1. Chapter 19 – The Environment and Human Health
Hong Kong residents concerned about SARS

2. © 2013 Pearson Education, Inc.
DDT vs. Malaria
Malaria is one of the most important diseases
Major issues in Africa
20% of children under 5 years old died from malaria
DDT was developed and was effective in controlling mosquitoes that vectored malaria
Helped eradicate malaria from many regions of world
DDT affects wildlife
Reduced use, banned in some regions
© 2013 Pearson Education, Inc.

3. "DDT - Powerful Insecticide, Harmless to Humans"

4. Introduction to Public Health
Measuring public health
Population level statistics
Life expectancy at birth
Worldwide 67 years (1950: 46 years)
Mortality rate
Infant mortality
Percentage of infants that die before age 1
Worldwide 4.9% (1950: 15.3%)
© 2013 Pearson Education, Inc. 4

5. Introduction to Public Health
Hazards and risks
May be immediate or delayed
Grouped into four categories
Physical
Chemical
Biological
Cultural
Latent consequences
Delayed effects
Exposure to radiation
© 2013 Pearson Education, Inc. 5

6. Introduction to Public Health
Risk perception and reality
Human perception differs from reality
Key factors influence risk perception
Myth of zero risk
Public awareness
Risk–risk tradeoffs
Control
Risk and time
© 2013 Pearson Education, Inc. 6

8. Environmental Health
In some parts of Eastern Europe and the former USSR, up
to 90 % of all children suffer from environmentally linked
diseases.

10. At any given time, about 2 billion people suffer from
worms, protozoans, and other internal parasites.

11. Physical Hazards in the Environment
Geological hazards
Earthquakes, tsunamis, volcanoes
Weather hazards
Hurricanes/typhoons
Floods
Fire in the environment
Wildfires
© 2013 Pearson Education, Inc. 11

12. Chemical Hazards in the Environment
Toxicology: The study of toxins (poisons) and their effects on living systems.
Scientific discipline that studies chemical poisons and effect on human health
Dose-response curves
Toxicity threshold
Median lethal dose (LD50)
The dose makes the poison
Acute exposure
Chronic exposure
© 2013 Pearson Education, Inc. 12

13. Chemical Hazards in the Environment
Human vulnerability to toxins
Effects of toxins depend on various factors
Genetics
Environmental cause
Age
Health
Socioeconomic status
© 2013 Pearson Education, Inc. 13

14. Chemical Hazards in the Environment
Toxin transport and fate
Impact of certain toxins depends on movement through environment
Persistence
Volatility
Solubility in water
Uptake and fate in other organisms
Bioaccumulation
Body burden
Persistent organic pollutants (POPs)
© 2013 Pearson Education, Inc. 14

15. Movement, Distribution, and Fate of Toxins

16. Bioaccumulation and Biomagnification
Bioaccumulation - dilute toxins in the environment can reach dangerous levels inside cells and tissue
Biomagnification - the effects of toxins are magnified through food webs

17. Persistence
Some chemical compounds are very unstable and degrade rapidly under most conditions, thus their concentrations decline quickly after release.
Others are more persistent.
Stability can cause problems because these materials persist in the environment and have unexpected effects far from their original use.
PBDE (flame-retardants in textiles)

18. Minimizing Toxic Effects
Every material can be poisonous under some conditions.
Taken in small doses, most toxins can be broken down or excreted before they do much harm.
Liver - primary site of detoxification
Tissues and organs - high cellular reproduction rates replace injured cells - down side: tumors, cancers possible

19. Every material can be poisonous under certain conditions.
Most chemicals have a safe threshold under which their effects are insignificant.
Metabolic Degradation
In mammals, the liver is the primary site of detoxification of both natural and introduced poisons.

20. Excretion
Effects of waste products and environmental toxins reduced by eliminating via excretion.
Breathing
Kidneys
Urine
Feces

21. Measuring Toxicity Animal Testing
Most commonly used and widely accepted
Expensive - hundreds of thousands of dollars to test one toxin at low doses
Time consuming
Often very inhumane
Difficult to compare toxicity of unlike chemicals or different species of organisms

22. A Typical Dose/Response Curve

23. LD50 - the dose
of a toxin that is
lethal to half the
test population

24. Acute Versus Chronic Doses and Effects
Acute effect - immediate health effect caused by a single exposure to a toxin (can be reversible)
Chronic effect - long lasting or permanent health effect caused by (1) a single exposure to a very toxic substance or (2) continuous or repeated sub lethal exposure to a toxin

25. Chemical Hazards in the Environment
Kinds of toxins
Corrosive toxins
Asphyxiants
Carcinogens
Teratogens
Allergens
Neurotoxins
© 2013 Pearson Education, Inc. 25

26. Endocrine Disruptors
Chemicals that disrupt normal endocrine hormone functions.
Hormones are chemicals released in blood by glands to regulate development and function of tissues and organs elsewhere in the body.
Environmental Estrogens and Androgens

27. Chemical Hazards in the Environment
Toxin testing and regulation
Contains both ethical and practical challenges
EPA charged to monitor over 75,000 industrial chemicals
Most chemicals assumed to be nontoxic until proved otherwise
Model organisms
Used to test effects of chemicals for humans
© 2013 Pearson Education, Inc. 27

28. Biological Hazards in the Environment
Infectious disease and the environment
Environmental factors influence populations of disease agents and vectors
Population size, movement, climate, water quality
Pathogens
Virulence
Anthroponosis
Disease only in humans
Zoonosis
Disease shared by animals and humans
© 2013 Pearson Education, Inc. 28

29. Brown Recluse

30. Biological Hazards in the Environment
Respiratory disease
Influenza
Avian flu
H1N1
Diarrheal disease
Most from poor sanitation and polluted water
Most die from dehydration
Cholera, cryptosporidium
© 2013 Pearson Education, Inc. 30

31. Biological Hazards in the Environment
Blood-borne diseases
HIV
Malaria
Transmitted by mosquitoes
Caused by parasite Plasmodium
Evolutionary change
Coevolution between pathogen and hosts
Tends to diminish disease severity
Sickle-cell and malaria
© 2013 Pearson Education, Inc. 31

32. Biological Hazards in the Environment
Landscape change
Altered landscapes and waterways provide habitats for disease agents
Climate change
Global warming altering habitats
Allows disease organisms and agents to expand range
© 2013 Pearson Education, Inc. 32

33. Factors Contributing to the Spread of Contagious Diseases
High population densities
Settlers pushing into remote areas
Human-caused environmental change
Speed and frequency of modern travel
Contact with water or food contaminated with human waste

34. Antibiotic and Pesticide Resistance
Indiscriminate use of antibiotics and pesticides - perfect recipe for natural selection
Protozoan that causes malaria now resistant to most antibiotics, and mosquitoes have developed resistance to many insecticides
Drug resistance: TB, Staph A, flesh-eating bacteria