BISC308 Midterm 1

What is toxicology?

The study of the adverse effects of chemical, physical, and biological agents on living organisms

What are the routes of exposure?

• ingestion

• inhalation

• dermal contact

What is the media of exposure?

• soil

• air

• water

• food

• consumer products

What is the toxicology pathway?

• sources

• exposure pathways

• intake/uptake

• internal does

• biologically effective dose

• effects

What was DDT used for?

• agricultural pesticide and malaria/typhus control agent

What does DDT degrade into?

DDE

What does biomagnification mean?

organisms higher in the food chain accumulate higher levels of cheicals/tosicants than those lower down the food chain

What are some commonalities among global environmental problems?

• habitat destruction impacting

• often involves one or several chemicals

• major impact on the environment

• due to anthropogenic activities

• lack of effective/precautionary management

What are risk assessments?

• conduction by regulatory agencies

• establish “safe” limits of exposure

• science-based (i.e many lab toxicity tests, some field tests, review of primary literature)

What is environmental toxicology?

• study of the impacts of pollutants upon the structure and function of ecological systems

• includes all organisms

• includes all levels of biological organization

  • molecular to ecosystem level effects

  • reductionist bottom-up approach

What is ecotoxicology?

• subdiscipline of environmental toxicology

• focus on organism and higher levels biological organization

• holistic, top-down approach

What are the levels of biological organization?

• molecular

• cellular

• tissue

• individual

• population

• community

• ecosystem

• biome

• biosphere

What is ecology?

study of the relationship between organisms and their environment

What is an ecosystem?

• environment

  • physical

  • chemical

  • biological

• relationships

  • interactions with physical aspects of environment

  • interactions with same and different species

What is a community?

• a group of species that occupy a given area, interacting either directly or indirectly

• attributes:

  • # of species

  • relative abundance of species

  • nature of species interaction

  • physical structure

What are some endpoints greater than or equal to population level?

• population dynamics:

  • species abundance

  • reproductive success

  • alterations in genetics

  • likelihood of extinction

• community structure:

  • reductions/increase in community structure

  • biodiversity changes

  • species abundance/dominance

  • predator/prey interactions

• ecosystem:

  • changes in ecosystem processes

• landscape level impacts:

  • spatial distribution/extent of different habitat types within landscape

What is the path of ecotoxicology?

• pollutant

• biochemical changes

• physiological changes

• whole organism response

• population changes

• community composition

• ecosystems

What are the major features in environmental toxicology?

• environmental contaminants

• environmental interactions

• individual effects

• ecological effects

• exposure

• sources

• risk assessment

• risk management

• regulation, enforcement

What is a contaminant?

• chemical that exists at levels above those that normally occur in any component of the environment

• non-naturally occurring/anthropogenic chemicals and naturally occurring chemicals

• may or may not cause harm

What is a pollutant?

• chemical that exists at levels above those that normally occur in any component of the environment

• non-naturally occurring chemicals and naturally occurring

• causes environmental harm

What is a toxicant?

• any chemical/agent that has an adverse effect in a living organism

What is a xenobiotic?

• a chemical foreign to a living organism

What is a toxin?

• a xenobiotic of natural origins that elicits an adverse effects on a living organism

What is an adverse effects assessment?

• combination of analysis and inference of possible consequences of the exposure to a particular agent based on knowledge of the does-effect relationship with that agent in a particular organism, system or (sub) population

What are adverse effects?

• abnormal, harmful, unwanted effect that can be defined in terms of a specific biological response, such as:

  • altered behaviour

  • change in food consumption

  • altered body or organ weights

  • changes in enzyme levels

  • changes in tissue structure

  • onset of pathological conditions

  • mortality

What is toxicity?

inherent capacity of a chemical to cause harm to a living organism

What is hormesis?

low doses of otherwise harmful conditions lead to adaptive response that enhance the functional ability of organism

What info is needed to determine individual effects of xenobiotics?

• fate and transformation/metabolism/biotransformation in organism

• interaction of xenobiotic with site of action

• impact on whole organism’s health

Who said “the dose makes the poison”?

Paracelsus

What are the general principles of toxicology?

• you’ll only find what you’re looking for only if there’s a measurable concentration and not all toxicants are measured routinely

  • detection limits and knowledge/technical limitations

  • personal care products and pharmaceuticals in sewage discharge are not measured, but are present

  • pesticides are not routinely measured in drinking water, but are often present

• the dose makes the poison is too simplistic

  • adverse effects may increase with increasing dose, but not always, a chemical can be harmless or beneficial or toxic at low doses

  • uptake and internal dose affected by many factors; form of chemical used, exposure route

  • bioavailability

• only living material can measure toxicity

What is a monotonic relationship?

relationship in which a measured dependent variable increases or decreases continuously in response to an increase or decrease in an independent variable

What is dose?

• known concentration is administered or consumed or applied

• oral, dermal, injection

• dose is an amount administered via one exposure route

What is concentration?

• environmental media exposure and exact dose is not known

• water, sediment, soil, air

• multiple exposure routes may occur simultaneously

• reported as environmental medium concentration

What are the 3 main categories used by agencies in evaluation and regulation of toxic chemicals?

1. human epidemiology

2. human controlled clinical exposures

3. plant and non-human animal toxicity tests

What are environmental quality guidelines defined as?

numerical concentrations or narrative statements that are recommended as levels that should result in negligible risk to biota, their functions, or any interactions that are integral to sustaining the health of ecosystems and the designated resource uses they support

What is the scale of toxicity testing?

• single species

• microcosm

• mesocosm

• limnocorrals

• field surveys

• natural systems

• watersheds

What are the dose/concentration-response curve terminology?

