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Chapter 16
Toxicology & Human Health
Causes of Death, a Risky Life
Annual deaths in the US from various activities
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
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.
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 60–200 animals total)
• period (often 14 days)
2. Major Hazards
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
Hazardous ChemicalsCause 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).
• 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
Harmful Chemicals, Viruses, Ionizing Radiation
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 > 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
Hormone Disrupters
Substances (i.e. some pesticides) with similar shape attach
Hormone DisruptersPrevent hormones from attaching to their receptors
Biological Hazardsnontransmissible 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
Global tuberculosis epidemic (a bacteria). Kills 2 million & infects 8 million people per year
Worldwide distribution of Malaria Kills 1.5 million people a year
45% of word’s populationlives in Malaria areas
MalariaOther disease:yellow fewer,encephalitis &dengue fewer
Chapter 17
Air & Air Pollution
Where are we going?1. The Atmosphere
layers, processes
2. Urban Air Pollutionphotochemical & industrial smog
3. Acid Depositionconsequences, solutions
4. Indoor Air Pollutiontypes, radon
5. Effects of Air Pollutionhuman health, plants, aquatic life, property
6. Preventing & Reducing Air Pollutionlaws, technology
1. The Atmosphere
Troposphere
• where weather occurs;
• contains 75% of Earth's air;
• heated from beneath (reflection); decreasing temperature with altitude.
The AtmosphereThe Atmosphere
Stratosphere
• includes ozone layer, which filters ultraviolet radiation;
• increasing temperature with altitude makes layer stable.
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.
2. Urban Air Pollution
Photochemical Smog in every CityChemical reactions triggered by light. Over 100 chemical substances i.e. O3
Acid rainThe hotter theday the more O3
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 –> SO2
Industrial Smog
• some sulfur dioxide reacts with oxygen to form sulfur
trioxide: 2 SO2 + O2 –> 2 SO3
• sulfur trioxide reacts with water to form sulfuric acid:
SO3 + H2O –> 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.
3. Acid DepositionAn Acid: any chemical that releases hydrogen ions (H+) when dissolved in water.For example:Hydrochloric acid: HCl -> H+ + Cl- (in stomach)
Sulfuric acid: H2SO4 -> 2H+ + SO42-
Nitric acid: NHO3 -> 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 < 7 basic
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 -> 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
3. Acid Deposition
3. Acid Deposition
A buffer is a substance that can react with hydrogenions (H+) in a solution & thus holds the pH fairlyconstant. Calcium carbonate (CaCO3) or limestone(remember Corals produce it too!) is a natural bufferthat protects many soils and lakes from acid rain.Hydrogen ions are neutralized when reacting with a buffer such as calcium carbonate.
CaCO3 + 2H+ -> Ca2+ + CO2 + H20
Acid deposition, which consists of rain, snow or gas with a pH lower than 5.6 is commonly called acid rain. Soils andlakes vary in their ability to buffer or remove excess acidity
Effects of acid rain on Trees & Soils
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
• 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).
Effects Effects of acid rain on Propertyon Property
Effects air pollution on HealthEffects air pollution on Health
• carbon monoxide (CO): reacts with hemoglobin in red blood cells & reduces ability of blood to carry oxygen;
• particulates: long–term exposure contributes to lung disease & cancer, aggravates bronchitis & asthma;
• sulfur dioxide (SO2): causes constriction of airways & can cause bronchitis;
Effects air pollution 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.
6. Preventing & Reducing Air Pollution6. Preventing & Reducing Air Pollution
4. Indoor Air Pollution is higher than outdoor
Radon–222• colorless, odorless gas
• natural breakdown product of the radioactive decay from uranium–238
• causes lung cancer & other health problems
• prevented by ventillation
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.
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: 1970–90 $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.
Technology to reduce air pollution
Reducing Emissions
Solutions to prevent& reduce indoor air pollution.
Chapter 18
Climate Change & Ozone Loss
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
What is the Greenhouse Effect?What is the Greenhouse Effect?natural process that traps heat near the Earth’s surface in the troposphere.
• short wave radiation in
• long waveradiation out
• re-radiationdownward by“greenhousegases”
• 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
Climate During Past 160,000 Years
What is Scientific Consensus?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
Ecological Implications
•Shift of habitat to higher latitudes
•Shift of habitat to higher elevations
•Potential large loss of biodiversity
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.
Solutions for Greenhouse effects
What is the Ozone Shield??natural process that filters ultraviolet (UV) in the stratosphere radiation before it reaches the lower atmosphere
Ozone Shield: in Stratosphere
Human inputsHuman inputs
Ozone Shield:
• chlorofluorocarbons (CFCs)
• other stable halogen–containing gases (halogens = chlorine, fluorine, & bromine)
b) CFCs
Ozone Shield with some Holes
Halogens are used in:- aerosol propellants, - plastic foams,- coolant in AC &- refrigerators etc..
•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
How Does Depletion Occur?
Consequences of Ozone Depletion
• Increase in skin cancer & cataracts, especially in southern hemisphere
• More ozone near earth’s surface, produced in photochemical smog – lung problems, suppressed immune response, cancer
• phase out use of ozone–depleting chemicals
halons, CFCs, methyl chloroform, methyl bromide
• phase in use of CFC substitutes
non–halogen aerosol propellants, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), hydrocarbons (HCs), ammonia, water & steam, terpenes, helium
Solutions to Ozone Depletion
Summary
Where:
Process:
Gases:
Inputs:
Problems:
greenhouse effect
troposphere
traps heat near earth’s surface
H20, CO2, CH4
CO2, CH4, CFCs, N2O
global warming
ozone shield
stratosphere
filters ultraviolet (UV) radiation
O2, O3
CFCs, other halogen–containing gases
ozone depletion