Prevalence of toxic agents in the environment Persistent, organic pollutants (POP’s)

1. Environmental Toxicology • Prevalence of toxic agents in the environment • Persistent, organic pollutants (POP’s) • Bioaccumulation • Biomagnification • Epidemiology, animal testing, and dose-response analysis • Factors affecting toxicity

2. Toxicology • The study of poisonous substances and their effects on humans and other organisms • Toxicologists assess and compare toxic agents, or toxicants, for their toxicity, the degree of harm a substance can inflict. • Environmental toxicology focuses on effects of chemical poisons released into the environment.

3. Synthetic chemicals are everywhere ! • Many thousands have been produced and released. • Some persist for long time periods or travel great distances. • Of the 100,000 synthetic chemicals on the market today, very few have been thoroughly tested for harmful effects.

4. Environmental Toxicology • Studies toxicants that come from or are discharged into the environment, and: Health effects on humans Effects on animals Effects on ecosystems • Animals are studied: For their own welfare To warn of possible effects on humans

5. Synthetic Chemicals People are largely unaware of the health risks of many toxicants.

6. Types of Toxicants • Carcinogens: cause cancer • Mutagens: cause mutations in DNA • Teratogens: cause birth defects • Allergens: cause unnecessary immune response • Neurotoxins: damage nervous system • Endocrine disruptors: interfere with hormones

7. Industry Overview

8. Toxicants Concentrate in Water • Surface water and groundwater can accumulate toxicants. • Runoff from large areas of land drains into water bodies, becoming concentrated. • Toxicants in groundwater or surface water reservoirs used for drinking water pose potential risks to human health.

9. Airborne Toxicants • Volatile chemicals can travel long distances on atmospheric currents. • PCBs are carried thousands of miles from developed nations of the temperate zone up to the Arctic, where they are found in tissues of polar bears and seals.

10. Persistence • Some chemicals are more stable than others, • persisting for longer in the environment. DDT and PCBs are persistent. Bt toxin in GM crops is not persistent. • Temperature, moisture, sun exposure, etc., affect rate of degradation. • Most toxicants degrade into simpler breakdown products. Some of these are also toxic. • (DDT breaks down to DDE, also toxic.)

11. Poisons move up the food chain • At each trophic level, chemical concentration increases: biomagnification. • DDT concentrations increase from plankton to fish to fish-eating birds. Figure 10.9

12. Poisons Accumulate in Tissues • The body may excrete, degrade, or store toxicants. • Fat-soluble ones are stored. • DDT is persistent and fat soluble, • … so builds up in tissues: bioaccumulation. • Bioaccumulated chemicals may be passed on to animals that eat the organism—up the food chain…

13. Effect of POP’s on living organisms In birds: Impacts upon ability to conceive and raise young. Affects egg development and mating behaviour in bird species In mammals: 1. Leads to malformations in reproductive organs, fewer young or infertility 2. Hormone disrupters mimic hormones because they are similar enough in structure to fit into the body’s biochemical receptors 3. Can affect the immune system, especially in the young 4. Carcinogenic

14. Specifics on other contaminants: DDT Pesticide: toxic to more organisms than intended to kill Birds of prey began to die in large numbers in affected areas Evidence of long-range transport: Detected in the blubber of ringed seals in 1970 Banned for decades in circumpolar countries PCB’s Used in transformer fluids Carcinogenic, mutagenic

15. Dioxins and furans Used in high temperature processes (stable) and herbicides Disturbed reproduction, suppressed immune function and highly carcinogenic Hexachlorobenzene (HCB) Used in pesticides and produced in waste incineration and metallurgical processes Affects reproductive and immune function

16. The United Nations: “Dirty Dozen” Persistent Organic Pollutants (POPs)

17. General Background on PCBs • Polychlorinated biphenyls (PCBs) are a class of 209 organic compounds. Each one is often called a congener. • Only ~140 congeners of the 209 are found in the environment. • Sold in the U.S. as mixtures called Aroclors (Monsanto) from 1929 to 1978. In other countries, they were sold under the tradenames: Clophens (Germany), Phenoclors (Italy), etc. • Used as dielectric & heat transfer fluids, in lubricating and cutting oils, pesticides, paints, sealants, and plastics • Incredibly stable compounds.

19. Synthesis of PCBs Degree of chlorination depended on the length of the reaction. The longer the reaction, the more chlorines were added to the biphenyl. Key point is that this reaction did not create one congener but complex mixtures of PCBs.

20. PCBs nomenclature • In the US, mixtures of PCBs were sold as Aroclors by Monsanto. The main products were Aroclor 1242, 1254, and 1260. • The “12” comes for the number of carbons on the biphenyl. The last two numbers indicate the mass percentage of Cl in the PCB mixtures. Hence, Aroclor 1260 is 60% chlorine by mass and it contains more chlorinated congeners than Aroclor 1242, etc. • Individual congeners are numbered after a simple system, which is also used for other contaminants (dioxins, PBDEs, etc). General numbering system 2,2’,4,4’,5,5’-hexachlorobiphenyl (Shorthand CB-153; PCB-153, or 153)

21. Key Point on PCBs and many other halogenated organic hydrocarbons • While PCBs are one distinct group, all 209 congeners have wide ranging physical and chemical properties, which in turn can affect environmental fate and biological activity. Very subtle differences in the placement of a chlorine on the biphenyl structure can be dramatic in effects. • It is essential that we think about these compounds on a congener-specific basis!!!

22. Structural placement of chlorines affects biological activity 3,3’4,4’,5,5’-hexachlorobiphenyl CB-169; non-ortho PCB Non-ortho allows two rings to rotate. Generally more bioactive. 2,2’,3,3’,6,6’-hexachlorobiphenyl CB-136; all ortho positions filled. Structurally rigid. Generally less bioactive.

