1. Environmental Science
Unit 4 - Risk, Toxicology, & Human Health
(STE 7th ed. Chapter 11)

2. Where are we going? - Types of hazards - Toxicology Chemical hazards
Biological hazards
- Risk Analysis
estimating risk, major risks, issues

3. Types of Hazards
Risk is a measure of the possibility of experiencing a hazard that can cause harm
expressed as a probability; 1 in 200, 1 in 1000 etc. e.g. risk of death from flying in US 1 in 7,000,000
risk assessment involves estimation of the probability of harm to human health, society, or the environment that may result from exposure to specific hazards
risk management involves the decision to reduce a risk and the costs associated

4. Types of Hazards
Identify the (i) Risk, (ii) Hazard and (iii) Risk Management

5. Types of Hazards Risk as a Probability
NYT Jan 29th 1995
NYT Jan 29th 1995

6. NOVA How Risky is Flying?
How Risky Is Flying? by David Ropeik
Trying to judge whether a particular risk is big or small is, well, a risky business. There's a lot more to it than you might think. Flying in airplanes is a case in point. You'd think that you could just find out the numbers—the odds—and that would be it. The annual risk of being killed in a plane crash for the average American is about 1 in 11 million. On that basis, the risk looks pretty small. Compare that, for example, to the annual risk of being killed in a motor vehicle crash for the average American, which is about 1 in 5,000.
But if you think about those numbers, problems crop up right away. First of all, you are not the average American. Nobody is. Some people fly more and some fly less and some don't fly at all. So if you take the total number of people killed in commercial plane crashes and divide that into the total population, the result, the risk for the average American, may be a good general guide to whether the risk is big or small, but it's not specific to your personal risk.
Then there's another numbers problem: what denominator are you using? (For the math-challenged, like me, that's the number at the bottom of a fraction.) You can calculate the risk of flying by:
Dividing the number of people who die into the total number of people, which gives you the risk for the average person;
Dividing the number of victims into the number of total flights all passengers took, which gives the risk per flight; Or
Dividing the number of victims into the total number of miles all of them flew, which gives you the risk per mile.
They all produce accurate numbers, but which one is most relevant to you depends on your personal flying patterns. Some fliers take lots of short flights and some take longer ones, for example. Since the overwhelming majority of the few plane crashes that do occur take place in connection with takeoffs and landings, the risk is less a matter of how far you fly and more a matter of how often. If you're a frequent flier, then the risk per flight means more. For occasional long-distance fliers, the risk per mile means more. A frequent, long-distance flier would want to consider both.
Here's another number problem with the risk of flying: do you calculate the risk on the basis of one year, or an average of five years, or 10, or 20? Most years no plane crashes occur, or at least very few. So the number of victims per year goes up radically in years when there are crashes. Just look at the spikes in the number of deaths from plane crashes by year in the graph at right.
Risk perception is not just a matter of the facts.
