Title: Environmental Health and Toxicology
1Environmental Health and Toxicology
2Outline
- Environmental Health Hazards
- Infectious Organisms
- Emergent Diseases
- Antibiotics and Pesticide Resistance
- Toxic Chemicals
- Distribution and Fate of Toxins
- Minimizing Toxic Effects
- Measuring Toxicity
- Risk Assessment
- Public Policy
3ENVIRONMENTAL HEALTH HAZARDS
- Health - A state of complete physical, mental,
and social well-being. - Disease - A deleterious change in the bodys
condition in response to an environmental factor. - Diet and nutrition, infectious agents, toxic
chemicals, physical factors, and psychological
stress all play roles in morbidity (illness) and
mortality (death).
4Infectious Organisms
- For most of human history, the greatest health
threats have been pathogenic organisms. - Infectious diseases are still responsible for
about 33 of all disease-related deaths. - Majority of deaths in poorer countries with poor
nutrition, sanitation, and vaccination programs.
5Morbidity and Quality of Life
- Death rates do not tell everything about burden
of disease. - Total economic and social consequences of
diseases are difficult to obtain. - Disability-Adjusted Life Year (DALY) combines
premature deaths and loss of healthy life
resulting from illness or disability.
6Table 8.1
7Disability-Adjusted Life Year
- WHO reports communicable diseases are responsible
for nearly half of all 1.2 billion DALYs lost
each year. - About 90 of all DALY losses occur in developing
world where one-tenth of all health care dollars
are spent. - Malnutrition exacerbates many diseases.
8Emergent Diseases
- An emergent disease is one never known before, or
has been absent for at least 20 years. - An important factor in the spread of many
diseases is speed and frequency of modern travel. - Foot and Mouth Disease
- Ebola
9Emerging Ecological Diseases
- Domestic animals and wildlife also experience
sudden and widespread epidemics. - Distemper (Seals)
- Chronic Wasting Disease (Deer and Elk)
- Transmissible Spongiform Encephalopathies
- Black Band Disease (Coral)
10Infectious Disease Outbreaks
11Medication and Pesticide Resistance
- Protozoan parasite that causes malaria is now
resistant to most medications, while the
mosquitoes that transmit it have developed
resistance to many insecticides. - Short life spans.
- Speeds up natural selection and evolution.
- Human tendency to overuse pesticides and
antibiotics.
12Antibiotic and Pesticide Resistance
13Antibiotic Use
- At least half of the 100 million antibiotic doses
prescribed in the US every year are unnecessary
or are the wrong drug. - Many people do not finish full-course.
- More than half of all antibiotics manufactured in
the US are routinely fed to farm animals to
stimulate weight gain.
14Toxic Chemicals
- Dangerous chemicals are divided into two broad
categories - Hazardous - Dangerous
- Flammable, explosive, irritant, sensitizer, acid,
caustic. - Toxic - Poisonous
- Can be general or very specific. Often harmful
even in dilute concentrations.
15Toxic Chemicals
- 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. - Other allergens act indirectly by binding to
other materials so they become antigenic.
16Toxic Chemicals
- Sick Building Syndrome
- Headaches, allergies, and chronic fatigue caused
by poorly ventilated indoor air contaminated by
molds, carbon monoxide, nitrogen oxides, and
other toxic chemicals. - Worker absenteeism and reduced productivity.
- EPA estimates 60 billion annual loss.
17Toxic Chemicals
- Neurotoxins - Special class of metabolic poisons
that specifically attack nerve cells. - Different types act in different ways.
- Heavy Metals kill nerve cells.
- Anesthetics and Chlorinated Hydrocarbons disrupt
nerve cell membranes. - Organophosphates and Carbamates inhibit signal
transmission between nerve cells.
18Table 8.5
19Table 8.3
20Toxic Chemicals
- Mutagens - Agents that damage or alter genetic
material. - Radiation
- Teratogens - Specifically cause abnormalities
during embryonic growth and development. - Alcohol - Fetal Alcohol Syndrome
- Thalidomide Appendages did not form
- Carcinogens - Substances that cause cancer.
