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