Chapter 14 Environmental Health and Toxicology

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Chapter 14 Environmental Health and Toxicology
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Chapter Overview

• Case Study - Lead
• Basics including some key terms
• Categories of Pollutants (10 kinds - 6 pages)
• Effects of pollutants including Dose - response
  concepts
• Risk assessment

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Some Basics

• Many causes of disease, one of these are
  environmental factors.
• Water, air, soil, etc
• One belief - naturegood, not always true
• Floods, volcanoes (tsunamis)
• Lake Nyos example

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Lake Nyos
CO2
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Terms

• Pollution - an unwanted change in the environment
  due to introduction of chemicals or conditions
• Contamination - to make something unfit for use

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More terms

• Toxic - poisonous to people and other living
  things
• Toxicology - study of poisons and their effects
• Carcinogen - a toxin that causes cancer

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More terms

• Synergism - combined effect of two variables is
  greater than their sum.
• Ex. SO2 and particulates are each harmful, but
  together they are much more harmful than the
  combined effect of each alone. Like two rude
  friends who get each other going.

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More terms

• Point sources - smokestacks, drains, spills
• Area Sources - urban runoff, car exhaust

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Units for measuring pollution

• Release may be measured in gallons or tons per
  day or year
• Concentration in the environment may be in ppm
  (parts per million) or ppb (parts per billion).
  This may be volume, mass, or weight
• In toxicology often milligrams per kg of body
  ppm

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Units

• In water often mg/L or ug/L
• mg/L is close to ppm
• Air pollutants often in ug/m3

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Categories of Pollutants

• Infectious agents
• Infectious agents which could be controlled by
  improving sanitation and treating water are
  environmental health concerns
• Can be spread by mosquitos, contaminated food or
  water, ventilation systems

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Examples of Infectious Diseases

• Legionnaires Disease - spread by water such as
  from shower heads
• Giardiasis - protozoan spread by food and water
• Salmonella - food poisoning
• Lyme disease - spread by ticks

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Category 2 - Toxic Heavy Metals

• Mercury, lead, cadmium, nickel, gold, platinum,
  silver, bismuth, arsenic, selenium, vanadium,
  chromium, thallium
• Used in society and byproduct of mining,
  refining, etc

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Heavy Metals 2

• Have direct health effect
• Can be stored in our body
• Stored amount called body burden - measured in
  mg/kg or ppm

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Toxic pathways

• Many pathways available (see fig 14.4)
• Cadmium - present in ash from coal in low
  concentration
• Can be incorporated into plants at higher
  concentration biomagnification

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Organic Compounds

• Carbon-based compounds, produced both naturally
  or by humans
• Many kinds with many effects
• Used in industrial processes, pesticides,
  pharmaceuticals, food additives, etc

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Radiation

• Result of nuclear processes - discussed more in
  chapter 18

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Thermal Pollution

• Heat pollution
• Natural sources include forest fires and
  volcanoes
• Major source is heat released from electrical
  generating plants
• Changes average temp of water

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Thermal Pollution cont.

• Many aquatic species have a very narrow range
  tolerating only 1-3 degree change
• Temperature change can effect food chains
• Solutions include cooling towers or cooling
  lagoons

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Particulates

• Dust released into atmosphere by industrial
  processes
• Much added by farming, dust storms, fires,
  volcanoes.
• Inhalation hazard as well as climatic effects,
  heavy metal contents and synergistic effects

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Asbestos

• Small elongated mineral fragments
• Used for fire prevention and insulation
• Certain types of asbestos under certain
  conditions cause lung diseases
• All types of asbestos are not equally hazardous

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Asbestos cont.

• 95 of asbestos in US is chrysolite
• Studies show this type is not especially harmful
• Public health risks have been overstated and many
  actions were probably taken unnecessarily

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Electromagnetic fields

• Created by electric motors, power lines, cell
  phones, appliances.
• Possible health effects controversial BUT
• Possible associations with leukemia, lymphomas
  (blood cancer), and cancers of the nervous system
  in children.

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Noise Pollution

• Defined as unwanted sound
• Sound measure in decibels (dB)
• Interior of a home is 45 dB
• Scale is logarithmic 55 dB is ten times louder
  than 45
• 140 dB causes pain
• Effects depend on volume and duration of exposure

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Voluntary Exposures
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General Effects of pollutants

• Almost every part of bodies can be effected
• Affected area and symptom area may differ
• See figure 14.8

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Concept of Dose and Response

• Everything is poisonous, yet nothing is
  poisonous.
• Selenium is required by living things, but in
  high amounts can cause cancer in wildlife

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Dose- Response Curve
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LD-50
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Other Measures

• ED-50 - Effective Dose
• TD-50 - Toxic Dose
• There is sometimes an overlap, see fig 14.11. The
  dose which is effective on 95 of individuals
  might be toxic to 5.

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Threshold effects

• Read about Minimata
• What happened?
• Why?
• What is Threshold and how does it apply?

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Threshold Effects
Response
Dose
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Ecological Gradient

• The types of plants which grow closest to a site
  of contamination may differ from those growing
  further away.

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Tolerance

• 3 kinds behavior, physiological, genetic
• Behavioral - Mice learn to avoid traps
• Physiological - body has mechanisms to deal with
  effect on repeated exposure ie ozone

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• Genetic Tolerance - Natural Selection like
  insects and pesticides
• Acute Effects - Occurs soon after exposure,
  usually to a large dose
• Chronic effects - Occurs over a long time, some
  times to small dose

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Risk Assessment - 1

• Identify Hazard
• Test materials to see if they may have toxic
  effects.
• One way investigate populations who have been
  exposed.
• Or test materials on cells, then extrapolate to
  predict effects on an organism

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Risk Assessment - 2

• Dose-response assessment
• ID relationship between dose and adverse effect
• Sometimes involves high doses in animals
  extrapolated to low dose in humans
• Can be controversial because of statistics and
  other issues such as threshold.

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Risk Assessment -3

• Exposure assessment
• Estimate the intensity, duration, and frequency
  of human exposure
• Difficult to determine accuracy of small
  concentrations

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Risk Assessment - 4

• Risk Characterization
• Delineate the health risk
• Combines steps 2 and 3 and includes all of their
  uncertainties.

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Risk Assessment - 1

• Identify Hazard
• Test materials to see if they may have toxic
  effects.
• One way investigate populations who have been
  exposed.
• Or test materials on cells, then extrapolate to
  predict effects on an organism