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GB 15193.3-2014: National Food Safety Standard -- Acute toxicity test
GB/T 15193.3-2014
NATIONAL STANDARD OF THE
PEOPLE?€?S REPUBLIC OF CHINA
National food safety standard - Acute toxicity test
ISSUED ON: DECEMBER 24, 2014
IMPLEMENTED ON: MAY 01, 2015
Issued by: Health and Family Planning Commission of PRC
Table of Contents
Foreword ... 3??
1 Scope ... 4??
2 Terms and definitions... 4??
3 Test purpose and principle ... 4??
4 Test methods ... 5??
5 Data processing and result evaluation ... 14??
6 Report ... 14??
7 Interpretation of the test ... 15??
Appendix A Calculation of LD50 value in Horn's method (calculation table for the
determination of LD50 by dose escalation method) ... 16??
Appendix B Dose gradient table for up-down procedure (UDP) with different slopes
... 21??
Appendix C Calculation of LD50 point estimates and confidence limits for formal test
... 23??
Appendix D Response rate-probability unit table ... 25??
Appendix E Probability units equivalent to 0% and 100% response rates ... 26??
Appendix F Observation items in experimental animal poisoning performance ... 27??
Appendix G Dose grading of acute toxicity (LD50) ... 28??
National food safety standard - Acute toxicity test
1 Scope
This standard specifies the basic test methods and technical requirements, for acute oral
toxicity test.
This standard applies to the evaluation of the acute oral toxicity of the test substance.
2 Terms and definitions
2.1 Acute oral toxicity
The toxic effects on animals, in a short period of time, after one or more oral
administration of the test substance to experimental animals within 24 h.
2.2 The half lethal dose (LD50)
The dose of the test substance, that can cause animal mortality to be 50%, after oral
administration of the test substance once or multiple times within 24 h. It is the
calculated value, which is obtained through statistics. Its unit is the number of
milligrams or grams of the test substance, which is ingested per kilogram of body
weight, that is, mg/kg body weight or g/kg body weight.
3 Test purpose and principle
The acute oral toxicity test is the most basic test, for detecting and evaluating the toxic
effects of the test substance, that is, after the test substance is administered orally once
or multiple times within 24 hours, the toxic reactions produced by animals, including
poisoning sign and death, are observed in a short period of time. It is usually expressed
as LD50.
This test can provide information on health hazards, which are caused by oral exposure
to the test substance in the short term. It serves as the basis for acute toxicity grading.
It provides the basis for dose selection and observation indicators for further toxicity
tests. It preliminarily estimates the target organs of toxic effects AND the possible toxic
action mechanism.
4 Test methods
4.1 Test substance
4.1.1 Preparation of test substances
It shall dissolve or suspend the test substance in a suitable solvent. The preferred solvent
is water. The test substance, which is insoluble in water, can use vegetable oil (such as
olive oil, corn oil, etc.). The test substance, which is insoluble in water or oil, can also
use carboxymethyl cellulose, starch, etc., to prepare a suspension or paste. The test
substance shall be freshly prepared, unless there is data showing that its solution or
suspension is stable during storage.
4.1.2 Administration of test substance
4.1.2.1 Approach
Oral gavage.
4.1.2.2 Fasting before the test
Animals need to fast before the test. Generally, rats need to fast overnight (generally
about 16 h); mice need to fast for 4 h ~ 6 h; BUT they can drink water freely. After
administration of the test substance, rats need to continue fasting for 3 h ~ 4 h; mice
need to continue fasting for 1 h ~ 2 h. If the test substance is administered in batches
multiple times, the animals can be given a certain amount of feed, according to the
length of the exposure interval.
4.1.2.3 Gavage volume
The gavage volume of each test substance group shall be the same, which is 10 mL/kg
body weight for rats AND 20 mL/kg body weight for mice. If the solvent is water, the
maximum gavage volume of rats can reach 20 mL/kg body weight and that of mice can
reach 40 mL/kg body weight.
4.1.2.4 Method
The test substance is generally administered at one time. It can also be administered
multiple times in one day (each interval is 4 h ~ 6 h, no more than 3 times within 24 h,
the maximum dose is reached as far as possible, which is calculated as a single dose).
