Environmental Health and Toxicology

1
Environmental Health and Toxicology
2
Outline

• Environmental Health
• Infectious and Emergent Diseases
• Antibiotics and Pesticide Resistance
• Toxicology
• Movement, Distribution, and Fate of Toxins
• Minimizing Toxic Effects
• Measuring Toxicity
• Risk Assessment
• Establishing Public Policy

3
ENVIRONMENTAL HEALTH

• 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).

4
Environmental Health Risks
5
Global Disease Burden

• WHO reports communicable diseases are responsible
  for nearly half of all 1.4 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.
• By 2020, heart disease may become leading source
  of disability and disease worldwide.

6
Recent Outbreaks of Infectious Diseases
7
Infectious Diseases

• For most of human history, the greatest health
  threats have been pathogenic organisms,
  accidents or violence.
• Communicable diseases are still responsible for
  about 1.3 of all disease-related deaths.
• Majority in countries with poor nutrition,
  sanitation, and vaccination programs.
• Malaria is a major disease in tropical areas.

8
Emergent 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 the speed and frequency of modern
  travel.
• SARS
• West Nile Virus

9
Funding Health Care

• Heaviest burden of illness borne by poorest
  people who cannot afford a healthy environment or
  adequate health care.
• WHO estimates 90 of all disease burden occurs in
  developing countries where less than 10 of all
  health care dollars are spent.
• Worldwide, only 2 of people with AIDS have
  access to modern medicines.

10
Ecological Diseases

• Domestic animals and wildlife also experience
  sudden and widespread epidemics.
• Distemper in seals in western Europe.
• Chronic Wasting Disease in deer and elk in North
  America.
• Sudden Oak Death Syndrome in California.

11
Antibiotic and Pesticide Resistance

• Protozoan parasite that causes malaria is now
  resistant to most antibiotics, 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.

12
Antibiotic 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.

13
Antibiotic Resistance
14
Toxicology

• Dangerous chemicals are divided into two broad
  categories
• Toxic - Poisonous
• Can be general or very specific. Often harmful
  even in dilute concentrations.
• Hazardous - Dangerous
• Flammable, explosive, irritant, acid, caustic.

15
Toxic 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.
• Sick Building Syndrome

16
Toxic Chemicals

• Endocrine Disrupters disrupt normal hormone
  functions.
• Thyroxine
• Insulin
• Adrenalin
• Endorphins

17
Steroid Hormone Action
18
Toxic Chemicals

• Neurotoxins - 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.

19
Toxic Chemicals

• Mutagens - Agents that damage or alter genetic
  material.
• Radiation
• Teratogens - Specifically cause abnormalities
  during embryonic growth and development.
• Alcohol - Fetal Alcohol Syndrome
• Carcinogens - Substances that cause cancer.
• Cigarette smoke

20
Diet

• Sixty-percent of all U.S. adults are now
  considered overweight.
• Estimated 1 billion worldwide.
• U.S. Centers for Disease Control warn one in
  three U.S. children are at risk of becoming
  diabetic.

21
MOVEMENT, DISTRIBUTION, AND FATE OF TOXINS

• 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.

22
(No Transcript)
23
Exposure and Susceptibility

• Airborne toxins generally cause more ill health
  than any other exposure.
• Lining of lungs easily absorbs toxins.
• Largest toxin exposure reported in industrial
  settings.
• Condition of organism and timing of exposure also
  have strong influences on toxicity.

24
Exposure Routes
25
Bioaccumulation and Biomagnification

• Cells have special mechanisms for Bioaccumulation
  - Selective absorption and storage.
• 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.

26
Bioaccumulation and Biomagnification
27
Persistence

• 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)

28
Persistence

• Persistent Organic Pollutants (POPs)
• Polybrominated diphenyl ethers (PDBE)
• Perfluorooctane sulfonate (PFOS) and
  Perfluorooctanic acid (PFOA).
• Phthalates
• Bisphenol A (BPA)
• Atrazine

29
Chemical 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 exacerbates
  the effect of the other.

30
MECHANISMS 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.

31
Excretion and Repair

• Effects of waste products and environmental
  toxins reduced by eliminating via excretion.
• Breathing
• Kidneys
• Urine
• Tissues and organs often have mechanisms for
  damage repair.
• Any irritating agent can be potentially
  carcinogenic.

32
MEASURING 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.

33
Toxicity Ratings

• Moderate toxin takes about (1) g/kg of body
  weight to produce a lethal dose.
• Very toxic materials require about 10 of that
  amount.
• Extremely toxic materials require 1 of that
  amount.
• Supertoxic chemicals can be lethal in a dose of a
  few micrograms.

34
Toxicity Ratings

• Many carcinogens, mutagens, and teratogens are
  dangerous at levels far below their direct toxic
  effect because abnormal cell growth exerts a form
  of biological amplification.

35
Acute versus Chronic Doses and 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.

36
RISK ASSESSMENT AND ACCEPTANCE

• Risk - Possibility of suffering harm or loss.
• Risk Assessment - Scientific process of
  estimating the threat that particular hazards
  pose to human health.
• Risk Identification
• Dose Response Assessment
• Exposure Appraisal
• Risk Characterization

37
(No Transcript)
38
Understanding Risks

• 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.

39
Accepting 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 / 1 million is acceptable
  risk for environmental hazards.

40
ESTABLISHING PUBLIC POLICY

• It is difficult to separate the effects of
  multiple hazards and evaluate their risks
  accurately, especially when exposures are near
  the threshold of measurement and response.
• May not be reasonable to mandate protection, no
  matter how small the risk, from every
  potentially harmful contaminant in our
  environment.

41
Summary

• Environmental Health
• Infectious and Emergent Diseases
• Antibiotics and Pesticide Resistance
• Toxicology
• Movement, Distribution, and Fate of Toxins
• Minimizing Toxic Effects
• Measuring Toxicity
• Risk Assessment
• Establishing Public Policy

42
(No Transcript)