• NOEC = no observed effect concentration

• LOEC = lowest observed effect concentration

• LC50 = median lethal concentration

• EC50 = meidan effective concentration

What are exposure gradients?

• range finding - broad concentration range, e.g. increasing stepwise by 10 fold

• definitive - repeat the test with a narrow range of test concentrations

  • more precise estimate of toxicity

  • ideally gradient includes concentrations that include no effects, progressively greater responses, and max response to fully characterize the relationship

What are the quality assurances?

• negative control

• solvent control

• replication

What are the principles of toxicity tests?

• focus on sublethal endpoints

• longer 7d to >18 months depending on organism lifespan

• examples of endpoints:

  • behaviour

  • carcinogenesis

  • organ damage

  • growth

  • reproduction (brood size, hatching success)

What statistical analysis of toxicity tests?

• analysis of variance (hypothesis testing) - test for significant difference from control and between all treatment groups

• regression analysis

What are the advantages of standard methods?

• tests are uniform and comparable to previous results within the same or other labs

• can be replicated by other labs

• makes it easier for decision makers to accept test results

• logistics are simplified, development work already done

• methods establish baseline from which modifications can be made if necessary

• data generated can be combined with those from other labs for use in QSAR, ERA’s

• detailed list of apparatus, dilution water, test material, test organisms, etc.

• experimental, analytical and documentation procedures are detailed

• acceptability criteria are listed

• can rank potency of chemicals

What are disadvantages of standard methods?

• often very specific → hard to apply to other situations or answer other questions

• may or may not be applicable to natural environment

• currently mainly single chemicals only

What are the types of chemical combos?

• additive - the toxicity of 2 chemicals when administered together equate to the sum of the chemicals when administered individually

• antagonistic - less than sum

• synergistic - more than sum

What is acute toxicity test?

• can broadly classify toxicity tests based on length of exposure

• drop dead testing

• time depends on species

• not very ecologically relevant but quick, relatively cheap

• rank hazards

• usually a precursor to chronic toxicity testing - useful in designing

• can check change in gene expression, happens quickly as opposed to change in body weight which takes time

What traits to test species have?

• lab hardiness

• common

• known life cycle

• cheap

• short-lived

What is the limitation of using test species?

number of animals we test on vs number of animals in world

What are multi species toxicity tests?

• attempt to recreate complexity of natural systems

• goal - indicate potential population and higher adverse effects of toxicants

• more complex, expensive, variability between replicates

What are the differences between microcosm and mesocosm?

• microcosm

  • multiple species

  • functional and structural endpoints

  • not all trophic levels

  • <15m3 of water

• mesocosm

  • multiple species

  • functional and structural endpoints (more developed)

  • more trophic levels (no top level predators)

  • >15m3 of water

What are functional and structural endpoints?

• functional - measuring something that’s happening in micro or mesocosm

  • decomposition of leaf litter

  • primary productivity

  • nutrient cycling

  • phosphates

  • carbon

• structural - biological structure

  • population of species present

  • biodiversity

  • relative abundance of species

What are ecological survey and monitoring?

• surgery - descriptive and doesn’t involve experimentation or manipulation

• monitoring - surveys repeated at regular intervals following a fixed spatial pattern designed to reflect findings of initial survey

What is biomonitoring?

• biomonitoring of the characteristics of biota to evaluate contaminant impacts on biota

• use of transplanted organisms as sentinels in the environment or native species:

  • contamination of source waters is usually episodic, therefore monitoring must be continuous and time-relevant

  • ‘canary in the coal mine’

  • use biological responses to assess changes in environment

  • whole organism and/or biochemical/molecular endpoints

What is environmental effects monitoring?

• EEM includes:

  • sublethal toxicity testing of effluent

  • field surveys

• every 3yrs, if no effects then 6yrs

What are the advantages and disadvantages of field experiments?

• advantage - realistic exposure scenarios, native species

• disadvantage - unpredictable site conditions, presence of predators, site access

What is paleo-ecotoxicology?

• reconstructing past ecological and chemical conditions

• study of long-term environmental change caused by chemical contamination through the analysis and interpretation of substrate cores (i.e. sediment, soil, glacial ice)

What is epidemiology, epizootiology, and ecoepidemiology?

• epidemiology - study of the distribution and determination of health-related events in populations

• epizootiology - epidemiology applied to diseases in animal populations

• ecoepidemiology - application of epidemiology to identify the distribution and determinants of ecological change, and the links and pathways between them

Why use ecoepidemiology?

• real world exposure

• natural gradients

• biological variability

• multiple stressors

• ecological endpoints

What are the differences between inorganic and organic pollutants?

• inorganic - naturally present in Earth’s crust, not subject to degradation, uptake normally takes place by facilitated transport, often biological essential

• organic - absent from Earth’s crust, subject to degradation, uptake by simple diffusion, complex defence mechanisms against accumulation of toxic compounds

How do contaminants and pollutants enter the ecosystem as a consequence of human activity?

1. unintended release from human activities - nuclear accidents, accidental release of byproducts using industrial operations, shipwrecks, fires

2. disposal of water - sewage

3. deliberate application - pesticides, fertilizers

Ocean dumping is allowed for what materials or substances?

• dredged material

• fish waste and other organic matter resulting from industrial fish processing operations

• ships, aircraft, platforms or other structures

• inert, inorganic geological matter

• uncontaminated organic matter of natural origin

• bulky substances that are primarily composed of iron, steel, concrete or other similar matter

What are pros and cons of ocean dumping in Canada?

• pros

  • discourages dumping

  • incineration at sea is banned

• cons

  • still allow some dumping

  • can get permit to dump