Environmental Science PowerPoint Lecture

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Environmental Science PowerPoint Lecture
Principles of Environmental Science - Inquiry and
Applications, 2nd Edition by William and Mary Ann
Cunningham
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(No Transcript)
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Chapter 8 - 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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Objectives of Chapter 8

• Define health and disease in terms of major
  environmental factors that affect humans
• Identify some major infectious organisms and
  hazardous agents that cause environmental
  diseases
• Distinguish between toxic and hazardous
  chemicals, between chronic and acute exposure and
  responses
• Compare toxicity of natural and synthetic
  compounds and how these are determined
• Evaluate major environmental risks and how
  determine susceptibility

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Rachel Carson - A Voice for Nature

• In 1962, Silent Spring alerted the public to the
  dangers of indiscriminate pesticide use.
• Carson called for selective, ecologically sound
  use of pesticides.
• All 12 of the most toxic agents in her book were
  banned or severely restricted.

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Part 1 Types of Environmental Health Hazards
In some parts of Eastern Europe and the former
USSR, up to 90 of all children suffer from air
pollution related respiratory diseases.
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What is Health?

• The World Health Organization defines health
  state of complete physical, mental, social
  well-being not just absence of disease.
• Disease - a deleterious change in the bodys
  condition in response to an environmental factor
• Morbidity - illness
• Mortality - death

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Iron-deficiency anemia Vitamin deficiencies Minera
l deficiencies Toxicities Poor resistance to
disease
Down syndrome Hemophilia Sickle-cell anemia
Adult bone loss Cancer Infectious diseases
Diabetes Hyper-tension Heart disease
Nutrition-unrelated (genetic)
Nutrition-related
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1997 data
Ex Tuberculosis
Deforestation causes insect vectors to move to
cities
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Morbidity and Quality of Life in Poor Households
Problems people live in crowded conditions new
global mega cities - poor at managing human
generated wastes etc
Death rates not total picture but quality of life
severely diminished important
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Elephantiasis caused by parasitic worm
At any given time, about 2 billion people (1/3
global population) suffer from worms, protozoans,
other internal parasites
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Recent outbreaks of lethal infectious diseases
At least 30 new infectious diseases appeared in
past two decades while many well-known reappeared
in more virulent, drug-resistant forms.
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Factors Contributing to the Appearance and Spread
of Contagious Diseases

• High population densities
• Settlers pushing into remote areas
• Human-caused environmental change (use of
  fertilizers, pesticides etc)
• 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 antibiotics, pesticides -
  perfect recipe for natural selection
• Protozoans cause malaria now resistant to most
  antibiotics, mosquitoes developed resistance
  to many insecticides
• Drug resistance TB, Staph A, flesh-eating
  bacteria

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Hazardous and Toxic Chemicals

• Allergens activates immune systems
  (formaldehyde, sick building syndrome)
• Immune system depressants pollutants suppress
  immune system (linked to pesticides seals,
  dolphins)
• Neurotoxins metabolic poisons attack nerve
  cells (chloroform, ether, lead, DDT)
• Mutagens chemicals, radiation damage, alter DNA
  (birth defects, tumors)
• Teratogens chemicals cause abnormalities during
  embryonic growth, development (thalidomide,
  alcohol)
• Carcinogens- cancer (uncontrolled cell growth)

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Gas, paint
Gold mining
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Lung cancer
Breast cancer
Mortality rate most major cancers stabilized or
falling in recent years. One exception is lung
cancer (90 blamed on increased smoking esp women)
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Importance of Diet

• At least half of all Americans considered
  overweight
• Strong correlation between cardiovascular disease
  and amount of salt and animal fat in diet
• Fruits, vegetables, whole grains, complex
  carbohydrates, dietary fiber have beneficial
  health effects (anti-cancerous)
• Eating too much food negative effects on health.

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Part 2 Toxins Movement, Distribution, Fate
Movement, fate of chemicals in environment
(processes that modify, remove or sequester
compounds)
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Part 2 Toxins Movement, Distribution, Fate
Routes by which chemicals enter body determine
toxicity
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Bioaccumulation and Biomagnification

• Bioaccumulation selective absorption / storage
  of molecules dilute toxins in the environment
  can reach dangerous levels inside cells and
  tissue
• Biomagnification - the effects of toxins are
  magnified through food webs

Top carnivores game fish, fish-eating birds,
birds, humans accumulate toxic levels adverse
health effects
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DDT - Powerful Insecticide, Harmless to Humans
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Pelegrine falcons disappeared from the eastern US
in 1960s due to excess pesticide use
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Not just in olden days happening today
A Farm Worker Sprays Disinfectant onto the Shoes
of Two Girls on a Quarantined Farm During an
Outbreak of Avian Flu in Middleton South Africa,
SOUTH AFRICA August 10, 2004 , Story by HB/MD,
Photo by HOWARD BURDITT, REUTERS NEWS PICTURE
SERVICE
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Children more susceptible than adults accumulate
environmental contaminants in higher
concentrations in body, eat more food with higher
contaminant loads (apple products
etc) Persistence Chemical Interactions -
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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
  belief in 1800s, arsenic (Napoleon)
• 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
Animal Testing

• Used to be most commonly used and widely accepted
  but now less common
• 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

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A Typical Dose/Response Curve toxin sensitivity
among members of a population
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LD50 - the dose of a toxin that is lethal to
half the test population
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mouse
rat
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
  sublethal 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
  (ACCEPT HIGHER RISK WHEN ENJOY SOMETHING)

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WHEN MORE CONTROL RISK LEFT OR RIGHT OF FIGURE?
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Even though actual number of deaths from
automobile accidents, smoking or alcohol are
thousand times greater than from pesticides,
nuclear energy, or genetic engineering, the
latter preoccupy us far more than the former.
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Part 6 Establishing Public Policy
In setting standards for environmental toxins,
we need to consider

• 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

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Regulatory Decisions EPA framework
Other Factors Not Specific to the Problem
The Science Specific to the Problem
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• How determine what risk is from human compared to
  naturally occurring physical/ chemical changes in
  the environment?
• How much of ranking is based on our values do
  they reflect science?

Lots uncertainty