Lecture 7: Persistent Organic Pollutants Flashcards
________ is the study of
the fate and effects of toxicants in an
ecosystem
Environmental toxicology
what are the 3 important parts of env. toxicology?
distribution, degredation, eventual fate
_______ is the portion of a toxicant
that can potentially be absorbed by an
organism
Bioavailability
_______ is the study of effects
toxicants on the biota
Ecotoxicology
Toxicants can move between different “matrices”:
____, ______, ______, and ____
atmosphere, lithosphere, hydrosphere and
biosphere
________ of
pollution are from a
discrete source (e.g.,
Discharge pipes)
Point sources
________ of
pollution cannot be
precisely narrowed
down to a single
source. Can be from
numerous sources
Nonpoint sources
People sometimes build simplified simulated ecosystems called _______ to test
the effects of toxicants
mesocosms
what are the benefits of mesocosms?
Controlled ecosystem.
* Replication!
* Can measure potential toxicant
bioaccumulation and biomagnification.
* Can measure subchronic effects on
organisms (reduced fecundity, changes
in trophic levels, etc.).
where do we measure toxic effects in ACTUAL ecosystems in Canada? i.e. whats the area called
Experimental Lakes Area
what is the brief history of the ELA?
Started in 1968
* In May 2012, the Federal government at the time cut its $2 million per year
budget
* Governments of Ontario and Manitoba kept it going…
* The 2015 budget restored federal funding
* Currently operated by the International Institute for Sustainable
Development (IISD) – so now it is the IISD-ELA
harmful algal blooms, acid rain, atmospheric Hg emissions were all issues where publications referenced research from…. which area?
ELA, has had an impact on many scientific issues!!
_______ = concentration in an organism is higher than the
concentration in the environment by absorption AND ingestion
Bioaccumulation
________ = concentration in an organism is higher than the
concentration in the environment by absorption only (via water in aquatic
systems or inhalation in terrestrial systems)
Bioconcentration
_____ is a unitless parameter calculated from the ratio of the
steady-state toxicant concentration in the whole organism or
tissue to its concentration in the surrounding environment
BCF
why would biomagnification depend on the sex of the animal?
females offload toxicants to offspring and lactation, resulting in smaller stores than males
________ (also known as “biodilution”) - where concentrations
decrease with increasing trophic level
Trophic dilution
i.e. opposite of biomagnification!
when does trophic dilution occur?
when rates of
contaminant
biotransformation and
elimination exceed
rates of ingestion and
absorption
what are the factors that influence biomagnification?
degree of hydrophobicity
ability of animal to biotransform the compound
properties of the animal (endotherm ectotherm)
why are endotherms more likely to experience biomagnification?
because they eat more, so generally injest more toxicants
how do things get broken down in the env?
photolysis
oxidation
hydrolysis
microbial metabolism
Persistent organic pollutants (POPs) don’t readily break down from these processes
due to their chemical structure, which is what makes them…
persistent!!
T/F: Some soil and aquatic microbes have
metabolism mechanisms that are not found in
eukaryotes
true!!
Microbes that have _______ enzymes can
remove the chlorines from POPs
dehalogenase
VERYYYY slow process
in what env. do microbes remove chlorines from POPs, why is this not as helpful as we’d like?
more often in soil on land
most POPs accumulate in aquatic systems
T/F: POPs cant be broken down
they can! it just takes a long time
what are the ‘dirty dozen’?
aldrin
chlordane
DDT
dieldrin
endrin
HCB
heptachlor
Mirex
PCBs
PCDDs
PCDFs
toxaphene
why were the dirty dozen banned or being phased out?
due to the Stockholm Convention of 2001
which came into effect in May 2004 when ratified by 50 countries
why were the dirty dozen banned?
very persistent in the env., have many Endodcrine disrupting properties
_____ = polychlorinated biphenyls
PCB
______ = polychlorinated dibenzodioxins
PCDD
______ = polychlorinated dibenzofurans
PCDF
what are the three examples of polyhalogenated aromatic hydrocarbons?
PCB
PCDD
PCDF
In general, ______s are:
- Highly lipophilic - increases with halogenation
- Relatively non-volatile – volatility decreases with halogenation
- Slow to break down in the environment
- Highly prone to biomagnification
- Potential for interactions with other toxicants
PHAH
PCBs have been widely manufactured in many countries. _____s and
______s have only been intentionally produced in laboratory settings
PCDD
PCDF
_______:
Generally formed as products of
reaction between organics and
halogens (e.x., Cl, Br, Fl).