- Cigarette smoke
21Table 8.4
22US Age-Adjusted Cancer Death Rates
23Endocrine Hormone Disrupters
- Chemicals that disrupt normal endocrine hormone
functions. - Hormones are chemicals released in blood by
glands to regulate development and function of
tissues and organs elsewhere in the body. - Environmental Estrogens and Androgens
- - Amphibians and Reptiles
24Diet
- Strong correlation between cardiovascular disease
and the amount of salt and animal fat in an
individuals diet. - Highly-processed foods, fat, and smoke-cured,
high nitrate meats appear to be associated with
cancer. - Nearly 2/3 of all Americans are considered
overweight.
25DISTRIBUTION AND FATE OF TOXINS
- Solubility - Chemicals are divided into two major
groups - Dissolve more readily in water.
- Dissolve more readily in oil.
- Water-soluble compounds move rapidly through the
environment, and have ready access to most human
cells. - Oil-soluble molecules generally need a carrier to
move through the environment.
26Bioaccumulation and Biomagnification
- Cells have special mechanisms for Bioaccumulation
- Selective absorption and storage. Lipid Soluble
- Dilute toxins in the environment can build to
dangerous levels inside cells and tissues. - Biomagnification - Toxic burden of a large number
of organisms at a lower trophic level is
accumulated and concentrated by a predator at a
higher trophic level.
27Sensitivity and Developmental Stage
- Many factors help determine reaction of an
individual to a given dose. - Age
- Sex
- Body Weight
- Nutritional / Immunological Status
- Repair Mechanisms
28Persistence
- Some chemical compounds are very unstable and
degrade rapidly under most conditions, thus their
concentrations decline quickly after release. - Others are more persistent.
- Stability can cause problems as toxic effects may
be stored for long period of time and spread to
unintended victims. - (DDT)
- - Chlorinated, Fluorinated Hydrocarbons
29Bioaccumulation
30Chemical Interactions
- Antagonistic Reaction - One material interferes
with the effects, or stimulates the breakdown, of
other chemicals. - Additive Reaction - Effects of each chemical are
added to one another. - Synergistic Reaction - One substance multiplies
the effect of the other.
31MECHANISMS FOR MINIMIZING TOXIC EFFECTS
- Every material can be poisonous under certain
conditions. - Most chemicals have a safe threshold under which
their effects are insignificant. - Metabolic Degradation
- In mammals, the liver is the primary site of
detoxification of both natural and introduced
poisons.
32Excretion
- Effects of waste products and environmental
toxins reduced by eliminating via excretion. - Breathing
- Kidneys
- Skin
33MEASURING TOXICITY
- 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.
34LD50
35Population Sensitivity Variations
36Acute vs. Chronic Effects
- Acute Effects - Caused by a single exposure and
result in an immediate health problem. - Chronic Effects - Long-lasting. Can be result of
single large dose or repeated smaller doses. - Very difficult to assess specific health effects
due to other factors.
37RISK ASSESSMENT
- Factors influencing risk perception
- Rating risks based on agendas.
- Most people have trouble with statistics.
- Personal experiences can be misleading.
- We have an exaggerated view of our abilities to
control our fate. - News media sensationalizes rare events.
- Irrational fears lead to overestimation of
certain dangers. - Fear of the unknown.
38Table 8.6
39Accepting Risks
- Most people will tolerate a higher probability of
occurrence of an event if the harm caused by that
event is low. - Harm of greater severity is acceptable only at
low levels of frequency. - EPA generally assumes 1 in 1 million is
acceptable risk for environmental hazards.
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41RELATIVE RISKS TO HUMAN WELFARE
42ESTABLISHING PUBLIC POLICY
- Biggest problem in making regulatory decisions is
that we are usually exposed to many sources of
harm, often unwillingly. - May not be reasonable to demand protection from
every potentially harmful contaminant in our
environment, no matter how small the risk.
43ESTABLISHING PUBLIC POLICYENVIRONMENTAL
PROTECTION AGENCY
- In setting standards for environmental toxins,
need to consider - Combined effects of different exposures.
- Individual sensitivities within population.
- Effects of chronic and acute exposures.
44Summary
- Environmental Health Hazards
- Infectious Organisms
- Emergent Diseases
- Antibiotics and Pesticide Resistance
- Toxic Chemicals
- Distribution and Fate of Toxins
- Minimizing Toxic Effects
- Measuring Toxicity
- Risk Assessment
- Public Policy
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