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Toxicology > Biomagnification, Bioaccumulation, and Environmental Toxicants > Flashcards

Biomagnification, Bioaccumulation, and Environmental Toxicants Flashcards

1
Q

Ecotoxicology

A

study of the fate and effects of toxicants in an ecosystem

-distribution, degradation, eventual fate

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2
Q

matrices

A

atmosphere, lithosphere, hydrosphere, biosphere

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3
Q

Bioavailability

A

portion of a toxicant that can potentially be taken up by an organism

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4
Q

Bioaccumulation

A

concentration in an organism is higher than the concentration in the environment via absorption and ingestion

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5
Q

Bioconcentration

A

bioaccumulation by absorption only

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6
Q

Bioconcentration factor (BCF)

A

toxicant concentration in the whole organism or tissue to its concentration in the surrounding environment
-hydrophobic compounds

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7
Q

BCF less than 1

A

toxicant is actively excluded by the organism

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8
Q

BCF=1

A

toxicant exhibits no selectivity

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9
Q

BCF greater than 1

A

toxicant is accumulated within organism at higher quantity than in environment

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10
Q

Biomagnification

A

chemicals become increasingly concentrated at successively high trophic levels
-ratio of steady-state pollutant concentration in the organism

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11
Q

Trophic dilution

A

concentrations decrease with increasing trophic level

-rates of contaminant biotransformation and elimination exceed rates of ingestion and assimilation

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12
Q

breakdown in environment

A

-photolysis
-oxidation
-hydrolysis
(POPs don’t readily do the above 3)
-microbial metabolism

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13
Q

photolysis

A

high energy photons absorbed by a molecule resulting in the breaking or rearrangement of a covalent bond

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14
Q

oxidation

A

addition of oxygen

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15
Q

hydrolysis

A
  • addition of water molecule

- common in aquatic systems

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16
Q

Microbial metabolism

A
  • microbes have metabolism mechanisms that are not found in eukaryotic organisms
  • non-halogenated pollutants can be broken down fairly rapidly
  • dehalogenase enzymes can remove the chlorines form POPs and use remaining carbon backbone as a carbon source
  • very slow process, only switch on these genes when they are starving
  • occurs more readily in soil, POPs accumulate in the hydrosphere
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17
Q

Dirty Dozen

A
  • banned or being phased out due to the Stockholm Convention of 2001
  • Came into effect May 2004
  • Very persistent in the environment and many are endocrine disruptors
  • DDT and PCBs
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18
Q

Polyhalogenated Aromatic Hydrocarbons

A
  • PCB, PCDD, PCDF
  • Highly lipophilic, non-volatile, slow to break down, prone to biomagnification, potential for additive interactions
  • Halogens bonded covalently to carbon are rare in nature, more difficult to deal with
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19
Q

Polychlorinated Biphenyls

A
  • Class of compounds
  • Slightly different chemical structures called isomers and congeners
  • Toxic response depends on the properties of the chemical
  • thermal stability, low flammability, low vapour pressure, low acute toxicity, but chronic health effects
  • halogenation position affects toxicity (3rd or 4th most)
  • Must combine with a specific receptor to initiate a reaction which leads to toxic effects
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20
Q

PCB numbering

A
  • ring with fewest chlorines gets the dash
  • 1 is always bonded carbon
  • Ortho=next to the bond
  • Meta=one over from the bond
  • Para=across from the bond
  • Multi-ortho congeners more likely to be coplanar and less toxic
  • 2 in para position is most toxic
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21
Q

Controllable closed systems

A
  • incentive for recovery and ultimate disposal of material used
  • coolant in power transformers
  • not in direct contact with the environment
22
Q

Non-controllable closed systems

A
  • recovery and ultimate disposal of material is not monitored
  • hydraulic fluids and lubricants
  • in direct contact with environment
23
Q

Open systems

A
  • limited use results in direct environmental contamination when used
  • plasticizers agents in paints, adhesives, inks and copying paper
24
Q

Environmental contamination by PCBS

A
  • 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
25
Q

PCBs acute toxicity

A

-class 3: moderately toxic

26
Q

PCBs chronic toxicity

A
  • occupational exposure
  • chloracne-acne like skin condition caused by certain toxic chemicals
  • swallowing, inhaling, touching chemical
  • nausea, vomiting, fatigue vitamin A depletion, liver damage, hormonal changes, lung and live carcinogenicitiy
27
Q

Yusho Incident

A
  • contaminated rice oil from leaking heat exchanger at a factory in Japan
  • Birds died
28
Q

Yu-Cheng Incident

A
  • contaminated cooking oil

- severe acne, skin pigmentation, conjunctivitis

29
Q

Endocrine signalling-thyroid hormones

A
  • hormone is made in one area of the body, released into the blood stream, signal is received by another cell in the body, response in the cell
  • thyroid gland hormones increase metabolism
  • Thyroxine (T4) and triiodothyronine (T3)
  • Thyroid glands can absorb iodine
30
Q

