Health &
Environmental Risks
Human Health Hazards
1. Physical – includes environmental
factors such as natural disasters and
exposure to UV radiation
2. Biological – includes exposure to
pathogenic organisms
bacteria that cause cholera
Nontransmissible disease  does not
spread from one organism to another
ex. Cancer, Diabetes
Transmissible disease  Caused by
pathogens and can easily spread from one
organism to another using
vectors/carriers
AKA Infectious
disease
Notable infectious diseases
* Plague 
caused by a
bacterium that is
carried by fleas
* Malaria 
caused by
members of the
protozoan genus
called
Plasmodium. The
Anopheles
mosquito is the
vector.
RBCs infected
with Plasmodium
* Tuberculosis (TB)
 caused by a
bacterium that
primarily infects
the lungs and is
highly contagious
* HIV/AIDS 
viral disease that
emerged in the late
1970s
* H5N1 viral disease
that emerged in 2006,
the carriers are birds.
Closely related to H1N1
(bird flu), but much
more deadly.
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
3. Chemical – includes exposure to
naturally occurring and synthetic
chemicals
Toxins …
chemicals that cause harm
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
* Teratogens – chemicals that cause birth
defects
ex. alcohol, thalidomide (no longer available)
* Allergens – chemicals that cause allergic
reactions
ex. chemicals in peanuts, milk, penicillin
* 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
Response of body to toxin can be….
Acute - immediate reaction
OR
Chronic - long term effects
Toxicology …
study of chemical risks
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
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.
How do scientists determine the
toxicity of a chemical?
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
Dose measurements and their equivalents
Dose
Metric
Approx amount
of water
ppm
mg/kg
1 tsp per 1000
gal
g/kg
1 tsp per
1,000,000 gal
ppb
graph typically
produced by data at
the end of a dose
response study
The graph can be used to determine . . .
* Threshold level – maximum point at which
toxin does little or no harm
* LD50 – Lethal Dose at which the toxin kills
50% of the organisms
Threshold
level:
LD50:
Poisons are toxins that have an LD50 of
50 mg/kg or less. Would the toxin
represented above be a poison?
Toxicity
LD50
Lethal Dose
Examples
< 0.01
less than 1 drop
dioxin, botulism
mushrooms
<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.
>15K
>1qt.
Super
Extreme
Non-Toxic
ethyl alcohol, soaps
water, table sugar
(LD50 measured in mg/kg of body weight)
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.
2. Epidemiology
Study 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
(past)
ex. Bhopal disaster
or
Prospective
(future)
ex. track a target
population & their habits
Environmental Hazards
Anything in the environment that can
cause harm.
pollutants, human
activities, natural
catastrophes, etc
When policy makers, regulatory
agencies, and environmental
scientists assess the risk of a
environmental hazard, they
follow a three step process
known as…
Risk Analysis
1. Risk assessment
includes identifying the hazard,
determining it’s toxicity and the extent
of exposure
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.
3. Risk management
Determine policy with input from private
citizens, industry, and interest groups
TSCA – Toxic
Substance Control Act
FIFRA
Regulated by the EPA