1. CHAPTER 10: RISK, TOXICOLOGY AND HUMAN HEALTH
Cause of Death
Deaths
© 2004 Brooks/Cole – Thomson Learning
Tobacco use
440,000
Alcohol use
150,000
Accidents
95,600 (41,800 auto)
Pneumonia and
influenza
67,000
CHAPTER 10: RISK, TOXICOLOGY AND HUMAN HEALTH
Suicides
28,300
Above is the number of deaths caused by various cultural environmental hazards (pneumonia and influenze should be excluded) in the year No where is the environmental dilemma of humans and risk more manifested than with cultural environmental hazards – in particular, the problem of cigarette smoking. It is our worst environmental problem and it is the easiest to solve at the individual level. Although many people assess the risk associated with smoking correctly, many are unable to manage their lives in such a way that they can kick the habit. In fact, the second largest cause of cultural envrionmental, obesity, can also be solved at the local and individual level. And so the list reads on.
Homicides
16,100
Hard drug use
15,600
CULTURAL ENVIRONMENTAL
HAZARDS
AIDS
14,400
Figure 10-1 Page 203

2. © 2004 Brooks/Cole – Thomson Learning
Risk Assessment
Risk Management
Hazard identification
What is the hazard?
Probability of risk
How likely is the
event?
Consequences of risk
What is the likely
damage?
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?
First we assess risk (probability) and then decide how to manage it. It is foolhardy to do these in reverse order. These are important, difficult and controversial processes.
Figure 10-2 Page 204

3. TOPICS OF CHAPTER 10 TYPES OF HAZARDS
BIOMAGNIFICATION AND BIOACCUMULATION OF TOXINS WITHIN ORGANISMS AND FOOD CHAINS
TOXICOLOGY AND HOW TO MEASURE TOXICITY
HOW CAN RISKS BE ESTIMATED, MANAGED AND REDUCED
DIFFERENCES IN RISK PERCEPTIONS
SCIENTISTS
CITIZENS
POLITICIANS

4. TYPES OF HAZARDS
CULTURAL – see slide 1 of this chapter
CHEMICAL – bad chemicals in soil, water, air and food
PHYSICAL – natural hazards, ionizing radiation and fires
BIOLOGICAL – from pathogens, allergens such as pollen and venomous animals

5. BIOMAGNIFICATION OF DDT IN BALD EAGLES
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
Toxicity (how harmful a substance is) depends on the dose, frequency of exposure, stage of life history of victiv (adult vs. child), health at exposure and genetic sensitivity to substance. Harm caused by a substance is based on solubility (water moves ubiquitously, fat-soluble things accumulate in tissues); persistence and accumulation properties. Bioaccumulation refers to toxins being absorbed and stored in specific organs or tissues at higher than normal levels. Know the definition of bioaccumulation and biomagnification. Biomagnification is when levels of some toxins in the environment are magnified as they pass through food chains and webs. Examples include DDT, PCBs (oily chemicals used in electrical transformers) and some radioactive isotopes (the beta emitter strontium-90). Stored in body fat, these chemicals can be passed along to offspring during gestation or egg laying and as mothers nurse their young. Antagonistic interactions reduce harmful effects (vitamins A and E) whereas a synergistic interaction is one that multiplies a toxins harmful effects (asbestos fibers increase lung cancer probability 20Xs, but smokers increase it by 400Xs). Responses can be acute (immediate or rapid) or chronic (permanent or long-lasting).
DDT in water
ppm,
Or 3 ppt
Figure 10-4 Page 205
BIOMAGNIFICATION OF DDT IN BALD EAGLES
LEADS TO BIOACCUMULATION IN EGG SHELLS

