United States       Prevention, Pesticides     EPA712-C-98-199
          Environmental Protection    and Toxic Substances     August 1998
          Agency        (7101)
&EPA   Health Effects Test
          OPPTS 870.3100
          90-Day Oral Toxicity in

     This guideline is one  of a  series  of test  guidelines that have been
developed by the Office of Prevention, Pesticides and Toxic Substances,
United States Environmental  Protection Agency for use  in the testing of
pesticides and toxic substances, and the  development of test data that must
be submitted to the Agency  for review under Federal regulations.

     The Office of Prevention, Pesticides and Toxic Substances (OPPTS)
has  developed this guideline through  a process of harmonization that
blended the testing  guidance  and requirements that  existed in the Office
of Pollution Prevention and  Toxics  (OPPT) and appeared in Title  40,
Chapter I,  Subchapter R of the Code of Federal Regulations  (CFR),  the
Office of Pesticide Programs (OPP) which appeared in publications of the
National Technical  Information Service (NTIS) and the guidelines pub-
lished by the Organization  for Economic Cooperation and Development

     The purpose of harmonizing these  guidelines  into a single set of
OPPTS guidelines is to minimize  variations among the testing procedures
that must be performed to meet the data  requirements of the U. S. Environ-
mental Protection Agency  under  the Toxic  Substances  Control Act  (15
U.S.C. 2601) and the Federal Insecticide, Fungicide and Rodenticide Act
(7U.S.C. I36,etseq.).

     Final  Guideline Release: This guideline  is available from the U.S.
Government Printing Office,  Washington, DC 20402 on disks or paper
copies: call (202) 512-0132. This  guideline is also available electronically
in PDF (portable document format) from EPA's  World Wide Web  site
(http://www.epa.gov/epahome/research.htm) under the heading "Research-
ers and Scientists/Test Methods and Guidelines/OPPTS  Harmonized Test

OPPTS 870.3100 90-Day oral toxicity in rodents.
     (a) Scope—(1) Applicability. This guideline is intended to meet test-
ing  requirements   of both  the  Federal  Insecticide,  Fungicide,   and
Rodenticide Act (FIFRA) (7 U.S.C. 136, et seq.) and the Toxic Substances
Control Act (TSCA) (15 U.S.C. 2601).

     (2) Background. The source materials used in developing this har-
monized OPPTS test  guideline are 40 CFR 798.2650 Oral Toxicity;  OPP
82-1 90-Day Oral—Two Species, Rodent and Nonrodent; and OECD 408
Subchronic Oral Toxicity—Rodent: 90-Day.

     (b) Purpose. In the  assessment and evaluation  of the toxic character-
istics of a chemical, the determination of subchronic oral toxicity may be
carried out after initial information on toxicity has been obtained by acute
testing.  The subchronic oral study has been  designed to permit the deter-
mination of the no-observed-effect level (NOEL) and toxic effects associ-
ated with continuous or repeated exposure to a test  substance for a period
of 90 days. This study is not capable  of determining  those  effects  that
have a long latency period for development  (e.g., carcinogenicity and life
shortening). Extrapolation from the results of this study to humans is valid
only to  a limited degree. However, it can useful in  providing information
on health hazards likely to arise from repeated exposure by the oral route
over a limited period of time, such as target organs, the possibilities of
accumulation, and can be of use in selecting dose levels for chronic studies
and for establishing safety criteria for human exposure.

     (c) Definitions. The definitions in section 3 of the  Toxic Substance
Control Act (TSCA) and the definitions in 40 CFR  Part 792—Good  Lab-
oratory Practice Standards apply to this test guideline. The following  defi-
nitions also apply to this test guideline.

     Cumulative toxicity  is the adverse effects of repeated dosesoccurring
as a result  of prolonged  action on, or increased concentration of, the ad-
ministered test substance  or its metabolites in susceptible tissue.

     Dose in a  subchronic oral study is the  amount of test substance ad-
ministered  daily via the  oral route (gavage, drinking  water or diet) for
a period of 90 days.  Dose  is expressed as  weight of the test substance
(grams,  milligrams) per unit body weight  (BW)  of test animal (milligram
per kilogram)  or as weight  of the test substance in parts per million in
food or drinking water per day.

