Q. What are the sub-disciplines of toxicology?
Biochemical toxicology
Reproductive toxicology
Development toxicology
Teratology
Genetic toxicology
Clinical toxicology
Forensic toxicology
Analytical toxicology
Nutritional toxicology
Veterinary toxicology
Environmental toxicology
Occupational(Industrial) toxicology
Regulatory toxicology
Mechanistic toxicology
Aquatic toxicology
Ecotoxicology
Food toxicology
Formal toxicology
Descriptive toxicology
Q. Define occupational (Industrial) toxicology
Occupational (Industrial) toxicology is concerned with
health effects from exposure to chemicals in the workplace. It deals with the clinical study of workers of
industries and environment around him.
Q. Define regulatory toxicology:
It deals with administrative functions concerned with the
development and interpretation of mandatory toxicology testing programs and
controlling the use, distribution and availability of chemicals used
commercially and therapeutically. For example, Food and Drug Administration
(FDA) regulates drugs, cosmetics and food additives. Regulatory toxicology
gathers and evaluates existing toxicological information to establish
concentration-based standards of “safe” exposure. The standard is the level of
a chemical that a person can be exposed to without any harmful health effects.
Q. Define food toxicology
It deals with natural contaminants, food and feed
additives, and toxic and chemo-protective effects of compounds in food.
Explanation: Food Toxicology is involved in delivering
a safe and edible supply of food to the consumer. During processing, a number
of substances may be added to food to make it look, taste, or smell better.
Fats, oils, sugars, starches and other substances may be added to change the
texture and taste of food.
All of these additives are studied to determine if and
at what amount, they may produce adverse effects. A second area of interest
includes food allergies. Almost 30% of the American people have some food
allergy. For example, many people have trouble digesting milk, and are lactose
intolerant. In addition, toxic substances such as pesticides may be applied to
a food crop in the field, while lead, arsenic, and cadmium are naturally
present in soil and water, and may be absorbed by plants. Toxicologists must
determine the acceptable daily intake level for those substances.
Q. Define formal toxicology
It deals with the formal toxicological studies which are
pre-requisite for release of a new drugs/chemical e.g. calculation of LD50 and minimum toxic dose.
Q. Define descriptive toxicology
Descriptive Toxicology is concerned with gathering
toxicological information from animal experimentation. These types of
experiments are used to establish how much of a chemical would cause illness or
death. The United States Environmental Protection Agency (EPA), the
Occupational Safety and Health Administration (OSHA), and the Food and Drug
Administration (FDA), use information from these studies to set regulatory
exposure limits.
Q. Define mechanistic toxicology
Mechanistic Toxicology makes observations on how toxic
substances cause their effects. The effects of exposure can depend on a number
of factors, including the size of the molecule, the specific tissue type or
cellular components affected, whether the substance is easily dissolved in
water or fatty tissues, all of which are important when trying to determine the
way a toxic substance causes harm, and whether effects seen in animals can be
expected in humans.
Q. Define nutritional toxicology
Nutritional Toxicology is the study of toxicological
aspects of food/feed stuffs and nutritional products/habits.
Q. Define toxicodynamics
It deals with the study of
biochemical and physiological effects of toxicant and their mechanism of
action.
Q. Define toxicokinetics
It deals with the study of
absorption, distribution, metabolism and excretion of toxicants in the body.
Q. Define toxicovigilance
It deals with process of identification, investigation,
and evaluation of various toxic effects in the community with a view of taking
measures to reduce or control exposures involving the substances that produce
these effects.
Q. Define toxinology
It deals with assessing the toxicity of substances of
plant and animal origin and those produced by pathogenic bacteria/organism.
Q. Define toxicoepidemiology
It refers to the study of quantitative analysis of the
toxicity incidences in organisms, factors affecting toxicity, species involved
and the use of such knowledge in planning of prevention and control strategies.
Toxic or toxicity is relative terms commonly used in comparing
one chemical with another.
