Toxicity tests are performed using laboratory animals to assess the safety of substances like chemicals, pharmaceuticals, and consumer products. These tests characterize toxicity levels and target organs. Alternative test methods seek to reduce, refine, and replace animal use. New alternative methods include computer modeling, microarray technology, and non-mammalian models to predict toxicity without using animals. The ultimate goal is developing alternative methods that are fast, cheap, and scientifically valid.

1. Toxicity Tests
Alternative Methods in
Toxicology
SUBMITTED BY- IRFAN KHAN
SUBMITTED TO –Dr. SAUMYA DAS MAM

2. Toxicity Tests
 Toxicity tests are performed to assess the safety or hazards
of several substances such as industrial chemicals,
pharmaceuticals and consumer care products.
 Toxicity tests characterize the toxicity and the level of
toxicity. They help to find out the dose-response and the
target organ.

3. Toxicity tests differ from each other;
*Acute,
*Subchronic
*Chronic ( life-time, long-term ) toxicity
tests evaluate all potential toxicity.
Certain toxicity tests such as teratogenicity,
mutagenicity, carcinogenecity, reproductive
toxicity, immunotoxicity,
neurotoxicity…..evaluate certain type of
toxicity.
Many of the current toxicity testing
methods use laboratory animals (e.g. mice,
rats, rabbits).

4. Animals are useful models to predict the
toxicity of chemicals in humans because
they have similar cell organelles, cells and
organs.
If the model is not close to human,
uncertainity of results increase.
Toxicity tests can be performed in several
laboratories and the same results must be
obtained in different labs (tests must be
objective ).
Toxicity tests must be fast and cheap

5. Alternative Test Methods
 Alternative test methods are test methods that reduce,
refine and replace animal use. Reduction, refinement, and
replacement are commonly referred to as
 “the 3Rs of alternatives”.
 The concept of 3Rs was first proposed by William Russell
and Rex Burch in the “Principles of Humane Experimental
Technique”.

6. 1R= Replacement of test
animals
2R=Refinement ( better
tests)
3R=Reduction ( decrease of
the number of animals)
4R=Responsibility ( tests
scientifically acceptable)

7. Acute Toxicity Tests
LD50 TEST
 The lethal dose 50 (LD50) test was first introduced in 1927
by Trevan (1927), for testing substances intended for
human use such as digitalis and insulin.
 It covers the application of one high dose or several low
doses during 24hours. Effects are observed for 14 days
 The endpoint is the death of animals

8. REDUCTION
 In 1981, the Organisation for Economic Cooperation and
Development (OECD) incorporated the LD50 test into its
new Test Guidelines.
 By this time, it was generally agreed that the statistical
precision of the LD50 value, together with its confidence
intervals and the slope of the dose–mortality curve, which
this classical LD50 test could provide, were not needed for
normal hazard and risk assessment purposes.

9. Fixed Dose Procedure
(OECD 420)
 These studies showed that the FDP was able to provide
results that enable substances to be ranked according to the
EU system of classification.
 The FDP causes less compound-related mortality and
subjects those animals which are used to less pain and
distress.

10. Acute Toxic Class Method (ATC)
(OECD 423)
 In 1996, a second alternative method, the ATC was adopted
(OECD 423, 2001).
 The ATC also uses the concept of fixed dose levels but
retains mortality as a principal endpoint.
 The oral ATC method is a sequential testing procedure with
the use of three animals of one sex per step.

11. Replacement
 New Technologies and New Models:
 A number of new emerging fields and techniques are
contributing major new insights for replacing sentient
animal use within biomedical research and toxicity testing.
These can be classified as follows:

12. 1.Computerized Modeling:
Computerized modeling based on
(Q)SAR, in silico models in the
future may replace some of the
animal tests at least.

13. 2. Physiology and
Pharmacokinetic Modeling:
This kind of modeling predicts
the disposition of xenobiotics and
includes.
ADME parameter predictors
metabolic fate predictors
metabolic stability predictors
cytochrome p450 substrate
predictors
physiology-based
pharmacokinetic (PBPK)or
biokinetic (PBBK) modeling
software

14. 3. Microarray Technology:
Microarray consists of DNA or
protein fragments placed onto
a slide, which are then used as
“miniaturized reaction areas”.
Its aim is to detect any changes
in gene or protein expression
patterns in cells or tissues.

15. 4. Omics Technology: The aim of each
“omics” technology is to extract
information that has mechanistic and
predictive value.
-These include:
a) Genomics: The study of genes and
their function.
b) Proteomics: The study of proteins.
c) Metabonomics: The study of
molecules involved in cellular
metabolism.
d) Transcriptomics: The study of the
mRNAs.
e) Glycomics: The study of cellular
carbohydrates.
f) Lipomics: The study of cellular
lipids.

16. 5.Non Mammalian Models:
The use of invertebrates such
as drosophila, freshwater
snails and Caenorhabditis
elegans are widely used for the
assessment of toxicity of
several xenobiotics.

17. Others
Placenta (PCBs, PAHs,
phthalates)
Bones (Pb)
Faeces (Pb, Cd, PCBs)
Teeth