1 Chapter 8: Environmental Health and Toxicology Hong Kong residents concerned about SARS Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Chapter Eight Topics Environmental Health Toxicology Movement, Distribution, and Fate of Toxins Mechanisms for Minimizing Toxic Effects Measuring Toxicity Risk Assessment and Acceptance Establishing Public Policy

3 Part 1: Environmental Health In some parts of Eastern Europe and the former USSR, up to 90 % of all children suffer from environmentally linked diseases.

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5 At any given time, about 2 billion people suffer from worms, protozoans, and other internal parasites.

6 West Nile Virus 2001

7 What is Health? The World Health Organization (WHO) defines health as a state of complete physical, mental, and social well-being. Disease - a deleterious change in the body's condition in response to an environmental factor Morbidity - illness Mortality - death

8 West Nile Virus 2002

9 Factors Contributing to the Spread of Contagious Diseases High population densities Settlers pushing into remote areas Human-caused environmental change (change of habitat for organisms) Speed and frequency of modern travel Contact with water or food contaminated with human waste Climate change Increased consumption of wild species

10 Part 2: Toxicology Toxicology: The study of toxins (poisons) and their effects on living systems. What does toxic mean? Environmental Wisdom…visit What does Toxic mean

11 Antibiotic and Pesticide Resistance Indiscriminate use of antibiotics and pesticides - perfect recipe for natural selection Protozoan that causes malaria now resistant to most antibiotics, and mosquitoes have developed resistance to many insecticides Drug resistance: TB, Staph A, flesh- eating bacteria

12 Fig. 8.6

13 Hazardous and Toxic Chemicals Allergens - formaldehyde Immune system depressants Neurotoxins - lead, DDT Mutagens Teratogens - alcohol Carcinogens

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15 Part 3: Movement, Distribution, and Fate of Toxins

16 Clorox Kills Flu Virus Vapors may irritate, harmful if swallowed, do not get in the eye or clothes, avoid prolonged breathing of vapors, use in highly ventilated areas, not recommended for use by people that have heart problems, or breathing problems.

17 Factors to consider Solubility and mobility (organic Vs inorganic) Exposure and susceptibility Bioaccumulation and biomagnification Persistence Chemical interactions (antagonistic Vs synergistic)

18 Bioaccumulation and Biomagnification Bioaccumulation - dilute toxins in the environment can reach dangerous levels inside cells and tissue Biomagnification - the effects of toxins are magnified through food webs

19 " DDT - Powerful Insecticide, Harmless to Humans"

20 Part 4: Minimizing Toxic Effects Every material can be poisonous under some conditions. Taken in small doses, most toxins can be broken down or excreted before they do much harm. Liver - primary site of detoxification Tissues and organs - high cellular reproduction rates replace injured cells - down side: tumors, cancers possible

21 Part 5: Measuring Toxicity Most commonly used and widely accepted Expensive - hundreds of thousands of dollars to test one toxin at low doses Time consuming Often very inhumane Difficult to compare toxicity of unlike chemicals or different species of organisms Animal Testing

22 A Typical Dose/Response Curve

23 LD50 - the dose of a toxin that is lethal to half the test population

24 Acute Versus Chronic Doses and Effects Acute effect - immediate health effect caused by a single exposure to a toxin (can be reversible) Chronic effect - long lasting or permanent health effect caused by (1) a single exposure to a very toxic substance or (2) continuous or repeated sub lethal exposure to a toxin

25 Fig. 8.15

26 Part 6: Risk Assessment and Acceptance Risk - the probability of harm times the probability of exposure A number of factors influence how we perceive relative risks associated with different situations. Accepting risks - we go to great lengths to avoid some dangers, while gladly accepting others

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28 Part 7: Establishing Public Policy Combined effects of exposure to many different sources of damage Different sensitivities of members of the population Effects of chronic as well as acute exposures In setting standards for environmental toxins, we need to consider:

29 Regulatory Decisions