Environmental Hazards and Human Health

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Environmental Hazards and Human Health

• Chapter 18

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Essential Question 1

• What is risk, and what are the four major types
  of hazards people face?

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Risk

• The possibility of suffering harm from a hazard
  that can cause injury, disease, death, economic
  loss, or environmental damage.
• Probability mathematical likelihood harm will
  be suffered from a hazard

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Types of Hazards

• Biological Hazards
• Pathogens bacteria, viruses, parasites,
  protozoa, fungi
• Chemical Hazards
• Harmful chemicals in air, water, soil, food
• Physical Hazards
• Fire, earthquake, volcanic eruption, flood,
  tornado, hurricane, etc
• Cultural Hazards
• Poverty / Violence / Lifestyle choices smoking,
  diet, alcohol, drugs, unsafe sex, etc.

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Risk Assessment

• The scientific process of estimating how much
  harm a particular hazard can cause to human
  health or the environment.

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Risk Management

• Involves deciding whether or how to reduce a
  particular risk to a certain level and at what
  cost.

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Essential Question 6

• How can risks be estimated and recognized?

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Risk Analysis

• Risk Assessment
• Identify hazards evaluate their associated
  risks
• Comparative Risk Analysis
• Rank risks
• Risk Management
• Determine options and make decisions about
  reducing or eliminating risks
• Risk Communication
• Informing decision makers the public about risks

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Risk Management
Risk Assessment
Comparative risk analysis
Hazard identification
How does it compare with other risks?
What is the hazard?
Risk reduction
How much should it be reduced?
Probability of risk
How likely is the event?
Risk reduction strategy
How will the risk be reduced?
Consequences of risk
Financial commitment
What is the likely damage?
How much money should be spent?
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Estimating Risk from Technologies

• Estimating risks from using many technologies is
  difficult due to unpredictability of human
  behavior, chance, and sabotage.
• Reliability of a system is multiplicative
• If a nuclear power plant is 95 reliable and
  human reliability is 75, then the overall
  reliability is (0.95 X 0.75 0.71) 71.

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Comparative Risk Analysis

• Comparative Risk Analysis of the most serious
  ecological and health problems according to
  scientists acting as advisers to the EPA.
• Risks under each category are not listed in rank
  order.

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U.S. Comparative Risk Analysis

• Annual deaths in the U.S. from tobacco use
  compared to other causes in 2003.

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Global Comparative Risk Analysis

• Number of deaths per year in the world from
  various causes. Parentheses show deaths in terms
  of the number of fully loaded 400-passenger jumbo
  jets crashing every day of the year with no
  survivors.

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Comparative Risk Analysis

• Comparisons of risks people face expressed in
  terms of shorter average life span.

Figure 18-14
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Perceiving Risk

• Most individuals evaluate the relative risk they
  face based on
• Degree of control.
• Fear of unknown.
• Whether we voluntarily take the risk.
• Whether risk is catastrophic.
• Unfair distribution of risk.
• Sometimes misleading information, denial, and
  irrational fears can cloud judgment.

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Become Better at Estimating Risk

• Recognize that everything is risky.
• Recognize that the media often gives an
  exaggerated view of risks to capture our
  attention.
• Compare risks decide what risks are great
  enough to worry about.
• Concentrate on the most serious risks to YOUR
  life health that you have some control over.

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Essential Question 2

• What types of disease (biological hazards)
  threaten people in developing countries and
  developed countries?

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Disease

• Nontransmissible Disease
• Does not spread from person to person
• Ex cardiovascular disorders, asthma,
  malnutrition
• Transmissible Disease
• Infectious can spread from person to person
• Caused by a pathogen (bacteria, virus, parasite)
• Can spread by air, water, food or bodily fluids

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Pathways for Transmissible Disease
Wild animals
Food
Water
Air
Pets
Livestock
Mosquitoes
Fetus and babies
Other humans
Humans
Fig. 18-4, p. 420
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Transmissible Disease

• WHO estimates that each year the worlds seven
  deadliest infections kill 13.6 million people
  most of them the poor in developing countries.

