United States        Prevention, Pesticides      EPA712-C-96-199
           Environmental Protection     and Toxic Substances      June 1996
           Agency          (7101)
&EPA    Health Effects Test
           OPPTS 870.3100
           90-Day Oral Toxicity
                 "Public Draft'

     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.).

     Public Draft Access Information: This draft guideline is part of a
series of related harmonized guidelines that  need to  be considered as a
unit. For copies: These guidelines are available electronically from the
EPA Public Access  Gopher (gopher.epa.gov) under the heading "Environ-
mental Test Methods and Guidelines" or in paper by contacting the OPP
Public    Docket    at    (703)    305-5805    or     by    e-mail:

     To Submit Comments: Interested persons are invited to submit com-
ments. By mail: Public Docket and Freedom of Information Section, Office
of Pesticide Programs, Field Operations Division (7506C), Environmental
Protection Agency,  401  M  St.  SW.,  Washington, DC 20460. In  person:
bring to: Rm. 1132, Crystal Mall #2, 1921 Jefferson Davis Highway, Ar-
lington, VA. Comments may also be submitted  electronically by  sending
electronic mail (e-mail) to: guidelines@epamail.epa.gov.

     Final  Guideline Release: This guideline is available  from the U.S.
Government Printing Office, Washington, DC 20402 on The Federal Bul-
letin  Board.   By  modem   dial   202-512-1387,   telnet   and  ftp:
fedbbs.access.gpo.gov (IP,  or  call 202-512-0132 for disks
or paper copies.  This  guideline is also available electronically in ASCII
and PDF (portable document format) from the EPA Public Access  Gopher
(gopher.epa.gov) under the heading  "Environmental Test Methods and

OPPTS 870.3100  90-Day oral toxicity.
     (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 material  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 doses occurring
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 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, milli-
grams) 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

     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
BW (expected human exposure may indicate the need for a higher dose
level), using the procedures described for this study, produces no observ-
able 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 mammalian species should be used for testing. A variety of rodent spe-
cies may be  used, although the rat  is the preferred species. Commonly
used laboratory  strains  should be employed. Commonly used nonrodent
species is the  dog.  If other mammalian species are used, the tester should
provide justification/reasoning for their selection.

     (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 weeks
of age.

     (C) Dosing of dogs should begin  between 4 and 6 mon of age and
in no case later than 9 mon of age.

     (D) At the commencement  of the study the weight variation of ani-
mals used should not exceed + 20 percent of the mean weight for each

     (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)
or 8 nonrodents (4 males and 4 females) should be used at each dose

     (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.
Dogs should be housed individually.

     (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 30 and 70 percent.

     (D) Where lighting is  artificial, the  sequence should be  12 h light/
12 h 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. Rodents should be fed and watered ad libitum with
food replaced at  least  weekly.  For nonrodents feeding should be at least
daily and water ad libitum.

     (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.

     (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 of 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. For rodents, 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 ef-
fects 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 appropriate,
a vehicle control (corresponding to the concentration of vehicle at the high-
est dose  level) should be used. Doses should be spaced appropriately  to
produce  test groups with a range of toxic effects. The data should be suffi-
cient to produce a dose-response curve.

     (ii)  The highest dose level in rodents  should  result in  toxic effects
but not produce an incidence of fatalities which would prevent a meaning-
ful evaluation; for nonrodents there should be no fatalities.

     (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 is acceptable. If the test substance is  administered via  capsule
(nonrodents), or in the  drinking water (rodents), or  mixed in the diet (ro-
dents or  nonrodents), 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 or  capsule, 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. The animals should be observed for a period
of 90 days. Animals in the satellite group (if used) scheduled for follow-
up observations  should be kept for at least 28  days further without treat-
ment to detect recovery from, or persistence of toxic effects.

     (8) Observation of animals, (i) Observations should be made at least
once each day for morbidity and mortality. Appropriate actions should be
taken to minimize loss of animals to the study (e.g., necropsy or refrigera-
tion  of those animals found dead and isolation or sacrifice of weak or
moribund animals).

     (ii) A careful clinical examination should be made at least once week-
ly. Observations should be  detailed and  carefully recorded,  preferably
using explicitly  defined scales. Observations  should  include,  but not be
limited to,  evaluation of skin and fur, eyes and mucous membranes,  res-
piratory  and circulatory effects,  autonomic effects  such  as  salivation,
central nervous system effects, including tremors and convulsions, changes
in the  level of motor activity, gait and posture, reactivity to handling or
sensory stimuli,  grip  strength, and stereotypies or bizarre behavior (e.g.,
self-mutilation, walking backwards).