     No-observed-effect-level (NOEL)  is the  maximum dose used  in a
study which produces no adverse effects. The NOEL is usually expressed
in terms of the weight of a test  substance given  daily per unit weight
of test animal (milligrams per kilogram per day).

     Subchronic oral  toxicity is the adverse effects occurring as a result
of the repeated daily  exposure of experimental animals to a chemical by

the oral route for a part (approximately  10  percent) of the test  animal's
life span.

     Target organ is any organ of a test animal showing evidence of an
effect induced by a test substance.

     (d) Limit test. If a test at one dose level of at least 1,000 mg/kg
body weight (expected human exposure may  indicate the need for a higher
dose level),  using  the procedures  described for this study, produces no
observable toxic effects or if toxic effects would not be expected based
upon data of structurally related compounds, then a full  study using three
dose levels might not be necessary.

     (e) Test procedures—(1) Animal selection—(i) Species and strain.
A variety of rodent species may be used, although the rat is the preferred
species. Commonly used laboratory strains should be employed.

     (ii) Age/weight.  (A)  Testing  should be started with young healthy
animals as soon as possible after weaning  and acclimatization.

     (B) Dosing of rodents  should generally begin no later than  8-9 weeks
of age.

     (C) At the commencement of the study the weight variation of ani-
mals used should be within 20 percent of the mean weight for each sex.

     (iii) Sex. Equal numbers  of animals of each sex should be used  at
each dose level, and the females should  be  nulliparous  and nonpregnant.

     (iv) Numbers. (A) At least 20 rodents (10 males and 10  females)
at each dose level.

     (B) If interim sacrifices are planned, the number should be increased
by the number of animals scheduled to be sacrificed  before the completion
of the study.

     (C) To  avoid bias,  the use of  adequate randomization procedures for
the proper allocation  of animals to test  and control groups is required.

     (D) Each animal should be assigned a unique identification number.
Dead animals, their preserved  organs  and tissues, and microscopic slides
should be identified by reference to the animal's  unique number.

     (v) Husbandry.  (A)  Animals may  be  group-caged by sex, but the
number of animals per cage must  not interfere  with clear observation of
each animal. The biological properties  of the  test substance or toxic effects
(e.g., morbidity, excitability) may  indicate a need for individual caging.

     (B) The temperature of the experimental animal rooms should  be  at
22 + 3 °C.

     (C) The relative humidity of the experimental animal rooms should
be 50 + 20 percent.

     (D) Where lighting is artificial, the sequence should be 12 hours light/
12 hours dark.

     (E) Control and test animals should be fed from the  same batch and
lot. The feed should be analyzed  to assure adequacy of nutritional require-
ments of the  species tested and for impurities that might  influence the
outcome of the test. For feeding,  conventional  laboratory  diets may be
used with an unlimited supply of drinking water.

     (F) The study should not be  initiated until animals have been allowed
a period  of acclimatization/quarantine to environmental  conditions, nor
should animals from outside sources be placed on test without an adequate
period of quarantine. An acclimation period of at least five days is rec-

     (2) Control and test substances, (i) Where necessary, the test sub-
stance is dissolved or suspended  in a suitable vehicle. If a vehicle or dilu-
ent is needed, the vehicle should not elicit toxic effects  or substantially
alter the chemical or toxicological properties of the test  substance. It  is
recommended that wherever possible the usage of an aqueous solution be
considered first, followed by consideration  of a solution  in oil and then
solution in other vehicles.

     (ii)  If possible, one lot of the test substance tested  should be used
throughout the duration  of the study and the research sample should be
stored under conditions that maintain its purity and stability. Prior to the
initiation  of the study, there should be a characterization  of the test sub-
stance, including the purity of the test compound and, if technically fea-
sible, the names and quantities of contaminants and impurities.

     (iii) If the test or control substance is to be incorporated into feed
or another vehicle, the period during which the  test substance is stable
in such a mixture  should be determined prior to the initiation of the study.
Its homogeneity and concentration should be determined prior to the initi-
ation of the study and periodically  during the study.  Statistically random-
ized samples of the mixture should be analyzed to ensure that proper mix-
ing,  formulation,  and storage procedures are being followed, and that the
appropriate concentration of the  test or control substance is  contained  in
the mixture.

     (3)  Control  groups.  A  concurrent control group  is required. This
group should be an untreated or sham-treated control  group or, if a vehicle
is used in administering  the test substance,  a vehicle control group. If the
toxic properties of the vehicle are not known or cannot be  made available,
both untreated and vehicle control groups are required.

