Intro to Toxicology Flashcards
1
Q
what was toxicology initially defined as and what was it later redefined to?
A
1- Toxicology is the study of adverse effects of chemicals or physical agentson living organisms
2-the study of the adverse physiochemical effects of chemical, physical or biological agents on living organisms and ecosystem,
including the prevent and amelioration of such adverse effects
2
Q
any substance can be toxic as long as what needs are satisfied
A
As long as the substance is introduced in a dose capable of disturbing the normal physiological homeostasis of the exposed body
3
Q
what was the earlies use of toxicology
A
began with early cave dwellers that
-recognized poisonous plants and
animals used their extracts for hunting
and warfare, which also led to antidote
development
4
Q
why is the coronavirus not considered a toxin or toxic substance
A
The coronavirus is not a toxin because it is a biological agent that infects cells and replicates, while toxins are chemical substances that cause damage without replication and is produced by an organism
5
Q
what are the fumdamental concepts of Paracelus(1493-1541) (5)
A
- Speceific chemicals where responsible for the toxicity of plant and animal poisin
- The bodies response to chemicals depends on the dose recieved
- All substances are poisin, it is the dose that make the poisin
-Highly toxic chemicals can be life saving when given in appropriate doses. (Poisons are not harmful at a sufficiently low dose).
– A small dose of a substance may be harmless or beneficial, where as a larger does may be toxic(resulted i the derivation of the dose resposne relationship)
6
Q
Tell me about Orfila
A
-first prepared a systematic correlation between the chemical and biological properties of poisons – Concept of potency.
-demonstrated the effects of poisons on specific organs through analyses of autopsy material for poisins and their pathology ( Histopathology )
7
Q
what specific changes cause virtually all toxic effects
A
changes in cellular molecules and biochemicals
8
Q
What is potency
A
the dose of a drug/toxicant required to produce a specific effect of given intensity as compared to a standard refernce
9
Q
what is a xenobiotic
A
-A foreign substance that is not naturally produced by an organism or found in its environment.
-Can be harmful or harmless.
-Includes drugs, pollutants, synthetic chemicals, and some natural compounds.
-Example: Antibiotics in the human body, pesticides in water.
10
Q
what is a toxin
A
-A naturally occurring poisonous substance produced by living organisms (e.g., bacteria, plants, animals).
-Typically acts as a defense mechanism or byproduct of metabolism.
-Example: Botulinum toxin from Clostridium botulinum, snake venom, ricin from castor beans.
11
Q
what is a toxicant
A
-A man-made or environmental chemical that is toxic to living organisms.
-Usually results from human activities like industry, agriculture, or pollution.
-Example: Pesticides, heavy metals (like lead in water), dioxins in industrial waste.
12
Q
What is disposition in toxicology, and how does it affect toxicity of a xenobiotic in the body?
A
Disposition refers to how a toxic substance is absorbed, distributed, metabolized (biotransformed), stored, and excreted in the body. It determines how long and in what concentration a substance affects the body, influencing its toxicity.
13
Q
How does toxicokinetics influence toxicity?
A
A highly toxic substance that is poorly absorbed may be less hazardous than a low-toxicity substance that is highly absorbed.
Two substances with similar absorption & toxicity can differ in hazard level due to differences in biotransformation and metabolite effects.
14
Q
What factors influence the severity of toxicity?nb
A
-Duration & concentration at the point of entry.
-Absorption rate & quantity of the substance.
-Distribution & concentration in specific body sites.
-Biotransformation efficiency & nature of metabolites.
-Ability to pass cell membranes and affect key components (e.g., DNA).
-Storage duration & amount in body tissues.
-Rate & site of excretion.
-Age & health status of the exposed person
15
Q
How are toxicity categories used in regulation?
A
They help decide warning labels on products to inform people about dangers.
They determine if a substance needs special restrictions (e.g., only professionals can use it) or child-proof packaging to prevent accidental poisoning.
In some cases, weaker (diluted) versions of a toxic product may be classified differently for safer use.
16
Q
What is the EPA Toxicity Category system for pesticides?
A
The U.S. Environmental Protection Agency (EPA) classifies pesticide toxicity into four categories, with Category I being the most toxic. These categories help determine precautionary statements, personal protective equipment (PPE) requirements, and labeling regulations.
17
Q
What are the four EPA Toxicity Categories?
