SFU BISC 313 Final (Cumulative)

by aerolovely on quizlet

toxins

natural chemicals that can cause adverse effects at low concentrations

toxicant

chemical synthesized by humans that can cause adverse effects at low concentrations (ex: pesticides, pharmaceuticals)

pollutant

a contaminant that causes adverse effects

contaminant

chemical not normally found in that environment

melittin

chemical found in bee venom that destroys cell membranes and causes action potential in nociceptors (pain receptors)

Hannibal Barca

military commander who had large pots and would throw venomous snakes at enemies

toxicology in the American Civil War

drop Clostridium botulinum bacteria into a well and anyone who drank from the contaminated well would die

Ebers Papyrus

first known medical records in history; first known books of poisons and some antidotes

toxicology in Ancient Greece

Socrates (philosopher) was thrown into prison and forced to eat hemlock as a form of execution

xenobiotic

A chemical substance foreign to the biological system

Catherine de Medici

queen of France; the first experimental toxicologist; she tested out her potions/poisons/remedies on the sick/poor

what did Catherine de Medici study? (toxicology)

- onset of action

- potency (effective-ness)

- site of action

- clinical signs and symptoms

Paracelsus

father of toxicology, said "the dose makes the poison"

Claude Bernard

used toxic substances to understand basic biological systems

ex: he used carbon monoxide to study oxygen binding to hemoglobin

toxicology

the study of adverse effects of chemicals and physical agents on biological systems

poisons

a substance that through its chemical action can injure or kill

descriptive toxicologist

concerned directly with toxicity testing in animals to evaluate the risk in humans

- mostly about pharmaceuticals and food additives

mechanistic toxicologist

concerned directly with trying to elucidate the toxin's mechanisms of action

Lake Apopka

1970s they found that the alligator population was decreasing; later found that DDT was an endocrine disruptor and mimics estrogen therefore decreasing populations of alligator were due to dumping DDT into lake

regulatory toxicologist

examines effects on non-target organisms/environment and makes regulations based on toxicology data

agencies involved with regulations

- Food and Drug Administration (FDA)

- Health Canada

- Environment and Climate Change Canada

- Department of Fisheries and Oceans (DFO)

clinical toxicologist

works in the realm of medical science, concerned with disease cause by or associated with chemical exposure

- main focus is treatments and antidotes

forensic toxicologist

mainly concerned with the medical and legal aspects such as determining cause of death in investigations, analytical chemistry and analyzing tissue

environmental toxicologist

study the effects of chemicals on the ecosystem and its components (wildlife)

priority pollutants list

list of chemicals where we need more information because there is a potential for them to cause problems to humans and the environment

CEPA Domestic Substances List

list of chemicals (inventory) of ~23,000 chemicals in Canada used commercially

- categorizes chemicals according to certain criteria

5 factors for selecting priority chemicals (categorization)

1. persistence

2. bioaccumulative

3. inherently toxic

4. quantity

5. other effects

3 main factors looked at by Canadian government to categorize priority chemicals

PBT

- persistence

- bioaccumulative

- toxicity (inherent)

diazinon

organophosphate pesticide used to control insects, inhibits acetylcholinesterase in nervous system

half life

length of time required for half of the radioactive atoms in a sample to decay

half life of DDT

2-15 years

transformation processes that degrade chemical over time

- physical (UV, temp)

- chemical (reaction)

- biological (microbes & fungi)

example of widespread contamination

DDT used for mosquito/malaria treatment in tropics but lots of DDT is found in the Arctic and Antarctic; accumulates in penguin fat cells

soil incineration

when soil is too contaminated to be re-mediated, it is sent to a special location to be incinerated (set on fire)

Stockholm Convention on Persistent Organic Pollutants

program run by UN; goal is to eliminate or resist POPs (persistent organic pollutants)

"the Dirty Dozen"

original list of 12 contaminants by the UN which has now expanded 16 more

chemicals in the "Dirty Dozen"

- DDT

- hexachlorobenzene

- endrin

- mirex

- aldrin

- polychlorinated benzene

- dibenzo-dioxins

- dibenzo-furans

example of different half-lives under different conditions

GLYPHOSATE

- breaks down well in tropics (hot, wet, increased amount of microbs) but poorly in Skeena (cold, wet, decreased amount of microbes)

bioaccumulation

the process by which organisms uptake foreign chemicals through all routes of chemical exposure (dietary, transport across respiratory surface, dermal absorption, inhalation)

bioconcentration

process by which a chemical concentration in an aquatic organism exceeds that in water as a result of exposure to a waterborne chemical (uptake only from abiotic environment)

biomagnification

accumulation of pollutants at successive levels of the food chain (uptake only from diet)

example of species dependent toxicity

ethylene glycol (antifreeze) toxic for cats not humans

common endpoint to determine toxicity

how much of chemical X does it take to kill something

- expose to varying concentrations of chemical and look at resulting mortality

LC50

Lethal Concentration 50%, the concentration which kills 50% of the tested animals

- affects mostly aquatic organisms because you don't know how much exactly got into the organism

LD50

the amount of a chemical that kills 50% of the animals in a test population

- you know exactly how much of the chemical got into the organism and thus killed them

other effects to take into consideration when classifying priority chemicals

- ability to influence atmospheric chemistry (acid rain)

- ozone (increase in freons)

- CO2 emissions

- odors (organosulfur compounds)

- foaming (detergents)

hydrophilic

water loving

hydrophobic

Water fearing ; sparingly soluble in water

lipophilic

Oil loving

- hydrophobic chemicals tend to dissolve in lipids

fugacity

tendency to flee (driving force for movement between two compartments)

