Chapter 8: Environmental Health and Toxicology

1
Chapter 8 Environmental Health and Toxicology
By Anna Blum and Maggie Ellis
2
Environmental Health

• Environmental Health-focused on factors that
  cause disease, including elements of the natural,
  social, cultural, and technological world in
  which we live
• Ever since Silent Spring, focus on discharge,
  movement, fate, and effects of synthetic chemical
  toxins
• Risks come from
• Toxins
• Radiation
• Infectious Agents
• Trauma
• Pollution

3
The Global Disease Burden is Changing

• Disease burden calculated in terms of DALYs
• Chronic conditions now affect poor as well as
  affluent because people live longer
• Causes By 2020
• Heart disease to be leading cause of global
  disease
• Global cancer rates will increase by 50
• Psychiatric and neurological conditions will
  increase from 10 to 15 (Depression expected to
  be the second largest cause of all years lived
  with disability worldwide)
• Chronic obstructive lung diseases expected to
  increase

4
Things That Kill You (part 1)

• Heart disease number one killer, kills women more
  than men
• Suicide is the fourth largest cause of female
  deaths
• Smoking predicted to be single biggest cause of
  death worldwide

5
Infectious Diseases Are Scary

• Communicable diseases responsible for about 1/3
  of all disease-related mortality
• 11 million children under 5 die annually due to
  infectious diseases
• Most of these deaths could be eliminated through
  better nutrition, clean water, improved
  sanitation, and inexpensive inoculations

6
More Infectious Diseases

• Malaria- 515 million cases each year, 1 million
  people die
• Spreading as climate changes expands mosquito
  habitats
• Emergent diseases-those not previously known or
  have been absent for at least 20 years
• SARS
• Avian Flu
• H1N1
• Ebola
• West Nile Virus
• AIDS/HIV

7
Case Study Chronic Wasting Disease

• Chronic Wasting Diseasedeer and elk populations
  in North America
• Caused by strange prion protein
• One of a family of irreversible, degenerative
  neurological diseases known as transmissible
  spongiform encephalopathies (TSE) including mad
  cow
• Canadian government spending 65 million to fight
  CWD
• Cattle imported from Canada found to have TSE in
  2004
• Worry about it spreading to humans, as of yet no
  one in the US has died

8
Causes of Emergent Disease

• Environmental change stresses biological systems
• Cut down forests
• Drain wetlands
• Invasive species introduced by humans
• Increased human incursion into wilderness
• Increased consumption of wild species allows
  diseases to jump barriers---3/4 of all emerging
  diseases are zoonotic, or shared by animals and
  humans
• Climate change allows animals to expand their
  range

9
Increasing Resistance to Antibiotics and
Pesticides is

• Partially through natural selection and ability
  to evolve rapidly
• Mutated bacteria that are resistant live and
  multiply via natural selection
• Partially through human tendency to use control
  measures aimlessly
• DDT spread everywhere, so that some were only
  minimally exposedencouraged natural selection
  and the survival of resistant

10
Antibiotics, Farming, and Disease

• More than half of the antibiotics used in the US
  each year are fed to livestock
• These antibiotics and hormones are excreted in
  urine and feces
• Spread on land or water where they evolve into
  supervirulent pathogens
• At least half of the 100 million antibiotic doses
  prescribed to humans each year are unnecessary or
  wrongimproper disposal or use can lead to
  illness

11
Toxicology

• Study of toxins (poisons) and their effects on
  living systems
• Damage or kill living organisms because they
  react with cellular components to disrupt
  metabolic functions
• Toxins harmful even in dilute concentrations

12
Ecotoxicology

• All toxins hazardous, but not all hazardous
  materials are toxic
• Some materials are hazardous because they are
  flammable, explosive, etc.
• Environmental Toxicologyecotoxicology, deals
  with the interactions, transformation, fate, and
  effects of natural and synthetic chemicals in the
  biosphere, including individual organisms,
  populations, and whole ecosystems

13
How Do Toxins Affect Us?

• Allergens Antigens
• Immune system depressants
• Endocrine disrupters
• Sick building syndrome
• poor indoor air quality may
• cost USA 60 billion in sick
• days and reduced productivity

14
Teratogens

• Chemicals or other factors that specifically
  cause abnormalities during embryonic growth and
  development
• Example Fetal alcohol syndrome- a cluster of
  symptoms including craniofacial abnormalities,
  developmental delays, behavioral problems, and
  mental defects that last throughout a childs
  life
• Even on drink during pregnancy puts a child at
  risk
• By some estimates, between 300,000 and 600,000
  children born every year in the US are exposed in
  the womb to unsafe levels of mercury
• Effects include reduced intelligence, ADD, and
  behavioral problems, costing 8.7 billion
  annually

15
Carcinogens

• Substances that cause cancer
• According to the American Cancer Society, ½ males
  and 1/3 females will have some sort of cancer in
  their lifetime
• Debate over environment vs. lifestyle
• According to the EPA, 200 million US residents
  live in combined lifetime cancer risk form
  environmental carcinogens exceeds 1 in 100,000 or
  ten times the acceptable risk

16
Diet Affects Health

• Strong correlation between cardiovascular disease
  and the amount of salt and animal fat in ones
  diet
• Fruits, vegetables, whole grains, complex carbs,
  and dietary fiber have a positive affect
• Vitamins A,C, and E, substances produced in
  cruciferous vegetables, and selenium seem to have
  anticancer effects
• Every year in the US 300,000 deaths are linked to
  obesity
• 1/3 of US children may become diabetic unless
  people start eating less and exercising more,
  increased risk (1/2) for Black and Hispanic
  children