     (4) Satellite group. A satellite group of 20 animals (10 animals per
sex) may be treated with the high dose  level for 90 days and observed
for reversibility, persistence, or delayed occurrence of toxic effects for a
post-treatment period of appropriate length, normally not less than 28 days.
In addition, a control group of 20 animals (10 animals of each sex) should
be added to the satellite study.

     (5) Dose levels and dose selection, (i) In subchronic toxicity tests,
it  is desirable  to determine  a  dose-response relationship as  well  as a
NOEL. Therefore, at least three dose levels plus a control and,  where ap-
propriate, a vehicle control  (corresponding to the concentration  of vehicle
at the highest dose level) should be used. Doses should be spaced appro-
priately to produce  test groups with  a range of toxic  effects.  The data
should be sufficient to produce a dose-response curve.

     (ii)  The highest dose  level  should  result in toxic effects but not
produce an incidence of fatalities which would prevent a meaningful eval-

     (iii) The intermediate dose levels should be spaced to produce a gra-
dation  of toxic effects.

     (iv) The lowest dose  level should produce no evidence of toxicity.

     (6) Administration of the test substance, (i) If the  test substance
is  administered by gavage,  the animals are dosed with the test substance
on  a 7-day per week basis for  a period of at least  90 days.  However,
based primarily on practical considerations, dosing by gavage on a 5-day
per week basis is acceptable. If the test substance is  administered in the
drinking water, or mixed in the diet, then exposure  should be on  a  7-
day per week basis.

     (ii) All animals should  be dosed by the same method during the entire
experimental period.

     (iii) For substances of low toxicity, it is important to ensure that when
administered in the  diet the quantities of the  test substance involved  do
not interfere with normal nutrition. When the test substance is administered
in the  diet, either a constant  dietary concentration (parts per million) or
a constant dose level in terms of body weight should be used;  the alter-
native used should be specified.

     (iv) For a substance administered by gavage, the dose should be given
at approximately the same time each day, and adjusted at intervals (weekly
or biweekly) to maintain a constant dose level in terms of body weight.

     (7) Observation period, (i)  The  animals should be  observed for a
period  of 90 days.

     (ii) Animals in the satellite group (if used) scheduled for follow-up
observations should be  kept for at least 28 days further without treatment
to detect recovery from, or persistence of, toxic effects.

     (8) Observation of animals, (i)  Observations should be made at least
twice each  day for morbidity and mortality. Appropriate actions should
be taken to minimize  loss of animals  to the study (e.g., necropsy or refrig-
eration  of those  animals found  dead and isolation or  sacrifice of weak
or moribund animals).  General  clinical observations  should be made at
least once a day,  preferably at the same time each day, taking into  consid-
eration  the  peak period of anticipated effects  after dosing.  The  clinical
condition of the animal  should be recorded.

     (ii) A careful clinical examination should be made at least once prior
to the initiation of treatment (to allow for within subject comparisons) and
once weekly during treatment in all animals. These observations should
be made outside the  home cage, preferably  in a standard arena, and at
similar times on each occasion. Effort should be made to ensure that vari-
ations in the observation conditions are minimal.  Observations should be
detailed and carefully recorded, preferably using scoring systems, explic-
itly defined  by the  testing laboratory. Signs noted should include,  but not
be limited to, changes in skin, fur, eyes,  mucous membranes, occurrence
of secretions and  excretions   and  autonomic activity (e.g.,  lacrimation,
piloerection, pupil size, unusual respiratory pattern). Changes in gait, pos-
ture  and response to  handling as well as  the presence of clonic  or  tonic
movements,  stereotypies (e.g., excessive grooming,  repetitive  circling) or
bizarre behavior  (e.g., self-mutilation, walking  backwards) should be re-

     (iii) Once, near the end  of  the exposure period and in any case not
earlier than  in week  11, assessment  of motor activity, grip strength, and
sensory reactivity to stimuli of different types (e.g., visual,  auditory, and
proprioceptive  stimuli)  should be conducted. Further details of the proce-
dures that could  be followed  are described in the references listed under
paragraphs (h)(2), (h)(5), (h)(6), (h)(7), (h)(8),  and  (h)(ll) of this guide-

     (iv) Functional observations conducted towards the end of the study
may be omitted when data on functional observations are available  from
other studies and the daily clinical observations did not reveal any func-
tional deficits.

