1. Water and Health in an Overcrowded World

Question 1

Which two ‘revolutions’ improved the quality of human life?

Answer 1

Agriculture and urbanisation.

Question 2

What’s the most important reason of the population growth after humans invented agriculture?

Answer 2

Agriculture it led to an increase in the fertility rate.

• more food = better health for women, improved likelihood to become pregnant
• better chance of survival for babies
• larger number of surviving children in one generation = more adults to produce an even larger number in the next

Question 3

What is most obvious symptom of the environmental crisis caused party by humans?

Answer 3

The loss of biodiversity (number of species in a locality, region or the whole planet AND the number in the population of each species)

Question 4

Name some general features of developed countries.

Answer 4

• universal education for their children
• high rates of literacy
• comprehensive high-technology health services
• they meet certain other development indicators, such as
  100% access to safe drinking water and sanitation
• economies grew rapidly in the early 20th century as a result of industrialisation

Question 5

Name some features of developing countries.

Answer 5

• only partly industrialised and their national wealth is below that of the developed economies
• rely more on agriculture, small industrial businesses and low-paid unskilled or low-skilled labour

Major indicators of development, such as literacy and provision of clean water vary hugely between these countries

Question 6

What is the IMR and what does it say?

Answer 6

Infant mortality rate: internationally recognised health indicator

Refers to the number of babies in every 1000 live births who die in their first year of life

Question 7

What is natural selection?

Answer 7

Natural selection is the gradual process by which biological characteristics become either more or less common in a population as one particular characteristic improves the chance of survival in their environment.

Question 8

How is one of these improved characteristics after natural selection called?

Answer 8

Adaptive

Question 9

Humans belong to a group of …. called the ….

Answer 9

Humans belong to a group of mammals called the primates

Question 10

What are the main characteristics of primates?

Answer 10

• large brain
• well-developed eyes and hands that can grasp and manipulate objects
• most primates are arboreal (tree-dwelling) and are confined to woodland and forest

Question 11

How are the ancestors of humans called?

Answer 11

Hominids

Question 12

What effect on dental health occurred when settled agricultural communities replaced the nomadic way of life?

Answer 12

The ability to grind and cook cereal crops and vegetables rendered them soft enough to eat, but these foods are rich in sticky carbohydrates which form a coating on the teeth. (Modern diets in developed countries also contain large quantities of refined sugars.)

Bacteria in the mouth thrive in this habitat and attack the enamel surface of the teeth, causing gum disease and tooth decay.

Question 13

The upright posture humans evolved is called…

Answer 13

Bipedality

Question 14

What is an evolutionary-trade-off?

Answer 14

Evolution cannot produce a perfectly adapted human body so ‘trade-offs’ have to be made between competing demands.

Question 15

What is a proxy measure?

Answer 15

A readily measurable statistic that ‘stands in’ for something more complex

Question 16

What is the child mortality rate?

Answer 16

Number of children who die under five years of age in a given year, expressed per 1000 live births

Question 17

What is the most important disadvantage of human mobility?

Answer 17

The spread of infectious diseases around the world.

Question 18

What is the difference between epidemic and pandemic?

Answer 18

Epidemic: outbreak of an infectious disease in a community, region or country that involves a large number of people

Pandemic: cases spread on a worldwide scale

Question 19

Name some health benefits of living in a developed country.

Answer 19

• hygiene (water supplies, clean food free of harmful pathogens)
• immunisation programmes for childhood infectious diseases (polio, measles and diphtheria)
• antibiotics
• people with inherited or acquired physical defects can be helped (surgery, devices)
• contraceptives

Question 20

Name some health ‘costs’ of living in a developed country.

Answer 20

• cities, infectious diseases spread easily
• evolution of entirely new and harmful bacteria
• chemicals manufactured for use in industry, agriculture and the home are released into the environment, some of which are harmful
• inappropriate and excessive use of antibiotics exerts selection pressure that promotes the evolution of new, antibiotic­ resistant strains of bacteria

Question 21

Name some health problems associated with obesity.

Answer 21

Heart disease, high blood pressure, breast cancer, back pain, arthritis and diabetes

Question 22

What is the ‘stress response’?

Answer 22

The stress response is defined as a physiological reaction occurring in the body, which is triggered by the perception of aversive or threatening situations.

Question 23

Which hormones are being released in chronic stress?

Answer 23

Epinephrine and cortisol

Question 24

What is epidemiology?

Answer 24

The study of the 
- occurrence, 
- distribution, 
- potential causes and 
- control 
of diseases/disabilities in populations.

Question 25

What is the incidence?

Answer 25

The incidence of a condition is the number of new cases diagnosed in a population in a given period (usually one year)

Question 26

What is the prevalence?

Answer 26

The prevalence of a condition is the total number of people who have the condition at a particular point in time

Question 27

What are microbes?

Answer 27

Microscopic agents, known collectively as microbes (or microorganisms), i.e. viruses, bacteria, fungal cells and
single-celled parasites.