A
Category I – Highly toxic & severely irritating.
Category II – Moderately toxic & moderately irritating.
Category III – Slightly toxic & slightly irritating.
Category IV – Practically non-toxic & not an irritant.
18
Q
Q: What is child-resistant (CR) packaging?
A
Special safety packaging that prevents children from easily opening hazardous materials.
Commonly required for prescription drugs, over-the-counter medications, and nicotine products.
Mandated by regulatory laws to reduce accidental poisoning.
19
Q
What is toxicity classification?
A
Groups chemicals based on their most important toxic effect.
Examples: Allergenic, neurotoxic, carcinogenic, etc.
Important for administrative purposes, warnings, and regulatory information.
20
Q
what is toxicity
A
the ability of a substance to cause injury to a biological material
21
Q
what is selective toxicity
A
the ability of a chemical to cause injury to one kind of living matter without harming another form of life even when both are exposed to the same chemical
22
Q
steps in development of toxicity
A
Exposure – The toxic substance enters the body through ingestion, inhalation, skin contact, or injection.
Absorption – The substance moves from the site of exposure into the bloodstream.
Distribution – The toxicant spreads through the body, reaching different organs and tissues.
Metabolism (Biotransformation) – The body breaks down or modifies the substance, which may make it less toxic (detoxification) or more toxic (bioactivation).
Interaction with Target Molecules – The toxic substance or its metabolites bind to or damage important molecules (e.g., DNA, proteins, cell membranes), leading to harmful effects.dose effects extent of toxicity
Toxic Effects – The damage caused leads to cell injury, organ dysfunction, or systemic effects, which may be acute (immediate) or chronic (long-term).
Excretion – The body removes the toxic substance through urine, feces, sweat, breath, or bile. If excretion is slow, the substance may accumulate and increase toxicity.
23
Q
what are the type of toxic materials
A
-Discrete toxic chemical
-toxic materials(does not have an exact chemical composition but comprises of a variety of fibres and minerals)
-toxic substance(contains a mixture of chemicals)
24
Q
what is a Systemic toxicants
A
affects the entire body or many organs rather than a specific site
25
what is a Organ Toxicant
Affect only specific tissues or organs while not producing damage to the body as a whole
26
What is differential toxicity
the varying degrees or types of harm caused by a substance or agent to different organisms, tissues, or cells, even if the exposure is the same
27
What is individual susceptibility in toxicology?
It refers to how different people respond differently to the same toxic substance. Some may have no effect, while others may get seriously ill or even develop cancer
28
Why do people react differently to toxic substances?
-Genetics – Some people have genetic traits that make them more or less sensitive.
-Gender – Some toxicants affect one gender more (e.g., gasoline is nephrotoxic in male mice only).
-Age (Young) – Infants and children are more vulnerable due to:
Underdeveloped excretory system
Weak biotransformation (metabolism) enzymes
Incomplete blood-brain barrier
-Age (Elderly) – Older adults may have:
Slower excretion & metabolism
Higher body fat, which can store toxins
-Nutritional status & diet – Poor nutrition can increase toxicity risk.
-Health conditions & lifestyle – Chronic illnesses or habits (e.g., smoking) can influence toxicity.
-Previous or concurrent exposures – Prior exposure to toxins may increase or decrease sensitivity.
29
Why are children, especially neonates, more sensitive to toxicants than adults?
Their biotransformation, elimination, and other physiological systems are immature, leading to higher toxin levels in the blood for longer periods.
30
How does metabolism in newborns affect toxicity?
Their metabolic capacity is low for some chemicals.
They may use unique metabolic pathways that adults do not have.
Their metabolism rapidly matures, so by 6 months, toxicity response is usually similar to adults.
31
Why do children and adults respond differently to toxic exposures?
-Children’s bodies are still developing, making them more vulnerable to disruptions.
-Chemical exposure can mutate DNA, alter cell division, or interfere with hormones and enzymes, affecting growth and development.
32
What environmental factors can impact normal development?
-Nutritional status (e.g., protein, vitamins, folic acid availability).
-Maternal smoking and alcohol use during pregnancy.
-Prescription drugs taken during pregnancy.
-Chemical contaminants like lead and organic mercury.
33
what is a sensitive sub population
a group of persons that is at increased risk of some adverse health event or outcome after exposure to a contamint than the average healthy person in the total general population
34
what is risk, what is a risk estimate based upon, what is risk Charaterization?