Q. Define toxicity
It is a
state of being poisonous or capacity to cause injury in living organisms.
Q. Define toxicosis
It is the
condition or disease state that results from exposure to a toxicant. The term
toxicosis is often used interchangeable with the term of poisoning or
intoxication.
Q. Define
toxic effects
These are undesirable effects produced
by a toxicant/drug which are detrimental to either survival or normal
functioning of the individual.
Q. Define
side effects
These are undesirable effects which
result from the normal pharmacological actions of drugs. These results may not
be detrimental or harmful to the individual.
Q. Define
selective toxicity
It is the
toxicity produced by a chemical to one kind of living matter without harming
another form of life even though the two exist in intimate contact.
Q. Define plant toxins?
Different portions of a plant may contain different
concentrations of chemicals. Some chemicals made by plants can be lethal. For
example, taxon, used in chemotherapy to kill cancer cells, is produced by a
species of the yew plant.
Q. Define animal toxins?
Animal toxins can result from venomous or poisonous
animal releases. Venomous animals are usually defined as those that are capable
of producing a poison in a highly developed gland or group of cells, and can
deliver that toxin through biting or stinging. Poisonous animals are generally
regarded as those whose tissues, either in part or in their whole, are toxic. For
example, venomous animals, such as snakes, spiders, etc., and poisonous
animals, such as puffer fish, or oysters, which may be toxic to some
individuals when contaminated with vibrio vulnificus.
The
exposure of experimental animals to chemicals can be divided into four
categories: acute toxicity and repeated exposure (sub-acute, sub-chronic, and chronic).
Q. Define
acute toxicity
Acute
exposure is defined as exposure to a chemical for less than 24 hr. The exposure
usually refers to a single administration, repeated exposures may be given
within a 24 hr period for some slightly toxic or practically nontoxic
chemicals. Acute exposure by inhalation refers to continuous exposure for less
than 24 hr, most frequently for 4 hr.
Q. Define
repeated exposure
Repeated exposure is divided into three
categories:
sub-acute
ii) sub-chronic, and iii) chronic.
Sub-acute exposure to a chemical is for 1 month or less,
sub-chronic for 1 to 3 months, and chronic for more than 3 months (usually this
refers to studies with at least 1 year of repeated dosing).
Explanation: Acute or repeated exposure can be by any
route, but most often they occur by the oral route, with the chemical added
directly to the diet. In human exposure situations, the frequency and duration
of exposure are usually not as clearly defined as in controlled animal studies.
However, almost same terms are used to describe general exposure situations.
Thus, workplace or environmental exposures may be described as acute (occurring
from a single incident or episode), sub-chronic (occurring repeatedly over
several weeks or months), or chronic (occurring repeatedly for many months or
years).
Q. Define
transient or reversible or temporary toxicity
It is the
toxicity or harmful effect that remains for short duration of time. e.g., narcosis
produced organic solvents.
Q. Define
persistent or permanent or irreversible toxicity
It is the
toxicity or harmful effects that persists throughout life span of the
individual and are of permanent nature, e.g. scarring of skin produced by
corrosives.
Q. Define
immediate toxicity
It is the toxicity that develops
shortly after a single exposure to a toxicant e.g. cyanide poisoning.
Q. Define
delayed toxicity
It is the
toxicity or harmful effect which has delayed onset of action, e.g. peripheral
neuropathy produced by some organophosphorus insecticides
and radiation
sickness.
Q. Define
cumulative toxicity
It is progressive toxicity or harmful
effect produced by summation of incremental injury resulting from successive
exposures, e.g. liver fibrosis produced by ethanol.
Accumulative
effects: occurs two ways...
a) accumulation
of toxin: exposure to heavy metals (lead, mercury) that have long half-lives
result in disease due to metal accumulation.
b) accumulation
of effect: low level exposure to organophosphate pesticides depresses
acetylcholine esterase to a point where symptoms occur.
