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ESC110 Chapter Eight: Environmental Health and Toxicology

Principles of EnvironmentalScience - Inquiry and Applications,

2nd Editionby William and Mary Ann Cunningham

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Chapter Eight Readings

Required ReadingsCunningham & Cunningham, Chapter Eight: Environmental Health and Toxicology

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Chapter Eight Objectives

At the end of this lesson, you should be able to

• define health an disease in terms of some major environmental factors that affect humans

• Understand some of the risks of bioterrorism and emergent diseases

• distinguish between toxic and hazardous chemicals, and between chronic and acute exposures and responses

• compare the relative toxicity of some natural and synthetic compounds, and report on how such ratings are determined and what they mean

• evaluate the major environmental risks we face and how risk assessment and risk acceptability are determined.

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Chapter Eight Key Terms

McGraw-Hill Course Glossary

acute effects

allergens

antigens

bioaccumulations

biomagnification

cancer

carcinogens

chronic effects

Disability-Adjusted

Life Year (DALY) disease

emergent disease endocrine hormone disrupters fetal alcohol syndrome

hazardous

health

LD50

morbidity

mutagens

neurotoxins

• prospective study

• retrospective study

• risk

• synergism

• toxins

• teratogens

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Chapter Eight Topics

• Types of Environmental Health Hazards• Movement, Distribution, and Fate of Toxins• Mechanisms for Minimizing Toxic Effects• Measuring Toxicity• Risk Assessment and Acceptance• Establishing Public Policy

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Part 1: Types of Environmental Health Hazards

In some parts of Eastern Europe and the former USSR, upto 90 % of all children suffer from environmentally linked diseases.

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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

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

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Recent outbreaks of lethal infectious diseases

SARS2003

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Factors Contributing to the Spread of Contagious Diseases

• High population densities

• Settlers pushing into remote areas

• Human-caused environmental change

• Speed and frequency of modern travel

• Contact with water or food contaminated with human waste

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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

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Fig. 8.6

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Hazardous and Toxic Chemicals• Allergens -

formaldehyde

• Immune system depressants - PCBs?

• Neurotoxins - lead, DDT

• Mutagens

• Teratogens - alcohol

• Carcinogens

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Mortality rate for most major cancers has been stable or falling in recent years. One exception is lung cancer (rise blamed on increased smoking).

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Importance of Diet• At least half of all Americans are considered

overweight.• Strong correlation between cardiovascular

disease and the amount of salt and animal fat in one's diet

• Fruits, vegetables, whole grains, complex carbohydrates, and dietary fiber have beneficial health effects.

• Eating too much food has negative effects on health.

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Part 2: Movement, Distribution, and Fate of Toxins

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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

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"DDT - Powerful Insecticide, Harmless to Humans"

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Part 3: 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

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Part 4: 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

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A Typical Dose/Response Curve

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LD50 - the doseof a toxin that is lethal to half the test population

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It is useful to group materials according to their relative toxicity.

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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

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Part 5: 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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Part 6: 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:

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Regulatory Decisions

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