Terms and Definitions for ENSC 201 Test #3 (Lectures 13-20 inclusive)

What are species differences in environmental toxicology?

What are species differences in environmental toxicology?

1. Different species are more or less sensitive to the toxicity of a given toxicant

2. Individuals from the same species show differences in susceptibility to toxicity
   
   Examples: TCDD effects on different fish species, thalidomide sensitivity based on human genetic makeup (species vary in ability to detoxify ROS species via antioxidants)

Benefit of being more tolerant to toxicants

More tolerant individuals survive longer and are more likely to reproduce

Susceptible populations (aka vulnerable populations)

Populations that may be defined as having unique characteristics, or living in environments, that make them more susceptible to environmental risks

2 toxic effects of thalidomide

1. Compound caused cell death (due to reactive oxygen species production)

2. Reduced amount of certain differentiated cells (reduced growth and replication of affected tissues, missing or deformed limbs)

6 examples of vulnerable populations

1. Children and pregnant women

2. Elderly/seniors

3. Indigenous people

4. Non-healthy, immunocompromised

5. Lower socioeconomic status

6. Individuals in areas of war

7 biological factors that make infants/children a vulnerable population

1. Biological differences in pharmacokinetics (ex. basal metabolic rates)

2. Higher respiration

3. Higher skin absorption

4. Proportionally larger body surface area to their weight

5. Need more food, water, air per unit of body weight

6. Blood brain barrier is more permeable in infants

7. Wide difference in metabolism of toxicants

5 behaviours that make infants/children a vulnerable population

1. Children live, learn and play in different physical environmental than adults

2. Oral uptake much higher in children (hand-to mouth activities)

3. Eating with contaminated hands, uptake of soil

4. Hands and knees of crawling children prone to dermal absorption of chemicals, inhalation of dust

5. Close contact with pets (Insecticide exposure from pets) treated for parasites

Infant botulism

Occurs when infants consume contaminated honey due to an immature digestive system

• Spores are ingested and colonize in large intestines of babies

• Spores are usually harmless to adults and children over 1 year old, because microorganism in mature intestines keep the bacteria from growing

5 knowledge gaps when studying vulnerability of children/infants to toxicants

1. Changes to metabolism during pregnancy

2. Exposures are variable and often estimated retrospectively

3. Existing human studies are very limited in scope

4. Children are not mini-adults (ex. covid vaccine efficacy)

5. Due to gaps in knowledge, regulations often include additional safety factors

Outcome of National Children’s Study

NIH deemed study was not feasible in 2014 > $1.2 billion spent

• Due to too many variables and to difficult to conduct

National Children’s Study

A study initiated in 2000 to examine the effects of environmental influences on the health and development of more than 100,000 children across the United States

• Idea was to follow child from before birth until age 21

• Goal was to improve the health and well-being of children

• Biomarkers: blood, breast milk, hair, DNA from fingernails

• Environmental samples, housing, social, interviews

Why is environmental justice important?

Low-income communities and minority ethnic groups often bear a greater burden of the consequences of environmental contamination

7 factors that make elderly people a vulnerable population

1. Process of aging (ex. the kidneys and liver, some of the fastest aging organs, can be compromised and affect clearance of substances)

2. Altered metabolism (repair)

3. Weakened immune system

4. Drug to environmental chemical interactions

5. Physical or mental impairments may make it difficult for the elderly to care for themselves (ex. decreased mobility, increased chronic illness, changing nutritional needs, vision loss)

6. Financial concerns

7. More susceptible to certain contaminants (i.e smog)

7 examples of environmental injustice

1. Access to safe drinking water

2. Access to proper nutrition

3. Low-income families more likely to live in older homes with lead pipes and lead paint

4. Proximity to industry or waste sites

5. Migrant farm workers exposure to pesticides

6. Mental health (i.e covid)

7. Homeless populations and air pollution

Grassy Narrows Case Study

Near Grassy Narrows, ON a paper mill in Dryden released mercury (1962-1970) in the Wabigoon River and residents developed Minamata disease from eating contaminated fish

• More than 90% of residents in Grassy Narrows and Whitedog First Nations have symptoms of mercury poisoning

8 challenges for regulation specific to susceptible/vulnerable populations

1. May warrant separate risk assessment

2. Lack of data or limitation of data

3. Need behavior/lifestyle information

4. Extrapolation of dose to human exposure

5. How do we define baseline

6. What about delayed effects?

7. Lack of resources

8. Uncertainty as to how the data will be used

One World, One Health (environmental justice approach)

Intersections of human, animal, and environmental health

Ultimate goal of pulp and paper industry cleanup

To reduce all forms of waste by efficiently converting resources to products (the ultimate goal: zero effluent!)