So to calculate the risk per year can be misleading. One really bad year would skew the numbers toward the more frightening. A year with no crashes makes it look like it's zero. But if you average things over, say, five years, or 10, some other factors muddy the waters. In the last five years safety factors have changed. Advanced weather radar has been installed near major airports, and new FAA rules have gone into effect. A 10-year average might be misleading too. It would include the aberration of September 11, 2001.
Despite all these caveats, numbers are a great way to put risk in general perspective, and there is no question that by most metrics, flying is a less risky way to travel than most others. But wait: just when you thought it was safe to use numbers to put risk in perspective... Numbers are not the only way—not even the most important way—we judge what to be afraid of. Risk perception is not just a matter of the facts.
It's also a matter of the other things we know (e.g., airline companies are in financial trouble) and our experiences (maybe you took a really scary, turbulent flight once) and our life circumstances (my wife was more afraid of flying when our kids were little). And on top of all that, several general characteristics make some risks feel scarier than others.
Researchers in psychology like Paul Slovic and Baruch Fischhoff have found that when we have control (like when we're driving) we're less afraid, and when we don't have control (like when we're flying) we're more afraid. That probably explains why, in the first few months after the 9/11 attacks, fewer people flew and more people chose to drive. Driving, with its sense of control, feels safer. Studies at Cornell and the University of Michigan estimate that between 700 and 1,000 more people died in motor vehicle crashes from October through December of 2001 than during the same three months the year before.
Another "feelings factor" that informs our perception of risk is awareness. The more aware of a risk we are, the more concerned about it we are. Which explains why, when there is a plane crash in the news, flying seems scarier to many of us, even though that one crash hasn't changed the overall statistical risk much.
People are also more sensitive about risks that are catastrophic, which kill people all at once in one place, than we are about risks that are chronic, where the victims are spread out over space and/or time. Plane crashes, therefore, get more media attention than, say, heart disease, which kills 2,200 people in the United States each day, just not all in one place at one moment.
Then there's the factor the researchers call dread, which is basically a measure of suffering. The more awful/painful/nasty a way to die it is, the more afraid of it we are likely to be. What happens to people in a plane crash feels pretty high up on a list of awful/painful/nasty ways to go. It sounds a lot worse—and scarier—than dying of heart disease, for example, even though the likelihood of dying from heart disease is much higher (1 in 400 per year, for the average American.)
The challenge, then, in making an informed decision about the risk of flying, or any risk, is to balance these three components—the numbers about that risk (especially those that are most relevant to you), all the other things we know and our life circumstances, and the affective feelings the risk triggers. That way the choices we make, to fly or drive for example, will include what is right for each of us but will also hopefully be more in line with the scientific facts, and that should help us live healthier and longer lives.
NOVA: Deadliest Plane Crash

