Environmental Health and toxicology

1. Environmental
Health &
Toxicology

2.  Focuses on external
factors that cause
disease, including
elements of the natural,
social, cultural, and
technological worlds in
which we live.
 Rachel Carson’s Silent
Spring in 1962 focused
on the discharge,
movement, fate, and
effects of synthetic
chemical toxins.
ENVIRONMENTAL HEALTH

3. PATHOGENIC VS.
NON-PATHOGENIC
• 43% of all disease-
related deaths are
from pathogens
• 57% from
cardiovascular
disease, cancer, lung
disease, injuries, etc.
Pathogenic
Non-
Pathogenic

4. DISEASE ETC.
MILLIONS OF DEATHS PER
YEAR
Cardiovascular disease 9.7
Cancers 6.0
Chronic Lung Disease Ex: tuberculosis 5.5
Acute Lung Disease Ex: pneumonia, flu, pertussis (whooping cough) 4.1
Injuries Mostly in 18-39 age group due to car accidents 4.0
Perinatal conditions Mostly from Infections 3.2
Diarrhea
From bacteria & pathogens; excessive can
cause mental/developmental retardation
3.0
HIV/AIDS
2/3 of all cases are in Africa; most cannot afford
the $10,000 drugs (like people in U.S.)
2.3
Malaria
500 million new cases each year; making a
comeback
2.0
Vaccine-preventable
infections
Polio, Measles, Hepatitis B, Tetanus; LDC have
no access/money for these vaccines
1.7
Other known disease 3.9
Unknown causes 5.9
Total 51.0

5. DISEASE ETC.
MILLIONS OF DEATHS PER
YEAR
Cardiovascular disease 9.7
Cancers 6.0
Chronic Lung Disease Ex: tuberculosis 5.5
Acute Lung Disease Ex: pneumonia, flu, pertussis (whooping cough) 4.1
Injuries Mostly in 18-39 age group due to car accidents 4.0
Perinatal conditions Mostly from Infections 3.2
Diarrhea
From bacteria & pathogens; excessive can
cause mental/developmental retardation
3.0
HIV/AIDS
2/3 of all cases are in Africa; most cannot afford
the $10,000 drugs (like people in U.S.)
2.3
Malaria
500 million new cases each year; making a
comeback
2.0
Vaccine-preventable
infections
Polio, Measles, Hepatitis B, Tetanus; LDC have
no access/money for these vaccines
1.7
Other known disease 3.9
Unknown causes 5.9
Total 51.0

6. Part I: Infectious Diseases
• Onchocerciasis (river
blindness)
– Vector: Black fly
– Many roundworms get
into eyes & die
causing blindness
– Control with
insecticide sprays
– Merck & Co. are
providing free
ivermectin to help
eradicate.

7. Infectious Diseases
• Elephantiasis
– Vector: Mosquitoes
– Roundworm gets into
lymph system and
blocks lymph vessels
causing fluid build up
in the extremities.
– SmithKline Beecham
is supplying free
albendazole to
eradicate.

8. Infectious Diseases
• Drancunculiasis-
– Guinea worm
– Vector: Drinking
Water contaminated
with Cyclops
– 3 meter long worm
that lives under skin.
Forms blister & must
be wound out of skin
to remove

9. Infectious Diseases
• Hemorrhagic Fever
– Some Types…
• Ebola: Vector- unknown
• Lassa: Vector- Mastomys
rat species
• Hanta: Vector- Deer mice
– All cause tissue
deterioration, bleeding,
pulmonary edema.
– Ebola has 90% mortality
rate.

10. Infectious Diseases
• Dengue Fever
– Vector: Mosquitoes
– 20 million new cases;
2.5 billion current
cases

11. Infectious Diseases
• Malaria
– Vector: Mosquitoes
– 3 million die each year,
90% of them in Africa
– In 1950’s & 60’s, sprayed
DDT & knocked down from
millions cases each year to
thousands, now back to 2.5
million new cases
– Some Aedes aegypti
mosquitoes seen along
Gulf Coast of America- due
to climate change?

12. Infectious Diseases
• Cholera
– Cause: Bacteria in unclean
drinking water
– Severe stomach cramping,
severe diarrhea, vomiting
– Thought eradicated but has
made comeback due to
ships dumping bilges in
harbors of cities with
inadequate water treatment

13. Infectious Diseases
• Tuberculosis
– Cause: bacillus bacteria
Mycobacterium tuberculosis
– Eliminated but has
returned stronger than
ever
– Some strains drug
resistant
– Spreads rapidly
– EX: Russian prisons

14. What causes disease to spread so
rapidly?
• Population density , so contact 
• Moving into remote areas for
agriculture  exposure.
• Deforestation, pollution causing
local & global climate change ( in
temp =  in mosquito pop.)
• Eliminating predators so  in
rodent, roach, mosquito pop.
•  in speed & frequency of travel
(airplanes, ships) to other countries
•  in resistance (Malaria) =
“Superbugs”
• Taking medication improperly
leads to “superbugs”
• Antibiotics given to farm animals
increases their resistance.

