Toxicology

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Chapter 16 Toxicology Human Health
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Causes of Death, a Risky Life
Annual deaths in the US from various activities
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Bioaccumulation

• when a chemical becomes absorbed and concentrated
  in specific organs or tissues
• e.g., DDT accumulates in fatty tissues
• contributing factors
• high persistence
• not easily broken down or excreted

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Biomagnification
The level of some toxins in the environment are
magnified as they pass through the food web e.g.,
DDT becomes higher in concentration in higher
trophic levels DDT is a fat-soluble chemical that
accumulates in the fatty tissues of animals, and
is not excreted.
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Median Lethal Dose (LD50)

• amount of a chemical that kills 50 of a test
  population
• Experimental design
• control (no dose) treatments (low to high dose)
• test organism (usually rats or mice)
• replicates (usually 60200 animals total)
• period (often 14 days)

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2. Major Hazards
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Toxic Chemicals

• generally defined by LD50
• poison legally defined as a chemical that has an
  LD50 of 50 milligrams or less per kilogram of
  body weight

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Hazardous Chemicals

• Cause harm in various ways
• flammable or explosive (e.g., gasoline)
• irritating or damaging to skin or lungs (e.g.,
  strong acids or alkalines)
• interfering with or preventing oxygen uptake
  distribution (e.g., carbon monoxide, CO)
• inducing allergic reactions of the immune system
  (allergens).

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Harmful Chemicals, Viruses, Ionizing Radiation

• mutagens cause random mutations (changes in the
  DNA)
• -e.g., radioactivity
• carcinogens cause cancer (uncontrolled division
  of cells) over 100 types
• -e.g., cigarette smoke

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Hormone Disrupters

• hormones molecules that act as messengers to
  regulate various bodily processes, including
  reproduction, growth, development.
• hormone disrupters interfere with hormone
  function
• so far gt 60 chemicals shown to act as hormone
  disrupters on wildlife, laboratory animals,
  humans
• e.g., dioxins, certain PCBs, various chemicals in
  plastics, some pesticides, lead mercury
• 1997 study shows that sperm count of men in U.S.
  Europe has declined 50
• Biomagnification in humans

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Hormone Disrupters
Substances (i.e. some pesticides) with similar
shape attach
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Hormone Disrupters
Prevent hormones from attaching to their
receptors
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Biological Hazards

• nontransmissible diseases
• does not spread from one persons to another
• cardiovascular disorders, cancers, emphysema,
  malnutrition
• transmissible diseases
• spread from one person to another
• caused by bacteria, viruses, protozoa, or
  parasites
• colds, flus, hepatitis, sexually transmitted
  diseases, malaria
• many transmissible diseases spreading over broad
  geographic areas
• Lyme disease

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Global tuberculosis epidemic (a bacteria). Kills
2 million infects 8 million people per year
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Worldwide distribution of Malaria Kills 1.5
million people a year
45 of words population lives in Malaria areas
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Other disease yellow fewer, encephalitis
dengue fewer
Malaria
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Chapter 17 Air Air Pollution
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Where are we going?
1. The Atmosphere layers, processes 2. Urban Air
Pollution photochemical industrial smog 3. Acid
Deposition consequences, solutions 4. Indoor Air
Pollution types, radon 5. Effects of Air
Pollution human health, plants, aquatic life,
property 6. Preventing Reducing Air
Pollution laws, technology
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1. The Atmosphere

• Troposphere
• where weather occurs
• contains 75 of Earth's air
• heated from beneath (reflection) decreasing
  temperature with altitude.

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The Atmosphere

• Stratosphere
• includes ozone layer, which filters ultraviolet
  radiation
• increasing temperature with altitude makes layer
  stable.

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Human Inputs to Troposphere

• modify Earth's gaseous nutrient cycles.
• N S compounds released by burning fossil
  fuels
• CO2 other greenhouse gases from burning fossil
  fuels clearing forests.