- probability of a specific adverse effect to occur and is expressed as the percentage of cases in a given population and during an interval of time
- based upon actual cases or a projection of future cases
- Risk characterization integrates the hazard identification, the exposure assessment, and the dose response assessment to estimate
the probability that a non-desirable effect or harm occurs in a particular human population.
35
what are toxicogenetics
* refer to stable and heritable alterations in the genome that can influence the relative susceptibility of an individual (or group of individuals) to the adverse health effects resulting from exposure to an exogenous material.
* It predispose the individual to the same adverse effects as the parent genome relative to same chemical exposure.
36
what is meant by the term toxicogenomic
* Describes analysis of changes in gene--expression, induced in a biological system by exposure to a xenobiotic.
* It deals with the changes in structure and function of the genome (gene composition) as it responds to adverse xenobiotic exposure.
37
how can toxicogenetic differences underpin variations in toxicogenomic response
polymorphisms that alter biological function may change the spectrum of genes regulated in response to a toxicant.
38
what is polymorphism
Polymorphism is the presence of different forms or variations of a gene, trait, or species within a population. It can refer to genetic differences (like different alleles) or physical traits (like color variations in animals).
39
what is a dose
the actual amount of a chemical that enters the body,may be due to acute(<24 hrs) or chronic exposure(>24hrs)
40
What is a dose-response relationship?
describes the magnitude of the response of an organism, as a function of exposure (or doses) to a stimulus or stressor (usually a chemical) after a certain exposure time
41
What are the molecular targets of chemical compounds
* Receptors
* Ion Channel Receptors
* Carrier Proteins
* G-Protein Coupled Receptors
* Tyrosine-Kinase Receptors
* Ah Receptors
* Steroid Hormone Receptors
42
What is an AH Receptor(AHR)
* The aryl hydrocarbon receptor is a
protein encoded by the AHR gene in humans).
* It is a ligand-activated transcription factor present in many cells.
* Find within the cell & that binds to aryl hydrocarbons forming a complex that moves into the nucleus of the cell.
* The AhR links environmental chemical stimuli with adaptive responses, such as detoxification, cellular homoeostasis or immune responses
43
What is A G protein coupled receptor
membrane-bound receptor that transmits signals into a cell by activating G proteins when a ligand binds to it.
- made up of 7 transmembrane alpha-helices spanning the membrane
44
What are carrier proteins
bind specific solutes and transfer them across the lipid bilayer by
undergoing conformational changes that expose the solute-binding site
sequentially on one side of the membrane and then on the other
45
What are ion channel receptors?
Ion channel receptors are membrane proteins that regulate cellular excitability and are crucial in physiological processes.
46
What are the three superfamilies of ion channels based on their stimulus?
Voltage-gated ion channels
Ligand-gated ion channels (LGICs)
Mechano-sensitive ion channels
47
What are ligand-gated ion channels (LGICs)?
LGICs are transmembrane ion-channel proteins that open when a ligand (e.g., neurotransmitter) binds, allowing ions like Na+, K+, Ca2+ , and Cl− to pass through
48
A fundamental principle of pharmacology
the intensity of effect produced by a drug → function of the quantity of drug administered (or the concentration of the drug at the target site).
49
read lecture 2 pg13-15. which drug is most effective
A
50
Effects of a drug depend on the dose, expand on this
as dose increases, effects increase to a maximum as increased dose increases effects, until all receptors on the cell surface are occupied by a drug, the effects plateau atp and then begi to decrease due to desensetization.
51
What are the two types of response to a drug
-Quantal dose response(all or nothing)
-Graded dose respons(when dose increases, the response increases in graded fashion)
52
what is the shape of the dose-response curve for most toxic effects
sigmoid
53
what does it mean when the dose response curve is linear from dose 0 within a certain range
no threshold exists and even a small dose may represent a risk.
And above that dose range the risk may increase at greater than a linear rate
54
What are graded dose-response curves?
Graded dose-response curves are graphical representations of the relationship between the dose of a drug and the effect produced.
55
What is used in graded dose-response relationships: drug concentration or actual dose?
Drug concentration is used rather than the actual dose.
