Key Questions What types of hazards do humans face? What
chemical hazards do humans face? What types of diseases threaten
people in developing and developed countries? How can risks be
estimated and reduced?
Slide 3
DeathsCause of Death Tobacco use440,000 Alcohol use Accidents
Pneumonia and influenza Suicides Homicides Hard drug use AIDS
150,000 95,600 (41,800 auto) 67,000 28,300 16,100 15,600 14,400
2004 Brooks/Cole Thomson Learning Annual Deaths in the U.S.
Slide 4
What Is a Risk? The possibility of suffering harm from a hazard
that can cause injury, disease, economic loss, or environmental
damage Expressed in terms of probability Risk = Exposure x
Harm
Slide 5
How Are Risks Assessed? 1. What is the hazard? 2. How likely is
the event? 3. How much damage is it likely to cause? Example: to
assess the risk of exposure to a toxic chemical, you must look at
the following: 1. Number of people/animals exposed 2. How long they
were exposed 3. Age, health, sex, interaction with other chemicals,
etc.
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How Are Risks Managed? How serious is the risk compared to
other risks? How much should the risk be reduced? How can the risk
be reduced? How much money will be needed?
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2004 Brooks/Cole Thomson Learning Hazard identification What is
the hazard? Probability of risk How likely is the event?
Consequences of risk What is the likely damage? Risk AssessmentRisk
Management Comparative risk analysis How does it compare with other
risks? Risk reduction How much should it be reduced? Risk reduction
strategy How will the risk be reduced? Financial commitment How
much money should be spent?
Slide 8
What Are the Major Types of Hazards? Cultural Hazards: unsafe
working conditions, poor diet, smoking, poverty Chemical Hazards:
harmful chemicals in the air, water, soil, food (human body
contains about 500 synthetic chemicals whose health effects are
unknown) Physical Hazards: fire, earthquake, flood Biological
Hazards: allergens, bacteria, viruses, bees, poisonous snakes
Slide 9
What Determines Whether a Chemical is Harmful? 1. Size of dose
over a certain period of time 2. How often an exposure occurs 3.
Who is exposed (adult or child?) 4. How well the body can detox 5.
Genetic makeup of the individual
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Harm Can Also be Affected by Solubility: can the toxin get into
the water supply? Persistence: does not break down easily; long-
lasting effects on people and animals Bioaccumulation: molecules
are absorbed and stored in organs or tissues at a high level
Biomagnification: some toxins are magnified as they pass through
food chains Chemical interactions: can multiply harmful effect of a
toxin
Slide 11
DDT in fish-eating birds (ospreys) 25 ppm DDT in large fish
(needle fish) 2 ppm DDT in small fish (minnows) 0.5 ppm DDT in
zooplankton 0.04 ppm DDT in water 0.000003 ppm, Or 3 ppt
BIOACCUMULATION
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2004 Brooks/Cole Thomson Learning Very sensitive Majority of
population Very insensitive 020406080 Dose (hypothetical units)
Number of individuals affected Variations in sensitivity due to
genetic makeup
Slide 13
Response Response: type and amount of health damage that
results from exposure Acute effect: immediate harmful reaction Ex:
dizziness or rash Chronic effect: permanent, long-lasting
consequence Ex: kidney or liver damage
Slide 14
How Concerned Should We Be? Most chemicals have threshold
levels of exposure below which we are safe because Human body has
ways of breaking down and diluting toxins Cells have enzymes that
