ECOTOX Final

-Data analysis (acute)

• Focus: Short-term, high-concentration exposure to assess immediate toxic effects.

• Point Estimates:

  • LC50 – Lethal concentration for 50% of the population.

  • EC50 – Effective concentration for 50% of the population (often used for chronic or sublethal effects).

-Data analysis (chronic)

• Focus: Long-term, low-concentration exposure to assess sublethal and reproductive effects.

• Main Metrics:

  • NOAEC (No Observed Adverse Effect Concentration) – Highest concentration without statistically significant adverse effects.

  • LOAEC (Lowest Observed Adverse Effect Concentration) – Lowest concentration with statistically significant adverse effects.

  • MATC (Maximum Allowable Toxicant Concentration) – Geometric mean of NOAEC and LOAEC.

-Statistical analysis (acute)

• Probit Method (Parametric) – Requires homogeneity of variances; more powerful if assumptions are met.

• Trimmed Spearman-Karber (Non-Parametric) – Tolerates non-homogeneous variances but is less powerful.

-Statistical analysis (chronic)

• Use ANOVA followed by multiple comparison tests.

• NOAEC is found by moving from the lowest concentration up until you find the highest concentration without significant adverse effects.

• LOAEC is found by identifying the lowest concentration that shows a significant adverse effect.

Linear dose response curve (Linear-no threshold)

Threshold dose response curve

Hormetic dose response curve

Hormesis

·      Low doses of a contaminant appear to be beneficial (Gamma rays and mouse malignant tumor incidence)

·      Stimulatory effect at low doses; inhibition at high doses

-LC50 values

·      Lethal concentration for 50% of the population.

-Problems with ANOVA/MATC Analysis

·      Assumes safe level has been found

·      Depends highly on selection of test concentrations

·      Sloppiness rewarded higher variability → less likely to detect a difference → higher MATC

Source

Sink

·       pre/post-Clean Water Act

·       hydrophobic persistent chemicals

Bioturbation

·       Movement by benthic organisms (e.g., worms, crabs) can resuspend contaminants.

-Sediment toxicity testing

• Benthic Organisms: Live on or in the substrate.

• Problems

  • Clean, Reference Sediments: Hard to find for accurate comparisons.

  • Natural vs. Artificial Sediments:

    • Natural: Can contain other, unmeasured contaminants.

    • Artificial: Lacks some natural chemical and physical characteristics, like acid volatile sulfides.

-BSAFs (Biota-sediment accumulation factor)

·       Measures the accumulation of contaminants from sediments into organisms.

·       Used to estimate the potential for biomagnification.

·       EPA Database: Over 20,000 chemicals associated with Superfund sites.

-Sediment quality guidelines

-Effects of contaminants on population size (through courtship behavior, hatching success, etc.)

• Reproductive Effects:

  • Disruption of reproductive hormones (e.g., estrogen, testosterone).

  • Impacts on gonads (ovaries, testes), leading to reduced fertility.

  • Reduced hatching success and embryo survival.

• Survival Effects:

  • Increased death rates.

  • Shifts in age structure within populations

• (e.g. Fish Kill in Plaquemines Parish)

-Effects of contaminants on genetic diversity on the population lvl (through bottleneck effect, natural selection, etc.)

• Population Bottlenecks:

  • Toxins can reduce effective population size, decreasing the number of individuals contributing alleles to the next generation.

  • Results in loss of genetic diversity.

  • Random chance determines which alleles are preserved (not natural selection).

• Natural Selection:

  • Over time, populations may evolve to tolerate specific contaminants.

  • This can reduce genetic diversity by eliminating sensitive genotypes.

  • Trade-Off: Populations adapted to one stressor may be more sensitive to others (e.g., Baetis tricaudatus mayflies tolerant to metals but potentially more vulnerable to other stressors).

-Effects of contaminants on community interactions (competition, predation, parasitism, etc.)

• Predation and Interactions:

  • Predator-prey dynamics

    • Sea otters being killed by oil then affecting sea urchins in the kelp forest

  • Examples:

    • Industrial Melanism: Peppered moths preyed on by birds, with survival influenced by industrial pollution.

    • Climate Change and Eucalyptus: Increased stress in eucalyptus plants, leading to higher toxin concentrations, affecting koalas.

    • Parasitism: Sea lamprey in the Great Lakes preying on trout, causing wounds and infections by increased contaminants.

