ENVIRONMENTAL CHEMISTRY A Global Concern

1. ENVIRONMENTAL CHEMISTRY A Global Concern Chem-440 Dr Seemal Jelani

2. CHAPTER 4ENVIRONMENTAL HEALTH AND TOXICOLOGY Dr Seemal Jelani

3. Health Hazards • Infectious Diseases • Respiratory diseases • pneumonia • tuberculosis • influenza • whooping cough Dr Seemal Jelani

4. Malaria • Parasitic Nematodes • Schistosomiasis • Onchocerciasis (river blindness) • Trachoma • STD’s Dr Seemal Jelani

5. Toxic Chemicals • Irritants • Respiratory fibrotic agents • Asphyxiants • Allergens • Neurotoxins • Mutagens • Teratogens • Carcinogens Dr Seemal Jelani

6. Natural and Synthetic Toxin • Physical Agents • radiation • Trauma • stress • Diet Dr Seemal Jelani

7. Toxic Chemicals • Hazardous chemicals – dangerous (eg, flammables, explosives, irritants, acids, etc) • Toxins – poisonous, kills cells • Allergens – activate the immune system • Mutagens – chemicals or radiation that damage/alter genetic material (DNA) • Teratogens - chemicals or other factors that cause abnormalities during embryonic growth & development • Carcinogens – substances that cause cancer (out of control cell growth) Dr Seemal Jelani

8. Chemical Hazards and Toxicology • Dose and response • LD5O factor • Acute effect • Chronic effect • Types • toxic substances • hazardous • carcinogens • mutagens • teratogens Dr Seemal Jelani

9. What is a LD50 • LD stands for "Lethal Dose". • LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals. • The LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material. Dr Seemal Jelani

10. Toxicologists can use many kinds of animals but most often testing is done with rats and mice. • It is usually expressed as the amount of chemical administered (e.g., milligrams) per 100 grams (for smaller animals) or per kilogram (for bigger test subjects) of the body weight of the test animal. Dr Seemal Jelani

11. The LD50 can be found for any route of entry or administration but dermal (applied to the skin) and oral (given by mouth) administration methods are the most common. Dr Seemal Jelani

12. Why study LD50's? • Chemicals can have a wide range of effects on our health. • Since different chemicals cause different toxic effects, comparing the toxicity of one with another is hard. • We could measure the amount of a chemical that causes kidney damage, for example, but not all chemicals will damage the kidney Dr Seemal Jelani

13. . We could say that nerve damage is observed when 10 grams of chemical A is administered, and kidney damage is observed when 10 grams of chemical B is administered. • However, this information does not tell us if A or B is more toxic because we do not know which damage is more critical or harmful. Dr Seemal Jelani

14. Therefore, to compare the toxic potency or intensity of different chemicals, researchers must measure the same effect. • One way is to carry out lethality testing (the LD50 tests) by measuring how much of a chemical is required to cause death. • This type of test is also referred to as a "quantal" test because it is measures an effect that "occurs" or "does not occur". Dr Seemal Jelani

15. What are some other toxicity dose terms in common usage? • LD01 Lethal dose for 1% of the animal test population • LD100 Lethal dose for 100% of the animal test population • LDLO The lowest dose causing lethality • TDLO The lowest dose causing a toxic effect Dr Seemal Jelani

16. Acute and Chronic • The difference between acute and chronic when used for diseases is that acute means extremely severe pain, brief and dangerous disease whereas chronic refers to a medical condition that lasts over a long period Dr Seemal Jelani

17. What is Environmental toxicology ? ‘Ecotoxicology’ ‘Study of impacts of pollutants on the structure and function of ecosystems’ Manmade poisonous chemicals and their effect on the environment Dr Seemal Jelani

18. Environmental toxicology is highly interdisciplinary field Dr Seemal Jelani

19. Xenobiotic • A chemical that is foreign to the biosphere i.e. is not produced by a natural biological or abiotic source • Also called anthropogenic, man-made, synthetic, pollutant, contaminant, recalcitrant, persistent, and toxicant Dr Seemal Jelani

20. Movement, Distribution and Fate of Toxins • Solubility • Bioaccumulation • Biomagnification • Persistence • Chemical Interactions Dr Seemal Jelani

