Environmental Hazards and Human Health Chapter 17
Mar 26, 2015
Environmental Hazards and Human Health
Chapter 17
Core Case Study: The Global HIV/AIDS Epidemic
Acquired immune deficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV); many secondary infections
In 2007, ~60,000 people in the US infected No vaccine to prevent or cure AIDS Expensive drugs—live longer, only 90% can
afford 25 Million deaths, so far; alter country’s age
structure
Lesions That Are a Sign of Kaposi’s Sarcoma
Global Outlook: Worldwide, AIDS Is the Leading Cause of Death for Ages 15–49
17-1 Risks Are Usually Expressed as Probabilities
Risk is the probability of suffering harm from a hazard that cause injury, disease, death, economic loss, or damage
Probability (estimate of the likelihood ) and possibility (could happen)
Risk Assessment• Scientific process of using statistical methods to
estimate how much harm a particular hazard can cause to human health
Risk Management• Involves deciding whether or how to reduce a
particular risk
6
© 2
004
Bro
oks
/Co
le –
Th
om
son
Lea
rnin
g
7-10 yearsPoverty
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
6-10 years
5 years
2 years
1 year
7 months
5 months
4 months
4 months
3 months
2 months
1 month
1 month
8 days
5 days
5 days
4 days
1 day
1 day
10 hours
Flu
Air Pollution
6 years
5 months
1 month
7.5 years
Hazard Shortens average life span in the United States by
We Face Many Types of Hazards
Five major types of hazards• Biological: pathogens• Chemical: harmful chemicals in air, water, soil• Physical: fire, earthquakes, floods, storms• Cultural: criminal assault, poverty, working
conditions• Lifestyle choices: smoking, drinking, eating too
much, unsafe sex
17-2 Some Diseases Can Spread from One Person to Another
Nontransmissible disease• Cardiovascular disease, cancer, asthma,
diabetes
Transmissible disease (contagious or communicable disease) • Caused by a pathogen (bacteria, virus or
parasite) that invades the body transmitted from one person to the next•Flu, HIV, malaria, measles
Some Diseases Can Spread from One Person to Another
Since 1950, death from infectious diseases have declined due to• Better health care• Antibiotics• Vaccines
Infectious Diseases Are Still Major Health Threats
Infectious diseases spread through• Air
• Water
• Food
• Body fluids
Epidemics (area or country) and pandemics (global)
Resistance of bacteria and insects
Science Focus: Genetic Resistance to Antibiotics Is Increasing
Bacteria: rapid reproduction, easily spread Over use of antibiotics
Science Focus: Genetic Resistance to Antibiotics Is Increasing
Methicillin-resistant Staphylococcus aureus (MRSA)
Case Study: The Growing Global Threat from Tuberculosis
Effects ~9.2 million people per year Kills 1.7 million a year (84% in developing
countries Why is tuberculosis on the rise?
• Not enough screening and control programs
• Genetic resistance to a majority of effective antibiotics
• Person-to-person contact has increased
• AIDS individuals are very susceptible to TB
04/10/23 14
Deaths per100,000 people
<2.5
2.5-10
10-35
35-70
70-100
100+
Current tuberculosis epidemic
Some Viral Diseases Kill Large Numbers of People
Influenza or flu virus• #1 Killer
• Transmission
HIV• #2 Killer
• Antiviral drugs
Some Viral Diseases Kill Large Numbers of People
Global strategy to slow down the spread of HIV• Reduce the number of new infections
• Concentrate on those most likely to spread HIV
• Free testing
• Education for prevention
• Provide free or low-cost drugs
• Research
Some Viral Diseases Kill Large Numbers of People
Hepatitis B virus (HBV)• #3 Killer
• Mode of transmission
Viruses that move form animals to humans• West Nile virus
• Severe acute respiratory syndrome (SARS)
Reduce chances of infection: Wash your hands
Case Study: Malaria—Death by Parasite-Carrying Mosquitoes
Malaria on the rise since 1970• Drug resistant Plasmodium• Insecticide resistant mosquitoes • Effect of global warming• AIDS patients particularly vulnerable
04/10/23 19
Anopheles mosquito (vector)in aquatic breeding area
1. Femalemosquito bitesinfected human,ingesting bloodthat containsPlasmodiumgametocytes
4. Parasite invadesblood cells, causingmalaria and makinginfected persona new reservoir
3. Mosquito injects Plasmodiumsporozoites into human host
2. Plasmodiumdevelops inmosquito
eggs
larvapupa
adult
The Life Cycle of malaria
04/10/23 20Malaria
Endemic in more than 100 countries.Caused by four protozoa species.270–500 million new cases and1 million deaths per year.