56
What is the EC50 (effective concentration)
The EC50 is the concentration which brings about 50% of the maximal
tissue response and is used to determine the potency of drugs
57
what 4 main parameters describe the graded dose response curve
* Potency, i.e. the EC50 which relates to a drugs' affinity for its receptor
* Slope: a useful parameter – A shallow suggests a greater chance of overlap between desired effects and side
effects, - But a too steep slope suggests it will be difficult to precisely control the effects.
* Maximum or the Emax, - the maximum effect achievable by that drug - very often this will not be available
from even in vitro data, and it may be represented by a blank patch on the graph
* Threshold dose or minimum dose-the lowest dose at which a drug effect is seen; this may be represented by the zero
point,
58
what is the efficacy of a drug
Efficacy is the ability of a drug after binding with receptors to initiate change leading to definite effects.
* It is the ability/capacity
of a drug to elicit a physiologic response
when it interacts with a receptor
* Efficacy (Emax) is the capacity of a drug to produce a maximum
response
59
what is the potency of a drug
* Potency is a comparative measure of different doses of two drugs,
needed to produce the same pharmacological effect.
* It is known as drug strength.
* Potency is the amount of drug needed to produce a certain response.
60
ratio of TD50 and ED50 is used for what in a quantal dose effect relationship
used to determine the therapeutic index of
a drug, (numerical index, NI)of the drug’s safety and generally = ≥1.
61
what is an ordered dose-response relationship
an Ordered dose-response relationship is a sequence of quantal dose-response relationships which represent several quantal response end-points which are seen when dose is increased.
62
Explain briefly the involvement of
toxicology in research and the application
of its outcome.
Toxicology plays a crucial role in research by studying the harmful effects of chemicals, drugs, and environmental agents on biological systems. It helps identify toxic substances, understand their mechanisms of action,the types of adverse effects that may be
produced after exposure, and establish safe exposure limits.
The outcomes of toxicology research have wide applications, including:
Pharmaceutical Development: Ensuring drug safety and determining proper dosages.
Environmental Protection: Assessing pollution impact and setting regulations for contaminants.
Food Safety: Evaluating additives, pesticides, and contaminants in food.
Occupational Health: Identifying workplace hazards and establishing safety guidelines.
Forensic Science: Investigating poisoning cases and substance-related deaths.
63
sub disciplines of toxicology
Mechanistic toxicologists = mechanism of action: study the absorption, distribution, and excretion.
*In academic settings or private industries and develop antidotes. Descriptive toxicologists evaluate the toxicity of drugs, foods, and other products. They often perform experiments in a pharmaceutical or academic setting.
Clinical toxicologists (physicians or vet)
=interested- prevention, diagnosis, and treatment of poison cases.
=Have specialized training in emergency medicine and poison management.
* Forensic toxicologists -application of toxicology to law. -uses chemical analysis to determine the cause and circum. of death in
a postmortem investigation.
* Environmental toxicologists
=effects of pollutants on organisms,populations, ecosystems, and the biosphere.
* Food Toxicology
* Regulatory toxicologists -concerned- to protect humans and animals from excessive risk.
* Analytical toxicology: identifies the toxicant through analysis of
body fluids, stomach content, excrement, or skin
* Occupational toxicology:
64
Commonly used tests to check liver function are the
alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), albumin, and bilirubin tests.
* The ALT and AST tests measure enzymes that the liver releases in response to damage or disease.
65
Kidney function tests
ACR (Albumin to Creatinine Ratio) and GFR (glomerular
filtration rate). – GFR is a measure of kidney function and is performed through a blood test.
... Too much albumin in your urine is an early sign of kidney damage.
66
Factors Determining the impact of exposure on the organism
* How the agent enter the organism, & duration
* How the agent moves throughout the organism;
* Transformation by interacting with living cells and tissues;
* Organs affected by the toxicant
* The health impact of the exposure.
Others include
* ambient environment
* condition of workplace
* exposure to food and drugs
67
IN VIVO TOXICOLOGICAL TESTING
* In vivo – research conducted on whole organisms, e.g. mice, rats,
zebra fish, yeast etc
Advantages:
* Can evaluate the progression of toxic effects
* Can more clearly determine the effects of intoxication on a whole
organism
* More relevant to modelling or predicting human disease/intoxication
* Gives a clear picture of the drug action in the presence of other
physiological body processes
Disadvantages:
* Strict regulation, justification, and oversight to prevent unnecessary
pain and suffering
* Much more expensive and time intensive
* More difficult to link an outcome to a toxicant
68
IN VITRO TOXICOLOGICAL STUDY
* Studies that are conducted outside of the whole organism
* Isolated components of an organism from their usual biological surroundings are used.