PCBs alter thyroid signalling

A
  • reducing serum levels of T4

- directly activating the thyroid hormone receptors in developing infants

31
Q

Reducing serum levels of T4

A
  • organochlorines activate phase II enzymes, glucuronidate T4, lead to its excretion via the kidneys
  • competition for binding with the serum proteins that carry T3 and T4, less T3 and T4 circulating in the body
32
Q

Directly activating the thyroid hormone receptors in developing infants

A
  • reduce birth weigh and poor IQ scores
  • activate the development of oligodendrocytes (produce myelin sheathes) in tissue culture
  • having more oligodendrocytes early in development leads them to die off by apoptosis, less around and neuron development is impaired
33
Q

PCDDs

A
  • 2 benzenes attached via 2 oxygen atoms

- TCDD most toxic, used in agent orange

34
Q

PCDD numbering

A
  • first chlorine is numbered 1, then counts up

- Want to number with the most chlorines first

35
Q

PCDD production

A
  • not produced intentionally
  • formed when PCBs are subjected to heat
  • combustion of waste with organic waste in presence of inorganic chloride
  • by-product of wood pulp bleaching
  • manufacturing other chlorinated aromatics
36
Q

PCDD sources

A
  • processes involving chlorine
  • higher the reaction temperature, greater the amount of dioxins produced
  • pulp and paper industry
37
Q

TCDD remediation

A
  • alternatives to chlorine bleach
  • elemental chlorine replaced by chlorine dioxide
  • use of alternative chemicals: oxygen or ozone
  • enzymes used by wood-eating insects and bacteria
  • addition of catalysts to reduce need for delignifiers
38
Q

PDCC sources (2nd set)

A
  • present in the combusted material and not destroyed during combustion process
  • organochlorine precursors are present
  • high-temperature reaction between non chlorinated organic molecules and chlorine ions
  • dioxines have been present at least since anthropogenic combustion of coal and wood commenced
  • present in cows milk (high accumulation)
  • present in breast milk of women that eat more fats and proteins
39
Q

Toxicity comparison

A
  • TCDD is among the most toxic anthropogenic compounds
  • use it as a reference for toxicity of others
  • relative toxicity using LD50 values
40
Q

Long term effects of dioxin poisoning

A
  • not directly mutagenic
  • bind to the aryl hydrocarbon receptor
  • transcription factor protein
  • moves into the nucleus and switches on the transcription of 60 genes
  • natural compounds transiently activate this pathway
  • because we can’t metabolize POPs this pathway gets activated more than it should
  • lead to developmental defects, promote liver cancer, increasing cell division
  • transcription factors are proteins that regulate whether a gene will be expressed to make its encoded protein
41
Q

PAHs

A
  • fused benzene rings (2 or more)
  • contain only carbon and hydrogen atoms
  • contain only fused benzene rings
  • structure leads to toxic affects
42
Q

PAH produced via combustion

A
  • burning reaction in which a substance combines with gas
  • heat and light accompany combustion reactions
  • involve oxygen
43
Q

Complete vs incomplete combustion

A
  • complete has enough oxygen

- incomplete lacks oxygen, free radicals react with each other when temperature cools to form PAHs

44
Q

Quantity and type of PAH depends on

A
  • amount of oxygen
  • combustion temperature
  • nature of organic materials
45
Q

Some types of organic matter combusted

A
  • coal
  • tobacco
  • cellulose
  • polyethylene
  • PAH production during grilling is small due to low temperatures
46
Q

PAH production in USA

A
  • industrial processes
  • traffic
  • residential combustion and power generation
  • incineration
47
Q

PAH characteristics

A
  • strong UV absorption
  • PAHs occur naturally so ample time for microbial adaptation (biodegradation)
  • Larger PAH molecules are more lipophilic
48
Q

TCDD and PAHs

A
  • TCDD induces the synthesis of enzymes (cytochrome P450)
  • Catalyses the biotransformation of lipophilic substances such as hormones, fatty acids, and PAHs
  • These products are carcinogenic or exhibit other forms of toxicity
  • almost all PAHs are suspected to be carcinogenic
49
Q

Measuring toxic effects from the wild challenges

A
  • Variation in exposures
  • Variation in animal genotype
  • Complex interactions in food webs
  • Complex interactions with environmental factors
  • No controls or replication
50
Q

Simplified simulated ecosystems

A

-called mesocosms=an intermediate in complexity between lab experiments and entire ecosystems
Benefits:
-controlled ecosystem
-replication
-can measure toxicant bioaccumulation and biomagnification
-can measure subacute effects on organisms

51
Q

ELA history and legacy

A
  • started in 1968
  • federal government cut yearly budget
  • government of Manitoba and Ontario kept it going
  • 2015 budget restored federal funding
  • operated by the international institute for sustainable development
  • cited changed in environmental legislation for harmful algal blooms, acid rain, atmospheric mercury emissions

Toxicology (14 decks)

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