3 key points of pulp and paper lecture

1. Economic benefits vs environmental damage

2. Complex effluents create complex effects

3. End-of-pipe solutions are more expensive than process control

3 products of pulp and paper industry

1. Market pulp

2. Boxboard, Cardboard

3. Paper: sanitary, tissue, clay-coated, printing, writing, packaging, industrial, newsprint

5 recent trends in the pulp and paper industry

1. Continued growth globally (esp. Asia, driven by packaging from on-line shopping)

2. Decline in printing papers and Newsprint (on-line news)

3. Most new mills in Asia and Latin America (bigger and more efficient than older mills in North America and Europe)

4. Accelerating industry consolidation – larger conglomerates; closures of smaller mills

5. Recent (2022-23) mill closures in Canada—> impacts are felt in mill towns and in communities that supply timber

4 big-picture environmental impacts of the pulp and paper industry

1. Habitat destruction (deforestation, changes to lakes and rivers, dams, physical damage to benthic habitats via log floating)

2. Water consumption for processing

3. Soil pollution from disposal of solid wastes (e.g wood products like bark, biosolids)

4. Air pollution (high CO2 emissions, reduced CO2 fixation, toxic emissions (sulfur compounds, methanol, etc))

5. Water pollution (oxygen consuming substances, toxic chemicals, persistent bioaccumulative compounds)

3 Physical impacts of pulp mills— Hydroelectric dams

1. Change flow and temperature regimes

2. Block fish migrations

3. Upstream sediment accumulation

3 Physical impacts of pulp mills— Log driving

1. Scour river bottoms

2. Create fibre deposits

3. Release toxic wood extractives

3 Chemical impacts of pulp mills— components of wood

Products: fibres (cellulose and hemicellulose)

Numerous potential byproducts: sugars (= energy); lignin (= glue); extractives (tall oil (fatty acids), turpentine (alcohols, phenolics), resin acids, phytosterols)

Lignin

A random polymer of phenolic compounds

• Lignin degradation by pulping and bleaching creates a wide array of toxic phenolics and polyphenolics

Table of pulping processes

Chemical impacts of pulp mills— stats

• Total pulp production (million ADMT*/yr) = 22.9

• Average water consumption (m3/ADMT) = 100

• Total estimated water use (million m3/yr) = 2,300!

• Estimated loss of organic material (T/y) = 230,000

3 categories of effluent chemicals affecting aquatic environments

1. Oxygen consuming wastes

2. Chemical spills

3. Persistent, bioaccumulative and toxic (PBT) compounds

3 types of oxygen consuming wastes

1. BOD ( Biological Oxygen Demand)

2. COD (Chemical Oxygen Demand)

3. Wood fibre

2 types of chemical spills

1. Alkaline pulping solutions

2. Acid bleachery wastes

5 types of persistent, bioaccumulative and toxic (PBT) compounds

1. Mercury (Hg)

2. Resin and Fatty acids (and chlorinated derivatives)

3. Chlorinated phenols

4. Chlorinated dioxins and furans (e.g., TCDD or 2,3,7,8 tetrachlorodibenzo-p-dioxin)

5 water quality zones when affected by oxygen consuming wastes

Clean Zone —> Decomposition Zone —> Septic Zone —> Recovery Zone —> Clean Zone

3 steps for pulp mills to become a source of mercury (Hg) contamination

1. Electric current causes the evolution of chlorine gas used in bleaching and NaOH (alkali) used in pulping

2. Electric currents transfer elemental (Hgo) to the chlorine gas and Hg ions (Hg2+) dissolve in the brine —> the Hgo and Hg2+ contaminate liquid and solid wastes and receiving environments

3. Hg methylation by sediment microbes causes food web contamination

2 major mercury sources in the pulp and paper industry

1. Phenyl-mercuric acetate

Used as a paper mill slimicide (hydrophobic, bioaccumulative)

2. Chlor-alkali mercury

Mercury combined with chlorine gas used for bleaching paper

4 pulp bleaching agents

1. Chlorine, hypochlorous acid (Cl2,

   HClO)

Alternatives most commonly used since 1995

2. Chlorine dioxide, hypochlorous acid (ClO2,

   HClO)

3. Peroxide (H2O2)

4. Ozone (O3)

Chlorine, hypochlorous acid (Cl2, HClO) as a bleaching agent

• Very efficient, not much fibre breakage

• Generates chlorinated compounds

• Abandoned in the early 1990’s (crisis of chlorinated dioxins in fish & shellfish)