* It permits a more detailed or more convenient analysis than can be done with whole organisms.
* Also known as “test tube” or “petri dish” experiments.
In vitro –research conducted on tissues, cells, or proteins outside of a whole organism (cell culture)
Advantages:
* Can easily expose cells to a toxicant
* Can use bioassays to determine the effect
* More controlled – can more clearly link toxic effects to the toxicant
* Faster and less expensive
* More ethically acceptable
Disadvantages:
* Less relevant to what happens in a whole organism
69
What are mycotoxins
A mycotoxin is a toxic secondary metabolite produced by organisms of the fungi
kingdom, → known as molds–under specific environmental conditions,
and are harmful to human and animal health.
69
What are the different sources of poisonous substances called
Poisonous substances are produced by plants, animals, or bacteria.
Phytotoxins (from plant)
Zootoxins ( Animal poisons)
Bacteriotoxins (from bacteria)
mycotoxins (from microbes)
69
Point of human contact with toxicans
* Home
* Workplace: chemicals, machinery
* Environment:
* Food and drinking water:
70
Industrial toxicants are classified as
chemicals,
* mobilized through anthropogenic processes or
anthropogenic-derived chemicals, released into the environment, contaminating waterways and aquifers, soil, air, and organisms including food.
* These contaminants can reach food -
– directly from point source contamination or
– indirectly through long-range atmospheric and biogeochemical processes.
70
Routes of Exposure
* The skin (dermal absorption)
* The respiratory tract (inhalation)
* The digestive tract (ingestion
71
A complete exposure pathway has five elements:
1. A source of contamination, e.g. a smoke factory chimney;
2. Media for the contaminant to travel, such as groundwater, surface
soil, surface water, air, subsurface soil, sediment, and biota (animal
and plant life);
3. A point of exposure, or a point of contact with contaminated
material;
4. A route of exposure, or how contaminants enter or contact the body
(i.e. ingestion, inhalation, dermal contact, and dermal absorption); and
5. A receptor population, people who are exposed or potentially
exposed to contaminants.
71
Acute exposure and experiment procedure
Acute, which is exposure to a chemical for 24 hours or less.
Endpoints could be
* Lethal dose (death)
* Toxic dose (e.g. Liver injury)
* Effective dose (e.g. Relief from itching)
Animals:
* Mouse and rat are the species most commonly used for testing
* Both sexes are used
Procedure:
* Food is withheld the night before testing
* The number of animals that reach a prescribed endpoint at each dose are tabulated
* 10 animals per dose
* 5 dose levels
71
Sub acute exposure and experiment
* Which is exposure to a chemical for 1 month or less. At least 3 doses
Procedure:
* A high dose that produces toxicity and death in less than 10% of the animals
* A low dose that does not produce apparent toxic effects during an acute exposure - find apparent toxic effect
* An intermediate dose- therapeutic effect
72
what is sub-chronic exposure and what are the procedures for the experiment
Sub-chronic,
which is exposure to a chemical between 1 to 3 months. Three dose levels may be used.
Animals:
* Mouse and rat are the species most commonly used for testing
* Both sexes are used
Procedure:
* 1, 2 or more groups of same animals are required
* Both sexes can be used depending on the design and aims/ objectives of the study.
* Designed to determine short-time cumulative effects
* May involve more than one drug
* May be lab or field based
73
what is chronic exposure and what are the experimental procedures to test it
Chronic, which is exposure to a chemical for more than 3 months
or more, e.g. 6months
Animals:
* Mice
* Rats
Procedure:
* Drug Testing – 6 months
* Food Additives with potential lifetime human exposure – 2 years required
* Designed to assess cumulative toxicity of chemicals including consideration of carcinogenic potential
73
what is Absorption
Absorption is the transfer of a xenobiotic from the site of exposure into the systemic circulation.
* During this process, xenobiotics cross body membranes and enter the bloodstream.
* It is the first rate limiting step in the toxicokinetics of a xenobiotic.
73
The selective permeability of a cell membrane is dependant on what
*molecular size,
*lipid solubility, and
*electrical charge of the toxic molecule,
*cell membrane active and passive transport
mechanisms.