-Effects of contaminants on community structure (richness, diversity, sensitive versus tolerant species, Index of Biological Integrity, etc.)

Microcosms (Ecosystem effects):

• Small, controlled studies that simulate parts of an ecosystem.

• Often used indoors with fewer species.

Mesocosms (Ecosystem effects):

• Larger, more complex outdoor studies with multiple species.

• More realistic, but more costly and difficult to control.

Whole Ecosystem Studies (Ecosystem effects):

• Entire lakes, forests, or other large-scale systems (Experimental lakes in Can.).

-Risk:

·       chance of harmful effects to human health or to ecological systems resulting from exposure to an environmental stressor

-RA (risk assessor) vs. RM (risk manager)

·       RA: the scientist who does the field work and report assessing the severity of the case

·       RM: the person with the say in action from report and science (could be a scientist or not)

-(Framework of RA) Analysis:

• Exposure Assessment: Identify sources, concentrations, and exposure routes.

• Effects Assessment: Dose-response testing, acute and chronic effects.

-(Framework of RA) Risk Characterization:

• Estimate the likelihood of adverse effects.

• Include uncertainties and data gaps.

-(Framework of RA) Risk Management:

• Make decisions based on risk assessment.

• Set discharge limits, air pollution controls, or declare Superfund sites.

-Hudson River PCBs example

• Background:

  • Contamination from GE capacitor plants.

  • ~1.3 million pounds of PCBs discharged.

  • 200 miles of the river declared a Superfund site.

• Risk Assessment Steps:

  • Problem Formulation: Are fish safe to eat?

  • Analysis: PCB concentrations in sediments, fish, and water.

  • Risk Characterization: High risk to human health if consuming fish.

  • Risk Management: Dredging, capping w/ anthracite, habitat restoration.

-Rachel Carson and Silent Spring → environmental movement

• Published Silent Spring in 1962, highlighting the dangers of DDT and other chemical pesticides.

• Sparked public awareness of pesticide impacts on wildlife, particularly songbirds and raptors.

• Criticized by chemical companies but credited with inspiring the modern environmental movement.

• Called for responsible pest control rather than outright bans.

-Clean Air Act (1970)

• Regulates air emissions from stationary and mobile sources.

• Amended in 1990 to include controls for acid rain and ozone-depleting substances.

-Clean Water Act (1972)

• Regulates pollutant discharges into U.S. waters.

• Requires permits for point source discharges and sets water quality standards.

• Includes provisions for Total Maximum Daily Loads (TMDLs) to limit pollutant levels.

-Resource Conservation and Recovery Act

·       Control of hazardous waste

·       Generation, transportation, storage, treatment, and disposal

-Comprehensive Environmental Response, Compensation and Liability Act (Superfund)

• Provides funding and legal authority for cleaning up hazardous waste sites.

• Holds responsible parties financially liable for contamination.

• Example: Love Canal – 21,000 tons of chemical waste buried and capped, later contaminated groundwater and homes.

-Love Canal example

• Abandoned canal filled with chemical waste (caustic, carcinogenic, dioxins), later capped and sold to the city for $1.

• Contamination discovered in 1977, leading to evacuations and long-term health effects for residents.

• 1977: snow melt seeped into canal, carried chemical waste into groundwater & to the surface, into yards and basements

-Uses of Asbestos

·      fire retardant coatings, concrete, bricks, pipes and fireplace cement, pipe insulation, ceiling insulation, ceiling tiles, acoustic tiles, drywall, vinyl flooring, roofing, lawn furniture, and drywall joint compound

-Physical properties of Asbestos

·      6 different silicate minerals

·      long, thin, crystal fibers

·      resistant to fire, heat, chemical, and electrical damage

Asbestos

• Scarring of lung tissue (Asbestosis).

• Shortness of breath, cough, chest pain, clubbing of fingers.

• Ranges from mild to severe.

·       Takes years of exposure to develop.

Mesothelioma

Lung cancer

• Definition: Cancer that originates in the lung tissue (not the lining).

• Symptoms: Shortness of breath, cough, wheezing, bloody mucus, fatigue.

• Causes: Can be caused by asbestos but also by other factors like smoking, PAHs (polycyclic aromatic hydrocarbons), and radon.

• Can metastasize and spread to other organs.

