Transcript Toxicology 1

For most of human history, the greatest
health threats have been pathogenic organisms,
accidents, and violence.
Disability-Adjusted Life Year (DALY)
combines premature deaths and loss of
healthy life resulting from illness or
disability. (1.4 billion a year)
90% of DALY occur in developing countries
WHO reports 50% due to communicable disease
Infectious diseases are still responsible for
about 24% of all disease-related deaths.

Majority of these deaths in poorer
countries with poor nutrition, sanitation,
and vaccination programs.
AIDS now largest single cause of
communicable death in the world.

EMERGENT DISEASE – Never known before or has
been absent for 20 years or more
Spreads Rapidly – modern travel means
Example – FOOT & MOUTH DISEASE
Risk Assessment & Management
Risk = probability of exposure x probability of harm
Risk Assessment
Risk Management
1) ID potential hazard
1) How Serious?
2) Probability of occurrence
2) Can it be reduced?
3) Determine how much damage
3) How can it be reduced?
(social; env; economic)
4) $$ to clean it up?
Controversy over assessments – WHY?
Disputes over variables such as - #
exposed, level of exposure, and impact
due to age/health/sex of organism
After Assessment
4 Main Types of Hazards
Cultural
smoking (case study), unsafe working
conditions, diet, drinking, driving, poverty!
synthetic chemicals from water & air pollution –
Chemical
human body contains over 500 syn.chemicals
not known prior to 1920
Physical
ionizing radiation, earthquakes, volcanoes,
hurricane, tornadoes
pathogens (bacteria, viruses, parasites), pollen
Biological
and other allergens; animals (bees, snakes)
Biological Hazards
Epidemiology – the study of factors affecting the health and illness of a population
Non-Transmittable Disease – not caused
by living organisms and does not spread
from person to person
Cardiovascular disease, obesity,
diabetes, most cancers, bronchitis
Transmissible Disease – caused by living
organisms (bacteria, protozoa, and
parasites) and viruses
Dose Response Curve
Pathogens (disease causing organisms)
spread through water, air, food,
insects, & body fluids - VECTORS
TRANSMISSIBLE DISEASE
According to the WHO & UNICEF 2 million children in developing
countries die each year due to preventable infectious disease.
80% of the infectious disease is spread through waterborne
infections (diarrhea, hepatitis, typhoid fever, and cholera)
Seven Deadliest Infectious Disease:
1)
Tuberculosis (TB) bacterial disease
2) Malaria – protozoa
3) Respiratory Disease – mostly pneumonia (bacteria and
viruses)
4) Diarrheal Disease – bacterial & viruses (unclean water)
5) Measles – viral
6) Hepatitis – viral
7) HIV/AIDS – Viral
CHEMICAL Hazards
Immune Systems – protects the body against disease
Disruptors – viruses, bacteria, parasites, malnutrition,
ionizing radiation, synthetic chemicals
Nervous System – brain; spinal cord; peripheral nerves
Neurotoxins – synthetic chemicals = chlorinated hydrocarbons
(DDT, PCBs, dioxins); organophosphates (malathion);
formaldehyde; heavy metals (mercury, lead, cadmium)
Endocrine – glands and hormones that regulate body functions
Disruptors – (HAA’s – hormonally active agents) = can mimic or
block natural hormone responses – many synthetic chemicals such as
atrazine, DDT, PCB’s
Endocrine disruptors have major impacts on reproductive systems
Toxicity – measure of how harmful a substance is.
Dosage – the amount inhaled,
absorbed, or ingested
Factors affecting Toxicity
1) Size of the dose over
time
2) How often exposure
occurs
3) Who is exposed
4) How well the body’s
detox system works
5) Genetic make-up of
organism
Many chemicals are used because of their long persistence or
resistance to breakdown: plastics, CFC’s, Chlorinated
Hydrocarbons (DDT)
This also means they have a lasting
impact on the environment
Bioaccumulation –
chemicals are stored in
specific organs or tissues at
levels higher than normal
Biomagnification – levels of
toxins in the environment
are magnified as they pass
through food chains
EXAMPLES: DDT (synthetic organic pesticide),
PCB’s (oils used in electrical equipment);
Mercury (heavy metal)
DANGEROUS CHEMICALS
Dangerous chemicals are divided into two broad
categories:
•
Hazardous - Dangerous