Q. Define cheminformatics?
Cheminformatics (also known
as chemoinformatics, chemioinformatics and chemical informatics):
Cheminformatics is the use of computer and informational techniques applied to
a range of problems in the field of chemistry. These in silico techniques are
used in, for example, pharmaceutical companies in the process of drug
discovery.
Q. Define end point study record?
Endpoint study record or IUCLID (International Uniform
Chemical Information Data base) format of the technical dossier is used to
report study summaries and robust study summaries of the information derived
for the specific endpoint according to the REACH Regulation.
Q. Define end point of study design?
Endpoint: an observable or measurable inherent property/data
point of a chemical substance. For example, a physical-chemical property like
vapor pressure or degradability or a biological effect that a given substance
has on human health or the environment, e.g. carcinogenicity, irritation,
aquatic toxicity.
Q. Define in vitro test?
In vitro test: literally stands for “in glass” or “in
tube”, refers to the test taking place outside of the body of an organism,
usually involving isolated organs, tissues, cells, or biochemical systems.
Q. Define in vivo test?
In vivo test: a test conducted within a living organism.
Q. Define in silico test?
In silico: In silico (a phrase coined as an analogy to the familiar phrases in vivo and in vitro), is an expression used to denote “performed on computer or via computer simulation.” Means scientific experiments or research conducted or
produced by means of computer modeling or computer simulation.
Q. Define IUCLID flag?
IUCLID flag: an
option used in the IUCLID software to indicate submitted data type (e.g.
experimental data) or their use for regulatory purposes (e.g.
confidentiality).
Q. Define prediction model?
Prediction model is a theoretical formula, algorithm or
program used to convert the experimental results obtained by using a test
method into a prediction of the toxic property/effect of the chemical
substance.
Q. Define QSARs and SARs?
QSARs and SARs: theoretical models that can be used to
predict in a quantitative or qualitative manner the physic-chemical biological
(e.g. (eco)toxicological) and environmental fate properties of compounds from
knowledge of their chemical structure. A SAR is a qualitative relationship that
relates a (sub) structure to the presence or absence of a property or activity
of interest. A QSAR is a mathematical model relating one or more quantitative
parameters, which are derived from the chemical structure, to a quantitative
measure of a property or activity.
Q. Define test or assay, validation test and validation.
Test (or assay): an experimental system set up to obtain
information on the intrinsic properties or adverse effects of a chemical
substance.
Validated test: a
test for which its performance characteristics, advantages, and limitations has
been adequately determined for a specific purpose.
Validation: the process by which the reliability and
relevance of a test method are evaluated for the purpose of supporting a
specific use.
Q. Define vertebrate animal?
Animals that belongs to subphylum Vertebrata, chordates
with backbones and spinal columns is known as Vertebrate animal.
Q. Define accidental poisoning
Accidental
poisoning may occur when human beings or animals take toxicant accidentally or
is added unintentionally in food or through in its feed, fodder or drinking
water. Such toxicants come from either natural sources or manmade sources. The
natural sources include ingestion of toxic plants, biting or stinging by
poisonous reptiles, ingestion of food contaminated with toxins, contaminated
water with minerals, etc. Man made sources include therapeutic agents,
household products and agrochemicals, etc.
Q. Define malicious poisoning
It is the
unlawful or criminal killing of human beings or animals by administering
certain toxic/poisonous agents. Incidence of such poisonings is more prevalent
in human beings and less in animals.
Toxic agents are classified in number of ways depending on
the interests and needs of the classifier. There is no single classification applicable for the entire spectrum of toxic
agents and hence combinations of classification systems based on several
factors may provide the best rating system. Classification of poisons may take
into account both the chemical and biological properties of the agent, however,
exposure characteristics are also useful in toxicology.
Q. Classify toxic agents
In toxicology, compounds are
classified various ways, by one or more of the following classes:
Use e.g, pesticides (atrazine),
solvents (benzene), food additives (nutrasweet), metals, war gases,
Effects e.g. carcinogen
(benzo-a-pyrene), mutagen (methylnitrosamine), hepatotoxicant (CHCl3)
…….