Figure 18-5
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Global Transmission

• Epidemic
• A large-scale outbreak of an infectious disease
  in an area or country
• Pandemic
• A global epidemic
• Ex AIDS / 1918 Spanish Flu

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Case Study Growing Germ Resistance to Antibiotics

• Rabidly producing infectious bacteria are
  becoming genetically resistant to widely used
  antibiotics due to
• Genetic resistance Spread of bacteria around the
  globe by humans, overuse of pesticides which
  produce pesticide resistant insects that carry
  bacteria.
• Overuse of antibiotics A 2000 study found that
  half of the antibiotics used to treat humans were
  prescribed unnecessarily.

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Essential Question 3

• How are tuberculosis, viral diseases (HIV,
  influenza, hepatitis,etc), and malaria posing a
  threat to human populations?

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Case Study The Growing Global Threat from
Tuberculosis

• The highly infectious tuberculosis (TB) kills 1.7
  million people per year and could kill 25 million
  people 2020.
• Recent increases in TB are due to
• Lack of TB screening and control programs
  especially in developing countries due to
  expenses.
• Genetic resistance to the most effective
  antibiotics.

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Viral Diseases

• Flu, HIV, and hepatitis B viruses infect and kill
  many more people each year then highly publicized
  West Nile and SARS viruses.
• The influenza virus is the biggest killer virus
  worldwide.
• Pigs, chickens, ducks, and geese are the major
  reservoirs of flu. As they move from one species
  to another, they can mutate and exchange genetic
  material with other viruses.

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Viral Diseases

• HIV is the second biggest killer virus worldwide.
  Five major priorities to slow the spread of the
  disease ar
• Quickly reduce the number of new infections to
  prevent further spread.
• Concentrate on groups in a society that are
  likely to spread the disease.
• Provide free HIV testing and pressure people to
  get tested.
• Implement educational programs.
• Provide free or low-cost drugs to slow disease
  progress.

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Case Study Malaria Death by Mosquito

• Malaria kills about 2 million people per year and
  has probably killed more than all of the wars
  ever fought.

Figure 18-7
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Malaria Death by Mosquito

• Economists estimate that spending 2-3 billion on
  malaria treatment may save more than 1 million
  lives per year.

Figure 18-6
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Malaria Death by Mosquito

• Spraying insides of homes with low concentrations
  of the pesticide DDT greatly reduces the number
  of malaria cases.
• Under international treaty enacted in 2002, DDT
  is being phased out in developing countries.
• How would you vote?

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Ecological Medicine and Infectious Diseases

• Mostly because of human activities, infectious
  diseases are moving at increasing rates from one
  animal species to another (including humans).
• Ecological (or conservation) medicine is devoted
  to tracking down these connections between
  wildlife and humans to determine ways to slow and
  prevent disease spread.

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Solutions
Infectious Diseases
Increase research on tropical diseases and
vaccines
Reduce poverty
Decrease malnutrition
Improve drinking water quality
Reduce unnecessary use of antibiotics
Educate people to take all of an antibiotic
prescription
Reduce antibiotic use to promote livestock growth
Careful hand washing by all medical personnel
Immunize children against major viral diseases
Oral rehydration for diarrhea victims
Global campaign to reduce HIV/AIDS
Fig. 18-8, p. 424
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Essential Question 4

• What chemical hazards do people face and how can
  they effect immune, nervous endocrine systems?

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Chemical Hazards

• Toxic Chemicals
• Can cause temporary or permanent harm or death
• Hazardous Chemicals
• Can cause harm because it
• is flammable
• is explosive
• is an Irritant
• Interferes with oxygen uptake
• Induces allergic reaction

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3 Types of Toxic Chemicals

• Mutagens
• Increase the frequency of mutations in DNA
• Teratogens
• Cause harm or birth defects to a fetus or embryo
• Carcinogens
• Cause or promote cancer

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Effects of Chemicals on Body Systems

• Immune System
• Specialized cells tissues that protect the body
  against disease harmful substances
• Some chemicals can weaken immune system, leaving
  body vulnerable to pathogens
• Nervous System
• Brain, spinal cord peripheral nerves
• Some chemicals can inhibit, damage or destroy
  nerve cells
• Endocrine System
• Network of glands that regulate hormone
  production release into the bloodstream
• Hormonally Active Agents (HAAs) can act as
  hormone mimics or hormone blocks

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Effects of Chemicals on the Endocrine System

• HAAs include DDT, PCBs, atrazine (widely used
  herbicide), aluminum, mercury, Bisphenol-A (BPA)
  phthalates.
• May cause impaired reproductive systems / sexual
  development, physical / behavioral disorders,
  feminization of males, hermaphroditism, thyroid
  disorders

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Essential Question 5

• How do toxicologists assess whether a chemical is
  harmful?