Chlorine dioxide, hypochlorous acid (ClO2, HClO) as a bleaching agent

• Main bleaching agent in Canada

• Most efficient

• Minimal chlorinated contaminants

• Worker safety issues

Peroxide (H2O2) as a bleaching agent

• No chlorinated contaminants

• Less efficient

• Used alone or in combination with ClO2

Ozone (O3) as a bleaching agent

• No chlorinated contaminants

• Less efficient

• Used alone or in combination with ClO2

Effect of untreated pulp and paper industry effluents on fish

Wood extractives ‘mimic’ cholesterol, block cholesterol uptake, and impair sexual maturation

2 End-of-pipe solutions for effluent

1. Effluent Treatment

2. Aeration-Stabilization Ponds (Less sophisticated than activated sludge, less costly to operate, but require much more land)

2 benefits of treating pulp-mill effluent

1. Reduces oxygen demand

2. Reduces acute toxicity

4 changes to pulp mill impacts (post 1980’s)

1. Physical – smaller ‘footprint” with a greater reliance on recycled fibre

2. Lower discharge of BOD, COD, toxic chemicals

3. Virtual elimination of dioxins and furans

4. Fish kills rare with less sublethal toxicity

5. Effluent treatment (1° universal; 2° almost universal; 3° rare)

New issue with pulp mill impacts

Eutrophication due to nutrient enrichment from waste treatment

The Great Pulp Mill Effluent Onion (conundrum + question)

Conundrum:

• As each contaminant problem is solved by more effluent treatment, an unknown or unexpected problem is revealed

The ultimate question:

• If the effluent is not clean enough to re-use in the mill, why is it clean enough to discharge to the

  environment?

Is more effluent treatment the answer?

NO!

Instead of end-of-pipe solutions, improve the pulping and bleaching processes

5 ways to improve the pulping and bleaching processes

1. Recover carbon from pulping liquors and waste fibre and recycle as green energy

2. Replace Cl2 for bleaching with oxygen delignification

3. Re-use and recycle wash waters

4. Reduce mill ‘upsets’ with computer process control

5. Identify toxic waste streams and focus controls on specific sources before they are diluted and difficult to treat

Ultimate goal of improving the pulping and bleaching processes

A zero discharge, closed loop mill (re-use water)

Challenges of improving the pulping and bleaching processes

Remove chemicals from effluents without:

1. Increasing toxicity

2. Creating solid waste

3. Releasing air pollutants

Toxin

Naturally occurring molecules that are injurious to some living organisms

Toxicant

Any toxic substance, whether anthropogenic or naturally occurring

3 toxic plants

1. Poison hemlock

2. Monkshood

3. Black henbane

Toxic effects of poison hemlock

• Produces alkaloids that affect neuromuscular functions

• Causes respiratory failure

• Other members of the Apiaceae (carrot) family (Queen Anne’s lace, Cow parsley, carrot) are less toxic or nontoxic

• Giant Hogweed produces photosensitizing furanocoumarins— react with the skin in light

Toxic effects of monkshood

• Produces alkaloids (e.g., Aconitine)— when consumed interact with sodium-ion channels, affecting respiratory and heart functions

• Used as wolf poison

Toxic effects of black henbane

• Hyoscyamine, Atropine and other alkaloids affect parasympathetic activity by competing with acetylcholine

• Coma, respiratory paralysis, and death

• These alkaloids are also psychogenic

• Now grown or synthesized for pharmaceutical purposes– e.g., analgesic, ophthalmic uses, and to treat brachycardia

3 toxic lower plants

1. Cyanobacteria (blue-green algae) (e.g., Anabaena, Microcystis)

2. Dinoflagellates (e.g., Kerenia brevis)

3. Diatoms (e.g., Pseudo-nitzschia australis)

Toxic effects of cyanobacteria (blue-green algae)

• Contain neurotoxins, hepatotoxins, and dermatoxins - cyclic peptides, alkaloids and lipopolysaccharides

• Death in domestic animals (cattle) and wild animals from consumption or drinking water

• Cyanophyte toxins also contribute to paralytic shellfish poisoning (PSP) (filter feeders ingest the algae and accumulate the toxin)

Toxic effects of dinoflagellates

• Produce alkaloids that are neurotoxic - brevetoxin and saxitoxin

• HAB–dense blooms called red tides can reach 200,000 cells/ml

• Blooms can cause fish kills and contaminate filter-feeding bivalves and whelks resulting in paralytic shellfish poisoning (PSP) in humans

Toxic effects of diatoms

• Produces domoic acid (DA,) a neurotoxin

• Diatoms are consumed by shellfish (no harmful effects), and toxin can be transferred to seabirds and mammals

• DA causes amnesic shellfish poisoning (ASP) in human and other animal consumers

• Ecotoxicological effects through the food chain

Tetrodotoxin

An alkaloid, a selective sodium blocker causing neuronal, gastrointestinal and cardiovascular symptoms.

