health & environmental risks. human health hazards 1. physical – includes environmental...
TRANSCRIPT
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Health & Environmental Risks
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Human Health Hazards1. Physical – includes environmental factors such as natural disasters and exposure to UV radiation
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2. Biological – includes exposure to pathogenic organisms
bacteria that cause cholera
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Nontransmissible disease does not spread from one organism to another
ex. Cancer, Diabetes
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Transmissible disease Caused by pathogens and can easily spread from one organism to another using vectors/carriers
AKA Infectious disease
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Notable infectious diseases
* Plague caused by a bacterium that is carried by fleas
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RBCs infected with Plasmodium* Malaria
caused by members of the protozoan genus called Plasmodium. The Anopheles mosquito is the vector.
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* Tuberculosis (TB) caused by a bacterium that primarily infects the lungs and is highly contagious
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* HIV/AIDS viral disease that emerged in the late 1970s
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* H5N1 viral disease that emerged in 2006, the carriers are birds. Closely related to H1N1 (bird flu), but much more deadly.
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Factors that affect the spread of diseases
Travel, migration, deforestation, climate change, loss of biodiversity, agriculture, urbanization, & nature
disasters
It sure is nice to get away from the colon for awhile
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3. Chemical – includes exposure to naturally occurring and synthetic chemicals
Toxins … chemicals that cause harm
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5 main categories of TOXINS* Neurotoxins – disrupt the nervous system by attacking neurons or interfering with communication between neurons ex. DDT, PCB, dioxins, arsenic, organophosphate pesticides, etc* Carcinogens – cause cancer, uncontrolled mitosis (cell growth) ex. Asbestos, radon, formaldehyde, etc
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* Teratogens – chemicals that cause birth defects
ex. alcohol, thalidomide (no longer available)
* Allergens – chemicals that cause allergic reactions
ex. chemicals in peanuts, milk, penicillin
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* Endocrine Disrupters – chemicals that interfere with the normal functioning of hormones in an animal’s body.
aka Hormonally Active Agents (HAA) ex. atrazine and other pesticides
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Response of body to toxin can be….
Acute - immediate reaction
OR
Chronic - long term effects
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Toxicology … study of chemical risks
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Toxicity measure of the harmfulness of a chemical
(dependent on toxin and the organism affected)
Toxin Organism
Dose Age
Solubility (water or fat)
How frequently exposure occurred
Persistence Genetic makeup
Interactions with other chemicals in the organism
Health of detoxification
systems
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Solubility of a toxin affects how readily it bioaccumulates in an organism and biomagnifies in an ecosystem.
Persistence determines how long the toxin remains in the environment.
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How do scientists determine the toxicity of a chemical?
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1. Dose-Response Studies (bioassays)Expose plants or animals(rats) to
different amts of a chemical and observe responses
The amount of the chemical is measured by…concentration (amount in air, water or food)
or by dose (amount absorbed or consumed by the organism)
Usually measure mortality as response
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Dose measurements and their equivalents
Dose Metric Approx
amount of water
ppm mg/kg1 tsp per 1000
gal
ppb g/kg1 tsp per
1,000,000 gal
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graph typically produced by data
at the end of a dose response
study
* Threshold level – maximum point at which toxin does little or no harm
The graph can be used to determine . . .
* LD50 – Lethal Dose at which the toxin kills 50% of the organisms
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Threshold level:
LD50:
Poisons are toxins that have an LD50 of 50 mg/kg or less. Would the toxin
represented above be a poison?
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Toxicity LD50 Lethal Dose Examples
Super < 0.01 less than 1 drop dioxin, botulismmushrooms
Extreme <5 less than 7 drops heroin, nicotine
Very 5-50 7 drops to 1 tsp. morphine, codeine
Toxic 50-500 1 tsp. DDT, H2SO4, Caffeine
Moderate 500-5K 1 oz.-1 pt. aspirin, wood alcohol
Slightly 5K-15K 1 pt. ethyl alcohol, soaps
Non-Toxic >15K >1qt. water, table sugar
(LD50 measured in mg/kg of body weight)
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At times toxicologists do not measure mortality but measure how a chemical may alter behavior. These are sublethal effects.
* ED50 – Effective Dose at which the toxin causes 50% of the organisms to display harmful but not lethal effects.
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2. EpidemiologyStudy of large populations of organisms exposed to chemicals in their everyday life and determines whether these exposures are related to any health problems.
CAN BE
Retrospective or Prospective (past) (future) ex. Bhopal disaster ex. track a target population & their habits
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Environmental HazardsAnything in the environment that can cause harm.
pollutants, human activities, natural catastrophes, etc
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When policy makers, regulatory agencies, and environmental scientists assess the risk of a environmental hazard, they follow a three step process known as…
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1. Risk assessment
includes identifying the hazard, determining it’s toxicity and the extent of exposure
Risk Analysis
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2. Risk acceptance
what is acceptable when balanced against social, economic and political considerations
According to the EPA, a 1 in 1 million risk is acceptable for most environmental hazards.
The EPA takes the LD50 & divides it by 10 for most animals to determine the safe
concentration. Then divided by 10 again for humans.
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3. Risk management
Determine policy with input from private citizens, industry, and interest groups
TSCA – Toxic Substance Control
Act
FIFRA
Regulated by the EPA