ENVIRONMENTAL CHEMISTRY A Global Concern Chem-440 1/19/2016Dr Seemal Jelani1

CHAPTER 4 ENVIRONMENTAL HEALTH AND TOXICOLOGY 1/19/2016Dr Seemal Jelani2

Health Hazards Infectious Diseases Respiratory diseases –pneumonia –tuberculosis –influenza –whooping cough 1/19/2016Dr Seemal Jelani3

Malaria Parasitic Nematodes Schistosomiasis Onchocerciasis (river blindness) Trachoma STD’s 1/19/2016Dr Seemal Jelani4

Toxic Chemicals Irritants Respiratory fibrotic agents Asphyxiants Allergens Neurotoxins Mutagens Teratogens Carcinogens 1/19/2016Dr Seemal Jelani5

Natural and Synthetic Toxin Physical Agents –radiation Trauma –stress Diet 1/19/2016Dr Seemal Jelani6

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) 1/19/2016Dr Seemal Jelani7

Chemical Hazards and Toxicology Dose and response –LD5O factor Acute effect Chronic effect Types –toxic substances –hazardous –carcinogens –mutagens –teratogens 1/19/2016Dr Seemal Jelani8

What is a LD 50 LD stands for "Lethal Dose". LD 50 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 LD 50 is one way to measure the short- term poisoning potential (acute toxicity) of a material. 1/19/2016Dr Seemal Jelani9

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. 1/19/2016Dr Seemal Jelani10

The LD 50 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. 1/19/2016Dr Seemal Jelani11

Why study LD 50 '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 1/19/2016Dr Seemal Jelani12

. 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. 1/19/2016Dr Seemal Jelani13

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 LD 50 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". 1/19/2016Dr Seemal Jelani14

What are some other toxicity dose terms in common usage? LD 01 Lethal dose for 1% of the animal test population LD 100 Lethal dose for 100% of the animal test population LDLO The lowest dose causing lethality TDLO The lowest dose causing a toxic effect 1/19/2016Dr Seemal Jelani15

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 1/19/2016Dr Seemal Jelani16

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 1/19/2016Dr Seemal Jelani17

Environmental toxicology is highly interdisciplinary field 1/19/2016Dr Seemal Jelani18

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 1/19/2016Dr Seemal Jelani19

Movement, Distribution and Fate of Toxins Solubility Bioaccumulation Biomagnification Persistence Chemical Interactions 1/19/2016Dr Seemal Jelani20

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. Solubility – 1/19/2016Dr Seemal Jelani21

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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. 1/19/2016Dr Seemal Jelani23

Exposure Routes 1/19/2016Dr Seemal Jelani24

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. 1/19/2016Dr Seemal Jelani25

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. 1/19/2016Dr Seemal Jelani26

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) 1/19/2016Dr Seemal Jelani27

Persistence Persistent Organic Pollutants (POP’s) –Polybrominated diphenyl ethers (PDBE) –Perfluorooctane sulfonate (PFOS) and Perfluorooctanic acid (PFOA). –Phthalates –Bisphenol A (BPA) –Atrazine 1/19/2016Dr Seemal Jelani28

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. 1/19/2016Dr Seemal Jelani29

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 1/19/2016Dr Seemal Jelani30

Minimizing Toxic Effects Metabolic Degradation Excretion Repair Mechanisms 1/19/2016Dr Seemal Jelani31

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. 1/19/2016Dr Seemal Jelani32

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. 1/19/2016Dr Seemal Jelani33

Measuring Toxicity Animal Testing Toxicity Ratings Acute vs. Chronic Doses and Effects Detection Limits 1/19/2016Dr Seemal Jelani34

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. 1/19/2016Dr Seemal Jelani35

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. 1/19/2016Dr Seemal Jelani36

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. 1/19/2016Dr Seemal Jelani37

References users.ipfw.edu/.../cha... Indiana University – Purdue University Fort Wayne 1/19/2016Dr Seemal Jelani38