74
explain the distribution of xenobiotic substances throughout the body
* After entering the blood, – a xenobiotic may distribute throughout the body to organs or
tissues.
– Only the free fraction is active.
– The xenobiotics are often concentrated in a specific tissue (may or may not be their site of toxic action).
– As a xenobiotic is biotransformed or excreted from the body, more is released from the storage site.
* Is a Rapid process relative to absorption and elimination
Extent depends on:
- blood flow (well perfused tissue: liver and kidneys)
- size, M.W. of molecule
- lipid solubility and ionization
- plasma protein binding
- tissue binding
75
Factors determining the rate of distribution of chemicals
-Protein binding – chemicals highly bound to protein havesmall volume of distribution
- Plasma concentration – small volume of distribution of chemicals, most of the chemical remains in plasma
- Physiological barriers – chemicals will not uniformly distributed to the body → blood brain barrier
- Affinity of chemicals to certain tissues – the conc. of a chemical in certain tissues after a single dose maypersist even when its plasma concentration is reduced
e .g Lead concentrate in bone tissue
76
Biotransformation, what it is and explain its 2 phases and the 2 types
* “Biotransformation: conversion from one chemical form to another”.
* « the term is used synonymously with metabolism»
* *Generates more polar (water soluble), inactive metabolites readily excreted from body
* Metabolites may have potent biological activity (or may have toxic properties)
* Generally applicable to metabolism of all xenobiotics as well as endogenous compounds such as steroids, vitamins and fatty acids.
* Phase I– functionalization reactions (the drug is converted into more polar compound e .g oxidation, reduction, & hydrolysis)
* Phase II– conjugation reactions (a drug or its metabolite is conjugated with an endogenous substance)
* Enzyme inhibition- by this the biotransformation of drugs is delayed & is a cause of increased toxicity
* Enzyme induction- by this the biotransformation of drugs is accelerated & is a cause of therapeutic failure
76
What is bioavilability
is the fraction of the administered dose
reaching the systemic circulation
76
Talk about storage sites of xenobiotic substances, and fat soluble toxicants
The toxicants may be stored in – the target tissue, possibly resulting in an adverse response, or – it may be stored in other tissue types, which may not be readily affected.
The fat-soluble toxicants are,
*easily absorbed into fatty deposits throughout the body (DDT)
*stored for long periods of time (low bld suppl). Eg. Lead is readily absorbed and stored in bone but -not toxic to it.
*Liver and kidneys are also storage sites for toxic substances
77
what is bioactivation and detoxification talking about when referring to metabolism
Bioactivation: Production of metabolites that are more toxic than parent substance
Detoxification: Production of metabolite that is less toxic than parent substance
(often done by enzymes)
78
The main way a chemical is excreted from the human body:
kidneys(urine), lungs and the liver (GIT)
78
What are some minor excretion routes
Minor excretion routes
Mother's milk, sweat and saliva
* Excretion into milk is →important to offspring.
* It is more acidic than plasma (~pH=6.5).
* Lipid soluble xenobiotics diffuse along with fats from plasma into the mammary gland and are excreted with milk during lactation.
* Toxic substs. →can passed from cow's milk to people.
* In great perspiration, sweat may be a sig. excretion route.
78
what are the targets for toxicodynamic actions of toxic chemicals
The targets for the toxicodynamic actions of toxic chemicals
– Enzymes
– Membrane receptors
– Intracellular receptors
– Ion chann
79
How toxicants Cause Toxicity
Toxic effects generally result from adverse cellular, biochemical, or macromolecular changes through-
– Damage to an enzyme system
– Disruption of protein synthesis
– DNA damage
– Modification of an essential biochemical function
* Toxicants cause toxicity by disrupting normal cell functions:
* Bind and damage proteins (structural, enzymes)
* Bind and damage DNA (mutations)
* Bind and damage lipids
* React in the cell with oxygen to form
“free radicals” which damage lipid, protein,
and DNA
80
what is toxicodynamics
Toxicodynamics is the mechanism of action of a toxic chemical to the body (what chemicals do to the body).
* refers to the molecular, biochemical, and physiological effects of toxicants or their metabolites in biological systems.
