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

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/Co

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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

04/10/23 32

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