4.1.2.5 Observation period
General observation period is 14 d, which may be extended to 28 d if necessary. It shall
be observed for at least 7 d, in special emergency situations.
4.2 Experimental animals
4.2.1 Animal selection
The selection of experimental animals shall comply with national standards and
relevant regulations (GB 14923, GB 14922.1, GB 14922.2). Choose healthy adult rats
(180 g ~ 220 g) and/or mice (18 g ~ 22 g) of two genders, OR choose other experimental
animals. Females shall be unmated and unpregnant. The difference in body weight,
between animals of the same gender, shall not exceed ??20% of the average body weight.
4.2.2 Animal preparation
Before the test, the experimental animals shall undergo at least 3 d ~ 5 d environmental
adaptation and quarantine observation, in the test environment.
4.2.3 Animal feeding
The feeding conditions, drinking water, feed of experimental animals shall comply with
national standards and relevant regulations (GB 14925, GB 5749, GB 14924.1, GB
14924.2, GB 14924.3). Animals in each test group are raised in separate cages by gender.
The number of animals per cage shall not affect the free movement of animals AND it
can observe the physical signs of animals. For the special biological characteristics and
toxic reactions (such as irritability, cannibalism, etc.), which are often caused by some
test substances, it can be raised in a single cage. During the test, the experimental
animals are fed with basal feed AND allowed for free access to water.
4.3 Design methods for several commonly used acute toxicity tests
4.3.1 Horn's method
4.3.1.1 Pre-test
According to the nature of the test substance and the known data, the following methods
are used: Generally, it uses the dose of 100 mg/kg body weight, 1000 mg/kg body
weight, 10000 mg/kg body weight, each of which uses 2 ~ 3 animals for pretest.
According to the death situation within 24 h, estimate the possible range of LD50.
Determine the dose group of the formal test. A single dose, such as 215 mg/kg body
weight, can also be simply used directly in a pretest, with 5 animals. Observe the
poisoning performance of animals, within 2 hours. If the signs of poisoning are severe,
it is estimated that most animals may die, THEN the dose series below 215 mg/kg body
weight can be used to perform the formal test. Otherwise, the dose series above this
dose can be used if the signs of poisoning are mild. Pretests are not required, if there
are relevant documents.
4.3.1.2 Formal test
4.3.1.2.1 Number of animals
Generally, there are 10 animals in each group, half male and half female.
4.3.3.1 Scope of application
This method is mainly applicable to the test substance, which has high purity, high
toxicity, low intake, AND the animal will die, within 1 d ~ 2 d after administration of
the test substance. For the test substance, which causes the animal to die at 5 d and
above, after administration, it is not applicable. The test can be carried out, according
to the dose sequence selected by the tester OR under the guidance of a special software
package; the test results can be counted.
4.3.3.2 Up-down procedure limit test
Use the dose of 2000 mg/kg body weight, to administer the test substance to 1 animal.
If the animal dies within 48 h, a formal test shall be carried out. If the animals survive
within 48 hours, take another 4 animals, to make them administered of the test substance
at the same dose. If 3 out of 5 animals die, a formal test shall be carried out; if 3 or more
animals survive, the test will be terminated. THEN, the test substance has a LD50 >
2000 mg/kg body weight.
If the dose of 5000 mg/kg body weight is required, administer the test substance to 1
animal; if the animal dies within 48 h, a formal test shall be carried out. If the animal
survives within 48 hours, take another 2 animals, to administer the test substance, at the
same dose. If all animals survive within the 14-day observation period, the test ends,
the test substance has a LD50 > 5000 mg/kg body weight. However, if 1 or 2 of the 2
animals dies, after the 14-day observation period, administer the test substance to
another 2 animals; if more than 3 of the 5 animals survive, within the 14-day
observation period, the test ends; the test substance has a LD50 > 5000 mg/kg. If 3 or
more of the 5 animals die within the 14-day observation period, a formal test shall be
carried out.
4.3.3.3 Formal test
4.3.3.3.1 Number of animals
For a single gender, the number of experimental animals is generally 6 ~ 9.