Malaria
We Can Reduce the Incidence of Infectious Diseases
Good news• Vaccinations on the rise• Oral rehydration therapy- only a few cents per person
• Used to prevent dehydration • 1980- 4.6 million deaths from dehydration• 2006 1.9 million deaths from dehydration
Bad news• More money needed for medical research in
developing countries
04/10/23 22
Disease(type of agent)
3.2 millionPneumonia and flu
(bacteria and viruses)
HIV/AIDS(virus)
Diarrheal diseases(bacteria and viruses)
Tuberculosis(bacteria)
Malaria(protozoa)
Hepatitis B(virus)
Measles(virus)
Deaths per year
3.0 million
1.9 million
1.7 million
1 million
1 million
800,000
17-3 Some Chemicals Can Cause Cancers, Mutations, and Birth Defects
Toxic chemicals• Carcinogens- cause cancer
• Mutagens- change in DNA
• Teratogens- causes harm or birth defects to a fetus
Case Study: PCBs Are Everywhere—A Legacy from the Past
Class of chlorine-containing compounds• polychlorinated biphenyls• Very stable• Nonflammable• Break down slowly in the environment• Travel long distances in the air• Fat soluble• Biomagnification• Food chains and webs
Banned in 1976, but found everywhere
Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems
Some natural and synthetic chemicals in the environment can weaken and harm• Immune system
•Are weakened arsenic, methyl mercury, dioxins
• Nervous system•PCBs, methyl mercury, arsenic, lead, and certain
pesticides
• Endocrine system•Aluminum, atrazine, DDT, mercury, PCBs,
bisphenol A
Science Focus: Mercury’s Toxic Effects
Hg: teratogen and potent neurotoxin• Once airborne, persistent and not
degradable
• 1/3 from natural sources
• 2/3 from human activities•Coal-burning power plants,
waste incinerators,
chemical manufacturing
plants,
• Enters the food chain: biomagnification
Science: Cycling of Mercury in Aquatic Environments
Science Focus: Mercury’s Toxic Effects
2007: Hg hotspots identified• New England, New York, Nova Scotia
How are humans exposed?• Inhalation: vaporized Hg or particulates
of inorganic salts• Eating fish with high levels of
methylmercury
Effects of Hg on humans• Brain damage in fetuses and young children• Lower IQ, poor school performance• Harm the heart, kidneys and immune system in adults
Science Focus: Bisphenol A
Estrogen mimic Found in many common products
• Water and baby bottles, food- containers and dental fillings
Laboratory findings• 94 studies by independent labs found numerous adverse health
effects from low level exposure• 12 studies funded by chemical industry found no adverse effects
Effects on human health• Brain damage, prostate disease, early puberty,
reduced sperm count, hyperactivity, decrease
sex drive in males, obesity
17-4 Many Factors Determine the Harmful Health Effects of a Chemical
Toxicology• Study of harmful effects of chemicals on humans
Toxicity • measures how harmful a substance is in causing injury, illness,
or death to a living organism
dependent on• Dose • Age• Genetic makeup • Multiple chemical sensitivity (MCS) • Solubility and persistence of the chemical
• Water soluble (move throughout environment)• Oil or fat soluble (accumulate in tissue)
• Biomagnification
04/10/23 31
DDT in fish-eatingbirds (ospreys)
25 ppm
DDT in largefish (needle fish)2 ppm
DDT in smallfish (minnows)0.5 ppm
DDT inzooplankton0.04 ppm
DDT in water0.000003 ppm,Or 3 ppt
Bioaccumulation and Biomagnifications
© 2004 Brooks/Cole – Thomson Learning
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Verysensitive
Majorityof population
Veryinsensitive
0 20 40 60 80
Dose (hypothetical units)
Nu
mb
er o
f in
div
idu
als
affe
cted
Typical variations in sensitivity to a toxic chemical
Many Factors Determine the Harmful Health Effects of a Chemical
Response• The damage to health resulting from exposure
to a chemical
• Acute effect• Immediate or rapid reaction
•Dizziness or nausea to death
• Chronic effect•Permanent or long- lasting consequences
• Kidney or liver damage
Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity
Dose-response curve: median lethal dose (LD50) • The dose that can kill 50% of the animals in a test
population within an 18- day period.
