1. Environmental Toxicology
Prevalence of toxic agents in the environment
Bioaccumulation
Biomagnification

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)
Compound
Year of
entry
S world production (tons)
Usage
Aldrin
1949
240,000
insecticide
Chlordane
1945
70,000
DDT
1942
3 million
Dieldrin
1948
Endrin
1951
4,000
rodenticide/insecticide
Heptachlor
~1,000
Hexachlorobenzene
1 to 2 million
fungicide
Mirex
1959
No data
Toxaphene
1.3 million
PCBs
1929
industrial chemical
Chlorinated dioxins ?
never produced purposely
Chlorinated furans

17. 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.

18. Meironyte et al 1999

19. 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

20. 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

21. Transient vs. Resident Orcas
Transients
Residents
Habitat
Offshore
Nearshore
Food
Marine Mammals
Fish
Pod Size
3-5
>20
Vocalization
Quiet
Very Vocal

22. 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

23. 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

24. Dead Orcas (Video Link donkeycritter.googlepages.com)
                                        

25. State of Southern Resident Orcas
Almost 20% orcas died between 1995 and 2000.
Reproductive females have not produced young in ten years.
Only four adult males in the entire community of 80 whales.

26. Puget Sound Orcas and PCBs
Highest levels of PCBs in blubber of any marine mammal in the world
Average almost 150 ppm
<10 ppm PCB is known to cause immune problems in seals
Dead female transient orca on Dungeness Spit in May 2002
1000 ppm PCB
12ppm- EPA’s standard for marine sediments