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Human Health &
Toxicology
Three Major Categories
• Physical
– Natural disasters
• Biological * Most deaths
– disease
• Chemical
– Natural or synthetic
Infectious Disease
• Caused by pathogens
– Bacteria, virus, fungi, protist, & helminths (parasitic
worms)
• Top three infectious diseases
– Respiratory
– AIDS
– Diarrhea
Infectious Disease Categories
• Chronic
– Disease that slowly impairs function
– Ex. Heart disease, most cancers
• Acute
– Rapidly impairs bodily functions
– Ex. Ebola
Risk Factors (Chronic)
• Low income countries
– Poverty
– Unsafe drinking water
– Poor sanitation
– Malnutrition
• High income countries
– Availability of tobacco
– Less active lifestyle
– Poor nutrition/overeating
Historically Important Infectious
Diseases
Plague
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Cause:Yersinia pestis (bacteria)
Vector: fleas
1300 – ¼ of European population died
Today - antibiotics
Historically Important Infectious
Diseases
Malaria
• Cause: Plasmodium (protist)
• Vector: mosquito
• Hardest hit: Africa, Asia, Middle East, &
Central & South America
• 1951 – eradicated from the US
Historically Important Infectious
Diseases
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Tuberculosis
Cause: Mycobacterium tuberculosis (bacteria)
Affects the lungs
Today – antibiotics
Drug resistant strains
– Hardest hit: Africa & Russia (20% MRTb)
Emergent Infectious Diseases
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HIV/AIDS
Cause: Human immunodeficiency virus
Discovered in the 1980s (coined in 1982)
Jump from chimpanzees to humans
Today – 33 million worldwide (1 million US)
can affect
With meds – 24 yrs Poverty
access to meds
Without meds – 10 yrs
HIV/AIDS Timeline of Events
• 1959 – first case confirmed from male in Congo from preserved
blood samples
• 1980 – first death in US
• 1996 – first meds published to block progression of AIDS
• 1999 – study published to suggestion the retrovirus began in
chimpanzees
• 2007 – first patient cured via bone marrow transplant
(Germany)
– Still HIV free in 2011
• 2013 – first toddler cured by bone marrow transplant but
relapsed
Emergent Infectious Diseases
Mad Cow Disease
• Cause: Prions (proteins that
act as pathogens)
• Vector: transmission requires
an uninfected cow to
consume the nervous system
of an affect cow
• 1980 in Europe – many cow
diets included ground up
remains of cattle for extra
protein
Emergent Infectious Diseases
Ebola
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Cause: Ebola virus
1st seen: Republic of Congo (Ebola River)
Also infected other primates
50-89% death rate
Source: Remains unknown
Harmful Chemical Categories
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Neurotoxins
Carcinogens
Teratogens
Allergens
Endocrine disruptors
Neurotoxins
• Disrupts the nervous
system of animals
• Insecticides
• Lead
– Improved – eliminate lead in
gas and paint
• Mercury
Carcinogens
• Chemicals that cause cancer
– Interfering with metabolic processes
– Damaging DNA
• Examples:
– Asbestos
– Formaldehyde
– Tobacco
Teratogen
• Chemicals that interfere with the normal
development of embryos or fetuses
• Famous teratogen: Thalidomide
– Morning sickness
– Birth defects
• Famous teratogen: Alcohol
– Fetal alcohol syndrome –
• Reduce birth weight
• Damage to brain & nervous system
Allergens
Chemicals that cause an abnormally high immune
response from the immune system
Endocrine Disruptors
• Chemicals that interfere with normal
hormone function in animals
• Hormone binding = response
• Sources: agriculture, birth control (unfiltered
in sewage, pesticides
Toxicology
The study of harmful effects of chemicals on
humans & other organisms
• Toxicity – measure of the harmfulness of a
substance (the ability to cause injury, illness,
or death)
• Basic principle:
Any synthetic of natural chemical can be harmful
if ingested in a large enough quantity
Exposure
• Key factors:
– Dose - the amount of a harmful chemical that a
person has ingested, inhaled, or absorbed
– Response – resulting damage to health
• Variables:
– Age
– Genetics
– Functionality of detox systems (liver, kidney, etc.)
– Solubility
– Persistence
Response
Health damage
• Acute – immediate or rapid
– Dizziness, nausea, or death
• Chronic
– Liver damage
Dose Response Curve
• Median Lethal Dose
– LD50
– The dose that can
kill 50% of the
population within a
18 day period