     (v) Exceptionally, functional observations may  be omitted for groups
that otherwise reveal signs of  toxicity to an extent that would significantly
interfere with functional test performance.

     (vi) Measurements  of food consumption and water consumption, if
drinking water is  the exposure route, should be made weekly.

     (vii) Individual weights of animals should be determined shortly be-
fore the test substance  is administered, weekly thereafter, and at  death.

     (viii) Moribund animals should be removed and sacrificed when no-
ticed and the time  of death should be recorded as precisely as possible.

     (ix) At termination, all survivors in the treatment and control groups
should be sacrificed.

     (9) Clinical pathology. Hematology and clinical chemistry examina-
tions should be made on all animals, including controls, of each sex in
each group. The hematology and clinical chemistry parameters should be
examined  at terminal sacrifice at the end of the study. Overnight fasting
of the  animals prior to blood sampling  is recommended. Overall, there
is  a need  for  a flexible approach in the measures examined,  depending
on the  observed or expected effects from a chemical, and in the frequency
of measures, depending on the duration of potential chemical exposures.

     (i) Hematology.  The  recommended  parameters are red blood  cell
count,  hemoglobin  concentration,  hematocrit,  mean corpuscular volume,
mean corpuscular  hemoglobin,  and mean corpuscular hemoglobin con-
centration,  white  blood cell  count,  differential leukocyte  count, platelet
count,  and a measure of clotting potential,  such  as prothrombin time or
activated partial thromboplastin time.

     (ii) Clinical chemistry. (A) Parameters which are considered appro-
priate to all studies are  electrolyte balance, carbohydrate metabolism,  and
liver and kidney function. The selection of specific tests will be influenced
by observations on the mode of action of the substance and signs of clini-
cal toxicity.

     (B) The recommended clinical chemistry determinations  are potas-
sium, sodium, glucose,  total cholesterol,  urea nitrogen, creatinine, total
protein  and albumin. More  than 2  hepatic enzymes, (such as alanine
aminotransferase, aspartate aminotransferase, alkaline phosphatase, sorbitol
dehydrogenase, or gamma glutamyl transpeptidase) should also  be  meas-
ured. Measurements of addtional enzymes (of hepatic or other origin) and
bile acids, may also be useful.

     (C) If a test  chemical has an effect  on the hematopoietic system,
reticulocyte counts and bone marrow cytology may be indicated.

     (D) Other determinations that should be carried out if the test chemi-
cal is known or suspected  of affecting related measures include calcium,
phosphorus,  fasting   triglycerides,   hormones,   methemoglobin,   and

     (iii) Optionally, the following urinalysis determinations could be per-
formed during the last week of the study using timed urine volume collec-

tion: appearance, volume, osmolality or specific gravity, pH, protein, glu-
cose and blood/blood cells.

     (10)  Ophthalmological  examination.  Ophthalmological examina-
tions using  an ophthalmoscope or an equivalent device should be made
on  all  animals prior to the administration of the  test substance  and on
all  high  dose and control groups at termination.  If changes in the eyes
are detected, all animals  in the  other dose  groups should be examined.

     (11) Gross necropsy, (i) All animals should be subjected to a full
gross necropsy which includes examination of the  external surface of the
body, all orifices, and the cranial, thoracic and abdominal cavities and their

     (ii) The liver, kidneys, adrenals, testes, epididymides,  ovaries, uterus,
thymus, spleen, brain,  and heart  should be trimmed and weighed wet,  as
soon as possible after dissection.

     (iii) The following organs and tissues, or representative samples there-
of,   should  be  preserved in  a  suitable medium  for  possible future
histopathological examination:

     (A)  Digestive  system—salivary glands, esophagus, stomach,  duode-
num, jejunum, ileum,  cecum, colon, rectum, liver, pancreas,  gallbladder
(when present).

     (B) Nervous system—brain (including sections of medulla/pons, cere-
bellum and  cerebrum), pituitary, peripheral nerve  (sciatic or tibial, pref-
erably in close proximity to the muscle), spinal cord (three levels: cervical,
mid-thoracic and lumbar), eyes (retina, optic nerve).

     (C) Glandular system—adrenals, parathyroid, thyroid.