6. © 2004 Brooks/Cole – Thomson Learning
Number of individuals affected
Very
sensitive
Majority
of population
Very
insensitive
One man’s meat is another man’s poison. Within populations of organisms there is always variability in dose sensitivity of organisms to a specific toxin. At the upper and lower limits will be ones most resistant and least resistant, respectively. This variation in population sensitivity is usually a genetic difference among individuals. We will come back to this later in the chapter as we discuss directional selection of microbes in response to antibiotics. The critical question is how much exposure to a particular toxic chemical causes a harmful response. With today's ultra sensitive detection capabilities, some toxins can be found virtually everywhere. Such findings result in political implications such as is now being seen with Seattle Schools and their old lead pipe fed water fountains. Detection levels have changed over the last half century from ppm to ppb to ppq 20 40 60 80
Dose (hypothetical units)
Figure 10-3 Page 205
TYPICAL DISTRIBUTION OF SENSITIVITY TO TOXINS

7. OUR STANDARD IS THE LETHAL DOSE 50
100 75 50 25 2 4 6 8 10 12 14 16
Percentage of population killed by a given dose
Dose (hypothetical units) LD
© 2004 Brooks/Cole – Thomson Learning
OUR STANDARD
IS THE LETHAL DOSE 50
The median lethal dose (LD50) is the amount received in one dose that kills 50% of the rats or mice in a test population within a 14-day period. Legally, a poison is a chemical that has a median lethal dose of 50 milligrams or less per kilogram of body weight. Know what a Lethal Dose 50 is.
Figure 10-5 Page 206

8. © 2004 Brooks/Cole – Thomson Learning
Nonlinear
dose-response
Nonlinear
dose-response
Linear
dose-response
Linear
dose-response
Effect
Effect
Threshold
level
To tests toxicity scientists expose a population of animals to measured doses of a specific substance under controlled conditions. These tests are lengthy and expensive. Cheaper methods are with bacteria, cell and tissue cultures chicken egg membranes and measuring cell electrical properties. For acute toxicity tests are run to develop a dose-response curve showing effects of dosages of a toxin on test organisms done with control (untreated) groups. High doses are used to lower costs. Results are then extrapolated to lower doses using models. With a "no threshold"dose-response model any dosage of a toxin or ionizing radiation causes harm that increases with dosage. With the threshold dose-response model a quantitative level must be reached before effects occur. Such tests are often good for testing for carcinogens (cancer causing agents) and are used to set exposure standards. There are 3 types of response here. Make sure you see them.
Dose
Dose
No threshold
Threshold
Figure 10-6 Page 207

9. DEFINITIONS & EXPLANATIONS OF CHEMICAL HAZARDS
Toxic chemicals are substances fatal to more than 50% of test animals at given concentrations (LD50)
Hazardous chemicals are flammable or explosive, irritate or damage skin or lungs, interfere with O uptake or induce allergic reactions.
Types of toxic agents
Mutagens cause random mutations in genetic structures
Teratogens cause birth defects while embryo is developing (gestation)
Carcinogens cause growth of a malignant (cancerous) tumor (uncontrolled cell growth). Metastasis is when malignant cells break off from tumors and start tumors in other parts of the body. Cancer has a yr. dormant period.
You should know and understand these terms.

10. Normal Hormone Process
HORMONES ARE CHEMICAL MESSENGERS THAT ARE RECOGNIZED WITH SUGARS ON THE CELL SURFACES
Hormone
Estrogen-like chemical
Antiandrogen chemical
Receptor
Cell
Long-term exposure to some toxic chemicals can disrupt the immune, nervous and endocrine systems of animals. The immune system forms antigodies that make invading antigens harmless. Antigens include allergens, bacteria, viruses and protozoans. The nervous system is the brain, spinal cord and peripheral nerves (neurotoxins attack nerve cells). The endocrine system is a network of glands that release hormones in the blood of vertebrates. Hormones regulate animal systems. Hormones have specific molecular shapes that fit (attach) to certain cell receptors. When bonded (attached) the cell is signaled to execute the hormone's chemical message. Some synthetic chemicals can mimic and disrupt natural hormone functions. These are called hormonally active agents (HAAs). They can be mimics or blockers. HAAs are often fat-soluble and so biomagnification and bioaccumulation occur as they move up food chains. DDT and PCBs are HAAs. The precautionary principle might be applied to this group of substances. Pollution control reduces the need for costly, controversial studies as well as the risk from exposure to these questionable problems.
Normal Hormone Process
Hormone Mimic
Hormone Blocker
Figure 10-7 Page 209