• In tetrodontid fish (ex. puffer fish or fugu, a delicacy in Japan but also octopus, crab and echinoderms, amphibians and algae)

• Organisms seem tolerant of certain levels of toxin and the toxins are passed up the food chain.

• Tetrodotoxin is synthesized by symbiotic bacteria/ dietary uptake of bacteria —> widespread similarities among unrelated organisms

3 toxic effects of bacterial toxins

1. Pathology (e.g., Clostridium difficile, Corynebacterium diphtheriae, Salmonella spp.)

2. Notorious for toxicity, such as botulism (fatal food poisoning). from Clostridium botulinum

3. Anthrax (Bacillus anthracis)— tri-partite toxins which cause cardiovascular collapse and death

2 types of fungal toxins

1. Moulds (e.g., Penicillium spp)

2. Mushroom poisoning (e.g., Amanita phalloides, the angel of death)

Venoms

Cocktails of many toxins (up to 100 different molecules) produced by a wide range of organisms and usually injected by a bite or sting, but also can be ingested;

• Ex. proteins, peptides and non-proteinaceous chemicals including neurotransmitters

• Contain neurotoxins and cytotoxins, some proteolytic enzymes (aid in digestion of prey)

3 plant toxins with medical applications

1. Digoxin (from Digitalis)

2. Opium (from Papaver Somniferum)

3. Quinine (from Cinchona tree)

Digoxin (from Digitalis)

A glycoside that binds to and inhibits the sodium pump within the plasma membrane of cardiac myocytes;

• Used to treat heart failure and arrhythmia

• Narrow therapeutic index (the dose makes the poison!)

Opium (from Papaver Somniferum)

• Morphine, codeine, heroin, and oxycodone are alkaloid derivatives of opium

• Opium is a controlled substance because of its medical benefits (control of chronic pain) but its potential for misuse

Quinine (from Cinchona tree)

• Bark contains quinine (an alkaloid)

• Controlling/preventing malaria by action on the Plasmodium parasite

• Treatment of malaria with quinine: first known controlled use of a natural chemical compound to treat an infectious disease

5 examples of pest control products from natural sources

1. BT —> Bacillus thuringiensis

Spores germinate in insect gut, lethal to Lepidoptera

2. Nicotinamides —> Nicotiana spp.

Pyrimidine base insecticide

3. Pyrethrins —> Chrysanthemum and other Compositae;

4. Rotenone —> Rhododendron Hortense

Insecticide, and non-selective piscicide

5. Juglone —> Juglans (walnut tree)

Biocide for fouling of aquatic structures

2 examples of species used for bioterrorism/biological warfare

1. Ricin —> highly potent toxin produced in the seeds of the castor oil plant, Ricinus communis

2. Anthrax —> bacterial disease produced in spores of Bacillus anthracis

5 possible ecological advantages of producing toxins

1. Competitive advantage (e.g., cyanophyte blooms)

2. Allelopathy (e.g., Juglans produced by walnut trees)

3. Grazing defence/deterrent (e.g., toxic plants and harmful

   algal blooms)

4. Prey capture and anti-predator deterrent (e.g., venoms, Tetrodotoxin)

5. Defense against parasites and infectious diseases

Bioaccumulation

Describes the fate of toxicants in the “biological organism compartment”

• Accumulation in food web

• Persistence in organism tissues

• Depends on chemical properties of toxicant

Two factors that make up bioaccumulation

1. Bioconcentration

2. Biomagnification

Bioconcentration

Partition of toxicant into biological organism

Biomagnification (aka trophic enrichment)

The increase in contaminant concentrations from one trophic level to the next through accumulation in food

• Assumes almost all contaminant in the prey (consumed) is retained by the predator (consumer) organism

• Linked to persistence

4 factors affecting assimilation efficiency of toxicants from food

1. Speciation— affects solubility and uptake by membrane proteins

2. Location of inorganics in the prey/substrate (sequestered in exoskeleton makes it not easily digested)

3. Genetic make-up and digestion by-products (ex. biotransformation and excretion)

4. Quality of food (digestability differences)

How is biomagnification factor (BMF) calculated

By considering lipid normalized tissue concentrations within an organism vs. lipid normalized concentrations of that in the prey of the organism