15. ECOTOXICOLOGY
 Study of toxins (poisons)
and their effects,
particularly on living
systems.
 A broad field, drawing
from biochemistry,
histology, pathology,
pharmacology, and
many other disciplines.
 Toxins are harmful even
in extremely dilute
concentrations. In some
cases billionths, or even
trillionths of a gram can
cause irreversible
damage.

16. Part II:Dangerous Chemicals
Hazardous (dangerous)
• Some are harmless
when diluted
• Classifications:
– Flammable
– Explosive
– Irritant
– Acids
– Caustic
Toxic (poisonous)
• Harmful even in small
amounts
• Ricin- protein in castor
beans is thought to be the
most toxic organic
compound on Earth.
• Ricin is 200x more lethal
than dioxin.

17. Toxic Chemicals
• Allergens
– overactivate immune
system
– Ex: formaldehyde
• Immune System
Depressants
– Suppress immune system
– Ex: PCB’s used as flame
retardants & electrical
insulators (seals & dolphins
died due to infections
brought on by suppressed
immune system)

18. Toxic Chemicals
• Mutagens
– Chemicals or radiation that
damages or alters DNA
– Can cause birth defects or
tumors
– Can be passed through
sperm/egg
– Ex: aflatoxin (from mold);
caffeine, LSD,
benzapyrene (in
cigarettes); nitrous oxide;
ozone

19. Toxic Chemicals
• Teratogens
– Chemicals that cause
abnormalities during embryonic
development
– Ex: Thalidomide
• Sold as OTC sleeping pill in
Europe
• Caused Phocomelia (had
hands & feet but no arms or
legs)
• Can have immediate affect
• Positive: can be used to treat
leprosy, AIDS, cancer, tissue
rejection
– Alcohol is most prevalent
teratogen- Fetal alcohol
syndrome results in low birth
weight, mental delays

20. Toxic Chemicals
• Carcinogens
– Cause cancer
– Increasing in developed countries
– 2nd cause of death in US
– Maybe result of toxic chemicals in
life
• Foods/preservatives
• Pesticides
• smoking
– Breast, Testicular, & Skin cancers
increasing
– Stomach, Uterine, Colon cancers
decreasing due to new technology
for treatment.
– Ex:
• Formaldehyde- particle board
• Paradichlorobenzene- toilet
cleaner
• Perchloroethylene- dry cleaning
• Pesticides- 2,4
dichlorophenoxyacetate
Some foods contain carcinogens
(broccoli) but the other benefits
outweigh the risk.

21. Resistance to drugs, antibiotics, pesticides is increasing.
How microbes
acquire antibiotic
resistance.
(a) Random mutations
make a few cells
resistant. When
challenged by
antibiotics, only those
cells survive to give
rise to a resistant
colony. (b) Sexual
reproduction
(conjugation) or
plasmid transfer move
genes from one strain
or species to another.
The protozoan parasite that causes
malaria is now resistant to most
drugs, while the mosquitoes that
transmit it have developed
resistance to many insecticides.

22. Antibiotic MisuseReasons for antibiotic
resistance to develop:
 Antibiotics do not work
against certain
diseases, e.g. viral
infections.
 Antibiotics are given
when the person could
recover fully without
them.
 Starting and not
finishing a full
prescription.
 Widespread use of
antibiotics in
animal agriculture.

23. Allergens are substances that
activate the immune system.
 Widely used in plastics, wood
products, insulation, glue, and
fabrics concentrations in
indoor air can be much higher
than in normal outdoor air.
 Sick building syndrome:
headaches, allergies, chronic
fatigue, and other symptoms
caused by poorly vented
indoor air contaminated by
mold spores, CO, nitrogen
oxides, formaldehyde, and
other toxins released from
carpets, insulation, plastics,
building materials, and other
sources.

24. Immune System Depressants suppress the
immune system. Dead animals contained high
levels of pesticide residues, polychlorinated
biphenyls (PCBs), and other contaminants
that are suspected of disrupting the immune
system and making it susceptible to a variety
of opportunistic infections.

25.  Endocrine hormone disruptors interfere with
the function of normal chemical messengers
in the body.
 Hormone mimics have similar shapes to
natural hormones and amply their effects.
 Hormone blockers prevent natural hormones
from attaching to their target organ.