7. NOVA How Risky is Flying?
How Risky Is Flying? by David Ropeik
Trying to judge whether a particular risk is big or small is, well, a risky business. There's a lot more to it than you might think. Flying in airplanes is a case in point. You'd think that you could just find out the numbers—the odds—and that would be it. The annual risk of being killed in a plane crash for the average American is about 1 in 11 million. On that basis, the risk looks pretty small. Compare that, for example, to the annual risk of being killed in a motor vehicle crash for the average American, which is about 1 in 5,000.
But if you think about those numbers, problems crop up right away. First of all, you are not the average American. Nobody is. Some people fly more and some fly less and some don't fly at all. So if you take the total number of people killed in commercial plane crashes and divide that into the total population, the result, the risk for the average American, may be a good general guide to whether the risk is big or small, but it's not specific to your personal risk.
Then there's another numbers problem: what denominator are you using? (For the math-challenged, like me, that's the number at the bottom of a fraction.) You can calculate the risk of flying by:
Dividing the number of people who die into the total number of people, which gives you the risk for the average person;
Dividing the number of victims into the number of total flights all passengers took, which gives the risk per flight; Or
Dividing the number of victims into the total number of miles all of them flew, which gives you the risk per mile.
They all produce accurate numbers, but which one is most relevant to you depends on your personal flying patterns. Some fliers take lots of short flights and some take longer ones, for example. Since the overwhelming majority of the few plane crashes that do occur take place in connection with takeoffs and landings, the risk is less a matter of how far you fly and more a matter of how often. If you're a frequent flier, then the risk per flight means more. For occasional long-distance fliers, the risk per mile means more. A frequent, long-distance flier would want to consider both.
Here's another number problem with the risk of flying: do you calculate the risk on the basis of one year, or an average of five years, or 10, or 20? Most years no plane crashes occur, or at least very few. So the number of victims per year goes up radically in years when there are crashes. Just look at the spikes in the number of deaths from plane crashes by year in the graph at right.
Risk perception is not just a matter of the facts.
So to calculate the risk per year can be misleading. One really bad year would skew the numbers toward the more frightening. A year with no crashes makes it look like it's zero. But if you average things over, say, five years, or 10, some other factors muddy the waters. In the last five years safety factors have changed. Advanced weather radar has been installed near major airports, and new FAA rules have gone into effect. A 10-year average might be misleading too. It would include the aberration of September 11, 2001.
Despite all these caveats, numbers are a great way to put risk in general perspective, and there is no question that by most metrics, flying is a less risky way to travel than most others. But wait: just when you thought it was safe to use numbers to put risk in perspective... Numbers are not the only way—not even the most important way—we judge what to be afraid of. Risk perception is not just a matter of the facts.
It's also a matter of the other things we know (e.g., airline companies are in financial trouble) and our experiences (maybe you took a really scary, turbulent flight once) and our life circumstances (my wife was more afraid of flying when our kids were little). And on top of all that, several general characteristics make some risks feel scarier than others.
Researchers in psychology like Paul Slovic and Baruch Fischhoff have found that when we have control (like when we're driving) we're less afraid, and when we don't have control (like when we're flying) we're more afraid. That probably explains why, in the first few months after the 9/11 attacks, fewer people flew and more people chose to drive. Driving, with its sense of control, feels safer. Studies at Cornell and the University of Michigan estimate that between 700 and 1,000 more people died in motor vehicle crashes from October through December of 2001 than during the same three months the year before.
Another "feelings factor" that informs our perception of risk is awareness. The more aware of a risk we are, the more concerned about it we are. Which explains why, when there is a plane crash in the news, flying seems scarier to many of us, even though that one crash hasn't changed the overall statistical risk much.
People are also more sensitive about risks that are catastrophic, which kill people all at once in one place, than we are about risks that are chronic, where the victims are spread out over space and/or time. Plane crashes, therefore, get more media attention than, say, heart disease, which kills 2,200 people in the United States each day, just not all in one place at one moment.
Then there's the factor the researchers call dread, which is basically a measure of suffering. The more awful/painful/nasty a way to die it is, the more afraid of it we are likely to be. What happens to people in a plane crash feels pretty high up on a list of awful/painful/nasty ways to go. It sounds a lot worse—and scarier—than dying of heart disease, for example, even though the likelihood of dying from heart disease is much higher (1 in 400 per year, for the average American.)
The challenge, then, in making an informed decision about the risk of flying, or any risk, is to balance these three components—the numbers about that risk (especially those that are most relevant to you), all the other things we know and our life circumstances, and the affective feelings the risk triggers. That way the choices we make, to fly or drive for example, will include what is right for each of us but will also hopefully be more in line with the scientific facts, and that should help us live healthier and longer lives.
NOVA: Deadliest Plane Crash