23. Background on DDT • First of the modern chemical pesticides. • Originally synthesized in late 1800s. • Paul Muller observed biological activities in late 1930s and won the Nobel Prize in 1948 for this effort. • Banned since about 1970 in many countries, including US and Canada because of its effect on wildlife, particularly fish-eating birds. • May still be used today in countries where malaria is endemic. Usage in 3rd world countries is a hot topic. Very cheap and surprisingly effective. • Interesting geochemistry as it transforms to DDE, which is more bioactive and more persistent.

24. Synthesis of DDT C l C l H H S O 2 4 C l C C l C l C C H O C l C H C l 3 3 O H C l C C l c h l o r o b e n z e n e C l t r i c h l o r o a c e t a l d e h y d e p,p-DDT (70%) The other main product of this reaction was o,p-DDT (~25%).

25. Reactions involving DDT Data is often presented as SDDT metabolites (sometimes called DDX).

26. Chlorinated dioxins and furans • Very different background than PCBs or DDT. • They were never intentionally produced but rather were by-products of industrial synthesis (often found in trace quantities in Aroclors, Agent Orange, pentachlorophenol). • Also formed during combustion of organic matter in the presence of chloride, etc. • Natural sources possible, too. • 75 possible structures for chlorinated dioxins. • 135 possible structures for chlorinated furans. dibenzofuran dibenzo-p-dioxin

27. Inadvertent industrial source(Agent Orange) 2,4-D (50%) 2,4,5-T (50%) trace impurity 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD)

28. Background on PBDEs • Polybrominated diphenyl ethers (PBDEs) are used as flame retardants. • They are added to materials to decrease the likelihood and intensity of fire in a wide variety of products, including vehicles, furniture, textiles, carpets, building materials, electronic circuit boards and cases... just about anywhere that plastics are used. • Synthesized mainly as mixtures (similar to PCBs). • Production started in the 1960s. • Gained a lot of attention lately. • Currently unregulated on a federal level in the US. 2,3,4’-tribromodiphenylether (PBDE-22)

29. Meironyte et al 1999

30. O C H 3 O B r B r B r B r Unknown source B r O R B r O H O C H O C H 3 3 O B r O B r B r O B r B r B r B r B r B r B r R = H R = C H Isolated from marine sponges Andersen et al. (1974) 3 O B r B r n m m + n = 1 t o 1 0 Industrial flame retardant

31. Three phases in the environment Water Air Organic matter (tissue, sorbed to sediment or dissolved in water)

32. Organic matter • Animal tissue. • Sediments or particles have a film of organic matter. • Dissolved organic matter

33. Chemical/Physical Properties That Control Fate • Water solubility (S)* • Vapor pressure (VP) • Octanol-water partition coefficient (Kow)* • Organic matter-water partition coefficient (Kom) • Henry’s Law Constant (H)

34. Water solubility (S) • Water solubility (S): the maximum concentration of a chemical in water at a specific temperature and pressure, usually 25°C and 1 atm. Possibly the most important property concerning the fate of organic contaminants. Units are in mole per liter. -The larger the value, the more likely a compound will stay in water and not go into air, sediment, and or tissue.

36. Vapor Pressure (VP) • Vapor pressure (VP): the pressure of a vapor exerted from a liquid or solid compound. Units are in atmospheres. This term indicates how “volatile” a compound is and is important in understanding whether it will evaporate. Example: moth ballsnaphthalene

38. Octanol-water partition coefficient (Kow) • Octanol-water partition coefficient (Kow): the ratio of the concentration of a water to the concentration in octanol. Units are (mole per liter of water) per (moles per liter of water). This term is inversely proportion to the water solubility and indicates how “hydrophobic” a compound is. Very important for determining whether a compound will bioaccumulate. • Example, salad dressing (oil and vinegar)

39. Kow Octanol Octanol CONC oct Kow= CONCwater Water Benzene’s Kow is 135 Log Kow is 2.13 10^2.13=135

41. Kom • Octanol-water partition coefficient (Kom): the ratio of the concentration of a compound in sediment organic matter to the concentration of water surrounding it. Units are (mole per kg of organic carbon) per (moles per liter of water). This term is very similar to Kow. Used to determine the extent of sorption to sediment or dissolved organic matter.

42. Henry’s Law constant (H) • Henry’s Law constant (H): the ratio of the vapor pressure of a compound to its water solubility. Units atm L/mole • H=VP/water solubility (estimate) • It describes the willingness of a compound to go into the air from water or vice versa. • The larger the value, the more likely the compound will partition into air.

44. General trends • The larger the compound, -smaller water solubility -smaller vapor pressure -larger Kow -smaller Henry’s Law Constant

45. Where do these compounds go? Air 2-chlorobiphenyl Water 2,2’,6,6’-tetrachlorobiphenyl Sediment Fish 795 L of water; 200 L of air 15 kg of sediment; 0.5 kg of fish decachlorobiphenyl

46. Orca Biology • Average Birth Weight: 395 lbs • Average Adult Weight: 2.6 – 9 tons • Males are larger than females • Lifespan: • Males ~40 years • Females >60 years • Sexually mature ~13 years

47. Orca Natural History • Found in all the world’s oceans • Travel in pods from 3 to >150 members • Feed on fish, squid and marine mammals

48. Transient vs. Resident Orcas

49. Resident Orcas • Resident orcas live in coastal areas feeding mostly on fish • Live in extended familial units called pods • Pods are matriarchal • Northeast Pacific resident orcas are found from Puget Sound to Alaska • Puget Sound orcas are Southern Resident Orcas

50. Southern Resident Orcas • Consists of three pods: J, K and L • Summer in the area around the San Juan Islands feeding on salmon runs • Winter on outer coast, but do not know where