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Toxicology

• The science examining the effects of harmful
  chemicals on humans, wildlife, ecosystems
• Toxicity
• A measure of how harmful a substance is in
  causing injury, illness or death
• Dose
• The amount of a substance a person has ingested,
  inhaled or absorbed
• Response
• The type amount of health damage resulting from
  exposure to a chemical agent

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Chemical Sensitivity

• Typical variations in sensitivity to a toxic
  chemical within a population, mostly because of
  genetic variation.

Figure 18-10
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Assessing Chemical Hazards

• Estimating human exposure to chemicals and their
  effects is very difficult because of the many and
  often poorly understood variables involved.

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Factors Affecting Response

• Solubility
• Can be stored in cells or fat tissues
• Persistence
• Resistance to breakdown can cause long-lasting
  impacts
• Bioaccumulation
• Absorbed stored in tissues or organs. Can
  build to harmful levels.
• Biomagnification
• Toxins that become magnified in body
  tissues/organs as they pass through food
  chains/webs.
• Chemical Interaction
• Antagonistic interaction reduces harmful
  effects
• Synergistic interaction multiplies harmful
  effects

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Children Toxic Chemicals

• Children are more susceptible to the effects of
  toxic substances because
• Children breathe more air, drink more water, and
  eat more food per unit of body weight than
  adults.
• They are exposed to toxins when they put their
  fingers or other objects in their mouths.
• Children usually have less well-developed immune
  systems and detoxification processes than adults.

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Why do we know so little about the harmful
effects of chemicals?

• Under existing laws, most chemicals are
  considered innocent until proven guilty, and
  estimating their toxicity is difficult,
  uncertain, time consuming, and expensive.
• Federal and state governments do not regulate
  about 99.5 of the commercially used chemicals in
  the U.S.

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Precautionary Principle

• Some scientists and health officials say that
  preliminary but not conclusive evidence that a
  chemical causes significant harm should generate
  preventive action (precautionary principle).
• Manufacturers contend that wide-spread
  application of the precautionary principle would
  make it too expensive to introduce new chemicals
  and technologies, because they would have to
  establish the safety of the items.

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Estimating Toxicity

• Exposing a population of live laboratory animals
  (mice/rats) to measured doses of a chemical is
  the most widely used method for determining its
  toxicity.

• Tests can take 2-5 years, involve thousands of
  test animals cost as much as 2 million per
  substance

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Median Lethal Dose (LD50)

• The amount received in the dose kills 50 of the
  animals in a test population
• Usually w/in an 18-day period

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Toxicity Ratings Average Lethal Doses for
Humans
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Top 5 Toxic Substances in Terms of Human
Environmental Health

• Arsenic
• Lead
• Mercury
• Vinyl Chloride (used in making PVC plastics)
• Polychlorinated biphenyls (PCBs)

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Difficulty with Laboratory Testing

• Validity of extrapolating data from test animals
  to humans
• Humans are rarely exposed to just one chemical in
  their lives
• Studying synergistic effects of chemicals is a
  physical financial impossibility
• Testing just 3 of the 500 most widely used
  industrial chemicals would take 20.7 million
  experiments!!!

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Other Methods for Estimating Harmful Effects of
Chemicals

• Case Reports
• made by physicians reporting adverse health
  effects or death usually relating to overdoses,
  poisonings, homicides or suicides
• Wildlife Studies
• Toxicological studies of effects of chemicals on
  wildlife
• Epidemiological Studied
• Compare health of people exposed to a chemical to
  a similar group not exposed