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Case Studies
• Environmental health is the branch of public
health that is concerned with all aspects of
the natural and built environment that may affect
human health.
• Environmental Health works make things like this
The Frontline
o Center for Disease Control
• US Agency
o World Health Organization
• International Agency
o Food and Drug Administration
• US Agency
o Environmental Protection Agency
• US Agency
o Arizona Department of Environmental Quality
• State Agency
Transmissible vs.
• Transmissible:
o A pathogen (bacterium, virus, or parasite) invades the body and multiples in its
cells and tisses
o These can be passed from one human to another through various pathways
• Human to human
• Mother to fetus and baby
• Pet to human
• Livestock and wildlife to human
• Mosquitoes, ticks, flies (etc) to human
• Food to human
• Water to human
• Air to huma
• Nontransmissible:
o NOT caused by a living organism and does not spread from one person to
o Diseases tend to develop slowly and have multiple causes
• Heart disease, diabetes, asthma, emphysema, some cancers, and
Case Study: Growing Germ Resistance To
• Rapidly producing infectious bacteria are
becoming genetically resistant to widely used
• Watch the video: A Growing Threat
• Other contributors are:
o Human Global Travel
o Overuse of pesticides
Case Study: Tuberculosis
• Tuberculosis kills 1.7 million people per year and
could kill 25 million MORE people by 2020.
• Why?
• Watch: TB in Russia
• Watch: Fully Resistant TB
Case Study: Toxic Mold
• A living source of indoor air pollution is toxic
airborne spores of molds (fungal growths) and
mildew that can cause:
Allergic reactions
Aggravation of asthma and other respiratory diseases
Could be the single greatest cause of allergic reactions to indoor air
• Watch video: Military Housing
• Watch video: Mold Effect
Case Study: Infectious Disease
• Viral Diseases
o Flu, HIV, and hepatitis B infect and kill many more people each year than
highly publicized West Nile and SARS viruses.
o The biggest potential killer is the influenza or Flu virus
• Could lead to a pandemic killing millions of people in only a few
o 2nd biggest killer is HIV (highest current killer)
• 4.9 million new people infected each year
• 3 million killed annually
o 3rd killer is Hepatitis B
• Damages the liver and kills 1 million every year
• Vaccinations
o Watch Bill Gates Video:
• LD stands for lethal dose
• LD50 is the amount of any material, given all at once,
which causes the death of 50% of a group of test
• LD50 is a means of measuring the short-term poisoning
potential (acute toxicity) of a material.
• Acute toxicity is the ability of a chemical to cause ill
effects relatively soon after one oral administration or a
4-hour exposure to a chemical in air.
• "Relatively soon" is usually defined as a period of minutes,
hours (up to 24) or days (up to about 2 weeks) but rarely
• LD100 would indicate the dose at which the entire
population would die
What is the LD50 of this
• A dose of 500 units
The Dose is Not The Same From One
Species to Another
• LD50s for dichlorvos, an insecticide commonly used
in household pesticide strips, are listed below:
Oral LD50 (rat): 56 mg/kg
Dermal LD50 (rat): 75 mg/kg
Intraperitoneal (injection into the body cavity) LD50: (rat) 15 mg/kg
Inhalation LC50 (rat): 1.7 ppm (15 mg/m3); 4-hour exposure
Oral LD50 (rabbit) 10 mg/kg
Oral LD50 (pigeon:): 23.7 mg/kg
Oral LD50 (rat): 56 mg/kg
Oral (mouse): 61 mg/kg
Oral (dog): 100 mg/kg
Oral (pig): 157 mg/kg
• NOTE: how you are exposed matters too.
Risk Assessment
• Risk = Hazard x Exposure
Risk Assessment
• The process that scientists and government officials
use to estimate the increased risk of health
problems in people who are exposed to different
amounts of toxic substances.
o Hazard Identification
o Probability of risk
• How likely is the event?
o Consequences of risk
• What is the likely damage?
Risk Management Is…
• Comparative risk analysis
o How does it compare with other risks?
• Risk Reduction
o How much should it be reduced?
• Risk Reduction Strategy
o How will the risk be reduced?
• Financial Commitment
o How much money should be spent?
Case Study: DDT
Rachel Carson
o Wrote: Silent Springs
o Exposed the dangers of DDT to wildlife populations (video)
o Began the current “wave of conservation”
o Instrumental in the US ban on DDT
o "A Review of the Twenty Greatest Unfounded Health Scares of Present Times."
• The report lists the ban on DDT as one of these unfounded scares, because - in the opinion of
the American Council on Science and Health - the benefits of DDT's power to kill insects who
may carry diseases that threaten humans outweigh the chemical's effects on wildlife and
humans. In addition, ACSH questions whether DDT effects wildlife and humans adversely at
o Despite the 1972 DDT ban, the effects of the chemical continue to be evident in wildlife
• British Columbia orchards have been sprayed with pesticides for 40 years.
• DDT levels in the eggs of birds in these orchards are remarkably higher than levels reported
20-25 years ago
• which suggests that although DDT is not in use, the residue continues to affect these birds.
• Questions remain: What are the real effects of DDT on the robins? Does it cause acute
poisoning of adult birds, or does it have longer-term reproductive effects on their offspring?
o Died of a heart attack in 1964 while weakened from radiation treatments for breast cancer that
had spread to her liver.
o The EPA was in part founded as a result of her life’s work
Case Study: MTBE
An additive to gasoline used as an oxygenate (reduced CO)
MTBE is often introduced into water-supply aquifers by leaking
underground storage tanks (USTs) at gasoline stations or by gasoline
containing MTBE spilled onto the ground.
The higher water solubility and persistence of MTBE cause it to travel
faster and farther than many other components of gasoline when
released into an aquifer
MTBE gives water an unpleasant taste at very low concentrations, and
thus can render large quantities of groundwater non-potable.
Use in the US is declining in part because of its occurrence in
groundwater and legislation favoring ethanol
MTBE is biodegraded by the action of bacteria
MTBE is not classified as a human carcinogen.
researchers have limited data about the health effects of ingestion of
MTBE. The United States Environmental Protection Agency (EPA) has
concluded that available data are inadequate to quantify health risks of
MTBE at low exposure levels in drinking water, but that the data support
the conclusion that MTBE is a potential human carcinogen at high doses