Biomagnification, Bioaccumulation, and Environmental Toxicants Flashcards
(51 cards)
1
Q
Ecotoxicology
A
study of the fate and effects of toxicants in an ecosystem
-distribution, degradation, eventual fate
2
Q
matrices
A
atmosphere, lithosphere, hydrosphere, biosphere
3
Q
Bioavailability
A
portion of a toxicant that can potentially be taken up by an organism
4
Q
Bioaccumulation
A
concentration in an organism is higher than the concentration in the environment via absorption and ingestion
5
Q
Bioconcentration
A
bioaccumulation by absorption only
6
Q
Bioconcentration factor (BCF)
A
toxicant concentration in the whole organism or tissue to its concentration in the surrounding environment
-hydrophobic compounds
7
Q
BCF less than 1
A
toxicant is actively excluded by the organism
8
Q
BCF=1
A
toxicant exhibits no selectivity
9
Q
BCF greater than 1
A
toxicant is accumulated within organism at higher quantity than in environment
10
Q
Biomagnification
A
chemicals become increasingly concentrated at successively high trophic levels
-ratio of steady-state pollutant concentration in the organism
11
Q
Trophic dilution
A
concentrations decrease with increasing trophic level
-rates of contaminant biotransformation and elimination exceed rates of ingestion and assimilation
12
Q
breakdown in environment
A
-photolysis
-oxidation
-hydrolysis
(POPs don’t readily do the above 3)
-microbial metabolism
13
Q
photolysis
A
high energy photons absorbed by a molecule resulting in the breaking or rearrangement of a covalent bond
14
Q
oxidation
A
addition of oxygen
15
Q
hydrolysis
A
- addition of water molecule
- common in aquatic systems
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
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
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
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
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
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
PCBs acute toxicity
-class 3: moderately toxic
26
PCBs chronic toxicity
- 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
Yusho Incident
- contaminated rice oil from leaking heat exchanger at a factory in Japan
- Birds died
28
Yu-Cheng Incident
- contaminated cooking oil
| - severe acne, skin pigmentation, conjunctivitis
29
Endocrine signalling-thyroid hormones
- 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
PCBs alter thyroid signalling
- reducing serum levels of T4
| - directly activating the thyroid hormone receptors in developing infants
31
Reducing serum levels of T4
- 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
Directly activating the thyroid hormone receptors in developing infants
- 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
PCDDs
- 2 benzenes attached via 2 oxygen atoms
| - TCDD most toxic, used in agent orange
34
PCDD numbering
- first chlorine is numbered 1, then counts up
| - Want to number with the most chlorines first
35
PCDD production
- 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
PCDD sources
- processes involving chlorine
- higher the reaction temperature, greater the amount of dioxins produced
- pulp and paper industry
37
TCDD remediation
- 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
PDCC sources (2nd set)
- 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
Toxicity comparison
- TCDD is among the most toxic anthropogenic compounds
- use it as a reference for toxicity of others
- relative toxicity using LD50 values
40
Long term effects of dioxin poisoning
- 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
PAHs
- fused benzene rings (2 or more)
- contain only carbon and hydrogen atoms
- contain only fused benzene rings
- structure leads to toxic affects
42
PAH produced via combustion
- burning reaction in which a substance combines with gas
- heat and light accompany combustion reactions
- involve oxygen
43
Complete vs incomplete combustion
- complete has enough oxygen
| - incomplete lacks oxygen, free radicals react with each other when temperature cools to form PAHs
44
Quantity and type of PAH depends on
- amount of oxygen
- combustion temperature
- nature of organic materials
45
Some types of organic matter combusted
- coal
- tobacco
- cellulose
- polyethylene
- PAH production during grilling is small due to low temperatures
46
PAH production in USA
- industrial processes
- traffic
- residential combustion and power generation
- incineration
47
PAH characteristics
- strong UV absorption
- PAHs occur naturally so ample time for microbial adaptation (biodegradation)
- Larger PAH molecules are more lipophilic
48
TCDD and PAHs
- 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
Measuring toxic effects from the wild challenges
- Variation in exposures
- Variation in animal genotype
- Complex interactions in food webs
- Complex interactions with environmental factors
- No controls or replication
50
Simplified simulated ecosystems
-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
ELA history and legacy
- 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