Question 28

Many microbes and parasites are harmless to people, but those that cause disease are often referred to as…

Answer 28

Pathogens (‘pathogenic’ means disease-causing)

Question 29

What is the morbidity rate?

Answer 29

The morbidity rate is the number of cases of a disorder in a population, relative to the total number of people at risk of developing it.

Question 30

Counting the number of cases of a disorder is

notoriously difficult - why?

Answer 30

If you try to count all the new cases diagnosed in a year (the incidence), can you be sure that the diagnoses are accurate?

If you try to count the prevalence (all cases present at one point in time), have you found them all?

Illnesses are often self-treated, so they go unrecorded, or people conceal them, or the data-collection system is inadequate or it fails to reach remote populations.

Some conditions have periods of remission, or they fluctuate unpredictably (e.g. asthma, multiple sclerosis), so do you leave out all the people who are not showing symptoms in the data-collection period?

Question 31

What is the DALY?

Answer 31

Disability adjusted life year

= a measure of the total number of years lived with a disease, disorder or disability, taking its severity into account, and the years lost due to premature death.

Question 32

What happens during transpiration (water cycle)?

Answer 32

Transpiration is the release of water vapour by plants.

Plants take in carbon dioxide from the atmosphere, and release oxygen. To maintain a flow of nutrients through their stems and leaves they take up water in their roots and release it as water vapour through tiny holes in their leaves, called stomata, through which they also take in carbon dioxide.

Question 33

What is the most significant use of water worldwide?

Answer 33

Agriculture: in 2025 it will account for 60% of all the water extracted from natural water resources

Question 34

Name the two general types of diseases caused by water.

Answer 34

Water-borne infectious diseases are those in which the
pathogen causing the disease lives part of its life cycle in water.

Water-associated infectious diseases are those, like malaria, in which the animal that transmits the pathogen between people (mosquitoes) lives part of its life in water.

Question 35

To eliminate water-borne infectious diseases in a human population, two things have to be achieved. Which?

Answer 35

1. a reliable supply of water that is not contaminated by pathogens.
2. an effective sanitation system that removes and disposes of human, animal and other waste that may be contaminated by pathogens, without allowing it to come into contact with the water supply.

Question 36

What is cholera?

Answer 36

Cholera is a diarrhoeal disease, caused by the bacterium Vibrio cholerae.

Question 37

What health-damaging effect does diarrhoea have?

Answer 37

Water and body salts are lost in such large quantities that the chemistry of the whole body is disrupted.

Diarrhoeal infections also prevent the gut from breaking down and absorbing nutrients, causing malnutrition and increased susceptibility to other infections.

Question 38

What happens in the body during diarrhoea?

Answer 38

1. The diarrhoeal pathogens infect the gut and irritate the cells lining its surface.
2. The cells respond by secreting large amounts of water, and dissolved salts, into the gut which,
3. in turn, responds by contracting to expel the watery, infected waste.

Question 39

What is immunodeficiency?

Answer 39

Immunodeficiency is a condition in which the immune system fails to respond normally to an infection; it can be caused by a genetic defect and by HIV/AIDS, as well as by malnutrition.

Question 40

What is the incubation period?

Answer 40

The incubation period of a disease is the time between a pathogen entering its host and the host beginning to show disease symptoms.

Question 41

What does cholera do in the body?

Answer 41

Vibrio cholerae attaches to the wall of the gut and produces a
toxin that causes the cells in the gut wall to produces a copious, painless, watery diarrhoea that can quickly lead to severe dehydration and death if treatment is not promptly given. Vomiting also occurs in most patients.

Question 42

What is a toxin?

Answer 42

A toxin is a poisonous substance produced by a living organism, usually injurious to potential prey, predators or competitors.

Question 43

Most individuals infected with V. cholerae do not become ill, even though the bacterium is present in their faeces for 7–14 days.

What are the implications of this for the spread of the disease?

Answer 43

In the absence of proper sanitation, people infected with V. cholerae but not suffering from cholera symptoms, can none the less transmit it to uninfected people, thus causing it to spread rapidly through a population.

Question 44

What is the infectious dose?

Answer 44

The infectious dose is defined as the number of individual pathogens required to cause disease in an infected person.

So: the higher the infectious dose, the more of a pathogen is required to cause the disease.

Question 45

What is a disinfectant?

Answer 45

A disinfectant is a chemical that reduces microbial contamination of water, surfaces, etc.

Question 46

What means ‘xenobiotic’?

Answer 46

Literally meaning ‘alien to nature’, in the context of this module this word refers to chemicals ‘of human origin’.

Question 47

What are endocrine disruptors?

Answer 47

Xenobiotic chemicals - hormone mimics, environmental pollutants that are threatening human health by disrupting the body’s hormonal system.

Question 48

How do endocrine disruptors work?

Answer 48

Endocrine disruptors work because, although they are not hormones, and often bear no obvious similarity to hormones, they happen to have in their molecular structure, features that mimic the ‘key’ section of specific hormone molecules.

Thus a substance that is not a hormone has the ability to ‘unlock the lock’ on target organs, which then behave as if the relevant hormone had become bound to them.