Ecotoxicology

1. Ecotoxicology Ecotoxicological study is a multi-step process, involving: The entry, distribution and fate of pollutants within the environment; The entry and fate of pollutants in living (biota) organisms within an ecosystem; and The harmful effects of the chemical pollutants on the constituents (biotic & abiotic) of ecosystems (which include man).

7. Transport and fate Ingested Contacts human Toxin emitted Ecosystem effects Population effects Community effects Beyond our toxin trailIs the grave deeper than we thought? Metabolized and/or stored Reaches an organ molecular mechanism Adverse health effect Physiological chain of events

8. Toxicology Host defense mechanisms Individual susceptibility states Single effects Cumulative exposure Ecotoxicology Bioaccumulation Bioconcentration (in water) Biomagnification Never single effects Movement between media (air, water)

9. Ecological bases of Ecotoxicology • The basis for determining the effects of contaminants on ecosystem is at organism level • At organism level, response can be: • Acute toxicity causing mortality • Chronically accumulating damage ultimately causing death • Sublethal impairment of various aspects of physiology and morphology • Sublethal behavioral effects • Measurable biochemical changes

10. At population level, response can be: • Size and dynamics (based on birth rates, death rates, gains, from immigration and losses from emigration) • Cause a reduction or an increase in the natural flowchart of numbers, in the biomass, sex ratio, etc. • At community level, response can be: • species diversity • predator prey relationship, etc • Change in ecosystem • nutrient cycling rates, patterns of nutrient flow, • physical-chemical conditions etc.

12. Assessment of Structural Changes changes in species / population  structure                  -  appearance/disappearance of an indicator species                   -  number of individuals of a species                   -  biomass of a species                   -  presence or absence of a species Biomass-a quantitative estimate of the total mass of living plant or animal materials

13. changes in community/ecosystem structure                        -  biomass                         -  abundance                         -  biotic indices (e.g. trophic types)                         -  species richness / diversity                         -  dominance                         -  food chain length/complexity

14. Chemicals of ecotoxicological interest They are toxic and in many cases their metabolites are also harmful e.g. DDT & DDE (metabolite of DDT) They are very stable both chemically and environmentally Their stability has lead to their persistence and ubiquitous nature in the environment Almost all chemicals of ecotoxicologigal interest are bioavailable and in most cases undergo bioaccumluation and biomagnification (food chain)

15. BioavailabiltiyThe fraction of a chemical that is in an available form to an organism e.g. fish: food, absorption from water Bioconcentration - where the chemical concentration in an organism exceeds the concentration in the surrounding media (i.e. aquatic environment) as a result of exposure through the respiratory surfaces (i.e. gills/dermal surfaces) - not food! Bioconcentration Factor = conc. in organism conc. in ambient medium (usually water)

16. Bioaccumulation - where the chemical concentration in an organism achieves a level that exceeds that in the water/media as a result of chemical uptake through all routes of exposure. • Bioaccumulation factor = Conc. in organism • Conc. in food • (or ingested water) • Bio-accumulation of Cd is higher than most metals as it is assimilated rapidly and excreted slowly • depends on the rate of excretion

18. Biomagnification - where the chemical concentration in an organism achieves a level that exceeds that in the organism’s diet due to dietary absorption. i.e. higher trophic levels accumulate more chemical Biomagnification Factor = Conc. in predator Conc. in prey Factors that influence bioaccumulation -Environmental persistence -Lipophilicity -Biotransformation

20. Toxic Effects The biochemical (molecular in nature) or physiological (observed at organ and whole organism levels) changes which adversely affect individual organisms’ birth, growth or mortality rates. Both biochemical and physiological changes could lead to behavioral (whole organism level) changes.

21. Toxicant binding: Reversible vs. Irreversible binding Irreversible binding (covalent) causes harmful effects. Types of bonding: Covalent > ionic > Hydrogen binding > Vanderwaals > hydrophilic Biochemical responses: Biochemical response could be protective or non-protective (may or may not cause harmful effect). Non-protective biochemical responses have carcinogenic, mutagenic, teratogenic and neurotoxic potentials.

22. Protective biochemical responses Monoxygenase (OCs and PAHs) Induction and binding to metalothionein (Cu, Cd, Zn and Hg) Binding to blood plasma, bones and hair (Metals and xenobiotics) Dissolving in fat (organics- e.g. OCs) Mineralization ( e.g. MeHg to Hg 2+) Demineralization (As to MeAs)

23. Protective biochemical response Heavy metals for example can be stored and detoxified by organisms either by binding to specific proteins e.g. metallothioneins (-SH proteins) In some cases it is mineralized to inorganic form, which is less toxic: e.g. Hg bound to Se is a mineralized Hg (detoxified Hg: MeHg to Hg). On the other hand, the inorganic form, which is more toxic can be methylated to a less toxic form e.g. As.

24. Protective biochemical response PHASE 1 REACTION. Organic pollutants could also be metabolized and detoxified by Cytochrome P450 enzymes (Microsomal Monoxygenase; MMO). PHASE 2 REACTION The metabolites undergo conjugation with endogenous molecules e.g. GSH. Forsome chemicals the metabolites/conjugated form are more toxic than the parent compound and can lead to cancer formation.