repair damaged DNA Some cells can reproduce fast enough to replace
damaged cells
Slide 15
What is a Poison? Poison: chemical that has an LD 50 of 50
milligrams or less per kilogram of body weight LD 50 : amount of a
chemical that kills exactly 50% of animals
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100 75 50 25 0 24 6 8 10 12 14 16 Percentage of population
killed by a given dose Dose (hypothetical units) LD 50 2004
Brooks/Cole Thomson Learning
Slide 17
How Do We Estimate Toxicity? Case reports: accidental
poisonings, drug overdoses, suicide attempts, etc. Epidemiological
studies: experiments where healthy people are exposed to a
toxin
Slide 18
How Are Lab Experiments Used to Estimate Toxicity? Use live
laboratory animals Cost $200,000-$2 million per substance
Dose-response curveshows the effects of different doses of a toxin
on a group of test organisms Controlled experiments-compare test
group to control group
Slide 19
Dose-response Models Nonthreshold dose-response model: any
dosage of a toxic chemical causes harm that increases with dosage
Threshold dose-response model: threshold dosage must be reached
before any harmful effects occur
Slide 20
What are Toxic and Hazardous Chemicals? Toxic chemicals:
substances that are fatal to more than 50% of test animals
Hazardous chemicals: cause harm by being explosive, damaging to
skin or lungs, interfering with oxygen, or causing allergic
reaction
Slide 21
What are Mutagens? Mutagens: agents that cause random mutations
(changes) in DNA. Example: mutations in sperm or egg cells can be
passed on and cause bipolar disorder, cancer, hemophilia, Down
Syndrome, etc. Most mutations are harmless (DNA repair
enzymes)
Slide 22
What are Teratogens? Teratogens: chemicals, radiation, or
viruses that cause birth defects during the first 3 months of
pregnancy Examples: PCBs, steriod hormones, heavy metals (lead,
mercury)
Slide 23
What are Carcinogens? Carcinogens: chemicals, radiation, or
viruses that cause the growth of a cancerous (malignant) tumorcells
multiple uncontrollably and may spread by metastasis to other parts
of the body Cigarette smoke, occupational exposure, environmental
pollutants, inheritance
Slide 24
How Can Chemicals Harm the Immune, Nervous, and Endocrine
System? Long-term exposure can affect these systems Immune System:
specialized cells and tissues that protect against disease and
harmful substances by forming antibodies Diseases such as HIV can
weaken the immune system, leaving body vulnerable to allergens,
bacteria, and viruses. Nervous System: ( brain, spinal cord, nerves
)-many poisons are neurotoxins which attack nerve cells (DDT, PCBs,
pesticides, lead, arsenic) Endocrine System: (hormones for
reproduction, growth, development, behavior)- hormonally active
agents mimic and disrupt the effects of natural hormones
Slide 25
Hormone Receptor Cell Normal Hormone ProcessHormone
MimicHormone Blocker Estrogen-like chemicalAntiandrogen
chemical
Slide 26
What is the Precautionary Approach? When we are uncertain about
the harmfulness of chemicals, decision makers should act to prevent
harm to humans and the environment better safe than sorry
Slide 27
What Are Nontransmissable Diseases? Nontransmissable disease:
not caused by living organisms and does not spread from one person
to another Example: heart and blood disorders, asthma,
malnutrition
Slide 28
What Are Transmissable Diseases? Transmissable Disease: caused
by living organisms (bacteria, parasite, etc.) and can be spread
from person to person Pathogens: infectious agents-spread by air,
water, food, body fluids, some insects, etc.
