ECOTOX Exam 2

-Key elements of a good experimental design

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

-Sample size, experimental unit

Number of experimental units per treatment

-Organophosphates: History and uses

-man-made, many are now banned

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

-Organophosphate Pesticides Example

-e.g., malathion(in use), parathion(banned), chlorpyrifos
-acute toxicity is high
-less persistent (days to weeks)

-Properties of Organophosphates:

-low log Kow (~3.0)

-will be taken up, but < organochlorines (DDT)

-does not biomagnify

-Persistence of Organophosphates:

-days to weeks

-hydrolysis, photolysis

-some break down into toxic compounds

-e.g., parathion → paraoxon

-Toxicity of Organophosphates

-acutely toxic to mammals (only short exposure needed for problems)
-mode of action: inhibits the enzyme that breaks down acetylcholine (neurotransmitter)
-neurotoxin
-some are possible carcinogens

-Jose Casillas, age 15 (Organophosphate fatality)

-migrant worker in Utah orchard supporting family
-hit with “water” in field → headache
-hit few days later with organophosphate from applicator → ill
-next day biked to work, but collapsed and died

-Perfluoroalkyl substances history and uses (PFAS)

-invented in 1930s; commercial uses by 1950s, 3M’s Scotchguard

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

-Forms/Structure of Perfluoroalkyl substances (PFAS)

-short C chains, lots of fluorine

-PFOA, PFOS

-Properties of Perfluoroalkyl substances (PFAS)

-moderate to high Kow
-bioaccumulate in tissue and blood
-act like PCBs, DDT, PBDEs, but accumulate through different pathways

-1/2 of 4 years in body

-shorter chains leave faster

-Persistence of Perfluoroalkyl substances (PFAS)

-Decades (known as “forever chemicals”)
-Can now be found in all matrices, around the globe
-Still in use, so will continue to increase
-EPA working on remediation strategies
-Landfill? Incinerator? Recycling?

-Toxicity of Perfluoroalkyl substances (PFAS) including the body

-Go to blood, liver, kidney
-Cancer, affects kidney, liver, endocrine system
(thyroid, pancreas, increased cholesterol), immune system (autoimmune issues),
-No official criteria or limits yet (propose 4 ppt)
-Tentative limit of 12 ppt in some states

-Problems with removing PFAS

-New proposed Federal standards: 4 ppt (parts-per-trillion) for PFOA and PFOS
-Very expensive to remove PFAS. Need to update utilities’ technologies (e.g., activated carbon filters)
-May not be able to meet this standard of 4 ppt and activated carbon filters

-Too many PFAS to collect toxicity and persistence of each to get a good answer for removing the most PFAS

-Primary (physical)

-Remove large solids with grates, screens, settling tanks

-secondary (bacteria and other microbes to break down organic matter – aerated)

-trickling filter
-rotating biological contactors
-activated sludge

-tertiary treatments (as needed; not all plants)

-remove additional suspended solids, nutrients, toxic materials

-reverse osmosis (lead, VOCs, PFAS), Alum (coagulant for SS, settler), wetlands (nutrients)

-disinfection

-Cl contact basins, O3, UV, sometimes omitted during the winter

-sludge treatments (digestion)

-Reduce organic matter, odor, water content
-May be landfilled, used as fertilizer

-generates methane CH4

-Processes involved in partitioning: Volatilization

transport of a chemical from the aqueous phase (water) to the gas phase (atmosphere)

-Processes involved in partitioning: Atmospheric deposition

– transport of chemical from atm to surface
-wet- rain, snow, fog
-dry- gases, aerosols, particulates

-Processes involved in partitioning: Adsorption

-chemical attaches to a surface
(sorption/desorption)

-Processes involved in partitioning: Sedimentation

-deposition of suspended solids onto bottom of water body

-Processes involved in partitioning: Precipitation

-formation of a solid phase
when chemical exceeds solubility

-Bioaccumulation

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

-Bioconcentration

-net uptake of a chemical from water alone

-Biomagnification

-large (orders of magnitude) increase in contaminant concentration from one trophic level to the next through accumulation in food

-Biomagnification factors

-Properties of the chemical (e.g., lipophilic)
-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

 -Uptake at the cellular level (lipid route)

-Lipophilic uptake

-Diffusion of lipophilic contaminants across membrane lipid bilayer (Benzene)

-High Kow values

-Uptake at the cellular level (aqueous route)

-contaminants enter through diffusion, facilitated diffusion, active transport

-Facilitated diffusion: diffused with a carrier protein, better for larger molecules (metals)