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2. Urban Air Pollution
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Photochemical Smog in every City
Chemical reactions triggered by light. Over 100
chemical substances i.e. O3
The hotter the day the more O3
Acid rain
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Industrial Smog

• consists mostly of sulfur dioxide (SO2), sulfuric
  acid (H2SO4) suspended in droplets,
  particulates (soot)
• sulfur compounds in coal oil react with oxygen
  to form sulfur dioxide
• S O2 gt SO2

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Industrial Smog

• some sulfur dioxide reacts with oxygen to form
  sulfur trioxide 2 SO2 O2 gt 2 SO3
• sulfur trioxide reacts with water to form
  sulfuric acid SO3 H2O gt H2SO4
• Acid rain
• Industrial smog is less common in developed
  countries, but a major problem in countries like
  China, India, Russia where oil coal are
  burned without sufficient pollution control.

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3. Acid Deposition
An Acid any chemical that releases hydrogen ions
(H) when dissolved in water. For
example Hydrochloric acid HCl -gt H
Cl- (in stomach) Sulfuric acid H2SO4
-gt 2H SO42- Nitric acid NHO3
-gt H NO- pH values ranges from
from 0 to 14 and expresses the concentration of
H less than 7 acidic around 7 neutral,
more than lt 7 basic
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3. Acid Deposition
A naturally occurring reaction water and carbon
dioxide in the atmosphere react to carbonic acid
which has a pH 5.6, hence rainfall is weakly
acidic H2O CO2 -gt H2CO3 Human induced
acid deposit consists of rain, snow, dust, or gas
with pH lower than 5.6, called acid rain. Sulfur
dioxide (SO2) leads to Sulfuric acid H2SO4
Nitrogen oxides (NOx) leads to Nitric acid NHO3
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3. Acid Deposition
A buffer is a substance that can react with
hydrogen ions (H) in a solution thus holds the
pH fairly constant. Calcium carbonate (CaCO3) or
limestone (remember Corals produce it too!) is a
natural buffer that protects many soils and lakes
from acid rain. Hydrogen ions are neutralized
when reacting with a buffer such as calcium
carbonate. CaCO3 2H -gt Ca2 CO2 H20
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Acid deposition, which consists of rain, snow or
gas with a pH lower than 5.6 is commonly called
acid rain. Soils and lakes vary in their ability
to buffer or remove excess acidity
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Effects of acid rain on Trees Soils
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Effects of acid rain on Aquatic Life

• high acidity (low pH) leaches harmful minerals
  such as aluminum into the environment
• kills fish other organisms inhibits
  reproduction disrupts food chains decreases
  productivity.
• Massive plant, invertebrate, fish bird
  extinctions
• Norway and Sweden over 16,000 lakes are dead
• Canada 14,000 lakes are affected
• US over 9,000 lakes are affected

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Effects of acid rain on Property

• breaks down paints on cars buildings,
  deteriorates roofing, etches glass, dissolves
  discolors marble
• causes billions of dollars of damage to various
  materials (e.g., damage to buildings in U.S.
  estimated at 5 billion annually).

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Effects air pollution on Health

• carbon monoxide (CO) reacts with hemoglobin in
  red blood cells reduces ability of blood to
  carry oxygen
• particulates longterm exposure contributes to
  lung disease cancer, aggravates bronchitis
  asthma
• sulfur dioxide (SO2) causes constriction of
  airways can cause bronchitis

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Effects air pollution on Health

• nitrogen oxides (especially NO2) irritate lungs,
  cause conditions similar to bronchitis
  emphysema
• volatile organics ( toxic particulates) cause
  mutations, reproductive problems, cancer
• ozone causes coughing, chest pain, shortness of
  breath, eye, nose, throat irritation.

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6. Preventing Reducing Air Pollution
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4. Indoor Air Pollution is higher than outdoor
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Radon222

• colorless, odorless gas
• natural breakdown product of the radioactive
  decay from uranium238
• causes lung cancer other health problems
• prevented by ventillation

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Clean Air Acts of 1970, 1977, 1990

• require Environmental Protection Agency (EPA) to
  establish national ambient air quality standards
  (NAAQS)
• NAAQS apply to seven pollutants suspended
  particulate matter, sulfur oxides, carbon
  monoxide, nitrogen oxides, ozone, volatile
  organic compounds, lead
• prevention of significant deteriorization
• national emission standards for toxic air
  pollutants require the EPA to regulate many toxic
  air pollutants.

