1. Environmental Toxicology
Environmental Health

3. What is Toxic?
A characteristic of certain chemicals that are extremely stable and may take many years to be broken down into simpler forms by natural processes
Synthetic chemicals (those not found in nature)
Ex: DDT

4. Then what is Poison??

5. Important Concepts
Bio-accumulation: The buildup of a persistent toxic substance in an organism’s body, often in fatty tissues
Synthetic chemical do not metabolize well
They remain in the body for extended periods of time
Bio-magnification: The increased concentration of toxic chemicals in the tissues of organisms that are at higher levels in food webs

6. Continue
Exposure:
Any condition which provides an opportunity for an external environmental agent to enter the body
Agent:
Any chemical (cyanide), biological (venom), or physical material (radiation) capable of eliciting a biological response
Difference between agent and vector??

7. Exposure Assessment Exposure = How much x How often x How long
Exposure = Intensity x Frequency x Duration

8. Patterns of Exposure

9. What is Xenobiotic?
Environmental xenobiotic are xenobiotic compounds with a biological activity that are found as pollutants in the natural environment
Examples: Antibiotics, PCBs (Poly Chlorinated Biphenyls)

10. Endocrine Disruptors
A chemical that mimics or interferes with the actions of the endocrine system in humans and wildlife
i.e. It effects the ability of the hormones in the organisms to function properly
Examples include:
PCBs, Dioxins
Heavy metals – lead and mercury
DDT

11. Toxicology
Toxicology is the study of the effect of toxicants on the human body
Toxicant- chemical with adverse human health effects

12. Continue Acute toxicity
Adverse effects occur within a short period after exposure to toxin
Chronic toxicity
Adverse effects occur some time after exposure, or after prolonged exposure to toxin
Symptoms often mimic other diseases- hard to assess source

13. How to measure Toxicity?
Toxicity measured by dose and response
Dose: amount that enters that body of an exposed organism
Response: the amount of damage caused by a specific dose
LD50
A common dose estimate for acute toxicity
Smaller the LD50, the more lethal the chemical
Determined for all new synthetic chemicals

14. LD50
Lethal dose (LD50) is the amount of an ingested substance that kills 50 percent of a test sample. It is expressed in mg/kg, or milligrams of substance per kilogram of body weight
Do you know about ED?

16. Dose-Response Curve Dose-Response Curve
Illustrates the effect of different doses on a population
Threshold Level
Maximum dose with no measurable effects

17. Dose-Response Curve

18. Models
Stochastic Model: Risk (probability) of response is a function of dose
Assumes no threshold
No dose is safe
Any dose increases the risk
Deterministic Model: A safe dose and a threshold exist

19. Does-Response Curve

20. Toxicology-Paradigms (Assignment)
Dilution Paradigm: "the solution to pollution is dilution"
Boomerang Paradigm: "what you throw away can come back and hurt you"

21. Continue Toxicologists should:
Identify the mode / site of action of a xenobiotic
FATE and TRANSPORT / interaction of a xenobiotic with the biosphere (including specific organisms) after it is released / pollution occurs

22. Identify the effect the xenoboitic has on an ecosystems
Introduction of
xenobiotic
Ecosystem
effect
site of
action
biotransformation
physiology
behavior
community
parameters
biochemistry
population
dynamics

23. Toxicology Paradigm

24. Continue

25. Steps in reducing Lung Cancer Mortality

26. Thank You!!