     (iii) Signs of toxicity should be  recorded as they are observed includ-
ing the time of onset, degree, and duration.

     (iv) Measurements should be made weekly of food  consumption or
water consumption if drinking water is the exposure route.

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

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

     (vii) At termination, all  survivors in the treatment groups should be

     (9) Clinical pathology. Hematology and clinical chemistry examina-
tions should be  made on all animals, including controls, of each sex in
each group for rodents  and all animals when nonrodents  are used as test
animals.  For rodents, the hematology and clinical chemistry parameters
should be  examined  at terminal  sacrifice  at  the  end  of the study.  For
nonrodents, the  hematology and clinical chemistry parameters  should be
examined once prior to initiation of dosing, at monthly intervals or midway
through the test period and at the termination.

     (i) Hematology. The  recommended parameters are hemoglobin and
hematocrit concentrations,  red blood cell count, white blood cell count,
differential leukocyte count, platelet count, and  a measure of clotting po-
tential such as prothrombin time or 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) Suggested blood clinical chemistry determinations.

     (7) Electrolytes—calcium, chloride, magnesium,  phosphorus, potas-
sium, sodium

     (2)   Enzymes—alkaline   phosphatase,   alanine   aminotransferase,
aspartate aminotransferase,  gamma glutamyl transferase, sorbitol dehydro-

     (3) Other—albumin, blood creatinine, blood urea nitrogen, globulin,
glucose (fasting), total bilirubin, total cholesterol, total serum protein.

     (4) Other determinations  which may  be necessary for an adequate
toxicological evaluation include  analyses of lipids, hormones,  acid/base
balance,  methemoglobin and cholinesterase activity.  Additional  clinical
biochemistry may be employed where necessary to extend the investigation
of observed effects.

     (iii) Urinalysis is not recommended on a routine basis, but only when
there is an indication based on expected or observed toxicity.

     (10)  Optional immunotoxicity  screen. To fulfill, in part, require-
ments for an immunotoxicity screen, subpopulation of splenic or peripheral
blood lymphocytes in the  rodents should be enumerated and quantified.
Total T-, Total  B-, Total  T-helper,  T-suppressor/cytotoxic and  Natural
Killer (NK) cell populations should be determined on at least  10 rodents
of each sex in each group at the end of 90 days.

     (11)  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.

     (12)  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) In both the rodents and nonrodents the liver, lungs, brain, kidneys,
spleen, and gonads should be trimmed and weighed wet, as soon as pos-
sible  after  dissection.  In  addition,  the  thyroid with  parathyroids  in
nonrodents should be weighed.

     (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,  gall bladder

     (B)  Nervous system—brain (multiple  sections), pituitary,  peripheral
nerve(s), spinal cord (three levels), eyes (retina, optic nerve).

     (C) Glandular system—adrenals, parathyroids, thyroids.

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

     (E) Cardiovascular/hemopoietic system—aorta (thoracic), heart, bone
marrow, lymph nodes, spleen, thymus.

     (F)  Urinogenital system—kidneys, urinary  bladder, prostate, testes,
epididymides, seminal vesicle(s), uterus, ovaries.

     (G) Others—all gross lesions and masses, sternum and/or  femur.

     (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, all nonrodents, 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)  Lungs, liver, and kidneys of all animals. Special attention to ex-
amination of the lungs of rodents should be  made for evidence of infection
as this provides a convenient assessment of the state of health of the ani-

     (E) When a satellite group is used (rodents), histopathology  should
be performed on tissues and organs identified as showing effects in the
treated groups.

     (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 h prior
to trimming.  Tissues  should be  trimmed to  a  maximum  thickness of
0.4 cm for processing.

     (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) All observed results, quantitative  and incidental, should be  evalu-
ated by an appropriate  statistical method. Any generally accepted statistical
methods may be used; the statistical 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.

     (E) Identification and composition of any vehicle used.

     (ii) 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.
     (iii) 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.
     (iv) 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.
        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
     (3) Body weight data.
     (4) Feed and water consumption data, when collected.
     (5) Results of ophthalmological examination, when performed.
     (6) Results of hematological tests performed.
     (7) Results of clinical chemistry tests performed.
     ($) Results of immunotoxicity screen, when performed.
     (9) Necropsy  findings, including  absolute and relative organ weight
     (10) Detailed description of all histopathological findings.

     (11} 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) 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.

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

     (4) 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).

     (5) Organization for Economic Co-operation and Development. Guide-
lines for  Testing of  Chemicals,  Section 4-Health  Effects, Part  408
Subchronic Toxicity Studies, Paris, 1981.

     (6) United States Environmental Protection Agency. Office of Testing
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-

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

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

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