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Risk. Risk = probability of suffering harm from hazard.EVERYTHING we do involves some risk.Choices:To smoke or notTo use seat belt or notTo cross street or notThat life is risky is not an issueMaking life choices that manage risk is personal/family/social issue.. 17 June 2010. EnvHealth
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1. Environmental Health & Toxicology 17 June 2010 1 EnvHealth&Tox.ppt
2. Risk Risk = probability of suffering harm from hazard.
EVERYTHING we do involves some risk.
Choices:
To smoke or not
To use seat belt or not
To cross street or not
That life is risky is not an issue
Making life choices that manage risk is personal/family/social issue. 17 June 2010 EnvHealth&Tox.ppt 2
3. Risk Measuring risk.
Probability:
0 < P < 1.0
Example:
Lifetime Pcancer from exposure to [chemical] = 0.000001
= 1/ 1,000,000 (small risk)
Then, in population of USA, about 300 cases/75 years due to this cause
17 June 2010 EnvHealth&Tox.ppt 3
4. Risk Risk assessment
Using data, models to quantify risk.
Identifying real or potential hazard
Determining probabilities of harm, severity of risk Please list in order of risk severity:
homicide
automobile accident
obesity
cancer
heart disease
smoking (pack/day)
airplane crash
fire
accident at home 17 June 2010 EnvHealth&Tox.ppt 4
5. Risk Risk assessment
Determining probabilities of harm; severity
Nature of risk
Health risk
Environmental risk
Economic risk
Social impact 17 June 2010 EnvHealth&Tox.ppt 5
6. Hazards Physical
Ionizing radiation,
fire,
weather,
wind, tornado
lightening
noise,
etc.
17 June 2010 EnvHealth&Tox.ppt 6
7. Hazards Chemical
Natural vs. synthetic
Water is dangerous in large quantities!
Organic, inorganic
Pollution
air,
water,
land 17 June 2010 EnvHealth&Tox.ppt 7
8. Hazards Biological
Pathogens, parasites & vectors,
Allergens
pollen, mold spores, poison ivy
Dangerous animals
dogs, cattle, horses,
snakes
wasps, bees
jellyfish, Portuguese man-of-war 17 June 2010 EnvHealth&Tox.ppt 8
9. Hazards Cultural hazards
Working conditions,
diet,
drinking,
driving,
STDs,
poverty,
age (?)
Exposure to physical, chemical, & biological hazards!
17 June 2010 EnvHealth&Tox.ppt 9
10. Chemical Hazards 17 June 2010 EnvHealth&Tox.ppt 10 Toxicology: Science that studies effects of poisonous substances on humans and other organisms
Any chemical can be harmful
“The dose makes the poison.”
Toxicity: measure of how harmful [chemical, toxin] is.
11. Toxicology Whether [chemical] is harmful depends on
Quantity ingested, absorbed (dose)
Frequency of exposure
Who is exposed?
gender, age, personal sensitivity, etc.
Body’s detoxification systems & health
Example: Alcohol
17 June 2010 EnvHealth&Tox.ppt 11
12. Toxicology Effect = response
How much damage done, to what organs?
Time frame:
Acute effect: immediate, short term
Chronic effect: permanent or long-lasting
Symptoms may begin immediately, or delayed onset
Single toxin may have acute & chronic effects
17 June 2010 EnvHealth&Tox.ppt 12
13. Toxicology Other factors:
Solubility
Water soluble
Fat soluble
Persistence: How long it lasts in body or environment.
Excretion = elimination in urine
Natural degradability 17 June 2010 EnvHealth&Tox.ppt 13
14. Toxicology 17 June 2010 EnvHealth&Tox.ppt 14 Other factors:
Bioaccumulation: increased concentration in specific tissues over time.
Biomagnification: increased concentration up a food web.
15. Toxicology Three methods, used together, to assess health threat:
1. Case histories
2. Epidemiology
3. Animal testing
17 June 2010 EnvHealth&Tox.ppt 15
16. Toxicology 1. Case histories
Physicians send information of unusual patient complaints/conditions to [agency] (CDC, EPA, county health departments, etc.)
17 June 2010 EnvHealth&Tox.ppt 16
17. Toxicology 2. Epidemiology
Human population studies attempt to correlate exposure (who, state of health, dose & frequency) to occurrence of effects.
Limited by low numbers of individuals exposed, genetic & experience variability, other exposures, population movements. 17 June 2010 EnvHealth&Tox.ppt 17
18. Toxicology 2. Epidemiology
Framingham (Mass.) heart study.
Severe Acute Respiratory Syndrome (SARS), Fall 2003.
Bird flu (avian influenza virus H5N1)
direct contact with infected poultry
eye infections (conjunctivitis) to severe respiratory disease (pneumonia) to death
spread from person to person rare 17 June 2010 EnvHealth&Tox.ppt 18
19. Toxicology 3. Animal testing
Experiments on lab animals determine
Toxicity & dose-response curve,
Acute or chronic effects,
Residence time in body
Excretion rate,
What tissues & organs affected,
How harm occurs. 17 June 2010 EnvHealth&Tox.ppt 19
20. Toxicology Animal testing
Experiments on lab animals determine
Toxicity,
dose-response curve.
Dose-response curve
Difficult to use (not a simple science)
17 June 2010 EnvHealth&Tox.ppt 20
21. Toxicology Dose-response curve
Difficult to use (not a simple science)
Methodology
Usually, experiments use high doses and few (10's - 100's) of test animals.
Then, extrapolate to lower doses.
17 June 2010 EnvHealth&Tox.ppt 21
22. Toxicology Dose-response curve
“Linear dose-response model“
No threshold
Often assumed in absence of low dose data
Saccharin in rats & bladder cancer
17 June 2010 EnvHealth&Tox.ppt 22
23. Toxicology Dose-response curve
“Threshold dose-response model“
Some minimum dose (threshold) below which there is no effect
body clears substance without harm.
Above threshold dose harm does occur.
17 June 2010 EnvHealth&Tox.ppt 23
24. Toxicology Extrapolation from animal to human
Usually physiology of other mammals is like humans, so rats, mice, dogs, cats, etc. make good surrogates.
But, CATS CAN NOT take Tylenol, Aspirin;
DOGS can not take chocolate.
Then, what can experimental animals tolerate that humans can't ??
17 June 2010 EnvHealth&Tox.ppt 24
25. Toxicology Expense of laboratory studies
Drug approval by Food & Drug Administration (FDA) takes years, $$.
Safety of medicines
Effectiveness of medicines
Studies of environmental chemicals, biological agents also takes time & money.
17 June 2010 EnvHealth&Tox.ppt 25
26. Toxicology 17 June 2010 EnvHealth&Tox.ppt 26