8..
                                     -31-

-------
                              6.   RISK ASSESSMENT
6.1.   ACCEPTABLE INTAKE SUBCHRONIC (AIS)
    Methylene chloride has been demonstrated  to be  carcinogenic  In both rats
and mice.   Data  are  sufficient  for  estimating carcinogenic  potency;  there-
fore,  1t 1s Inappropriate to derive an AIS for this  chemical.
6.2.   ACCEPTABLE INTAKE CHRONIC (AIC)
    Methylene chloride has been demonstrated  to be  carcinogenic  In both rats
and mice.   Data  are  sufficient  for  estimating carcinogenic  potency;  there-
fore,  1t 1s Inappropriate to derive an AIC for this  chemical.
6.3.   CARCINOGENIC POTENCY (q^)
6.3.1.   Oral.   The  NCI  has performed an  oral  exposure bloassay  of  methyl-
ene chloride  1n  rats  and mice.  These data are not available,  as  this study
has been withdrawn pending further audit.
    The U.S.  EPA  (1985a)  reviewed  an  oral  bloassay  conducted  by the National
Coffee Association  (NCA,  1982a,b).  This  study provided  suggestive evidence
of  a  treatment-associated Increased  Incidence of  hepatocellular carcinomas/
adenomas 1n male mice.   In female rats  the  Incidence  of  neoplastlc nodules/
hepatocellular  carcinomas was  Increased  with respect  to matched but  not
historical  controls.   U.S. EPA  (1985a)  felt  this  study  was  Inadequate  for
quantitative  risk assessment.
6.3.2.   Inhalation.  The  study  by Burek et al. (1980, 1984)  associated  the
Incidence of  salivary gland sarcomas  1n  male  rats with exposure to methylene
chloride  (see Sections  3.2.  and  4.2.).    The  Incidence of tumors (control,
1/124; 500  ppm,  0/124;  1500 ppm,  5/124;  3500  ppm,  11/124)  was significantly
different  from  matched  controls  at  the highest  dosage  level.   The  Cancer
Assessment  Group  (U.S.  EPA,  1985a) has  used  these  data to  calculate  a human
q.* of 6.3xlO~4  (mg/kg/day)'1.
                                     -32-

-------
    More recently,  the results of the NTP (1985) bloassay have become avail-
able 1n draft  form.   The  U.S.  EPA (1985b) Is in the process of Devaluating
the  carclnogenlcHy  of  methylene chloride  1n  the  context  of   these  more
recent  results.   However, an  assessment In  final  quotable  form  1s  still
pending.
                                     -33-

-------
                                7.   REFERENCES

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for genetic damage using  Drosophlla melanogaster.   Prepared  for  FDA Contract
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ACGIH  (American  Conference   of  Governmental  and  Industrial   Hyg1en1sts).
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ACGIH  (American  Conference  of Governmental  Industrial Hyg1en1sts).   1983.
Threshold  Limit  Values  for  Chemical  Substances and Physical  Agents In  the
Workroom Environment with Intended  Changes  for 1984.  Cincinnati,  OH.

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(Cited 1n U.S. EPA, 1981a)

Barber,  E.D.,  W.H.  Donish and  K.R.  Mueller.   1981.   A  procedure for  the
quantitative measurement  of  volatile  liquids 1n the Hines  Salmonella/micro-
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Bornmann,  G.  and  A.   Loeser.   1967.   Zur  Frage wlner  Cronisch-Toxlchen
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                                     -34-

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Bornscheln,  et  al.   1980.   Behavioral  toxldty  1n  the  offspring  of rats
following maternal  exposure  to dlchloromethane.   Toxicol.  Appl. Pharmacol.
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Burek,  J.D., K.D.  NHschke, T.J.  Bell,  et al.  1980.  Methylene Chloride: A
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Burek,   J.D.,  K.D.  NHschke,  T.J.  Bell,  et al.  1984.   Methylene choMde: A
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Callahan, M.A.,   M.W.   Sllmak,  N.U.  Gabel,  et  al.   1979.   Water-Related
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Callen,   D.F.,  C.R.  Wolf,  and  R.M.  Phllpot.    1980.    Cytochrome  P^Q-
medlated  genetic  activity and  cytotoxldty  of  seven  halogenated aliphatic
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                                     -35-

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Cherry,  N., H. Venables,  H.A.  Waldron  and G.6. Wells.  1981.  Some  observa-
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sures to  methylene chloride  vapor.   Am.  Ind. Hyg.  Assoc.  J.  33:  125-135.
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                                     -36-

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Dunavskli,  G.A.    1972.    Functional   condition   of   circulatory   organs   1n



workers employed  1n the  production  of  organochloMne  compounds.   61g.  Tr.



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                                     -37-

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GerMtsen,  W.B.  and C.H. Buschmann.  1960.  Phosgene poisoning caused by  the



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                                     -38-

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                                     -41-

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                                            -47-

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                                                          APPENDIX
                                            Summary Table  for  Methylene Chloride
00
Carcinogenic
Potency
Inhalation
Oral
Species/Sex Experimental
Dose/Exposure
rats 12,159 mg/m3
6 hours/day,
5 days/week
for 2 years
NA NA
Effect
salivary gland
sarcomas
carcinoma
NA
q-|* Reference
6.3xlO~4 Burk et al.,
(mg/kg/day)"1 1980, 1984
ND NA
        NA = Not available
        ND = Not derived

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