Environmental Science

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Environmental Science

• Unit 4 - Risk, Toxicology, Human Health
• (STE 7th ed. Chapter 11)

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Where are we going?

• - Types of hazards
• - Toxicology
• Chemical hazards
• Biological hazards
• - Risk Analysis
• estimating risk, major risks, issues

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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

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Types of Hazards
Identify the (i) Risk, (ii) Hazard and (iii) Risk
Management
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Types of Hazards Risk as a Probability
NYT Jan 29th 1995
NYT Jan 29th 1995
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NOVAHow Risky is Flying?
NOVA Deadliest Plane Crash
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NOVAHow Risky is Flying?
NOVA Deadliest Plane Crash
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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
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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
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many more
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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?

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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.

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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
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Toxicology
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The dose makes the poisonAny chemical be it
natural or synthetic can be harmful
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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

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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

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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

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Table 171
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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

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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
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DoseResponse Curves
Any dosage is harmful (Assumed in most cases)
Lower limit to harmful dose
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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
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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

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Toxicology

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

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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

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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

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Background

• Birth defects due to exposure to synthetic
  chemicals
• Toxicity to mammals and birds
• Carcinogenic effects
• Xenoestrogenic effects

• Gt. Lakes cormorant with crossed bill

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EST Article
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Chemical Hazards
Toxic chemicals(kill)
Hazardous chemicals(harm)
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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
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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)

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Dioxin IncidentsTimes Beach, Missouri

NYT 121682
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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
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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.

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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

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

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Health EffectsEffects in Utero

• Exposure to low levels results in impaired
  intellectual development

NYT, September 12th 1998
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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
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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

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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

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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

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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

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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)

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Biological Hazards
Infectious disease pathways
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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

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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

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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

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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

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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
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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
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Bioterrorism

• Possible targets air, water, and food
• Inexpensive
• Fairly easy to produce biological agents
• Recombinant DNA techniques

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Risk Analysis

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

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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
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• 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.

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RISK ANALYSIS

• Annual deaths in the U.S. from tobacco use and
  other causes in 2003

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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.

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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

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RISK ANALYSIS

• Comparisons of risks people face expressed in
  terms of shorter average life span.

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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