17
Case Study Poisoning Bhopal

• December 3rd, 1984
• Bhopal, central India,
• Noxious gas methylisocyanate (MIC), a component
  of pesticide Temik, made at the Union Carbide
  plant in Bhopal.
• Water had gotten into tank and it exploded,
  sending MIC throughout the city
• 15,000 died instantly 800,000 suffered medical
  problems
• More than 20 years after the catastrophe, no one
  punished and most of the 470 million paid by
  Union Carbide has yet to be distributed

18
Solubility

• Solubility is important in determining how, when,
  and where a toxic material will move to the site
  of action
• Water soluble compounds move widely and rapidly
  and have ready access to most cells
• Oil or fat soluble compounds generally need a
  carrier to move but can easily penetrate cells
• more likely to accumulate and be stored in lipid
  deposits for years

19
Exposure Susceptibility

• Airborne toxins generally cause more ill health
• Toxins also enter through food, water, skin
  contact
• Largest exposure for toxins
• are found in industrial settings
• Condition of being timing
• of exposure influence toxicidty

20
Bioaccumulation Biomagnification

• Cells have mechanisms for bioaccumulation
• allows them to accumulate nutrients and essential
  materials but also leaves the risk of absorbing
  bad toxins
• Bioaccumulation
• Biomagnification When the toxic burden of a
  large number of organisms at a lower trophic
  level is accumulated and concentrated by a
  predator in a higher tropic level

21
Persistence

• Some chemical compounds are unstable and degrade
  rapidly so their concentrations decline quickly
  after release
• Others are more persistent and last for a few
  centuries
• cause more problems and unexpected effects

22
Things That Kill You (part 2)

• PBDEs are in textiles, upholstery, and plastic.
  They effect behavioral nervous system
  development
• PFOs and PFOA/C8s are found in nonstick,
  water-proof, stain-resistant products and
  everywhere. Literally.
• cause liver damage, cancer, reproductive and
  developmental problems in rats kill pet birds
• Phthalates are found in cosmetics, deodorants,
  and many plastics
• cause kidney and liver damage,
• cancer in rats endocrine hormone
• disrupters that cause reproductive
• abnormalities and decreased
• fertility/quality of sperm

23
Things That Kill You (part 3)

• Perchlorate is a waterborne containment left over
  from propellants and rocket fuels it pollutes
  water used to water crops.
• Disrupts adult metabolism and childhood
  developments
• BPA is in polycarbonate plastic.
• Causes abnormal chromosome numbers, aneuploidy
  (the leading cause of mental retardations and
  miscarriages)
• Atrazine is a widely used herbicide
• Causes birth defects, abnormal development

24
Interactions!

• Antagonistic reactions interfere with the effects
  or stimulate the breakdown of other chemicals
• Additive reactions occur together in exposure
• Synergism An interaction in which one substance
  exacerbates the effects of another

25
Degradation Excretion

• Enzymes process waster products and environmental
  poisons to reduce their toxicity
• can make chemicals more dangerous by breakdown
  ones that should not be broken down
• Factors that affect post reproduction stages
  usually don't effect reproductive success or
  exert selective pressure
• Excretion reduces the effects of
• waste products and environmental toxins by
• eliminating them from the body

26
Repair

• Our skin and organ linings have high cellular
  reproduction rates to replace injured cells
• Chance that cells will lose normal growth
  controls and create a tumor and irritants will be
  turned into carcinogens

27
Why Lab Animals Die

• Because we test toxins on them!
• Expensive, time-consuming, painful to animals
• takes hundreds of animals, years of work,
  thousands of dollars for one text
• however, most accurate and reliable data
• more human toxicity tests are being developed
• Problems
• differences in sensitivity in members of a
  population
• unrelated species can react very differently to
  same toxin

28
Acute versus Chronic

• Acute effects
• Chronic effects
• Usually difficult to detect
• the specific health risks
• because of other factors
• Different toxicity levels for everything
• Just because they are detectable doesn't mean
  you'll die

29
Risky Business

• Risk The possibility of something undesirable
  will happen as a result of exposure to a hazard
• Risk assessment The scientific process of
  estimating the threat hazards pose to health
• Includes risk identification, dose response
  assessment, exposure appraisal risk
  characterization

30
Why We Do Stupid Things (part 1)

• People downplay certain risks and emphasize
  others that suit their agenda
• Tolerate risks that we choose and
• object those we don't
• Have difficulty understanding and
• believing probabilities
• Personal experiences can be misleading
• Exaggerated view of our ability to control fate
• Media gives a biased perspective of things
• Irrational fear or mistrust of new technology

31
Why We Do Stupid Things (part 2)

• Most people will tolerate a higher probability of
  an event if the harm caused by it is low
• If we enjoy or find an activity profitable, we
  will ignore the risks
• Perception of risks based on whether they are
  known or unknown, we are in control of the
  outcome or not, and how bad the results can be

32
Things That Keep You Alive

• It is difficult to separate the effects of
  different hazards and evaluate their risks
  accurately
• When setting standards for environmental toxins,
  consider
• combined effect of exposure to many different
  areas of damage
• different sensitivities of members of the
  population
• effects of chronic and acute exposure
• how does it affect our overall environment?