25. Binding to DNA (DNA adduct) DNA structural damage (strands break) induced by genotoxic compounds Binding to SH-Protein (Protein adduct); enzymes and proteins Neurotoxicity: prolongation of K and Na flow and inhibition of AChE activity in the brain Non-protectiveresponse

26. Non-protective response Mitochondrial Poison (lost of proton gradient) Inhibition of vitamin K cycle (competition with vit K binding site) Inhibition of Thyroxine (competition with thyrosine binding site) Inhibition of ATPase (enzymes for transport of ions e.g. K, Na, Ca)

27. Non-protective response Environmental estrogens (eg DDT) and androgens (tributhyl Tin) Endocrine disrupters (binding to endocrine receptors) Photosystems of Plants (interruption of electron flow) Plant growth regulation

28. Physiological changes Non-protective biochemical responses lead to Physiological changes which could be observed at organ and organism levels Organ level: accumulation of Cd in kidney, which could cause cell death (cytotoxicity), resulting in dysfunction of the kidney PAHs and Lung cancer Organism level: decrease in production (growth and reproduction) changes in gene frequency decrease in resources acquisition and uptake

29. Behavioral Changes Either or both physiological and biochemical effects could lead to behavioral effects at organism level- migration, intraspecific attraction, aggregation, aggression, predation, vulnerability, mating caring for young ones and avoidance of predator. .

30. Population Changes Changes in population may come about as a result of direct changes in numbers of individual organism and gene frequency By indirect means (decrease in population of predators due to toxic chemicals could lead to increase in numbers of its prey).

31. Diclofenac residues as the cause of vulture population decline in Pakistan.Nature. 2004 Feb 12;427(6975):630-3. Diclofenac causes kidney damage, increased serum uric acid concentrations, visceral gout, and death.

32. Changes in community structure change in pyhtoplankton assemblage due to eutrophication acid rain affecting microorganisms in the soil, aquatic life Changes in Ecosystem level (earth as an ecosystem) carbon dioxide increase ozone depletion

33. What is an Endocrine Disruptor ? “An exogenous agent that interferes with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body that are responsible for the maintenance of homeostasis, reproduction, development and/or behavior. “

34. Mechanisms of endocrine disrupting compounds 1) Binding and activating the estrogen receptor 2) Binding but not activating the estrogen receptor (therefore acting as an anti-estrogen) 3) Binding other receptors 4) Modifying the metabolism of natural hormones 5) Modifying the number of hormone receptors in a cell 6) Modifying the production of natural hormones

37. Hormone regulation and feedback control • Estrogen levels depend on • Estrodiol sulfate • Estrodiol serum-binding proteins • -fetoprotein (AFP) • Testosterone-estradiol binding globulin • Xenoestrogens (ex. DES) • 100-fold lower affinity than E2 to these binding protein • Bioavailability increased

39. Non-genomic mechanisms of ED action Compounds of the azole type, such as ketoconazole and the fungicide fenarimol, inhibit CYP isoforms and consequently can also affect steroid synthesis while the now-banned anti-fouling agent tributyltin and its metabolites, which have strong ED potential, are thought to act by the same mechanism, probably by inhibition of aromatase.

40. Genomic mechanisms of ED action bind to oestrogen receptors and so act as pseudoestrogens in vivo, giving feminizing effects tamoxifen and diethylstilbestrol and industrial chemicals (e.g. octylphenol and bisphenol-A fungicide vinclozolin binds competitively to the androgen receptor, blocking the cellular actions of testosterone on androgen-dependent tissue growth and behaviour patterns chlordecone, inhibit binding to the oestrogen and progesterone receptors, whereas bisphenol-A can block ligand binding to the thyroid receptor

44. Timing, duration, and amount of exposure. Organization vs. activation Timing, duration, and amount of exposure are each important determinants of the outcome. There are windows of vulnerability during fetal development in which small exposures to endocrine disruptors may have profound effects not observed in adults. Studies of the intrauterine position of mice during fetal development show that slight fluctuations of steroid hormone levels influence genital morphology, timing of puberty, sexual attractiveness, sexual behavior, aggressiveness, and activity level of offspring.

45. Various Classes of EDCs Flame Retardants Fungicides Herbicides Insecticides Metals Pharmaceuticals Phenols Plasticizers Polyaromatic Hydrocarbons Soy Products Surfactants Polybrominated diphenyl ether Vinclozolin Atrazine Methoxychlor Tributyltin Ethynyl Estradiol Bisphenol A Phthalates PCBs, dioxins Genistein Alkylphenol Ethoxylates

46. PBDEs（多溴二苯基醚） • Polybrominated diphenyl ethers (PBDEs) are a class of recalcitrant and bioaccumulative halogenated compounds that have emerged as a major environmental pollutant. PBDEs are used as a flame-retardant and are found in consumer goods such as electrical equipment, construction materials, coatings, textiles and polyurethane foam (furniture padding).

47. Bioavailability of PBDEs • Found in animals • Increase in fish • Increase in whales • Sewage sludge • PCBs Found in Lake Washington Fish (PBDEs next?) • Found in human (breast milk)

48. PBDEs Breast Milk - Sweden (Norén and Mieronyté, 1998)

49. Health Effects of PBDEs • Similar to PCBs (Polychlorinated biphenyls) • Persistent Bioaccumulative Toxicant • No human data • Animals studies indicate • Changes in thyroid hormone levels • Neurobehavioral toxicity • Development effects- alters Behavior • Impairs memory and learning • Delays sexual development