4.3.3.3.2 Dosage
When selecting the starting dose and dose gradient coefficient, if there is no data on the
estimated value of the LD50 of the test substance, the default starting dose is 175 mg/kg
body weight. If there is no data on the slope of the dose-response curve of the test
substance, the default dose gradient coefficient is 3.2 (which is the gradient coefficient,
when the slope is 2); the dose series set are 1.75 mg/kg body weight, 5.5 mg/kg body
weight, 17.5 mg/kg body weight, 55 mg/kg body weight, 175 mg/kg body weight, 555
mg /kg body weight, 2000 mg/kg body weight, OR 1.75 mg/kg body weight, 5.5 mg/kg
body weight, 17.5 mg/kg body weight, 55 mg/kg body weight, 175 mg/kg body weight,
555 mg/kg body weight, 1750 mg/kg body weight, 5000 mg/kg weight. For the test
substance, which has a gentle or steep slope of the dose-response curve, the dose
gradient coefficient can be increased or decreased; the initial dose can be adjusted
appropriately. Appendix B lists dose gradients, which have slopes from 1 ~ 8.
4.3.3.3.3 Methods
At the beginning of the test, weigh the body weight of the fasted animals; calculate the
gavage volume. Perform oral gavage for one animal at a time, which has an interval of
48 hours for each animal. The dose of the second animal depends on the toxicity results
of the first animal; if the animal is moribund or dead, the dose is lowered by one level;
if the animal survives, the dose is raised by one level.
4.3.3.3.4 Provisions for termination of test
Whether to continue to administer the test substance, depends on the survival status of
all animals, within a fixed time interval. The test can be terminated, when any of the
following conditions are reached, for the first time:
a) 3 consecutive animals survived in the test at higher doses;
b) 5 opposite results appear after 6 consecutive animals are administered the test
substance;
c) After the first occurrence of the opposite result, continue to administer the test
substance to at least 4 animals; calculate the likelihood value of each dose, from
the first occurrence of the opposite result; the given likelihood ratio exceeds the
critical value.
The LD50 of the test substance can be calculated, according to the animal?€?s survival
state, at the end of the test. Appendix C describes the calculation method of LD50
estimates and confidence limits for formal tests, as well as the handling method of
special cases.
If the animals died in the later stage of the test after the test substance is administered,
whilst the animals with higher doses are still alive, the continued administration of the
test substance shall be temporarily stopped, to observe whether other animals also
experience delayed death. Continue the exposure when all animals, that have been
administered the test substance, have a clear outcome. If the latter animals also show
delayed death, it means that all exposure dose levels have exceeded LD50; two dose
levels that are more appropriate and lower than the lowest dose that causes death shall
be selected, to restart the test; meanwhile it shall extend the observation period. Animals
with delayed death are counted as death.
4.3.4 Korbor method
4.3.4.1 Pre-test
2S - The difference between LD84 and LD16, that is, 2S = LD84 - LD16 (or ED84 -
ED16);
N' - The sum of the number of animals in each group, within the probability unit of
3.5 ~ 6.5 (response percentage is 6.7% ~ 93.7%).
Note: The dose, which is equivalent to LD84 and LD16, can be found from the straight line.
Ordinary graph paper can also be used to make a graph; look up the Table to convert the dose
into logarithmic value; convert the percentage rate into probability unit. Take the abscissa of
the quadrille paper as the dose logarithm AND the ordinate as the probability unit; connect the
points of the dose logarithm and probability unit into a line; make a horizontal line from the
probability unit 5, to intersect the straight line; draw a vertical line from the intersection point
to the abscissa. The intersection point on the abscissa is the dose logarithm value. Find the
antilog LD50 value.
4.3.6 Acute combined toxicity test
4.3.6.1 Principle
When two or more test substances exist at the same time, three different combined
action modes of antagonism, addition or synergy may occur. These three different
actions can be determined, according to certain formulas and judgement criteria.
4.3.6.2 Procedure
4.3.6.2.1 Determine the LD50 of a single test substance respectively; the method is the
same as 4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5.
4.3.6.2.2 Prepare mixed test substances, which have equal toxicity, according to the
proportion of the LD50 values of each test substance.
4.3.6.2.3 For the determination of the LD50 of the mixture, when other LD50
determination methods are used, the sum of half of the LD50 value of each test substance
can be used as the middle group; then several groups can be calculated upward and
downward, according to the...