81
examples of organ specific toxicants
Central Nervous System – lead
Immune System – isocyanates
Liver - ethanol, acetaminophen
respiratory Tract - tobacco smoke, asbestos, ozone
Eye - UV light (sunlight)
Kidney - metals
Skin - UV light, gold, nickel
Reproductive System – dibromochloropropane
82
lecture 3 pg 89 revision
Gj
83
characterize alcohol fatty liver
-Accumulation of lipids around hepatocytes in the liver
-metabolism of ethanol in liver produces acetylaldehyde which results in the production of more lipids than usual
- less lipids used by mitochondria
84
Carcinogenity and its 2 stages
Carcinogenicity is a complex multistage process of abnormal cell growth and differentiation which can lead to cancer. (cells multiply at alarming rate and can no longer recognize each other due to loss of protein coat)
At least two stages are recognized
*-initiation in which a normal cell undergoes irreversible changes;
– promotion in which initiated cells are stimulated to progress to cancer. Chemicals can act as initiators or promoters.
* The initial neoplastic transformation results from the mutation of the cellular genes that control normal cell functions.
* The mutation may lead to abnormal cell growth. It may involve loss of suppresser genes that usually restrict abnormal cell growth.
85
define poullution and air pollution
Air pollution ► The presence of chemicals or compounds in the air which are usually not present and which lower the quality of the air or
cause detrimental changes to the quality of life (such as the damaging of the ozone layer or causing global warming).
Air Pollution is the deterioration of the quality of the air to an extent that:
* it becomes difficult to breathe, often toxic or detrimental,
* it complicates the health of living beings,
* it causes the body organs to malfunction,
* it damages the habitats of animal, plants, and other living organisms,
* it poses the threat to the natural environment and its habitats.
Pollution: defined as the excess discharge of any substance into the environment which adversely affects quality of the environment, causing damage to humans, plants andanimals.
Pollution → introduction of any substance into the environment that adversely affects the usefulness of its resources. Pollution can be in the form of solid, liquid or gaseous substance. Pollution causes damage to human, plant and animal life. The nature and concentration of pollutant determine the severity of effect of pollution
86
how to classify the source of pollutants
This is classification of the sources of pollutants:
(A)
Primary
Secondary
(B)
Combustion
Non-combustion
(C)
Stationary
Mobile
(D)
Point: These sources include facilities that emit sufficient amounts of pollutants.
Area: all other point sources that individually emit a small amount of pollutants are considered as area sources
Natural (biogenic):
87
Primary vs secondary air pollution
Primary pollutants are emitted directly from the sources.- carbon dioxide (CO2), carbon monoxide(CO), sulfur dioxide, nitric
oxide, ammonia, hydrogen sulphide, and radioactive substances. Industrial fumes and smokes, ash, dust, mist, are other primary sources of air pollution.
Secondary pollutants are not emitted from the sources. They are formed when primary pollutants interact with atmospheric
constituents eg. sulphur-trioxide (SO3), nitrogen-trioxide, ozone (O3),hydrocarbons, acid rain, etc
87
why may solid or liquid particles that are suspended in the air be dangerous
May contain materials with toxic or carcinogenic
effects
Extremely small particles, can become lodged in lungs
87
tell me about the major class of air pollutants, ie Sulfur Oxides
* Gases produced by the chemical interactions between sulfur and oxygen
* Causes acid precipitation (acid rain)
* Once emitted can be converted to sulfate SO4
* Removed from atmosphere by wet or dry deposition
* Major human sources; coal power plants, industrial processes.
Adverse effects depend on dose and concentration present
* Injury or death to animals and plants
* Corrosion of paint and metals
87
tell me about the major class of air pollutants, ie Nitrogen Oxides
* Gases produced by the chemical interactions between
atmospheric nitrogen and oxygen at high temperature
* Problems
* Greenhouse gases
* Cause difficulty in breathing
Adverse effects depend on dose and concentration present
* Injury or death to animals and plants
* Corrosion of paint and metals
88
tell me about the major class of air pollutants, ie Carbon oxides and hydrocarbons
Carbon Oxides
* Gases carbon monoxide (CO) and carbon dioxide (CO2)
* Greenhouse gases
Hydrocarbons
* Diverse group of organic compounds that contain only hydrogen and carbon (ex: CH4- methane)
* Some are related to photochemical smog and greenhouse gases
88
what are the Health effects of carbon monoxide
Carbon monoxide accounts for more than 50% of air pollution nationwide and worldwide.
It is a pervasive pollutant.