Physical state such as oxidant
(ozone), gas (CO2), dust (Fe2O3), liquid (H2O)
.........
Chemistry such as:
aromatic amine(aniline), halogenated hydrocarbon (methylene chloride) and so
on.
Sources of toxicants e.g. plant
or animal or natural and so on.
Mechanism of action: cholinesterase inhibitor
(malathion), methemoglobin producer (nitrite).... ….
Q. Classification based on sources of toxicants
i) plant toxins,
ii) animal toxicants,
iii) mineral toxicants,
iv) synthetic toxicants
v) physical or mechanical agents
Q. Classification based on physical state of toxicants
i) gaseous toxicants
ii) liquid toxicants
iii) solid toxicants
iv) dust toxicants,
Q. Classification based on target organ or system
i) neurotoxicants
ii) hepatotoxicants
iii) nephrotoxicants
iv) pulmotoxicants
v) hematotoxicants
vi) dermatotoxicants
vii) development and reproductive toxicants
Q. Classification based chemical nature/structure of
toxicants
i) metals
ii) non-metals
iii) acids and alkalis
iv) organic toxicants (carbon compounds other than oxides
of carbon, the carbonates, and metallic carbides and cyanides),
Q. Classification based on analytical behavior of
toxicants
i) volatile toxicants
ii) extractive toxicants
iii) metals and metalloids
Q. Classification based on type of toxicity
i) acute
b) subacute
c) chronic
Q. Classification based on toxic effects
i) carcinogens
ii) mutagens
iii) teratogens
iv) clastogens
Q. Classification based on their uses
i) insecticides
ii) fungicides
iii) herbicides
iv) rodenticides
v) food additives, etc
Q. Classification based on symptoms produced
i) corrosive poisons
ii) irritant poisons
iii) systemic poisons
iv) miscellaneous poisons
In addition, there are other types of classifications
that are based up on the environmental and public health considerations and so
on.
Q. Describe briefly the term “Toxicity rating”.
A system of “toxicity rating” has been evolved for common
poisons. The higher the toxicity rating for a particular substance (over a
range of 1-6), the greater is the potency. The toxicity rating based on toxic
potential of substances (super toxic, extremely toxic, very toxic, moderately
toxic, slightly toxic and practically non-toxic.
FURTHER READING
Gupta PK (2018)
Illustrative Toxicology with Question bank. 1st Edition. Elsevier, USA
Gupta PK (2016) Fundamentals
of Toxicology: Essential concepts and applications. 1st Edition.
ISBN-9780128054260, pp 438, BSP/Elsevier,
USA
The Merck Veterinary
Manual (2016). Chapter “Herbicide Poisoning” by PK GUPTA 11th edition,
Merck & Co. Inc Whitehouse Station, NJ, USA 2969-99
The Merck Veterinary Manual (2016). Chapter
“Pentachlorophenol Poisoning” by PK GUPTA 11th edition, Merck
& Co. Inc Whitehouse Station, NJ, USA pp 3052-53
Gupta PK
(2016) Essential Concepts in Toxicology. Published by PharmaMed
Press (A unit of BSP Books Pvt. Ltd), Hyderabad, India pp 362.
Gupta PK (2010)
Modern Toxicology, Basis of organ and reproduction toxicity. Vol 1.
Published by Pharma Med Press (A unit of BSP Books Pvt. Ltd).
Hyderabad, India pp 1-460.
Gupta PK (2010)
Modern Toxicology, Adverse effects of xenobiotics. Vol 2, Published by
PharmaMed Press (A unit of BSP Books Pvt. Ltd). Hyderabad, India pp 1-460.
Gupta PK (2010)
Modern Toxicology, Immuno and clinicsal toxicology Vol 3. Published by
PharmaMed Press (A unit of BSP Books Pvt. Ltd). Hyderabad, India pp 1-340.
