Transcript Chp. 4: “Risk Analysis, Environmental Health Hazards, and

Chapter 4
Human Health and
Environmental Hazards
Pesticides & Children
In 2005, 52% of Canadian households used
pesticides regularly on their lawns or
gardens
 Greater threat to children: why?
 Problems from pesticides?
 How are children
exposed?
 Effects on intellectual
development
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A Perspective On Risks
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Human health has
improved
Longer life span
Risk
 Probability of harm
occurring in
certain circumstances
 Part of daily life
Must understand nature and size of risk
Probabilities Of Risk
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Probability of 1 
risk certain to
occur
Probability of 0 
risk certain not to
occur
Risk Assessment
Quantifying risks of an action
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Four steps
1) Hazard identification
2) Dose-response assessment
3) Exposure assessment
4) Risk characterization
 Evaluate results
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Risk Assessment
Choose Your Risk
No choice for some
risks
 What risks do we
worry most about?
 Why do we choose
risky behaviour?
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Environmental Health Hazards
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We are exposed to many chemicals
Toxicology
 Study of toxicants
 Mechanisms of toxicity
 Prevent toxic effects
Acute toxicity
Chronic toxicity
Environmental Health Hazards
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Noninfectious disease
 Not transmitted from one person to
another
 Result of chronic toxicity
Infectious disease
 Transmissible between people
 Contaminated food and water
Polluted Water
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Water is tested for presence of sewage
Pathogen: agent that causes disease
Fecal coliform test
 E. coli
 Filter water
 Let bacteria grow
 Count bacterial colonies
Water And Disease
Environmental Change & Disease
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Epidemiologists
Links between human health and
environmental change
 Deforestation, dams, agriculture
 How do these cause
more disease?
Social factors
Travel
Avian Influenza
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Pandemic
Transferred from birds to humans
High fatality rate
Avian Influenza
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Major concern
 Evolution of a strain easily transferred
to humans
 Could kill millions of people in a single
year
Endemic in domestic wild birds in
 Asia, Africa, and Northern Africa
Toxicants In The Environment
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DDT
 Insecticide
 Persistent: stored in fatty tissues
 Bioaccumulation: builds up in an
organism
 Biological magnification: increases as it
passes up the food chain
Toxicant Mobility
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Who got the biggest dose of DDT?
Banned in Canada in 1970 and in 1972 in
U.S.
Biomagnification
English-Wabigoon River
System
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River system located in northwestern
Ontario
Contaminated by wastewater from pulp
and paper company
9000 kilograms of mercury dumped into
river between 1962 and 1970
Known as one of the most mercurycontaminated freshwater system in the
world
English-Wabigoon River
System
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1970, Ontario government ordered a
stop to mercury dumping
Consider the long term damage
What impacts did this contamination
have for nearby Aboriginal
communities?
Toxicant Mobility
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Chemicals move throughout environment
Toxicant Mobility
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Pollution intensity can no
longer be determined by
contamination levels near
industrial sites
Remote areas of the globe
are feeling the effects of
harmful chemicals
Long range transport of
harmful chemicals may
have an impact on the
entire arctic ecosystem
Persistent Organic Pollutants
12 very toxic
chemicals
 Persistent,
bioaccumulate,
mobile
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Persistent Organic Pollutants
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Stockholm Convention
 Countries must eliminate production
and use of POPs
 Exception to
this?
Determining Health Effects
Of Pollutants
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Dose: amount that enters the body
Response: type & amount of damage
Lethal dose
Sub-lethal dose
Determining Toxicity
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Lethal dose-50 percent
 LD50
 Dose that is lethal to 50% of the
population
 Determined for all new synthetic
chemicals
 Animal testing
Lethal dose-50 percent
Determining Toxicity
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Effective dose-50 percent
 ED50
 Dose that causes 50% of population to
exhibit specific response
 Animal testing
Dose-Response Curve
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Shows effect of different doses
Start with high doses
Work way down to threshold level
 Maximum dose with no measurable
effect
 Below is considered safe
For some toxicants, there is no safe dose
Dose-Response Curve
Cancer-Causing Substances
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Carcinogens
Expose animals to large
doses
 Realistic? Ethical?
 Assumes one can work
backward
 Process filled with
uncertainty
Epidemiological evidence
New methods being
developed
Chemical Mixtures
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Most studies on single chemicals: why?
Three types of chemical interactions
 Additive: add effects of chemicals
 Synergistic: greater combined effect
than expected
 Antagonistic: smaller combined effect
than expected
Usually assume additive
Children & Chemicals
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Children more susceptible: why?
Air pollution
 Lungs still developing
 Higher metabolism  more oxygen
needed
Precautionary Principle
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“An ounce of prevention is worth a pound
of cure”
New technology/chemicals not
introduced until:
 Risks are small
 Benefits outweigh risks
New evidence helps
Precautionary Principle
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Puts burden of proof on developers
Controversy
 Decreases role of science?
 Europe banned North American beef
 Protect
consumer?
 Protect
European
farmers?
Eco Canada Career Focus
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Consider a career
as a ecotoxicologist
Study the causes
and effects of
environmental
toxins that affect
living organisms
Case Study: Endocrine
Disrupters
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PCBs, dioxins, mercury, etc.
Interfere with body’s hormones
Alter reproductive development
Lake Apopka, Florida
 1980 chemical spill
 Alligator eggs have
high mortality rate
Case Study: Endocrine
Disrupters & Humans
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Increasing rates of:
 Reproductive disorders
 Infertility
 Some Cancers
Environment Canada has made EDS
research a top priority
Lack of human studies