Human Health and
Environmental Risks
Chapter 17
Categories of Human Health
• 3 major categories of risks
a. physical – natural disasters, radon, UV rays
b. biological – “diseases”
c. chemical – exposure to chemicals (arsenic)
Types of Diseases
• Infectious diseases
a. pathogens
b. top 3
1. respiratory infections
2. AIDS
3. diarrhea
c. after the top 3
1. tuberculosis
2. malaria
3. measles and tetanus
d. chronic v. acute
1. chronic
* slowly impairs functioning of body
2. acute
* rapidly impairs body
3. risk factors for chronic
* differ between income levels
Historically Infectious Diseases
• “passed between hosts”
- plague, malaria, tuberculosis
• Epidemic v. pandemic
a. epidemic – rapid increase in disease
b. pandemic – epidemic occurs over large
region
• Plague
a. “bubonic plague, black death”
b. fleas
c. transmitted through flea bites
d. symptoms
- swollen glands, black spots on skin, pain
e. treatment
- antibiotics
• Malaria
a. Plasmodium
b. relies on red blood cells of humans
c. flulike symptoms
d. sub-Sahara Africa, Asia, Middle East, Central
and South America
e. US mosquitos have been eradicated of
malaria parasite (DDT)
• Tuberculosis
a. highly contagious
b. Mycobacterium tuberculosis
c. infects the lungs
d. spread through coughing
e. symptoms
- weakness, night sweats, coughing up blood
f. treatment
- year long antibiotic
Emergent Infectious Diseases
• Arise from pathogens that normally affect
animal hosts, now affecting human hosts
• High-Profile Diseases
a. HIV/AIDS
1. Acquired Immune Deficiency Syndrome
- rare pneumonia weakening immune
systems
2. Human Immunodeficiency Virus
- weakened immune system through virus
3. transmitted through sexual contact and
drug users (sharing of needles)
4. similar virus in chimps of Cameroon
b. Ebola Hemorrhagic Fever
1. caused by the Ebola virus
2. high death rate (50-89%)
- occurs within 2 weeks (acute)
3. natural source is unknown
- kills primate source too quickly
c. Mad Cow Disease
1. neurological disease
2. damaged nervous system
3. 1996 – discovered it can be transmitted
to humans
- exposed to infected cattle
- Creutzfeldt-Jacob Disease
d. West Nile Virus
1. transmitted among bird by mosquitos
2. most survive
3. causes inflammation of the brain
• Future of human health
a. low-income country
- better nutrition
- availability to cleaner drinking water
- proper sanitation
b. high-income countries
- promotion of healthier lifestyle
- limit tobacco use
Toxicology
• Harmful chemicals fall into five categories
a. neurotoxins
1. disrupts nervous system
2. insecticides
3. lead and mercury
- damage to brain, kidneys, and nervous
system
b. carcinogens
1. cancer causing
2. lead to uncontrolled cell growth
- disrupts normal metabolic processes of cell
- damages genetic material of cell (mutagen)
3. asbestos, radon, formaldehyde, tobacco
c. teratogens
1. interfere with normal development of
embryos and fetuses
2. alcohol
d. allergens
1. cause allergic reactions
e. endocrine disruptors
1. interfere with normal functioning of
hormones in the animal’s body
2. hormones released into bloodstream in
low concentrations, they bind to cells,
and allows cell to regulate body function
Assessing Chemical Risks
• Dose-Response Studies
a. animals/plants exposed to various
concentrations of a chemical, and then
animal/plant’s response is observed (mortality,
behavior, reproduction)
b. acute studies
c. results take on a S-shaped
curve (threshold, LD50)
d. Conducted on rats and then results are
extrapolated to humans
e. ED50
1. “effective dose”
2. used for other tests related to other
chemicals such as carcinogens, neurotoxins, etc
3. causes 50% of individuals to show the
harmful but nonlethal effect of dose
• Testing Standards
a. Toxic Substances Control Act of 1976
- gives EPA authority to regulate many
chemicals, excluding food, cosmetics
and pesticides
b. Federal Insecticide, Fungicide, and Rodenticide
Act of 1996
- regulates pesticides
- manufacturer must show that the pesticide
will not cause unreasonable effects on the
environment
c. Determining safe levels
1. take the LD50 and ED50 obtained from the
rats and divide it by 1,000
• Chronic Studies
a. over a period of longer duration
b. examines long term effects of chemicals
such as the effect on survival and impact
on reproduction
• Retrospective v. Prospective Studies
a. retrospective
1. monitors people who have been exposed
at some point in their past
b. prospective
1. monitors people who could possibly be
harmed by chemicals in the future
2. synergistic interactions
• Determination of Concentrations
a. routes of exposure
b. solubility
- biomagnification v. bioaccumulation