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Chapter 11: Risk, Toxicology, and Human Health

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Title: Chapter 11: Risk, Toxicology, and Human Health


1
Chapter 11 Risk, Toxicology, and Human Health
2
What is Risk?
  • Risk - the possibility of suffering harm from a
    hazard that can cause injury, disease, economic
    loss, or environmental change
  • Expressed in terms of probability a mathematical
    statement about how likely it is that some event
    or effect will occur.
  • Risk Exposure x Harm

3
How Are Risks Assessed and Managed?
  • Risk Assessment
  • Identifying a real or potential hazard
  • Determining the probability of its occurrence
  • Assessing the severity of its health,
    environmental, economic, and social impact
  • Risk Management
  • How serious it is compared to other risks?
  • How much (if at all) the risk should be reduced?
  • How can such risk reduction be accomplished?
  • How much money should be spent?
  • RM More controversial because there is a lack of
    information and there can be economic, health,
    and political implications

4
What Are the Major Types of Hazard?
  • Cultural Hazards
  • Chemical Hazards
  • Physical Hazards
  • Biological Hazards

5
Toxicity Dose and Response
  • Toxicity - measures how harmful a substance is
  • Dose - the amount of a potentially harmful
    substance that has been ingested, inhaled, or
    absorbed through the skin
  • Whether a chemical is harmful depends on
  • The size of the dose over a certain period of
    time
  • How often the exposure occurs
  • Who is exposed
  • How well the bodys detoxification system works
  • Genetic make-up of an individual

6
Other Factors That Determine a Substances Harm
  • Solubility - water-soluble toxins can move
    through the environment and get into the water
    supplies fat-soluble toxins can accumulate in
    the body tissues and cells
  • Persistence - the chemicals resistance to
    breakdown and its long-lasting effects

7
Bioaccumulation, Biomagnification, and Chemical
Interactions
  • Bioaccumulation - where molecules are absorbed
    and stored in specific organs or tissues at
    higher levels than normally would be expected.
  • Biomagnification - where some toxins are
    magnified as they pass through food chains and
    webs
  • Chemical interactions - decrease or multiply the
    harmful effects of a toxin
  • Antagonistic Interaction - can reduce the harmful
    effects
  • Synergistic Interaction - can multiply the
    harmful effects

8
Response
  • Response - the type and amount of health damage
    that results from exposure to a chemical or other
    agent.
  • Acute Effect - an immediate or rapid, harmful
    reaction to an exposure
  • Chronic Effect - a permanent or long-lasting
    consequence of exposure to a harmful substance

9
Should We Be Concerned About Toxic Chemicals?
  • It depends on the chemical and its concentration
    - ANYTHING can be harmful if ingested in a large
    quantity
  • Most chemicals have a safe, threshold level
  • The human body can break down, dilute, and
    excrete
  • Enzymes can repair DNA and protein molecules
  • Cells reproduce quickly
  • Synthetic does not mean deadly and natural does
    not mean safe

10
What is Poison?
  • Poison - a chemical that has an LD50 of 50 mg or
    less per kg of body weight
  • Median Lethal Dose - LD50 - the amount of a
    chemical received in one dose that kills exactly
    50 of the animals in a test population (usually
    within a 14-day period)

11
Case Reports
  • Case Reports - provide information about people
    suffering from some adverse health effect or
    death after exposure to a chemical
  • Not reliable as the actual dosage and the
    persons health status are not known
  • Could include accidental poisonings, drug
    overdoses, homicides, or suicide attempts

12
Epidemiological Studies
  • Epidemiological Studies - the health of people
    exposed to the toxic agent are compared to the
    health of the people not exposed to the agent
  • Limited
  • too few people are exposed to high levels of many
    toxic substances
  • it is difficult to link effect to a particular
    exposure
  • cant be used to evaluate hazards from new
    technologies or chemicals to which people have
    not been exposed.

