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Environmental Science

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Title: Unit 4: Toxins Author: Dan Short Last modified by: Dan Created Date: 5/28/1999 5:29:55 PM Document presentation format: On-screen Show (4:3) Company – PowerPoint PPT presentation

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Title: Environmental Science


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
NOVAHow Risky is Flying?
NOVA Deadliest Plane Crash
7
NOVAHow Risky is Flying?
NOVA Deadliest Plane Crash
8
Types of Hazards Major Hazards
  • cultural hazards
  • chemical hazards
  • physical hazardsnoise, fire, tornadoes,
    hurricanes, earthquakes, volcanic eruptions,
    floods, ionizing radiation
  • biological hazardspathogens, 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 DeathAnnual Deaths
3 x 400 passenger jets crashing every day
WHO estimates 80 x 106 deaths 1950-2000 3 x more
than all wars of 20th century
US deaths in 2003
10
many more
11
MovieThe Realities of Risk (13 of 29 mins)
  • View the following moviehttp//vega.org.uk/vide
    o/programme/5(part of the series
    http//www.open2.net/nextbigthing/
  • Questions
  • (i) What is risk bootstrapping?
  • (ii) Why does the scientist think it was daft
    to ban the pesticide alar?

12
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13
Case Study A Black Day in Bhopal, India
  • The worlds worst industrial accident1984
    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 poisonAny 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
ToxicologyToxicity 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 171
21
ToxicologyResponses
  • 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
ToxicologyDose-Response
  • Acute toxicity tests
  • design
  • Controls (no dose) treatments (low to high
    dose)
  • test organism (usually rats or mice)
  • replicates (usually 60200 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
DoseResponse 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 100-1000 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

29
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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
EST Article
32
Chemical Hazards
Toxic chemicals(kill)
Hazardous chemicals(harm)
33
Chemical HazardsToxic Chemicals
  • Temporary or Permanent harm or death
  • mutagens cause random mutations (changes in the
    DNA) e.g. nitrous acid, UV, ?, a 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

http//en.wikipedia.org/wiki/International_Agency_
for_Research_on_Cancer
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 IncidentsTimes Beach, Missouri

NYT 121682
36
Dioxin IncidentsTimes Beach, Missouri
  • 1972-76dirt roads were sprayed with waste oil
    containing super concentrated dioxin from Agent
    Orange manufacture
  • 1992 - Town was demolished
  • 1997 - 265,000 tons of soil was incinerated on
    site
  • Now Route 66 State Park

Shown in History Channel Modern Marvels 20
37
Effects at Low Doses
  • Long-term exposure to some chemicals at low doses
    may disrupt the bodys
  • 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 EffectsEffects in Utero
  • Exposure to low levels results in impaired
    intellectual development

NYT, September 12th 1998
43
Health EffectsDioxins, 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 Preventionbetter 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

46
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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
  • http//www.bruceames.org/bnamedia.html

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

49
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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 worlds 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

http//www.doc3d.com/malaria/malaria_WMV.html http
//www.learner.org/channel/courses/biology/units/i
nfect/images.html
58
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59
Bioterrorism
  • Possible targets air, water, and food
  • Inexpensive
  • Fairly easy to produce biological agents
  • Recombinant DNA techniques

60
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61
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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 0.008 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
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