Related illness, include:
* headaches, dizziness and drowsiness. Reports show that about 11% heart failure caused by excess carbon monoxide.
* In the normal situation, the iron atom in the blood protein haemoglobin, picks up oxygen from the lung and transports into the body’s cells.
There, the haemoglobin
* releases oxygen and picks up the waste gas carbon dioxide, which it transports back to the lungs and releases Co2
* After releasing CO2, it picks up more oxygen.
* CO has 200 times more affinity for the iron in haemoglobin than O2 and interrupts this cycle by displacing oxygen.
* The result is low b/d oxygen level (heart)
- can lead to heart failure in sensitive people.
* Carbon monoxide interferes with the oxygen-carrying proteins in muscles.
* When humans are exposed to CO, forms carboxyhaemoglobin at the expense of oxyhaemoglobin.
* ↓O2tissues level and asphyxiation occurs.
* If the victim continues to receive a high dosage of CO, then permanent brain damage and death will result.
* Initial symptoms include dizziness, headache, nausea and faintness.
88
What is a Greenhouse Gas?
*Greenhouse gas is a gas that that is relatively transparent to solar radiation, but absorbs and emits in the infrared…the type of radiation the earth emits.
*Some examples:
*Water vapor
*Carbon dioxide
*Nitrous oxide
*Methane
89
What are the 4 types of air pollutants
Those with direct impact on:
1. *human health (nitrogen oxides (NO2), carbon monoxide (CO), sulphur oxides (SO2) or volatile organic carbon (VOC).
* *Vegetation, like nitrogen oxides (NO2), sulphur oxides (SO2) and chemical compounds of chlorine and hydrogen;
2. Pollutants with direct influence on climate, -carbon dioxide (CO2) and methane (CH4) with major impact on global warming issues
3. Pollutants that will form acids, (NO2) and (SO2), esply when found in high concentrations concurrently in a humid atmosphere;
4. Pollutants with long life cycle:
accumulated in soil and by the transfer thru biological plant-animal-human chain or accumulations in human body → serious consequences on human health;
90
wha are the effects of Rapidly Rising Greenhouse Gases Due
to Mankind
*There are a number of natural “amplifiers” of
mankind’s emission of greenhouse gases.
*The warming due to increased carbon dioxide,
methane, and other greenhouse gases will cause
-more water to be evaporated from the earth’s oceans.
this acts as an Amplifier
*The amount of evaporation increases with
temperature.
*Water vapor is the most potent greenhouse gas
and thus causes even MORE warming.
*This produces a positive feedback.
But it gets even worse…
*Warming temperatures melt snow and ice.
*Snow and ice help cool the planet because they
reflect much of the sun’s radiation….that is why you need sun glasses while skiing.
*As the snow melts less radiation is reflected to space and more is absorbed.
*Thus, the earth gets warmer,which melts more snow.
*Another positive feedback!
91
what is The greenhouse effect
the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere.
92
what are the 5 Source Classifications fo reporting air pollution
Classification for reporting air emissions to the public:
Transportation sources: Includes emissions from transportation sources during the combustion process
Stationary combustion sources: These sources produce only energy and the emission is a result of fuel combustion
Industrial sources: These sources emit pollutants during the manufacturing of products
Solid waste Disposal: Includes facilities that dispose off unwanted trash
Miscellaneous: sources that do no fit in any of the above categories like forest fires, coal mining etc.
93
What is the purpose of an Air Pollution Index?
It translates technical pollution data into an easy-to-understand scale (0-500) to inform the public about air quality and health risks.
93
what are the effects of air pollution(SO2, No's, CO, O3, and the effects on kids)
* Sulfur Dioxide and Particulate material
Irritate respiratory tract and impair ability of lungs to exchange gases
* Nitrogen Dioxides
Causes airway restriction
* Carbon monoxide
Binds with iron in blood hemoglobin
Causes headache, fatigue, drowsiness, death
* Ozone
Causes burning eyes, coughing, and chest discomfort
Greater health threat to children than adults
* Air pollution can restrict lung development
* Children breath more often than adults
* Children who live in high ozone areas are more likely to develop asthma
94
what are the effects of Ozone depletion
Effects of Ozone Depletion
* Higher levels of UV-radiation hitting the earth
* Eye cataracts
* Skin cancer
* Weakened immunity
* May disrupt ecosystems
* May damage crops and forest