11. BIOLOGICAL HAZARDS TYPES OF PATHOGENS
Viruses
HIV
(AIDS)
Hepatitis B
Smallpox
Ebola
On this scale, a human hair would be 6 meters (20 feet) wide
1 micrometer
Protozoa
Plasmodium
(malaria)
10 micrometers
Bacteria
Vibrio cholerae
(cholera)
Myobacterium
tuberculosis
(tuberculosis)
Treponema pallidum (syphilis)
6 micrometers
A non-transmissible disease is not spread by another living organism and has multiple causes and develops slowly (e.g., cardiovascular disease, cancers, diabetes, asthma, emphysema and malnutrition. Transmissible diseases is caused by another living organism (bacteria, virus, protozoa or other parasite) by air, water, food, body fluids, some insects and nonhuman carriers called vectors (mosquitoes are vectors of malaria and West Nile virus). In this slide common environmental pathogens and the disease they cause is given.
TYPES OF PATHOGENS
Figure 10-8 Page 210

12. A TYPICAL VIRUS Genetic material Surface proteins
A typical virus consists of a shell of proteins surrounding genetic material (DNA or RNA). The surface proteins are responsible for recognition of other cell surfaces (e.g., the host) to which they might attach and infect. To reproduce, viruses must use the genetic machinery of a cell.
Surface proteins
Figure 10-9 (1) Page 211

13. Virus Cell membrane Host cell Figure 10-9 (2) Page 211
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
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.
This is how a virus typically reporduces. You need to first understand this in order to appreciate the complexity of environmental problems associated with AIDS in northern Africa.
The new viruses emerge from
the host cell capable of infecting
other cells. This process often
destroys the first cell.
Figure 10-9 (2) Page 211

14. HIV replication animation.
Click to view animation.
Animation

15. AS A COUNTRY INDUSTRIALIZES
Disease
(type of agent)
Deaths per year
Pneumonia and flu
(bacteria and viruses)
3.2 million
HIV/AIDS
(virus)
3.0 million
Diarrheal diseases
(bacteria and viruses)
1.9 million
Tuberculosis
(bacteria)
1.7 million
Malaria
(protozoa)
Education, antibiotics and improved sanitation methods have resulted in improvement in infectious disease control. In spite of this, infectious diseases still kill 12.6 million people a year in poor, developing countries for the most part according to the World Health Organization. Both pathogens and disease vectors, however, are rapidly becoming increasingly resistant to antibiotics and pesticides.
Diseases that were formerly thought to be under control are currently on the rise again in some areas of the world. Tuberculosis is one example of this. Bacteria and viruses can become genetically resistant to antibiotics by directional selection, especially when a patient stops taking their medication prematurely. Also, bacteria can pass plasmids to one another conferring genes for resistance to an antibiotic before even being exposed to the agent. This is most likely to happen in a hospital. Causes of disease increase include increased exposure due to more international travel, overuse of antibiotics and pesticides, overuse of antibiotics with livestock, and more resistant strains in hospitals causing an increase in nonosocial diseases.
1 million
AS A COUNTRY INDUSTRIALIZES
IT MAKES AN EPIDEMIOLOGICAL TRANSITION. CHILD INFECTIOUS DISEASES DECREASE. CHRONIC ADULT DISEASES INCREASE.
Hepatitis B
(virus)
1 million
Measles
(virus)
800,000

16. WORLD TUBERCULOSIS EPIDEMIC
Deaths per
100,000 people
<2.5
2.5-10
Tuberculosis is called a silent global epidemic. The bacterium causing tuberculosis is transmitted in airborned droplets produced by coughing, sneezing, singing or talking. One-third of the people in the world now are infected by the TB Bacillus (the genus for the TB taxon) % of these infected people will become sick or infectious with active TB, especially when theiir immune system is weakened. 95% of the new cases are in developing countries where TB screening and control is lax. More and more genetically resistant strains of TB are developing and antibiotics must be modified to maintain effectiveness. As urbanization spreads in developing countries, population densities increase resulting in more infections. AIDS causes human immune systems to weaken and TB is often one of the first diseases to surface with this happens to AIDS victims. Early detection and treatment is the easy way to solve this problem.
10-35
35-70
70-100
100+
WORLD TUBERCULOSIS EPIDEMIC
Figure Page 212