K(ow)

octanol-water partition coefficient, determined by putting equal amounts of octanol and water in a container with compound X and measuring the concentration in each solvent after a period of time

low K(ow)

very polar (anything under 4)

high K(ow)

super hydrophobic/nonpolar

- characteristics of chemicals gets weird here

Bioconcentration Factor (BCF)

The concentration of a substance in biota divided by the concentration of the substance in surrounding WATER (Cf/Cw ==> concentration in fish over concentration in water)

bioaccumulation factor (BAF)

ratio of the concentration of a chemical in an organism to the concentration of the chemical in the surrounding environment

log K(ow)

used as a surrogate in determining if something is bioaccumulative

- log Kow > 5 = bioaccumulative

atmosphere solubility

chemical's tendency to partition to the atmosphere ; mostly controlled by vapour pressure

3 key chemical characteristics for examining environmental fate

1. hydrophobic or hydrophilic

2. "atmosphere solubility"

3. chemicals dissociation tendencies in an aqueous environment

point spill

significant amount entering environment at a single point in time & space; infrequent and contamination is very local

- ex: end of a pipe

non-point source

diffuse inputs on whole area/large time frames of agricultural releases

- difficult to control

widespread release

release of a substance in sufficient quantity and over a wide area

- measurable contamination of a part of Earth

horizontal atmospheric movement

atmospheric transport (Grasshopper event); mostly vapour phase

vertical atmospheric movement

deposition/particles moving up into the atmosphere

dry deposition

particles moving downward due to gravity (depending on atmospheric conditions)

wet deposition

acidic rain, fog, and snow (any precipitation)

- raindrops can pick up particles in atmosphere as it comes down

- vapour of chemical X can also partition into raindrop

surface water

Water above the surface of the land, including lakes, rivers, streams, ponds, floodwater, and runoff.

ground water

underground water that is held in the soil and in pervious rocks

advective transport

Water currents that move chemicals

diffusive transport

random motion of molecules

3 factors that affect surface water

1. pollution conditions

2. physical chemistry properties of pollutant

3. environmental conditions

log Koc

value that describes how well a chemical binds to organic carbon

types of processes in contaminant resuspension

1. physical

2. biological

types of physical processes

1. advection

2. diffusive

types of biological processes

1. microbenthic processes (microbial/mainly bacteria)

2. macrobenthic processes (organisms that live on the ocean floor)

how do microbenthic processes resuspend contaminant

- benthic microbes cause changes to sediment's chemistry (binding capacity, pH)

- bacteria enzymatically convert compounds from one form to another

- ebullition (sudden release of methane gas as bubbles)

how do macrobenthic processes resuspend contaminant

organisms in/on sediments burrow, hide, eating, etc

bioturbation

The process by which organisms rework existing sediments by burrowing

3 phases of toxic action paradigm

1. exposure phase

2. toxicokinetic phase

3. toxicodynamic phase

5 methods for passing membrane

1. filtration (channel protein assistance)

2. passive diffusion

3. active transport

4. facilitated diffusion

5. endocytosis

passive diffusion

movement of substances across a semipermeable membrane with the concentration gradient

- doesn't require energy

- most dangerous for hydrophobic chemicals

- first order process

important chemical characteristics for passive diffusion

- concentration/fugacity gradient

- lipid soluble

- non-ionized

Fick's Equation

rate of diffusion = [KA(C2-C1)]/d

- K = lipid solubility, size

- A = surface size

- C2-C1 = concentration gradient

- d = distance

factors for enhanced diffusion

high SA

high lipid solubility

high concentration gradient

low diffusion distance

active transport

the movement of materials through a cell membrane using energy

- zero order process (saturable)

facilitated diffusion

process of diffusion in which molecules pass across the membrane through cell membrane channels

- no energy required

- only occurs if there is higher [ ] outside than inside

endocytosis

- cell invagination enclosing particles in

- phagocytosis, pinocytosis and receptor-mediated endocytosis

sites of absorption/exposure

- skin

- gastrointestinal tract

- lungs

function of skin

to be a barrier (defense)

- 2 layers: epidermis (thinner. less blood more keratin) and dermis (thicker)

why lungs are good at gas exchange

- high surface area

- low diffusion distance

- high blood supply

perfusion-limited uptake

uptake of molecule depends on the amount of blood (low solubility in blood)

ventilation-limited uptake

uptake of molecule depends on the amount of chemical (high solubility in blood)

oxygen uptake in water breathers

- unidirectional flow of respiratory medium

- countercurrent exchange (blood moves in opposite direction than air intake)

ectotherm

an animal whose body temperature varies with the temperature of its surroundings

why GI tract is good at absorption

- high surface area

- low diffusion distance

- high blood supply

absorption in GIT affected by

- presence/absence of food in stomach

- gut microbiome

what can happen after absorption (4)

- storage

- biotransformation

- excretion

- action (target an organ for toxicity??)

blood is made of

plasma, white blood cells, red blood cells, proteins & lipids

- plasma = aqueous, everything else = organic

P-glycoprotein

a transporter protein that moves drugs out of cells and into the gut, urine, or bile

- uses ATP as energy

- large substrate base including xenobiotics

- able to grab xenobiotics from cytosol or between lipid bilayer

- multi-drug resistance (MDR)

- the ONLY method that kicks out hydrophobic chemicals

ivermectin & p-glycoprotein

- ivermectin is a neurotoxin used to treat parasites in dogs and other animals

- mutation in multi-drug resistance (MDR) could produce no p-glycoprotein & therefore ivermectin gets into brain of dog (fatal)

binding coefficients

the ability for chemical X to bind to tissue