Lecture 7: Persistent Organic Pollutants Flashcards by Zoe Phillips

________ is the study of
the fate and effects of toxicants in an
ecosystem

Environmental toxicology

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what are the 3 important parts of env. toxicology?

distribution, degredation, eventual fate

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_______ is the portion of a toxicant
that can potentially be absorbed by an
organism

Bioavailability

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_______ is the study of effects
toxicants on the biota

Ecotoxicology

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Toxicants can move between different “matrices”:
____, ______, ______, and ____

atmosphere, lithosphere, hydrosphere and
biosphere

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________ of
pollution are from a
discrete source (e.g.,
Discharge pipes)

Point sources

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________ of
pollution cannot be
precisely narrowed
down to a single
source. Can be from
numerous sources

Nonpoint sources

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People sometimes build simplified simulated ecosystems called _______ to test
the effects of toxicants

mesocosms

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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.).

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where do we measure toxic effects in ACTUAL ecosystems in Canada? i.e. whats the area called

Experimental Lakes Area

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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

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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!!

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_______ = concentration in an organism is higher than the
concentration in the environment by absorption AND ingestion

Bioaccumulation

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________ = 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

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_____ 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

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why would biomagnification depend on the sex of the animal?

females offload toxicants to offspring and lactation, resulting in smaller stores than males

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________ (also known as “biodilution”) - where concentrations
decrease with increasing trophic level

Trophic dilution
i.e. opposite of biomagnification!

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when does trophic dilution occur?

when rates of
contaminant
biotransformation and
elimination exceed
rates of ingestion and
absorption

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what are the factors that influence biomagnification?

degree of hydrophobicity

ability of animal to biotransform the compound

properties of the animal (endotherm ectotherm)

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why are endotherms more likely to experience biomagnification?

because they eat more, so generally injest more toxicants

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how do things get broken down in the env?

photolysis
oxidation
hydrolysis
microbial metabolism

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Persistent organic pollutants (POPs) don’t readily break down from these processes
due to their chemical structure, which is what makes them…

persistent!!

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T/F: Some soil and aquatic microbes have
metabolism mechanisms that are not found in
eukaryotes

true!!

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Microbes that have _______ enzymes can
remove the chlorines from POPs

dehalogenase

VERYYYY slow process

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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