•Nonthreshold dose-response model•Any dosage causes harm that increase with
dosage
•Threshold dose-response model •A threshold dose must be reached before any
detectable harmful effects occur
Can the data be extrapolated to humans?
04/10/23 35
LD50
0 4 8 12 16
Dose (hypothetical units)
Per
cen
tag
e o
f p
op
ula
tio
n k
illed
by
a g
iven
do
se LD50
141062
25
50
75
100
04/10/23 36
© 2004 Brooks/Cole – Thomson LearningE
ffec
t
Dose
Nonlineardose-response
Lineardose-response
No thresholdE
ffec
tThreshold
Thresholdlevel
Dose
37
Table 9-1 Toxicity Ratings and Average Lethal Doses for Humans
Toxicity Rating
Supertoxic
Extremely toxic
Very toxic
Toxic
Moderately toxic
Slightly toxic
Essentially nontoxic
LD50 (milligrams perkg of body weight)*
Less than 0.01
Less than 5
5–50
50–500
500–5,000
5,000–15,000
15,000 or greater
Examples
Nerve gases, botulism toxin,
mushroom toxins, dioxin (TCDD)
Potassium cyanide, heroin, atropine,
parathion, nicotine
Mercury salts, morphine, codeine
Lead salts, DDT, sodium hydroxide,
sodium fluoride, sulfuric acid, caffeine,
carbon tetrachloride
Methyl (wood) alcohol, ether,
Phenobarbital, amphetamines (speed),
kerosene, aspirin
Ethyl alcohol, Lysol, soaps
Water, glycerin, table sugar
Average Lethal Dose†
Less than 1 drop
Less than 7 drops
7 drops to 1 teaspoon
1 teaspoon to 1 ounce
1 ounce to 1 pint
1 pint to 1 quart
More than 1 quart
*Dosage that kills 50% of individuals exposed†Amounts of substances in liquid form at room temperature that are lethal when given to a 70.4-kg (155-pound) human
Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity
More humane methods using animals
Replace animals with other models• Computer simulations
• Tissue culture and individual animal cells
• Chicken egg membranes
What are the effects of mixtures of potentially toxic chemicals?
04/10/23 39
Reality
2% of chemicals in use have been tested
99.5% of used chemicals not regulated
Some Potentially Harmful Chemicals Found in Most Homes
Are Trace Levels of Toxic Chemicals Harmful?
We do not know
Pollution Prevention and the Precautionary Principle
Those introducing a new chemical or new technology would have to follow new strategies• A new product is considered harmful until it can
be proved to be safe
• Existing chemicals and technologies that appear to cause significant harm must be removed
2000: global treaty to ban or phase out the dirty dozen (POPs)
POPs – The Dirty Dozen
Individuals Matter: Ray Turner and His Refrigerator
1974: Ozone layer being depleted by chlorofluorocarbons (CFCs)
1992: International agreement to phase out CFCs and other ozone-destroying chemicals
Ray Turner: citrus-based solvents to clean circuit boards
17-5 The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices
Risk analysis
Greatest health risks• Poverty
• Gender
• Lifestyle choices
Fig. 17-18, p. 461
Cause of death Annual deaths
Poverty/malnutrition/ disease cycle
11 million (150)
Tobacco 5.4 million (74)
Pneumonia and flu 3.2 million (44)
Air pollution 3 million (41)
HIV/AIDS 2.1 million (29)
Diarrhea 1.9 million (26)
Tuberculosis 1.7 million (23)Automobile accidents 1.2 million (16)
Work-related injury and disease
1.1 million (15)
Malaria
1 million (14)Hepatitis B
1 million (14)
Measles 800,000 (11)
Comparison of Risks People Face in Terms of Shorter Average Life Span
Case Study: Death from Smoking (1)
Most preventable major cause of suffering and premature death
Nicotine: additive
Effects of passive smoking (secondhand smoke)
Case Study: Death from Smoking (2)
How to reduce smoking• Taxes
• Ban
• Classify and regulate nicotine
• Education
Fig. 17-20, p. 463
Cause of Death in US Deaths
Tobacco use 442,000
Accidents 101,500 (43,450 auto)
Alcohol use 85,000
Infectious diseases
75,000 (17,000 from AIDS)
Pollutants/toxins 55,000
Suicides 30,600
Homicides 20,622
Illegal drug use 17,000