8. Types of Hazards Major Hazards
cultural hazards
chemical hazards
physical hazards noise, fire, tornadoes, hurricanes, earthquakes, volcanic eruptions, floods, & ionizing radiation;
biological hazards pathogens, pollen & other allergens, & animals such as bees & poisonous snakes
unsafe working conditions, smoking, poor diet, drugs, drinking, driving, flying, criminal assault, poverty;
harmful chemicals in air, water, soil, & food;

9. Causes of Death Annual Deaths
3 x 400 passenger jets crashing every day
Notes: diet (>300,000) is left out, accidents includes drug overdoses
WHO estimates 80 x 106 deaths
3 x more than all wars of 20th century
US deaths in 2003

10. + many more

11. Movie The Realities of Risk (13 of 29 mins)
View the following movie: (part of the series
Questions:
(i) What is risk bootstrapping?
(ii) Why does the scientist think it was ‘daft’ to ban the pesticide ‘alar’?

13. Case Study: A Black Day in Bhopal, India
The world’s worst industrial accident: 1984 pesticide plant, Bhopal India.
An explosion at Union Carbide pesticide plant in an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas.
15,000-22,000 people died
Indian officials claim that simple upgrades could have prevented the tragedy.

14. Toxicology study of the adverse effects of chemicals on health
toxicity: measure of how harmful a substance is; depends on:
dose: amount of a potentially harmful substance ingested, inhaled, or absorbed through the skin;
response: resulting type & amount of damage to health may be acute or chronic
Also: frequency of exposure, age, effectiveness of detox systems, genetics

15. Toxicology

16. The dose makes the poison Any chemical be it natural or synthetic can be harmful

17. Should we be concerned? …traces of synthetic chemicals in our environment
Lack of data
Effects difficult to determine
Poor diet + pollution = brain damage
Which is major factor?
Life expectancy has increased
Lower levels and new contaminants are being detected due to new technology

18. Misconception
Misconception that all natural chemicals are safe and all sythentics are bad
e.g. fruit seeds and pips form cyanide in the stomach, green potatoes, naturally occuring pesticides, mould/fungi on food

19. Toxicology Toxicity of Chemicals
Animal testing, case and epidemiological reports
generally defined by LD50 – amount in a dose that kills 50 % of population in 14 days
poison: legally defined as a chemical that has an LD50 of 50 milligrams or less per kilogram of body weight

20. Table 17–1

21. Toxicology Responses Acute toxicity: Sudden and severe exposure
Rapid onset of symptoms
Chronic toxicity:
Continuous, long-term exposure
Relatively low dose
Cancer, birth defects, neurological damage
Same chemical may show both effects
e.g. skin irritation vs. cancer

22. Toxicology Dose-Response
Acute toxicity tests
design:
Controls (no dose) & treatments (low to high dose)
test organism (usually rats or mice)
replicates (usually 60–200 animals total)
period (often 14 days)
High doses are used to reduce no. subjects and increase speed of test
- Extrapolated down to low doses
2-5 years, $200,000-$2 million

23. Dose–Response Curves Any dosage is harmful (Assumed in most cases)
Lower limit to harmful dose

24. Question
If a dose of 0.1 μg is sufficient to kill a mouse, what mass would be fatal to you?
What average level of substance would have to be present in drinking water for you to receive a fatal dose in one week?
Ratio mass human : mouse = 200 : 1
Mass that would kill you = 200 x 0.1 μg = 20 μg
2 L water d-1 x 7 d w-1 = 14L
For fatal dose 20 μg / 14 L = 1 μg L-1 = 1 ppb

25. Toxicology Complications Different physiology
Synergestic effects – difficult and expensive to test for 1, no. tests multiply when consider more than 1
Because of complexity in determining toxicity allowed exposure levels are set x below harmful levels

26. Toxicology
Estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved.

27. Toxicology
Children are more susceptible to the effects of toxic substances because:
Children breathe more air, drink more water, and eat more food per unit of body weight than adults.
They are exposed to toxins when they put their fingers or other objects in their mouths.
Children usually have less well-developed immune systems and detoxification processes than adults

28. Toxicology
The U.S. Environmental Protection Agency proposed that regulators should assume children have 10 times the exposure risk of adults to cancer-causing chemicals
Some health scientists contend that regulators should assume a risk 100 times that of adults

30. Background Birth defects due to exposure to synthetic chemicals
Toxicity to mammals and birds
Carcinogenic effects
Xenoestrogenic effects
Gt. Lakes cormorant with crossed bill

31. ES&T Article

32. Chemical Hazards
Toxic chemicals (kill)
Hazardous chemicals (harm)

33. Chemical Hazards Toxic Chemicals
Temporary or Permanent harm or death:
mutagens: cause random mutations (changes in the DNA) e.g. nitrous acid, UV, γ, α radiation
teratogens: cause birth defects e.g., alcohol, PCBs, steroid hormones, heavy metals
neurotoxins: damage nervous system e.g., DDT, alcohol, heavy metals
carcinogens: cause cancer
over 100 types e.g. benzene, dioxin, radionuclides, asbestos