21. Solubility – One of most important characteristics in determining the movement of a toxin. • Chemicals are divided into two major groups: • Those that dissolve more readily in water. • Those that dissolve more readily in oil. • Water soluble compounds move rapidly through the environment, and have ready access to most human cells. Dr Seemal Jelani

22. Dr Seemal Jelani

23. Exposure and Susceptibility • Airborne toxins generally cause more ill health than any other exposure. • Lining of lungs easily absorbs toxins. • Largest toxin exposure reported in industrial settings. • Condition of organism and timing of exposure also have strong influences on toxicity. Dr Seemal Jelani

24. Exposure Routes Dr Seemal Jelani

25. Bioaccumulation and Biomagnification • Cells have special mechanisms for Bioaccumulation - Selective absorption and storage. • Dilute toxins in the environment can build to dangerous levels inside cells and tissues. • Biomagnification - Toxic burden of a large number of organisms at a lower trophic level is accumulated and concentrated by a predator at a higher trophic level. Dr Seemal Jelani

26. Bioaccumulation and Biomagnification • Cells have special mechanisms for Bioaccumulation - Selective absorption and storage. • Dilute toxins in the environment can build to dangerous levels inside cells and tissues. • Biomagnification - Toxic burden of a large number of organisms at a lower trophic level is accumulated and concentrated by a predator at a higher trophic level. Dr Seemal Jelani

27. Persistence • Some chemical compounds are very unstable and degrade rapidly under most conditions, thus their concentrations decline quickly after release. • Others are more persistent. • Stability can cause problems as toxic effects may be stored for long period of time and spread to unintended victims. • (DDT) Dr Seemal Jelani

28. Persistence • Persistent Organic Pollutants (POP’s) • Polybrominated diphenyl ethers (PDBE) • Perfluorooctane sulfonate (PFOS) and Perfluorooctanic acid (PFOA). • Phthalates • Bisphenol A (BPA) • Atrazine Dr Seemal Jelani

29. Chemical Interactions • Antagonistic Reaction - One material interferes with the effects, or stimulates the breakdown, of other chemicals. • Additive Reaction - Effects of each chemical are added to one another. • Synergistic Reaction - One substance exacerbates the effect of the other. Dr Seemal Jelani

30. Environmental toxicology depends on • Lab work • Effects of toxicants on biochemistry and physiology • Field work • Field observations of reproduction and survival in polluted vs. non-polluted sites Dr Seemal Jelani

31. Minimizing Toxic Effects • Metabolic Degradation • Excretion • Repair Mechanisms Dr Seemal Jelani

32. Mechanisms for minimizing toxic effects • Every material can be poisonous under certain conditions. • Most chemicals have a safe threshold under which their effects are insignificant. • Metabolic Degradation • In mammals, the liver is the primary site of detoxification of both natural and introduced poisons. Dr Seemal Jelani

33. Excretion and Repair • Effects of waste products and environmental toxins reduced by eliminating via excretion. • Breathing • Kidneys • Urine • Tissues and organs often have mechanisms for damage repair. • Any irritating agent can be potentially carcinogenic. Dr Seemal Jelani

34. Measuring Toxicity • Animal Testing • Toxicity Ratings • Acute vs. Chronic Doses and Effects • Detection Limits Dr Seemal Jelani

35. Measuring toxicity • Animal Testing • Most commonly used and widely accepted toxicity test is to expose a population of laboratory animals to measured doses of specific toxins. • Sensitivity differences stance a problem. • Dose Response Curves • LD50 - Dose at which 50% of the test population is sensitive. Dr Seemal Jelani

36. Toxicity Ratings • Moderate toxin takes about (1) g/kg of body weight to produce a lethal dose. • Very toxic materials require about 10% of that amount. • Extremely toxic materials require 1% of that amount. • Supertoxic chemicals can be lethal in a dose of a few micrograms. Dr Seemal Jelani

37. Toxicity Ratings • Many carcinogens, mutagens, and teratogens are dangerous at levels far below their direct toxic effect because abnormal cell growth exerts a form of biological magnification. Dr Seemal Jelani

38. References • users.ipfw.edu/.../cha... • Indiana University – Purdue University Fort Wayne Dr Seemal Jelani