Slide 29
Top 7 Deadliest Infectious Diseases 1. Acute respiratory
infection (pneumonia, flu) 2. AIDS (virus) 3. Diarrheal diseases
(bacteria and virus) 4. Tuberculosis (bacteria) 5. Malaria
(parasite) 6. Hepatitis B (virus) 7. Measles (virus)
Slide 30
Figure 11-8 Page 236 Viruses HIV (AIDS) Hepatitis B Smallpox
Ebola On this scale, a human hair would be 6 meters (20 feet) wide
1 micrometer Bacteria Vibrio cholerae (cholera) Myobacterium
tuberculosis (tuberculosis) Treponema pallidum (syphilis) 6
micrometers Protozoa Plasmodium (malaria) 10 micrometers
Slide 31
The viral genetic material uses the host cell's DNA to
replicate again and again. Each new copy of the virus directs the
cell to make it a protein shell. The new viruses emerge from the
host cell capable of infecting other cells. This process often
destroys the first cell. The virus attaches to the host cell. The
entire virus may enter or it may inject its genetic material, or
genome. Virus Cell membrane Host cell
Slide 32
North America 940,000 (20,000) Caribbean 420,000 (30,000) Latin
America 1.4 million (80,000) Western Europe 560,000 (6,800) North
Africa & Middle East 440,000 (30,000) Sub-Saharan Africa 28.1
million (2-3 million) Eastern Europe & Central Asia 1 million
(23,000) South & Southeast Asia 6.1 million (400,000) East Asia
& Pacific 1 million (35,000) Australia & New Zealand 15,000
(120) 40 Million people infected with HIV in 2001. Numbers in ( )
are # of deaths in 2001
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HIV immune suppression facilitates active TB development AIDS
can lead to job loss and poverty HIV/AIDS Malnutrition weakens body
and may facilitate HIV transmission and progress Malnutrition may
facilitate development of active TB MalnutritionTB TB can lead to
job loss and malnutrition because of lack of money Active TB
facilitates HIV replication and speeds up HIV progression
Slide 34
Figure 11-12 Page 243 Malaria-free areasMalaria largely
eliminatedMalaria transmission areas
Slide 35
Anopheles mosquito (vector) in aquatic breeding area 1. Female
mosquito bites infected human, ingesting blood that contains
Plasmodium gametocytes 4. Parasite invades blood cells, causing
malaria and making infected person a new reservoir 3. Mosquito
injects Plasmodium sporozoites into human host 2. Plasmodium
develops in mosquito eggs larva pupa adult
Slide 36
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 Slow global
warming to reduce spread of tropical diseases to temperate areas
Increase preventative health care
Slide 37
Scientists (Not in rank order in each category) Citizens (In
rank order) High-Risk Health Problems Indoor air pollution Outdoor
air pollution Worker exposure to industrial or farm chemicals
Pollutants in drinking water Pesticide residues on food Toxic
chemicals in consumer products High-Risk Ecological Problems Global
climate change Stratospheric ozone depletion Wildlife habitat
alteration and destruction Species extinction and loss of
biodiversity High-Risk Problems Hazardous waste sites Industrial
water pollution Occupational exposure to chemicals Oil spills
Stratospheric ozone depletion Nuclear power-plant accidents
Industrial accidents releasing pollutants Radioactive wastes Air
pollution from factories Leaking underground tanks Medium-Risk
Ecological Problems Acid deposition Pesticides Airborne toxic
chemicals Toxic chemicals, nutrients, and sediment in surface
waters Medium-Risk Problems Coastal water contamination Solid waste
and litter Pesticide risks to farm workers Water pollution from
sewage plants Low-Risk Ecological Problems Oil spills Groundwater
pollution Radioactive isotopes Acid runoff to surface waters
Thermal pollution Low-Risk Problems Air pollution from vehicles
Pesticide residues in foods Global climate change Drinking water
contamination
Slide 38
Hazard Shortens average life span in the United States by 7-10
years Poverty Born male Smoking Overweight (35%) Unmarried
Overweight (15%) Spouse smoking Driving Air pollution Alcohol Drug
abuse AIDS Drowning Pesticides Fire Natural radiation Medical X
rays Oral contraceptives Toxic waste Flying Hurricanes, tornadoes
Living lifetime near nuclear plant 7.5 years 6 years 5 years 2
years 1 year 7 months 5 months 4 months 3 months 2 months 1 month 8
days 5 days 4 days 1 day 10 hours Flu Air Pollution 6 years 5
months 1 month 2004 Brooks/Cole Thomson Learning
Slide 39
How Can We Estimate Risks? 1. Identify hazards 2. Rank risks
(comparative risk analysis) 3. Make decisions to reduce risks 4.
Communicating to the public about risks Most widely used method is
benefit-cost analysis
Slide 40
How Well Do We Perceive Risks? Most of us do poorly in
assessing the risks from the hazards that surround us