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Success of Clean Air Act

• decrease of six of seven major pollutants
• nitrogen dioxide levels increased slightly,
  primarily from automobiles
• 1996 study by EPA shows that benefits greatly
  exceed costs 197090 436 billion spent, health
  benefits of 2.7 to 14.6 trillion
• EPA estimates that 107 million Americans live in
  areas that exceed at least one outdoor air
  pollution standard.

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Technology to reduce air pollution
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Reducing Emissions
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Solutions to prevent reduce indoor air
pollution.
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Chapter 18 Climate Change Ozone Loss
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Where are we going?

• 1. Natural Global Processes
• greenhouse effect
• ozone shield
• 2. What Problems Result from Human Inputs
• global warming
• ozone depletion
• 3. Solutions
• 4. Summary

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What is the Greenhouse Effect? natural process
that traps heat near the Earths surface in the
troposphere.

• short wave radiation in
• long waveradiation out
• re-radiationdownward bygreenhousegases

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Climate During Past 160,000 Years

• End of last ice age about 10,000 yr BP
• Now in warm interglacial period
• Based on ice core data, analysis of trapped gas
• Correlation between CO2 mean temperature

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What is Scientific Consensus?

• Mean global temperature rose about 0.6º C (1º F)
  in past 100 years
• Warming greater at poles than equator, greater at
  night, mostly troposphere

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Ecological Implications

• Shift of habitat to higher latitudes
• Shift of habitat to higher elevations
• Potential large loss of biodiversity

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What is the Greenhouse Effect?

• Natural greenhouse effect, warms the earth
  makes it inhabitable for all life.
• Human induced greenhouse effect by releasing
  greenhouse gases i.e. CO2, CH4, N2O into the
  atmosphere.
• Leads to change of global climate. Consequences
  of global temperature increase include
• Melting of ice caps and glaciers, increased sea
  level, flooding, danger for cities near costs,
  habitats such as mangrove forest, bleaching of
  coral reefs. Northward Migration of plants and
  animals into cooler regions. Extinction of plants
  and animals which cannot move anymore.

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Solutions for Greenhouse effects
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What is the Ozone Shield? natural process that
filters ultraviolet (UV) in the stratosphere
radiation before it reaches the lower atmosphere
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Ozone Shield in Stratosphere
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Ozone Shield with some Holes

• Human inputs
• Ozone Shield
• chlorofluorocarbons (CFCs)
• other stable halogencontaining gases (halogens
  chlorine, fluorine, bromine)

• Halogens are used in
• - aerosol propellants,
• - plastic foams,
• coolant in AC
• refrigerators etc..

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How Does Depletion Occur?

• chlorofluorocarbons (CFCs) stable, move from
  troposphere to stratosphere
• UV breaks off chlorine molecule (Cl) from CFC
• Cl acts as a catalyst to break down ozone (O3)
• catalyst promotes a chemical reaction without
  itself being used up in the reaction
• shifts equilibrium of oxygen / ozone reaction
  O2 O3

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Consequences of Ozone Depletion

• Increase in skin cancer cataracts, especially
  in southern hemisphere
• More ozone near earths surface, produced in
  photochemical smog lung problems, suppressed
  immune response, cancer

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Solutions to Ozone Depletion

• phase out use of ozonedepleting chemicals
• halons, CFCs, methyl chloroform, methyl bromide
• phase in use of CFC substitutes
• nonhalogen aerosol propellants,
  hydrochlorofluorocarbons (HCFCs),
  hydrofluorocarbons (HFCs), hydrocarbons (HCs),
  ammonia, water steam, terpenes, helium

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Summary

• Where
• Process
• Gases
• Inputs
• Problems

greenhouse effect troposphere traps heat near
earths surface H20, CO2, CH4 CO2, CH4, CFCs,
N2O global warming
ozone shield stratosphere filters ultraviolet
(UV) radiation O2, O3 CFCs, other
halogencontaining gases ozone depletion