Libby, Montana Vermiculite Mine:

• Ore Contamination: Contained 10% tremolite asbestos.

• Health Impact: Over 400 deaths and 1,000+ cases of lung issues among miners and residents.

• Superfund Site: Declared after decades of contamination.

• Company Involved: W.R. Grace – filed for bankruptcy to protect against over 100,000 personal injury claims.

• Legacy: Vermiculite from this mine can still be found in millions of homes, primarily as Zonolite insulation.

-Scientific method (hypothetico-deductive; key steps)

1.    Observe

2.    Gather

3.    Hypothesize

4.    Predict

5.    Experiment

6.    Conclusion

7.    Communicate

-Key elements of a good experimental design

Control (comparative), replication (Samples and experimental units per treatment), randomization (avoid bias)

-Dependent V:

What is measured, response variable

-Independent V:

What you are manipulating or change in the environment (what you wish to determine)

-Aliphatic Properties

Non-polar, highly flammable, and insoluble, e.g. CH4

-Aromatic Properties

Cyclo of C, Being generally nonpolar, hydrophobic, and having a high carbon-to-hydrogen ratio,

Surfactant

Mixture of Aromatic and Aliphatic compounds; hydro philic and phobic

-Halogens, organohalogens

DDT, PCB, PBDE, Dioxins, CFC; tend to be persistent, bioaccumulate, and toxic

-Inorganic Chemical Contaminants: As

Persistent but typically bioaccumulates without significant biomagnification; its inorganic forms are more toxic than its organic forms and can cause enzyme inhibition, gastrointestinal problems, and cancers in humans

-Inorganic Chemical Contaminants: Hg

Highly persistent, neuro toxin, especially in its organic forms (e.g., methylmercury), and it biomagnifies in food webs, leading to neurological and developmental issues in both wildlife and humans.

-Dimethylmercury (CH3)2Hg (Organic form)

-potent neurotoxin!

-inhalation, absorption of 0.1 mL (= 100 μL) fatal

-passes through latex, neoprene, butyl gloves

-crosses blood-brain barrier

-symptoms may be delayed by months

-Polychlorinated biphenyls (PCB’s)

-Used in hydraulic systems, plasticizers, pesticides, & carbonless copy paper

-Highly persistent, high Logkow

-Endocrine, nervous, and immune disruptors

-Polybrominated diphenyl ethers (PBDE’s)

• Flame retardants

• High Logkow, high persistence

• Endocrine, nervous, and immune disruptors

-Organophosphates

-insecticides, herbicides, nerve gases, (solvents, plasticizers)

-acute toxicity is high, less persistent (days to weeks)

-low log Kow (~3.0), no biomagnifation

-neurotoxin

-Perfluoroalkyl substances (PFAS)

-Food packaging, makeup, stain-resistant furniture, Nonstick cookware, firefighting foam

-short C chains, lots of fluorine

-moderate to high Kow, very persistent (decades)

-Carcinogenic; go to blood, liver, kidney

-Bioaccumulation

-net uptake of chemical from the environment by all sources– respiration, diet, water, dermal

-Biomagnification factors

-Tend to be lipophilic contaminants

-Higher trophic level organisms are generally: longer-lived, larger, have more lipid
-Lower trophic level organisms tend to grow faster: more growth dilution, shorter lived

-Biotransformation of organics (Phase I)

-Oxidation, reduction, or hydrolysis reactions
-Catalyzed by P450 enzymes
-Functional group added (trailer hitch)
-Makes some chemicals hydrophilic enough to be excretable (although sometimes more toxic or carcinogenic)
-Other chemicals still too lipophilic...

-Biotransformation of organics (Phase 2)

-Conjugation reactions (hook up to trailer hitch)

-Adds water-soluble molecules to the contaminant.

– Amino acids

– Sulfates

– Glucuronic acid

-Catalyzed by Transferases (not CYT P450 enzymes)

Overall goal of Biotransformation

to make contaminants more hydrophilic for easier elimination

Biotransformation of Inorganics

-Biomethylation (microbes adding methyl groups)

-Binding of metallothioneins (detoxifying)

-Biomineralization (transform inorg. into bone, shell, chitin)

Steps of risk assessment

P: Problem (endpoints, safe to eat?)

A: Analysis (sources and frequency?)

R: Risk characterization (high or low)

M: Management (decision by RM)