26. Endocrine
disruption,
linked to
increased
risk of breast
cancer,
develop-
mental and
reproductive
toxicity;
allergies and
immuno-
toxicity.

27. BPA is known to be a hormone mimic used for plastic
products ranging from water bottles to tooth-
protecting sealants. The chemical can cause
abnormal chromosome numbers which is the leading
cause of miscarriages and several forms of mental
retardation. It also is an environmental estrogen and
may alter sexual development in both males and
females. Bills are considered to ban BPA and certain
phthalates in children’s toys and feeding products.
Use 1, 2, 4, 5 with your food! All the others are NOT good for you.

28. Neurotoxins specifically attack nerve cells
and are both extremely toxic and fast-acting.
 Lead and mercury kill nerve cells and cause
permanent neurological damage.
 Anesthetics (ether, chloroform, halothane,
etc.) and chlorinated hydrocarbons (DDT,
Dieldrin, Aldrin) disrupt nerve cell
membranes necessary for nerve action.
 Organophosphates (Malathion, Parathion)
and carbamates (carbaryl, zeneb, maneb)
inhibit the enzyme that regulates signal
transmission between nerve cells and the
tissues or organs they innervate.

29. These dozen
chemicals may be
responsible for
widespread
behavioral and
cognitive problems,
but the scope of the
chemical dangers in
our environment is
likely even greater!

30. Mutagens are agents, such
as chemicals and radiation,
that damage or alter genetic
material (DNA) in cells.
 This can lead to birth defects if the damage
occurs during embryonic or fetal growth, or
trigger neoplastic (tumor) growth in adults.
 When damage occurs in reproductive cells,
the results can be passed on to future
generations.
 There is no “safe” threshold for exposure to
mutagens. Any exposure has some
possibility of causing damage.

32. Teratogens are
chemicals that
cause birth defects
in an unborn fetus:
ethanol, benzene,
lead, mercury
Mercury can cause sensory impairment, lack
of coordination, and disrupt other nervous
system functions. Lead, another neurotoxin,
was used as an additive in gasoline until 1976.
Following a ban of its use, an 80% drop in
blood lead levels were observed, as well as a
6-point gain in the average IQ of children.

33. OTHER ENVIRONMENTAL HEALTH
HAZARDS
• Radiation- power lines,
nuclear power plants
• Noise
• Trauma- accidents &
violence
• Stress- heart attack, stroke,
ulcers increase chance for
infectious disease
• Diet- too much bad food
causes stress on body, leads
to cardiovascular disease

34. What determines
how “dangerous” a
chemical is?
• Persistence in
environment
• Route/method of
exposure
• Characteristics of target
organism
FACTORS RELATED TO TOXIC AGENT
1. Chemical composition & reactivity
2. Physical traits- solubility, state of matter
3. Presence of impurities
4. Stability and storage traits
5. Availability of vehicle to carry agent
6. Movement of agent thru environment & into cells
FACTORS RELATED TO EXPOSURE
1. Dose- concentration & volume of exposure
2. Route, Rate, and site of exposure
3. Duration and frequency of exposure
4. Time of exposure (time of day, season, year)
FACTORS RELATED TO ORGANISM
1. Resistance to uptake, storage, or cell permeability
2. Ability to metabolize or inactivate agent
3. Tendency to change non-toxic to toxic in body
4. Concurrent infections or physical stress
5. Species and genes of organism
6. Nutritional status of subject
7. Age, sex, body weight, immunological status &
maturity

35. Characteristics in determining how, when,
and where a toxic material will move thru
the environment:
• Solubility
– Dissolve in Water
• Move rapidly & widely
• Readily access cells in body
– Dissolve in Oil
• Need a carrier into & thru body
• Penetrate tissue readily, stored in fat cells of body
• Take many years to break down
– Bioaccumulation- accumulation of toxins within an
individual organism. May be dilute in environment but
reach dangerous levels in the body.

36. • Biomagnification-
accumulation of toxins
thru a food web.
– Chemical intensifies at
each step
– DDT, mercury, are
examples

37. Characteristics in determining how, when,
and where a toxic material will move thru
the environment:
• Persistence- how long does it last
in environment?
– Some unstable & degrade quickly
– Some resistant to degradation
(PVC plastic, DDT, CFC’s,
asbestos)
• This may be why they are used-
asbestos, PVC, DDT
• May be an unfortunate side-
effect
– DDT was valued because it
broke down slowly & did not
have to be reapplied.
– We did not know the affects it
would cause in fish, birds of
prey, and people
(biomagnification).