-Active transport: goes against [ ] gradient Cd instead of Ca

-Facilitated diffusion: (aq-route;non-lipid)

diffused with a carrier protein, better for larger molecules (metals)

-Active transport: (aq-route;non-lipid)

goes against [ ] gradient Cd instead of Ca

-Cellular uptake Kow trends

-the higher its Kow, the higher its solubility in lipids→ the higher the importance of the lipid route of uptake

-Elimination routes

Bile, Urine, Feces, Feathers, Molting (in reptiles, insects) , Exhalation (for volatile compounds), Eggs and milk (especially for lipophilic toxicants like PBDEs or DDT)

-Rate constant model of elimination, BAF

-Bioaccumulation Factor (BAF) = [organism] / [Sediment/Food]

-Rate constant model of elimination, BCF

-Bioconcentration Factor (BCF) = [organism] / [water] (ONLY H2O)

-Factors affecting bioavailability and bioaccumulation (chemical, environmental, organismal)

-Chemical structure

-Form (e.g., organic vs. ionic form of metals)

-Log Kow (low values below 6)

-Factors affecting bioavailability and bioaccumulation: environmental

-T, aerobic/anaerobic, hardness, alkalinity, pH

-Factors affecting bioavailability and bioaccumulation: Organismal

-Exposure route, lipid content, age, size, sex, behavior (avoidance IRL)

-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)

-Cytochrome P450 enzymes (CYPs) (phase 1)

-Light-absorbing pigments

-Located in cell membranes (e.g., liver, gills)

-Some species have multiple types

-Transferase enzymes (phase 2)

-found in the cytoplasm

Overall goal of Biotransformation

to make contaminants more hydrophilic for easier elimination

-Sublethal effects

-growth, development, reproduction, behavior, stress biomarkers, immune response, genetic diversity

-KEY: Diminish fitness

-Endocrine System

-A chemical-based communication system that allows integrated control of cell metabolism, division, and growth.

-Endocrine systems are similar among species. EDCs can act similar among species

-Endocrine disruption (EDC)

-Any natural or synthetic agent that interferes with the synthesis, transport, binding, action or elimination of natural hormones in the endocrine system

-endocrine disruptor examples

-Herbicides, fungicides, insecticides, Cd, Pb, Phytoesrtogens

-modes of action (EDCs)

-Agonists: mimic or partly mimic hormones

-Antagonists: prevent or alter hormonal binding to hormone receptors

-Agonists

mimic or partly mimic hormones

-Antagonists:

prevent or alter hormonal binding to hormone receptors

-modes of action (EDCs)

-May alter transport of hormones

• may bind to transport proteins

-modes of action (EDCs)

-May alter breakdown of hormones

• may inhibit certain enzymes

-Classic Examples of EDCs in the Environment

Lake Apopka alligators
      -DDE dumped here in 1980
      -small penises → pop decline
      -susceptible to disease

-Classic Examples of EDCs in the Environment

• Tyrone Hayes vs. Syngenta

  • Deformities and intersex in frogs
    atrazine as low as 1 ppb caused ovotestes

-EDC: Cadmium

Sources/Uses: Cd

• byproduct of mining/smelting zinc, lead, and copper, and of burning fossil fuels, tobacco

• pigments, metal-plating, batteries, plastics

Cd in the endocrine system

- binds to estrogen and androgen receptors

-reduces progesterone (ovulation, pregnancy)

-causes testicular hemorrhage w/edema

Needs for toxicity data

• For use in regulating inputs

  • establish surface water quality criteria

  • establish drinking water standards application limits or rates

• Risk Assessment

Acute Testing

-higher concentrations
-shorter exposure duration
-duration depends on species
-endpoint: mortality or immobilization
-animals not fed

Chronic Testing

-lower (mostly sublethal) concentrations

-based on acute testing
-longer exposure duration
-endpoints: growth, reproduction, etc.
-animals fed

Data collection Toxicity tests

• Acute: mortality (daily)

• Chronic: mortality (daily)

  • sublethal endpoints (daily: reproduction)

  • sublethal endpoints (at end: growth)

• All: water quality parameters (daily)

Transformation: Hydrolysis

Chemical reaction with water

Transformation: Photolysis

Breakdown by sunlight

Rate constant model of elimination: Single Compartment Model

Model Assumes uniform concentration in the body

Formula: dC/dt = -kC

Rate constant model of elimination: Multi Compartment Model

• “Fast” and “slow” compartments

  • Fast: e.g., blood or soft tissue

  • Slow: e.g., fat or bone

Rate constant model of elimination: PBPK Model

Physiologically Based Pharmacokinetic Models

More realistic—models specific organs (gills, liver, muscle, etc.)

Requires dissection and measurement of compartments