34. Hazardous Chemicals cause harm in various ways
flammable or explosive (e.g., gasoline);
irritating or damaging to skin or lungs (e.g., strong acids or alkalis)
interfering with or preventing oxygen uptake & distribution (e.g., carbon monoxide, CO);
inducing allergic reactions of the immune system (allergens)

35. Dioxin Incidents Times Beach, Missouri
NYT

36. Dioxin Incidents Times Beach, Missouri
dirt roads were sprayed with waste oil containing super concentrated dioxin from Agent Orange manufacture
Town was demolished
,000 tons of soil was incinerated on site
Now Route 66 State Park
Modern Marvels 20 – Engineering Disasters
Shown in History Channel Modern Marvels #20

37. Effects at Low Doses
Long-term exposure to some chemicals at low doses may disrupt the body’s:
Immune system: specialized cells and tissues that protect the body against disease and harmful substances.
Nervous system: brain, spinal cord, and peripheral nerves.
Endocrine system: complex network of glands that release minute amounts of hormones into the bloodstream.

38. Hormone Disrupters
hormones: molecules that act as messengers to regulate various bodily processes, including reproduction, growth, & development (endocrine system)
hormone disrupters: interfere with hormone function
so far 51 chemicals shown to act as hormone disrupters on wildlife, laboratory animals, & humans
e.g., dioxins, certain PCBs, various chemicals in plastics, some pesticides, lead & mercury
1997 study shows that sperm count of men in U.S. & Europe has declined 50%

39. Hormone Disrupters
Molecules of certain synthetic chemicals have shapes similar to those of natural hormones and can adversely affect the endocrine system

40. Biomagnification
A chemical whose concentration increases along a food chain is said to be biomagnified
DDT concentration in Lake Ontario Trout
Biomagnification results from a
sequence of bioaccumulation steps

41. Biomagnification
when a chemical becomes concentrated in specific organs or tissues
e.g., DDT, dioxin, PCBs accumulates in fatty tissues
Known as persistent organic pollution (POP)
contributing factors:
organic chemical (like dissolves like)
high persistence
not easily broken down or excreted

42. Health Effects Effects in Utero
Exposure to low levels results in impaired intellectual development
NYT, September 12th 1998

43. Health Effects Dioxins, Furans and PCBs in Food
95% of human exposure to
dioxins and furans is from
the presence of these
compounds from food
Fresh water fish has the
highest level of PCBs
Schecter et al., 1997
NYT July 2nd 2003

44. Why do we know so little?
Under existing laws, most chemicals are considered innocent until proven guilty, and estimating their toxicity is difficult, uncertain, and expensive.
Federal and state governments do not regulate about 99.5% of the commercially used chemicals in the U.S.
Only 10% of 80,000 chemicals have been tested for toxicity
Chemicals are considered innnocent until proven guilty

45. Pollution Prevention “better safe than sorry”
Some scientists and health officials say that preliminary but not conclusive evidence that a chemical causes significant harm should spur preventive action (precautionary principle)
Manufacturers contend that wide-spread application of the precautionary principle would make it too expensive to introduce new chemicals and technologies

47. Pollution and Cancer
Bruce Ames believes that the focus on man-made chemicals as causes of cancer is a distraction from the real threats of smoking and diet
Media:

48. Environmental Testing
Experiments with test animals are used to determine how carcinogenic a compound is, take many years
The simple Ames test can be used fairly rapidly to distinguish compounds likely to be human carcinogens

50. Biological Hazards nontransmissible diseases
cardiovascular disorders, cancers, emphysema, & malnutrition;
transmissible (infectious) diseases
caused by bacteria, viruses, protozoa, or parasites
colds, flus, hepatitis, sexually transmitted diseases, malaria
many transmissible diseases spreading over broad geographic areas
Lyme disease (bacteria)
Giardia (protozoa)

51. Biological Hazards
Infectious disease pathways

52. Transmissible Diseases
WHO estimates that each year the world’s seven deadliest infections kill 13.6 million people – most of them the poor in developing countries