17. Malaria largely eliminated Malaria transmission areas
Malaria-free areas
Malaria largely eliminated
Malaria transmission areas
Figure Page 214

18. VIRUSES
The 3 greatest causes of viral deaths are AIDS acquired immune deficiency syndrome, hepatitis B and flu and viral pneumonia
The media focuses on emergent diseases such as ebola, SARS, West Nile virus
An emergent disease is one that appears unknown or a disease that has been dormant or rare for 10 or more years
In the last 25 years, 35 million people have died of AIDS related diseases. Most people infected are in Nigeria and Ethiopia (Sub-Saharan Africa) and Russia, India and China.

19. LIFE CYCLE OF PLASMOCIUM THAT CAUSES MALARIA
Anopheles mosquito (vector)
in aquatic breeding area
eggs
adult
larva
pupa
LIFE CYCLE OF PLASMOCIUM THAT CAUSES MALARIA
1. Female
mosquito bites
infected human,
ingesting blood
that contains
Plasmodium
gametocytes
90% of malaria occurs in Africa, south of Sahara. Up to 500 million people are infected with malarial protozoan parasites. Malaria's symptoms come and go. It is caused by 4 species of protozoans in the genus Plasmodium transmitted when a female of the genus Anopheles mosquito bites an infected person and then another person. Plasmodium parasites multiply in the liver. Blood transfusions also transmit this disease as well as hepatitis and AIDS. Today both the plasmodium and mosquitoes have become resistant to their respective controls (drugs and pesticides). Before draining and spraying wetlands was used to prevent the spread of malaria. Prevention can be inproved by increasing water flow in irrigation systems to disrupt the mosquito reproductive cycle, fixing leaking water pipes and using mosquito nets dipped in nontoxic insecticide (permethrin), cultivating fish that eat mosquitoes, clearing vegetation around houses, planting trees in marshes boosting resistance in children with zinc and vitamin A.
4. Parasite invades
blood cells, causing
malaria and making
infected person
a new reservoir
2. Plasmodium
develops in
mosquito
3. Mosquito injects Plasmodium
sporozoites into human host
Malaria-free areas
Malaria largely eliminated
Malaria transmission areas

20. WE HAVE SOLUTIONS TO MOST OF THE WORLD’S BIOLOGICAL HAZARDS
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
Immunize children
against major viral
diseases
Oral rehydration for
diarrhea victims
Global campaign to
reduce HIV/AIDS
WE HAVE SOLUTIONS TO MOST OF THE WORLD’S BIOLOGICAL HAZARDS
Best way to slow the spread of infectious diseases is to provide adequate access to clean drinking water and sanitation facilities in developing countries, immunize children and eradicate malnutrition. A good local tool is education.
Figure Page 215

21. DIFFERENCE BETWEEN ACTUAL VS. PERCEIVED ENVIRONMENTAL RISKS
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
There is a marked difference between what scientists and lay people see as environmental risks. This leads to controversy in policy planning, implementation and effectiveness.
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
Figure Page 216

22. © 2004 Brooks/Cole – Thomson Learning
Poverty/malnutrition/
disease cycle
10 million (68)
Tobacco
4 million (27)
Pneumonia and flu
3.9 million (27)
Air pollution
3 million (21)
AIDS
3 million (21)
Diarrhea
2.1 million (14) TB
1.6 million (11)
Malaria
1.1 million (8)
Work-related
injury and disease
1.1 million (8)
Hepatitis B
1 million (7)
Due mostly to media distortions, people have a distorted view of the biggest killers.
Automobile
accidents
885,000 (6)
WHAT ARE THE MAJOR CAUSES OF PREMATURE DEATH (yearly data)
Measles
800,000 (5)
Airline crashes
1,126 (0.008)
Figure Page 217

23. THIS IS THE END OF CHAPTER 10