     (D) Respiratory system—trachea, lungs, pharynx, larynx, nose.

     (E)  Cardiovascular/hemopoietic system—aorta,  heart, bone  marrow
(and/or fresh aspirate), lymph nodes (preferably one lymph node covering
the route of administration and another one distant from the route of ad-
ministration to cover systemic effects), spleen, thymus.

     (F)  Urogenital system—kidneys,  urinary  bladder, prostate, testes,
epididymides, seminal  vesicle(s), uterus, ovaries, female mammary gland.

     (G) Others—all gross lesions and masses, skin.

     (13) Histopathology. (i) The following histopathology should be per-

     (A)  Full histopathology  on the organs and tissues, listed under para-
graph (e)(12)(iii) of this guideline, of all rodents in the control and high
dose groups, and all rodents  that died or were killed during the study.

     (B) All gross lesions in all animals.

     (C) Target tissues in all animals.

     (D)  When a satellite  group is used,  histopathology should  be per-
formed on tissues and organs identified as showing effects in the treated

     (ii) If excessive early deaths or other problems occur in the high dose
group  compromising the significance  of  the  data, the next  dose level
should be examined for complete histopathology.

     (iii) An attempt should be made to correlate gross observations with
microscopic findings.

     (iv)  Tissues  and organs designated for microscopic  examination
should be fixed in 10 percent buffered formalin  or a recognized  suitable
fixative as soon as necropsy is performed and no less than 48 hours prior
to trimming.

     (f) Data and reporting—(1) Treatment  of results, (i) Data should
be summarized in tabular form, showing for each  test  group the  number
of animals at the  start of the test, the number of animals showing  lesions,
the types  of lesions and the percentage of animals displaying  each type
of lesion.

     (ii) When applicable, all observed results, qualitative and quantitative,
should be  evaluated by an appropriate and generally accepted statistical
method. Any generally accepted statistical methods may be used;  the sta-
tistical methods, including  significance criteria, should be selected during
the design of the study.

     (2) Evaluation of study results. The findings of a subchronic oral
toxicity study should be evaluated in conjunction with the findings of pre-
ceding studies  and considered in terms of the toxic effects and  the ne-
cropsy and histopathological findings. The evaluation will include the rela-
tionship between the dose of the test substance and the presence or ab-
sence,  the incidence and severity,  of  abnormalities, including behavioral
and  clinical  abnormalities,  gross  lesions,  identified target organs, body
weight changes, effects on mortality and any other general or specific toxic
effects. A properly conducted  subchronic test should provide a satisfactory
estimation of a NOEL.  It also can indicate  the  need for an  additional
longer-term study and provide information on the selection of dose levels.

     (3) Test report. In addition to reporting requirements specified under
EPA Good Laboratory Practice  Standards at  40 CFR part  792,  subpart
J and  40  CFR part 160, and the OECD  principles of GLP (ISBN 92-
64-12367-9), the following specific information should be reported:

     (i) Test substance characterization should include:


     (A) Chemical identification.
     (B) Lot or batch number.
     (C) Physical properties.
     (D) Purity/impurities.
     (ii) Identification and composition of any vehicle used.
     (iii) Test system should contain data on:
     (A)  Species and strain  of animals used and rationale for selection
if other than that recommended.
     (B) Age including body weight data and  sex.
     (C) Test environment including cage conditions, ambient temperature,
humidity, and light/dark periods.
     (D) Identification of animal diet.
     (E) Acclimation period.
     (iv) Test procedure should include the following data:
     (A) Method of randomization used.
     (B) Full description of experimental design and procedure.
     (C) Dose regimen including levels, methods, and volume.
     (v) Test results should include:
     (A) Group animal data.  Tabulation of toxic response data by species,
strain, sex and exposure level for:
     (7) Number of animals exposed.
     (2) Number of animals showing signs of toxicity.
     (3) Number of animals dying.
     (B) Individual animal data.  Data should be presented  as  summary
(group mean) as well as for individual animals.
     (7) Date of death during the study or  whether animals  survived to
     (2) Date  of observation of each abnormal sign  and its subsequent
        Body weight data.
     (4) Feed and water (if collected) consumption data.

     (5) Achieved dose (mg/kg/day) as a time-weighted average if the test
substance is administered in the diet or drinking water.

     (6) Results of ophthalmological examination.

     (7) Results of hematological tests performed.