13
Laboratory Experiments
  • Use test animals under controlled conditions --
    good because it mimic biological interactions
    that happen in live animals
  • More humane methods include
  • Bacteria
  • Cell and tissue cultures
  • Chicken egg membranes

14
Dose Response Curves
  • Shows the effect of various dosages of a toxic
    agent on a group of test organisms
  • Controlled by keeping organisms at the same age,
    health status, genetic make-up, and same
    environmental conditions
  • Non-threshold Dose-Response Model - any dosage of
    a toxic chemical that causes harm that increases
    with the dosage
  • Threshold Dose-Response Model - a threshold
    dosage must be reached before any detectable
    harmful effects occur

15
Toxic and Hazardous Chemicals
  • Toxic Chemicals - fatal to more than 50 of test
    animals
  • Hazardous Chemicals - cause harm
  • by being flammable or explosive, irritating, or
    damaging to the skin
  • interfering with or preventing oxygen uptake and
    distribution
  • inducing allergic reactions

16
Mutagens
  • Mutagens - agents that cause random mutations, or
    changes, in the DNA molecules found in cells
  • Some are inherited, some are not
  • More mutations are harmless as organisms have
    biochemical repair mechanisms

17
Teratogens
  • Teratogens - chemicals, radiation, or viruses
    that cause birth defects while the human embryo
    is growing and developing during pregnancy
  • PCBs
  • Thalidomide
  • Steroid Hormones
  • Heavy Metals - arsenic, cadmium, lead, and
    mercury

18
Carcinogens
  • Chemicals, radiation, or viruses that cause or
    promote the growth of a malignant tumor
  • Smoke
  • Diet
  • Occupational exposure
  • Environmental pollutants
  • Inherited factors and viruses (20)
  • Time Delay - often 10 - 40 years between the
    initial exposure and the appearance of any
    symptoms

19
Chemicals and the Immune System
  • Examples of chemicals/situations that weaken the
    immune system
  • HIV
  • Ionizing radiation
  • Malnutrition
  • Weakening the immune system leaves the body
    vulnerable to
  • Allergens
  • Infectious bacteria
  • Viruses
  • Protozoans

20
Chemicals and the Nervous System
  • Certain neurotoxins can attack nerve cells
  • Chlorinated hyrdocarbons - DDT, PCBs, dioxins
  • Organophosphate pesticides
  • Formaldehyde
  • Arsenic, merculry, lead, cadmium
  • Industrial solvents - tricholorethylene (TCE),
    toluene, xylene

21
Chemicals and the Endocrine System
  • Toxins can effect
  • Sexual reproduction
  • Growth
  • Development and behavior
  • Hormonally Active Agents - mimic and disrupt the
    effects of natural hormones

22
Why Do We Know So Little About the Harmful
Effects of Chemicals?
  • Only 10 of 75,000 have been thoroughly screened
    for toxicity 2 adequately screened
  • Most commercial products have not been screened
    and 1,000 new chemicals are introduced to the
    marketplace every year.
  • Three major reasons for a lack of knowledge
  • Most chemicals are considered innocent until
    proven guilty
  • Not enough funds, personnel, facilities, and test
    animals
  • Analyzing the effects of multiple exposures to
    various chemicals and their possible interactions
    is too difficult and expensive

23
Should We Apply the Precautionary Principle?
  • Would reduce the need for toxicity studies and
    exposure standards.
  • Would reduce the risk posed by exposure to
    potentially hazardous chemicals and their poorly
    understood interactions

24
Nontransmissible Disease
  • Diseases not caused by a living organism
  • Does not spread from one person to the next
  • Has multiple causes
  • Tend to develop slowly and progressively
  • CV diseases
  • Most cancers
  • Diabetes
  • Asthma
  • Emphysema
  • Malnutrition

25
Transmissible Diseases
  • Diseases caused by a living organism or a virus
    (pathogens)
  • Can be spread from one person to the next
  • Spread by food, water, body fluids, some insects,
    and non-human carriers called vectors
  • Bacterium - one celled microorganisms that are
    capable of replicating itself by cell division
  • Can use antibiotics to treat they have reduced
    the incidence of disease, but they have also been
    misused and bacteria have increaed their genetic
    resistance
  • Virus - a microscopic, noncellular infectious
    agent DNA or RNA contains instructions for
    making more viruses