• Assumes all predator tissues concentrations are obtained from prey

How is biomagnification factor (BMF) interpreted

BMF >1 —> biomagnification occurring

BMF <1 —> no biomagnification occuring

Twin tracer technique (to estimate bioavailability)

Uses two radioisotopes —> one inert and one to be assimilated into the organism’s tissues

• Assimilated tracer is quantified once all the inert radiotracer has been eliminated

• A single active radiotracer without a paired inert radiotracer can be used, but estimation of assimilated radiotracer is less accurate

Two assumptions of twin tracer technique

Based on the two assumptions:

1. The two radiotracers have virtually identical specific activity concept with similar chemical and biological processing behaviour

2. All active radiotracers are assimilated after the inert radiotracer is eliminated

Trophic levels

The level in which a certain organisms feeds at within an ecosystem

• Some use discrete states (i.e: primary producer, primary consumer, etc)

• Difficult to class omnivores

Trophic transfer

Transfer of a contaminant across different trophic levels

Three possible outcomes of trophic transfer

1. Increase in concentration —> Biomagnification/trophic enrichment

2. No change in concentration

3. Reduction in concentration —> Biominification/trophic dilution

How to define trophic levels

• In labs, trophic levels are imposed (e.g: corn -> rat -> snake -> falcon)

• In field studies, organisms may be sorted into trophic levels via literature or visual observations

  • It is difficult to fit omnivores into discrete levels

How to determine food web

Natural biochemical tracers within organisms can be used to determine prey-predator interactions

• When ingested, fatty acids are incorporated into the predator’s cells and can be monitored

• Fatty acid compositions vary between taxonomic groups

Fatty acid naming convention

ex. 16:1n-7 , 16:4n-1 , 20:5n-3 …

2 methods of determining trophic status

1. Visual observations

2. Isotopic discrimination

Isotopic discrimination

This occurs during trophic transfer; where lighter isotopes are eliminated at higher rates than heavier isotopes

• i.e 13C is assimilated at higher rates than 12C

Isotopic discrimination of carbon

Carbon isotopes are discriminated by C3 and C4 plants

• C3 has higher δ13C than C4 plants

Most reliable isotope for determining trophic status

Nitrogen

Nitrogen as a determinant of trophic status

Normalized to isotope ratio of nitrogen in air

15N quotient increases with increasing trophic status

• 1.3 to 5.3 % increase/ trophic level, average 3.4% / level

• 15N quotient is also affected by age of the organisms and diet

Equation to estimate trophic status of a consumer within the food web

• Advantage over using discrete trophic levels

• Can position omnivores into intermediate levels

2 other factors affecting trophic transfer of inorganics

1. Bioreduction (ex. biomineralization of the metals into granules)

2. Competition between essential elements and their analogs can affect assimilation rates and potential biomagnification (ex. increasing potassium concentration reduces uptake of cesium)

2 major historic oil spills

1. Exxon Valdez Oil Spill (March 1989)

2. Deepwater Horizon Oil Spill (July 2010)

Exxon Valdez Oil Spill (March 1989)

Location: Bligh Reef, Prince William Sound, Alaska (US)

Cause: Oil tanker (Exxon Valdez) struck Bligh Reef enroute to California

Result: 11,000,000 US gallons (~ 42,000,000 litres) light crude oil spilled

Outcome: direct mortality, inhibited reproduction, habitat loss, impaired benthic ecosystem nutrient cycling

Affected organisms: Common mures, sea otters, salmon, herring, benthic species (sediment-dwelling— Ex: marine worms, crustaceans)

Deepwater Horizon Oil Spill (July 2010) —> largest marine oil spill to date

Location: Gulf of Mexico (Mexico and US waters)

Cause: Blowout (explosion) of offshore oil drilling rig (66 km from US)

Result: 210 million gallons (795 million litres) of heavy crude oil released over 87 days

Outcome: direct mortality, inhibited reproduction, habitat loss, impaired deep-pelagic ecosystem nutrient cycling

Affected organisms: Phytoplankton, Atlantic tuna, corals, sea turtles, marine mammals (dolphins, manatees, whales)

4 properties of petroleum

1. Non-polar

2. Hydrophobic/lipophilic

3. Low surface tension

4. Low density (less than water)

3 ways petroleum is indirectly toxic

1. Water

2. Soil and sediment

3. Air

How petroleum affects water

Persistent emulsions that spread easily cause secondary contamination (groundwater transport)

How petroleum affects air

Volatile organic compounds can contribute to greenhouse gas emissions, acid rain