Environmental Toxicology

Biomagnification

accumulation of tissue concentration of a substance as it moves up the food chain / trophic level
(Mercury and DDT)

Temporal Changes

Daily vs. Seasonal

Spatial Changes

Stream vs. river

Hormesis

beneficial response to low concentrations of a chemical (stimulates growth, ups reproduction due to stress)

EC50

amount of substance/volume that affects 50% of the test population (used for non-quantal responses)

LC50

amount of substance required to kill 50% of the test population (quantal responses)

Quantal

discrete results that are either A or B (Dead or Alive)

Non-Quantal

results that focus on continuous or multiple results from study (growth, reproduction)

Bioaccumulation

accumulation of pollutants from chemical partitioning from all sources (water,soil,air,food) in terrestrial organisms

Bioconcentration

accumulation of pollutants from chemical partitioning in specifically in the aquatic phase

MATC

Maximum Allowable Toxicant Concentration (geometric mean of the LOEC and NOEC)

ILL

Incipient Lethal Level (used to describe an LC50 that is independent of time)

Receptor Mediated

causes reaction at lower concentrations due to being specific to the receptor organism. (Hormone mimic, as toxin decreases, effect increases)

Narcotic Mediated

not very effective in organisms that are less susceptible to toxin

Limnocorrals

subdivides natural ecosystem with non-permeable plastic tubes.

Structural Responses

Decrease in population and change in diversity

Functional Responses

Changes in production and biomass

Structure

The makeup or arrangement of an ecosystem

Function

The purpose or job of a specific organism or an ecosystem as a whole.

Hazard Quotient

Used to determine level of hazard based on a scale from <0.10 (no hazard) to >10 (high hazard)
Exposure [X] / Effect [X]

Hazard

Set of inherent properties of a chemical or mixture which makes it capable of adverse effects when a particular exposure occurs

Toxicity

An extrinsic property that is dependent on # of molecules present

Littoral

shallow, near shore

Lentic

Stationary or relatively still water

Good Ecological Assessment Endpoint

An endpoint in ecotoxicology is what we measure to determine if a chemical

or stressor is harming the environment. Think of it as the “goal” we want to assess, like “keep fish populations stable.”

Good Endpoint Characteristics

specific, quantifiable, uniambiguous

clearly define what we are measuring and has to be easy to track without confusion or overlapping with other goals

Good Effect Measure

An effect measure is a way of quantifying the effects on our chosen endpoint

Good Effect Measure Characteristics

Good effect measures are easily linked to the endpoint and simple to measure in a lab. For example, measuring the number of eggs per female fish can tell us a lot about reproductive success, making it a straightforward and meaningful measure

Structural Assessment Endpoint

Measures an ecosystem's structure, such as the number of species or organisms. Structural endpoints are valuable because they tend to have high ecological importance and recover slowly if affected. Example: The diversity of species in an area or the number of certain types of algae

Functional Assessment Endpoint

Related to ecosystem processes like primary production (how much energy plants produce for the food chain). It’s about what the ecosystem “does” rather than what it “has.

Neonicotinoids

Neonicotinoids are pesticides linked to issues like pesticide contamination. They’re especially noted for impacting pollinators, like bees, potentially contributing to colony collapse disorder

Examples of Structural Endpoints

Structural endpoints include indicators of biodiversity and biomass, such as:

○ Diversity of algal species

○ Zooplankton abundance

○ Algal biomass

○ Vertical distribution of algae

Mesocosm Studies

Mesocosms are outdoor experimental setups designed to mimic natural environments. They allow scientists to study direct and indirect effects of chemicals on ecosystems.

Importance of Mesocosm Studies

They provide a controlled environment that can reflect real-world complexities, and organisms in these systems can often be more sensitive than lab-only tests suggest. Mesocosms are also great for testing hypotheses about how ecosystems respond to changes.

Do Assessment Endpoints Have to Include Societal Value

No, societal value isn’t required for an assessment endpoint, but it can be considered if the ecosystem's well-being is also important to people.

Testing Setup Preference for Exposure in Toxicity Testing

Order of Preference:

1. Flow-through: Continuous fresh exposure

2. Static with Renewal: Regularly refreshed exposure

3. Static without Renewal: Single, unrefreshed exposure (least preferred)

Exposure Uncertainty

Different populations might not all come into contact with the toxicant, leading to uncertainty in exposure.

Population Mobility

Mobile organisms can often avoid exposure, while immobile organisms may adapt or suffer from prolonged exposure.

Modifying Factors

Conditions or behaviors that can lower exposure and, therefore, reduce harmful effects. For example, dilution of a chemical in water may reduce its impact.

Field Conditions

Organisms in nature may be exposed to uncontrolled variables, which can protect them from exposure or make them less sensitive than in lab conditions

Toxicity Endpoints for Plants

Plants are best assessed using non-quantal endpoints, like growth rates or biomass changes, rather than simple alive/dead responses

Example of a Good Effect Measure

Number of Eggs per Female: This measure is linked to reproduction and population growth, making it both relevant and easy to measure

Microcosms

Microcosms (small ecosystems) can better represent natural interactions (e.g. competition) that are hard to replicate in a traditional lab.

Mobility and Persistence

For example, a chemical spill detected downstream shows the chemical’s ability to move and last in the environment

Endocrine Modulators

Chemicals that disrupt hormone balance, potentially causing long-term issues in organisms. They are persistent, bioaccumulative, and toxic (PBT) and often have serious effects on top predators through biomagnification.

DDT and Atlantic Salmon:

Key Issue: The accumulation of DDT in the food chain due to its persistent, lipid-soluble nature.

Solution: Constructing fish ladders and reducing pollution helped mitigate its impact on salmon populations

Minamata Disease (Mercury Poisoning):

Cause: Mercury contamination in water bodies due to industrial waste, which was methylated and biomagnified through the food chain.

Effect: Severe health impacts on local communities and animals, highlighting the dangers of bioaccumulation and biomagnification.

PBTs in the Great Lakes:

Impact: Persistent Bioaccumulative Toxic chemicals like DDT and PCBs caused deformities in birds and health issues in fish, emphasizing the importance of reducing long-lived, toxic pollutants in ecosystems

Colony Collapse Disorder CCD Causes

neonics, diease, habitat loss, climate change

Environmental Toxicology

A multidiscipplinary field of science in which the harmful effects of chemical, biological and physical agents on living organisms is studied.

Ecotoxicology

A sub-discipline that focuses on the effects of chemicals on populations and communities.

Structure* and Function

Structure – what is present in the system: (more important for risk assessment

- Abundance (How many?)

- Diversity (What types?)

- Biomass (How much?

Structure and Function*

Function – what the structural components are doing in the system (interactions between

populations and the abiotic environment); includes:

- Energy flow and nutrient cycling

- Primary production

- Consumption of biomass (grazing or predation)

- Providing food to predators

- Processing organic matter (decomposition)

Redundancy

different types of species that all do the same thing, just in maybe different times,

places