53. Case Study: Growing Germ Resistance to Antibiotics
Rabidly producing infectious bacteria ‘superbugs’ (e.g. MRSA) are becoming genetically resistant to widely used antibiotics due to:
Genetic resistance: Antibiotic resistance is a consequence of evolution via natural selection
Overuse of antibiotics:
(i) A 2000 study found that half of the antibiotics used to treat humans were prescribed unnecessarily
(ii) over 70% of all antibiotics used in US given to animals in the absence of disease

54. Case Study: The Growing Global Threat from Tuberculosis
The highly infectious tuberculosis (TB) kills 1.7 million people per year and could kill 25 million people 2020.
Recent increases in TB are due to:
Lack of TB screening and control programs especially in developing countries due to expenses
Genetic resistance to the most effective antibiotics

55. Viral Diseases
Flu, HIV, and hepatitis B viruses infect and kill many more people each year then highly publicized West Nile and SARS viruses
The influenza virus is the biggest killer virus worldwide
Pigs, chickens, ducks, and geese are the major reservoirs of flu. As they move from one species to another, they can mutate and exchange genetic material with other viruses
HIV is the second biggest killer virus worldwide. Five major priorities to slow the spread of the disease are:
Quickly reduce the number of new infections to prevent further spread
Concentrate on groups in a society that are likely to spread the disease
Provide free HIV testing and pressure people to get tested.
Implement educational programs
Provide free or low-cost drugs to slow disease progress

56. Case Study: Malaria – Death by Mosquito
Malaria kills about 2 million people per year and has probably killed more than all of the wars ever fought

57. Case Study: Malaria – Death by Mosquito
Spraying insides of homes with low concentrations of the pesticide DDT greatly reduces the number of malaria cases.
Under international treaty enacted in 2002, DDT is being phased out in developing countries

59. Bioterrorism Possible targets: air, water, and food Inexpensive
Fairly easy to produce biological agents
Recombinant DNA techniques

62. Risk Analysis
Scientists have developed ways to evaluate and compare risks, decide how much risk is acceptable, and find affordable ways to reduce it.

63. Risk Assessment
To perform risk assessment it is important to know:
Hazard evaluation information (acute, cancer ???)
Quantitative dose-response information
An estimate of the potential human exposure to the chemical
The highest dose at which no observable effects level is called NOEL
(expressed in terms of mg kg-1 body weight day-1)
To determine the threshold level for the most sensitive members of the human population, EPA uses Toxicity reference dose or RfD.
(RfD is also referred as Acceptable Daily Intake or ADI)
RfD (or ADI) = NOEL/100 (divide by safety factor of 100)
If NOEL for a chemical is 0.01 mg/kg/day, the ADI or RfD for a 80 kg man
would be (0.01 mg/kg/day /100) x 80 kg = mg

64. Estimating risks from using many technologies is difficult due to unpredictability of human behavior, chance, and sabotage.
Reliability of a system is multiplicative:
If a nuclear power plant is 95% reliable and human reliability is 75%, then the overall reliability is (0.95 X 0.75 = 0.71) 71%.

65. RISK ANALYSIS
Annual deaths in the U.S. from tobacco use and other causes in 2003

66. RISK ANALYSIS
Number of deaths per year in the world from various causes. Parentheses show deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors.

67. Perceiving Risk
Most individuals evaluate the relative risk they face based on:
Degree of control
Fear of unknown
Whether we voluntarily take the risk
Whether risk is catastrophic
Unfair distribution of risk
Sometimes misleading information, denial, and irrational fears can cloud judgment

68. RISK ANALYSIS
Comparisons of risks people face expressed in terms of shorter average life span.

69. Becoming Better at Risk Analysis
We can carefully evaluate or tune out of the barrage of bad news covered in the media, compare risks, and concentrate on reducing personal risks over which we have some control