38. Mechanisms for minimizing toxic effects
• Every material can be poisonous/toxic at some level.
• Most chemicals have safe levels or thresholds below
which their affects are undetectable.
• EX: 100 cups of coffee have enough caffeine to kill if
consumed all at once- but most people don’t
consume that much.
• Taken in small doses, chemicals can be broken down
by the body and released.

39. Measuring Toxicity
• How a material is delivered plays a vital role in
determining toxicity.
– At what rate? (a little over time or all at once)
– Through which route of entry? (skin, mouth, nose)
– In what medium? (solid, liquid, gas)
• Different species respond differently and
different individuals in a species can react
differently.

40. The question is: Should we set pollution levels that will protect
everyone, including the most sensitive people, or only aim to
protect the average person?
A convenient way to describe toxicity of a chemical is to
determine the dose to which 50 % of the test population is
sensitive. In the case of a lethal dose, this is called the LD50.

41. Animal Testing
• Most common & widely accepted
measure of toxicity
• Cons
– Expensive
– Time consuming
– Painful/debilitating
– Takes thousands of animals & lots of
money
• Alternates
– Cell cultures
– Computer simulation
• Some animals of a species are more
sensitive than others so some die off
quicker. Some are hardier than
others so they live longer. This
produces a bell shaped curve
• Should we set safety limits to protect
all including most sensitive or just the
average person?
• By protecting all, it might cost more
money…

42. Substance LD50 (mg/kg)
Table sugar 29,700
Monosodium Glutamate (MSG) 16,600
Vitamin C 11,900
Alcohol (Ethanol) 7,060
Table salt 3,000
Aspirin 200
Caffeine 192
Nicotine 50
Capsaicin (active component of
chili peppers)
47.2
Poison Dart Frog Toxin 0.002
Polonium-210 (Nuclear Waste) 0.000000001

43. Assessing Risk
• What factors influence how we perceive risk?
– People will downplay risk to suit their own agendas
– Some don’t understand probability.
– Personal experiences can be misleading- (Love Canal)
– We have an exaggerated view of our abilities.
– Media is mostly biased
– Fear or distrust of certain technologies (Nuclear Power)

44. Accepting Risk
• How much risk is acceptable?
• Individualized
• If you enjoy doing an activity you will accept those risks.
• If an activity benefits someone else, you may not take those
risks.
• EX:
– Chance of dying from lung cancer if you smoke 1 pack/ day is 1 in
1000.
– EPA limits for trichloroethylene is 2 in 1 billion. People will demand
water with 0 levels of trichloroethylene but still smoke cigarettes.
• See Table 9.7 page 206 for list of activities and death risks.

45. Relative Risks to Human Welfare (from
EPA)
• High Risk Problems
– Habitat alteration & destruction
– Species extinction & loss of diversity
– Stratospheric ozone depletion
– Global climate change
• Medium Risk Problems
– Herbicides/pesticides
– Toxics & pollutants in surface water
– Acid deposition
– Airborne toxics
• Low Risk Problems
– Oil spills
– Groundwater pollution
– Radionuclides (uranium, radon)
– Thermal pollution

46. Examples of labels that have
been required or proposed
as a result of public health
concerns.

47. Environmental Impact of Industries
Industry Air Water Land Human
Petroche
mical
noxious and
toxic
emissions
from refining,
processing
plants
factory
emissions to
water bodies
landfill disposal of
waste solids &
sludge; accidental
spills during
transport &
storage
toxicity and
disruption
of lifestyle
Metal particulate,
gas emissions
during forging,
working,
fabrication
discharge of
pickling
liquors & other
waste
disposal;
heavy metals
slag, waste
products from
processing
toxicity
Mining particulates
from surface
mining &
transportation;
noxious &
toxic fumes
from smelting
runoff from
mines and
waste disposal
dumping of
tailings &
processed
wastes; disruption
of agriculture,
forestry,
recreation
heavy
metals,
particulates

48. Environmental Impact of Industries
Industry Air Water Land Human
Food noxious fumes
from food
processing
sewage with
high organic
content
uncomposted
organics and other
wastes to landfill
toxicity
and
allergens
Agri-
culture
drift of
agricultural
chemicals
(pesticides,
herbicides,
fungicides,
fertilizers),
pollen, & dust
runoff of
agrochemicals
to surface
waters;
percolation to
groundwater;
silting of water
erosion, depletion
of organic material
& organisms
toxicity of
chemical;
loss of soil
Pulp &
Paper
Industry
noxious fumes emissions of
mercury,
chlorines,
organics; silt
from
deforestation;
loss of habitat
destruction of
habitat by clear-
cutting; erosion
mercury
contamina-
ted
seafood

49. “Do you want
to stop
reading those
ingredients
while we’re
trying to
eat?”