* Halogens bonded to carbon in
this fashion are relatively rare in
nature, which makes these
types of molecules more difficult
to metabolize
PHAHs
T/F: PCBs are complicated because there are 209 different
kinds
true!!
are PCBs a class of compounds?
yes
T/F: Specific locations of halogenation affect toxicity of PCBs
true! most toxic are in the 3rd/4th positions
_____ - same number of chlorines, but in different places.
Isomers
_______ – different number of chlorines
Congeners
Multi-ortho congeners more likely to be coplanar and are less ______
toxic
Meta, para, and mono-ortho PCB congeners are more ______
toxic
______: First synthesized in 19th century, large-scale commercial production
began ~1930. Peak production in the 1970s
PCBs
PCBs had high thermal stability, what are some examples of things they were used as? (They were mostly ortho congeners!!)
adhesives
lubricants
flame retardants
extenders/diluents of other agents
heat transfer fluids
plasticizers
which PHAH had higher levels in air indoors?
PCBs
Low acute toxicity, but extent of chronic health risks from _____ gained attention
in 1960s, led to discontinuation of use in 70s
PCBs
Can combine with a specific receptor or receptors to initiate toxic
effects.
– Most toxic forms of _____s are highly effective at binding at
cellular target sites and are resistant to detoxification
mechanisms.
PCB
production and new use of PCBs in the US is banned, what are the three areas that they still show up?
controllable closed systems
( coolant in power transformers, not in direct contact with env.)
non-controllable closed systems
(hydraulic fluids & lubricants, can be in direct contact with env.)
open systems
(result in direct env. contamination, adhesives/inks/paints)
environmental contamination by PCBs results from…
- Open burning and incomplete combustion of PCB-containing solid
waste - Vaporization from open system applications
- Accidental spills or leakages from closed system applications
- Disposal of waste into sewage systems
T/F: There is an estimate of more than 400,000 tons of PCBs in the
environment
* 60% in the hydrosphere
* 39% in terrestrial system
* 1% in the atmosphere
true!!
what is the acute toxicity of PCBs in humans? (probable oral lethal dose)
10 mL to 0.5 L
what are the symptoms of chronic PCB toxicity?
Chloracne is an acne-like skin condition
nausea, vomiting, fatigue, vitamin A depletion, liver
damage, hormonal changes (thyroidal effects), lung and liver cancer
how do people usually become chronically exposed to PCBs?
Most cases are due to occupational exposure, but it can also arise after
accidental environmental poisoning
_________ (1968):
* Contaminated rice oil from leaking heat exchanger
at a factory in Japan.
* ~14000 people exposed to PCBs, but also PCDFs
and others.
* Before effects observed in humans, many birds
that were fed with rice oil contaminated food died
Yusho (Japan) Incident
________ (1979):
* Contaminated cooking oil again.
* ~2000 people were exposed.
* Outbreaks of severe chloracne, skin pigmentation
and conjunctivitis
Yu-Cheng (Taiwan) Incident
Dioxins and dioxin-like PCBs bind to the aryl
hydrocarbon receptor, which is a…
transcription factor
Because its a transcription factor, once _______ gets activated, it leads to the transcription of ~60 genes, including
Phase I (CYP1A1) and Phase II (GSTs)
biotransformation genes.
aryl hydrocarbon receptor
________ is basically when a hormone is made in one area of the body, is released into the blood
stream, and the signal is received by another cell in the body. This leads to the response in the cell, which
can include changes to cellular metabolism, gene transcription, etc.
Endocrine signaling
Thyroid gland releases thyroid hormones ______ and ______ that signal to other
cells to increase metabolism among other things. T3
is the more potent hormone. They are also involved in
neurological development in utero and during early
childhood
[thyroxine
(T4) and triiodothyronine (T3)]
PCBs can alter thyroid hormone signalling, what are these two main ways?
reducing serum levels of T4
directly activating the thyroid hormone receptors in developing infants
how do PCBs reduce serum levels of T4?
Organochlorines (PCBs and others) activate phase II enzymes (UGTs),
which can biotransform T4 and lead to its excretion via the kidneys.
Then there is less T4 in the body
Epidemiology and rat studies have linked _____ exposure to reduced
birth weight and lower IQ scores.
* New studies have shown that ______s activate the development of
oligodentrocytes (cells that produce the myelin sheathes that surround
neurons) in tissue culture
PCB
The timing of neuron and oligodendrocyte development is important. why?
Having more
oligodendrocytes early in development leads them to die off by apoptosis. Then the
neuron development is impaired
_____: 2 benzenes attached via oxygen, any
number of chlorine atoms attached at
any other ring position on either ring
PCDDs
how many possible combinations of PCDDs?
over 200!
_____ are Not produced intentionally except for use in analytical work
PCDDs
what can form when PCBs are subjected to heat over long periods
PCDDs
PCDDs are also biproducts of….
Combustion of waste (e.g., dumps) with organic waste in presence of
inorganic chloride
- By-product of wood pulp bleaching
- By-product of manufacturing other chlorinated aromatics, such as
phenoxy herbicides
where does most of our PCDD intake come from? in foods
ocean fish
meat
dairy products
T/F: Cows are apparently really good at bioaccumulating dioxins
true!!
Because of differing levels of toxicity, some PCBs have been assigned ______s. If PCB binds to Ah receptor, is persistent and
biomagnifies, similar properties to dioxins
TEF
toxic equivalency factors