     (8) Results of clinical chemistry tests performed.

     (9) Results of urinalysis, if performed.

     (10) Necropsy findings,  including  absolute and  relative (to  body
weight) organ weight data.

     (11) Detailed description of all histopathological findings.

     (12) Statistical treatment of results, where appropriate.

     (g) Quality control. A system should be developed and maintained
to assure and document  adequate performance of laboratory staff and
equipment. The study must be  conducted in compliance with GLP regula-

     (h) References. The following references should be consulted for ad-
ditional background information on this test guideline.

     (1) Boyd, E.M. Chapter  14. Pilot Studies,  15. Uniposal Clinical Pa-
rameters, 16. Uniposal Autopsy Parameters. Predictive Toxicometrics. Wil-
liams and Wilkins, Baltimore (1972).

     (2) Crofton K.M., Howard J.L., Moser V.C., Gill M.W., Leiter L.W.,
Tilson H.A., MacPhail, R.C. Interlaboratory Comparison of Motor Activity
Experiments:   Implication   for    Neurotoxicological    Assesments.
Neurotoxicol. Teratol. 13, 599-609. (1991)

     (3)  Fitzhugh, O.G.  Subacute Toxicity, Appraisal of the Safety of
Chemicals in Foods, Drugs and Cosmetics. The Association of Food and
Drug Officials of the United States (1959, 3rd Printing 1975) pp. 260935.

     (4) Food Safety Council. Subchronic Toxicity Studies, Proposed Sys-
tem for Food Safety Assessment.  (Columbia: Food Safety  Council, 1978)
pp. 830996.

     (5) Gad S.C. A  Neuromuscular  Screen for Use in Industrial Toxi-
cology. Journal of Toxicology and Environmental Health. 9, 691-704.

     (6)  International  Programme on Chemical  Safety.  Principles  and
Methods for the Assessment of Neurotoxicity Associated  with Exposure
to Chemicals. Environmental Health Criteria Document No. 60. (1986)


     (7) Meyer O.A., Tilson H.A., Byrd W.C., Riley M.T. A Method for
the Routine Assessment of Fore- and Hind-Limb Grip Strength of Rats
and Mice. Neurobehav. Toxicol. 1, 233-236. (1979)

     (8) Moser V.C., McDaniel K.M., Phillips P.M.  Rat Strain and Stock
Comparisons using a Functional  Observational  Battery: Baseline  Values
and  Effects of Amitraz. Toxicol.  Appl. Pharmacol.  108,  267-283  (1991)

     (9) National Academy  of Sciences. Principles  and Procedures for
Evaluating the Toxicity of Household Substances, A report prepared by
the Committee for the Revision of NAS Publication 1138, under the aus-
pices of the Committee on Toxicology, National Research Council, Na-
tional Academy of Sciences, Washington, DC (1977).

     (10)  Organization  for  Economic  Cooperation and Development.
OECD Guidelines for Testing of Chemicals. Guideline 408:  Subchronic
Oral Toxicity-Rodent: 90-day Study, Adopted: May 12, 1981.

     (11) Tupper, D.E., Wallace R.B. Utility of the Neurologic Examina-
tion in Rats. Acta. Neurobiol. Exp. 40, 999-1003 (1980).

     (12) United States Environmental Protection Agency. Office of Test-
ing and Evaluation. Proposed Health Effects Test Standards for Toxic Sub-
stances Control Act Test Rules. 40 CFR Part 772. Standard for Develop-
ment of Test  Data. Subpart  D. FEDERAL REGISTER Vol.  44,  pp.  27350-

     (13) Weingand K., Brown G., Hall R. et al. Harmonization of Animal
Clinical Pathology Testing in Toxicity  and  Safety  Studies. Fundam.  &
Appl. Toxicol.  29:198-201. (1996)

     (14) World Health Organization. Guidelines for Evaluation of Drugs
for Use in Man, WHO Technical  Report Series No.  563. (Geneva: World
Health Organization, 1975).

     (15) World Health Organization. Part I. Environmental Health Criteria
6, Principles and Methods for Evaluating the Toxicity of Chemicals. (Ge-
neva: World Health Organization,  1978).

     (16) World Health Organization. Principles for  Pre-Clinical Testing
of Drug Safety, WHO Technical Report Series No. 341. (Geneva: World
Health Organization, 1966).