-
Flammable, explosive, irritant, acid, caustic.
Toxic -Harmful

Can be general or very specific. Often
harmful even in dilute concentrations.
-
Poison – has an LD50 of 50 mg or LESS
Allergens - Substances that activate the immune
system.
•
Antigens - Allergens that are recognized as
foreign by white blood cells and stimulate the
production of specific antibodies.

Neurotoxins - Special class of metabolic poisons that
specifically attack nerve cells.
•
-
Heavy Metals kill nerve cells.
Insecticides
Chlorinated Hydrocarbons disrupt nerve cell
membranes. (DDT, PCBs, dioxins)
-
Organophosphates inhibit signal transmission
between nerve cells. (malathion)
-
Mutagens - Agents that damage or alter genetic
material.
•
Radiation (x-ray equipment)

Teratogens - Specifically cause abnormalities
during embryonic growth and development.
•
Alcohol - Fetal Alcohol Syndrome

PCB’s, steroids, lead & mercury

Carcinogens - Substances that cause cancer.
•
Cigarette smoke, dioxins, radon gas,
asbestos

ANTIBIOTICS
100 million
Antibiotic doses
prescribed each
year in the US –
many unnecessary
RESISTANCE
Many protozoans and
insects are now
immune to most
antibiotics & pesticides
(rapid evolution)
More than ½ of the
antibiotics
manufactured in
the US are fed to
farm animals to
stimulate weight
gain
Humans overuse
and therefore add
pressure to adapt
and change.
RATE OF MOVEMENT & DISTRIBUTION
Solubility - One of most important
characteristics in determining the movement of a
toxin.
•
Chemicals are divided into two major groups:
•
Those that dissolve more readily in
water.
-
-
Those that dissolve more readily in oil.
Water soluble compounds move rapidly
through the environment, and have ready
access to most human cells.

Animal Testing
•
Most commonly used and widely
accepted toxicity test is to expose a
population of laboratory animals to
measured doses of specific toxins.

Sensitivity differences pose a
problem.
-

Dose Response Curves
LD50 - Dose at which 50% of the
test population is sensitive.

LD50 = median lethal dose: the amount of a chemical received in
one dose that kills exactly 50% of the organisms in a population
(typically in a 2 week period of time)
Animal Testing
Takes 2-5 years – costs
between 200,000 – 2 mil
Threshold = dosage amount
at which no negative effects
are seen
What
Where
example
Infectious
Agents
Environmentally transmitted contaminated food, water,
infectious disease
soil, air
Giardia - protist (water)
Salmonella - bacteria (food)
Toxic Heavy
Metals
heavy metals that pose
by-products of mining,
hazards to health conditions refinging
mercury, lead, nickel
often neuro-toxins
carbon baseded -synthetic
Organic Comp. organic material
decay of radioactive
isotopes measured in
Radiation
sieverts (unit)
Thermal
unwanted heat increase
from norm.
Particulates
small particles of dust
released into atmosphere
Asbestos
small, elongated mineral
fragments
pest control, fertilizers, food
additives
ACS reports over 4 million
known substances
radon exposure, nuclear
nuclear energy, naturally
accidents, x-rays, atomic
occuring decay (radon)
fallout
Temp range for life
natural events,power plants & Temp affects DO levels in
steam generators
aquatic environments
natural - volcanos, fires
un-natural - burning (coal)
Respiratory problems
farming practices
Normally synergistic effects
industrial use - building
materials, insulation in
repiratory disease, cancer
houses, pipes, cars, flooring causing (tumors)