Title: Environmental Science
1Environmental Science
- Unit 4 - Risk, Toxicology, Human Health
- (STE 7th ed. Chapter 11)
2Where are we going?
- - Types of hazards
- - Toxicology
- Chemical hazards
- Biological hazards
- - Risk Analysis
- estimating risk, major risks, issues
3Types 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
4Types of Hazards
Identify the (i) Risk, (ii) Hazard and (iii) Risk
Management
5Types of Hazards Risk as a Probability
NYT Jan 29th 1995
NYT Jan 29th 1995
6NOVAHow Risky is Flying?
NOVA Deadliest Plane Crash
7NOVAHow Risky is Flying?
NOVA Deadliest Plane Crash
8Types 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
9Causes 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
11MovieThe 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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13Case 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.
14Toxicology
- 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
15Toxicology
16The dose makes the poisonAny chemical be it
natural or synthetic can be harmful
17Should 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
18Misconception
- 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
19ToxicologyToxicity 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
20Table 171
21ToxicologyResponses
- 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
22ToxicologyDose-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
23DoseResponse Curves
Any dosage is harmful (Assumed in most cases)
Lower limit to harmful dose
24Question
- 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
25Toxicology
- 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
26Toxicology
- Estimating human exposure to chemicals and their
effects is very difficult because of the many and
often poorly understood variables involved.
27Toxicology
- 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
28Toxicology
- 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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30Background
- Birth defects due to exposure to synthetic
chemicals - Toxicity to mammals and birds
- Carcinogenic effects
- Xenoestrogenic effects
- Gt. Lakes cormorant with crossed bill
31EST Article
32Chemical Hazards
Toxic chemicals(kill)
Hazardous chemicals(harm)
33Chemical 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
34Hazardous 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)
35Dioxin IncidentsTimes Beach, Missouri
NYT 121682
36Dioxin 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
37Effects 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.
38Hormone 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
39Hormone Disrupters
Molecules of certain synthetic chemicals have
shapes similar to those of natural hormones and
can adversely affect the endocrine system
40Biomagnification
- 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
41Biomagnification
- 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
42Health EffectsEffects in Utero
- Exposure to low levels results in impaired
intellectual development
NYT, September 12th 1998
43Health 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
NYT July 2nd 2003
44Why 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
45Pollution 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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47Pollution 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
48Environmental 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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50Biological 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)
51Biological Hazards
Infectious disease pathways
52Transmissible Diseases
- WHO estimates that each year the worlds seven
deadliest infections kill 13.6 million people
most of them the poor in developing countries
53Case 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
54Case 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
55Viral 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
56Case 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
57Case 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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59Bioterrorism
- Possible targets air, water, and food
- Inexpensive
- Fairly easy to produce biological agents
- Recombinant DNA techniques
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62Risk Analysis
- Scientists have developed ways to evaluate and
compare risks, decide how much risk is
acceptable, and find affordable ways to reduce
it.
63Risk 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.
65RISK ANALYSIS
- Annual deaths in the U.S. from tobacco use and
other causes in 2003
66RISK 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.
67Perceiving 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
68RISK ANALYSIS
- Comparisons of risks people face expressed in
terms of shorter average life span.
69Becoming 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