26
Infectious Diseases
  • Cause 1 in 4 deaths each year
  • Worlds Deadliest
  • Acute respiratory infections - flu, pneumonia
  • AIDs
  • Diarrheal Diseases
  • Tuberculosis - TB
  • Malaria
  • Hepatitis B
  • Measles
  • Epidemiological Transition - when countries
    industrialize and the infectious diseases of
    childhood become less important and the chronic
    diseases become more important

27
Spreading of Viral Diseases and How Viral
Diseases Are Treated
  • Can adapt quickly - new flu viruses
  • Transmitted through sex
  • 23 of the American Population has an STD
  • AIDS situation
  • 40 million people worldwide have AIDs
  • 15,300 new infections a day
  • In sub-Saharan Africa - 20 or more of adults are
    infected with HIV within 7-10 years, those with
    HIV will develop AIDS
  • 39 of Botswana adults have AIDS - their life
    expectancy has dropped 30 years
  • Treating Viral Diseases
  • No antibiotics
  • Vaccines

28
Spreading of Viral Diseases
  • o Increased international air travel
  • o Migration to urban areas
  • o Migration to uninhabited rural areas and
    deforestation in tropical developing countries -
    exposes people to new diseases
  • o Migration to suburbs in developed countries -
    more contact with forested areas
  • o Hunger and malnutrition increases the number
    of children killed by infectious diseases

29
Spreading of Viral Diseases Continued
  • o Increased rice cultivation ideal breeding
    grounds for mosquitos and other insects that
    transmit diseases to humans
  • o Global warming leads to the spread of
    diseases
  • o High winds or hurricanes can transfer
    organisms and carriers of disease
  • o Accidental Introduction of Insect Vectors
  • o Deliberate introduction of pathogens as an act
    of bioterrorism
  • o Flooding - contaminates water supplies
    creates areas of standing water and moist soil
    which are breeding grounds for mosquitoes and
    other insects

30
Reducing Infectious Diseases
  • o Increase research on tropical diseases and
    vaccines
  • o Reduce poverty
  • o Decrease malnutrition
  • o Improve drinking water quality
  • o Reduce unnecessary use of antibiotics
  • o Educate people to take all of an antibiotic
    prescription
  • o Reduce antibiotic use to promote livestock
    growth
  • o Careful hand washing by all medical personnel
  • o Slow global warming to reduce the spread of
    tropical diseases
  • o Increase preventative health care

31
How Can We Estimate Risks?
  • Risk Analysis
  • Risk Assessment - identifying hazards and
    evaluating their associated risks
  • Comparative Risk Analysis - ranking risks
  • Risk Management - determining options and making
    decisions
  • Risk Communication - informing decision makers
    and the public about risks.
  • Risks determined by scientists are different than
    those determined by the public

32
What Are The Greatest Risks People Face?
  • o Poverty
  • o Voluntary choices people make about their
    lifestyle
  • o Not to smoke
  • o Avoid excess sunlight
  • o Not drink alcohol or drink in moderation
  • o Reduce consumption of foods containing
    cholesterol and saturated fats
  • o Eating fruits and vegetables
  • o Exercising
  • o Lose excess weight
  • o Drive safely
  • o Cannot control
  • o Gender
  • o Genes
  • o Social and psychological environment

33
How Can We Estimate Risks for Technological
Systems
  • System reliability () technological
    reliability x human reliability
  • Creates tragedies
  • To err is human -- all technologies rely on
    humans

34
What are the Limitations of Risk Analysis?
  • o Are data and models reliable?
  • o Who profits and who suffers from chemicals?
  • o Should we care more about short-term or
    long-term risks?
  • o Should we determine acceptability or how to do
    the least damage?
  • o Who should do the risk analysis?
  • o Should various risks be considered?
  • o How widespread is each risk?
  • o Should risk levels be higher for workers than
    for the general public?
  • o How much risk is acceptable? And to whom?

35
How Should Risks Be Managed? How Do We Perceive
Risks?
  • Includes the administrative, political, and
    economic actions taken to decide whether and how
    to reduce a particular societal risk to a certain
    level at a certain cost
  • How Well Do We Perceive Risks?
  • Motorcycling, smoking, hang gliding, driving
  • Commercial airplane crash, killed by a handgun,
    being struck by lightening, a train crash, a
    snakebite, shark attack
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