BIOL 3120 Ryan Stork Environmental Science Exam 3

What population trends do humans follow?

Humans follow same trends: birth, death, immigration, emigration

What are biotic vs abiotic factors?

Biotic = living factors; Abiotic = non-living (climate, water, etc.)

What are density-dependent vs density-independent factors?

Density-dependent = affected by population size (disease, competition)

Density-independent = unaffected by density (natural disasters, weather)

Do humans have a carrying capacity (K)?

What are two major perspectives on resource limits?

Carrying capacity = max population environment can support

Debate:

Tech/economy may increase K

OR resources already sufficient but poorly distributed

What limited early human population growth?

Limited by: disease, famine, war, cultural controls. Early societies regulated population (cultural taboos, abstinence, and infanticide)

What factors caused population growth to increase?

Increased by: agriculture, hygiene, healthcare, technology, power sources

How has human population growth changed over time?

What type of growth are humans experiencing?

What is the current global population?

Took thousands of years to reach 1B, 150 years to reach 3B in 1960, and from 5B to 6B in only 12 years

Growth is exponential

8.2 billion and increasing

What is the estimated human carrying capacity?

Best Estimate of Human K - 7.7 Billion (2 Billion - 1 Trillion)

What are planetary boundaries?

Planetary boundaries = limits needed for human survival

9 Planetary Boundaries Suggested

3 May Have Already Been Crossed

What is demography?

study of population statistics

What major events increased population growth?

Major events: agricultural revolution, industrial revolution, reduced disease

What did Thomas Malthus argue about population?

An Essay on the Principle of Population 1798

population grows faster than food -->scarcity, poverty or in other words

Populations Grow Geometrically but Food Production Arithmetically

Imbalance Leads to Scarcity & Poverty & Struggle to Survive

What did Karl Marx argue about population?

Population Growth Due to Capitalism NOT Natural Biology • Poverty & Overpopulation Due to Exploitative Capitalism

How has technology affected carrying capacity? What are the concerns about future carrying capacity?

Tech has increased K historically

Concerns: fossil fuel limits, environmental damage, climate change

How has technology affected carrying capacity?

What are concerns about future carrying capacity?

Tech has increased K historically

Concerns: fossil fuel limits, environmental damage, climate change

What did Julian Simon believe about population growth?

Believed human innovation will solve resource problems

Benefits: larger markets, more workers, more innovation and intelligence to overcome challenges

What key metrics do demographers study?

Growth rate, fertility rate, replacement level fertility, infant mortality, birth/death rates, transitions, population profile, population momentum, epidemiologic (relating to the branch of medicine which deals with the incidence, distribution, and control of diseases) transition, fertility transition, demographic transition

Fertility and Birth Rates

Replacement fertility = 2.1 children per couple

Population growth rate is decreasing, but the population is still increasing

Fertility rates declining globally

Lower in developed, higher in developing countries

How do crude death rates differ between countries? Why can growing countries still have low death rates?

Poor countries CDR = 20, wealthy = 10

Young populations -->fewer deaths even if life expectancy is low

What factors affect population growth rates?

Economic development, life expectancy, age distribution, social factors

What are the stages of the demographic transition model?

Stage I: high birth & death rates

Stage II: death rates drop, birth rates stay high

Stage III: birth rates drop

Stage IV: low birth & death rates

What is the difference between life span and life expectancy?

Life span = max age; life expectancy = average age

What caused recent population growth?

Growth driven by reduced mortality (medicine, sanitation, nutrition, and education)

What do age structure pyramids show?

Pyramids show age distribution

Growing = wide base

Stable = even

Declining = wider top

Ideal population structure - 20% in each 15 year cohort

What is dependency ratio and what problems can it cause?

Ratio of non-working to working population

Issues: supporting elderly, childcare, social security strain

What is cohort?

Cohort - group of individuals who share a common characteristic or experience

What are key trends in U.S. population?

Population still growing

TFR (total fertility rate) ~1.66 (below replacement)

In 2019 70 Million Displaced by Economics, Politics, Persecution, or War • 31 Million Moved to Other Countries

Growth supported by immigration

What is the main global population issue today?

The world has enough resources; the issue is the redistribution of those resources

What is the key future question for human population growth?

How many people can Earth support sustainably?

What are the three requirements to feed people while protecting the environment?

Produce more food

Reduce environmental harm

Distribute food properly

We already produce enough food globally, the main issues are environmental impact and unequal distribution

Substinece farming

Farming where families grow food mainly for their own survival

Labor-intensive, low technology, often on poor (marginally productive) land

Supports >2 billion people ("silent giant")

Vulnerable to crop failure (no insurance, credit, or markets)

Common in developing regions (Sub-Saharan Africa, Asia, Latin America)

Modern Industrialized Agriculture

Large-scale, high-efficiency farming that produces surplus food (especially in U.S.)

Enabled by:

Machinery (tractors, harvesters)

Infrastructure (transport, storage)

Government subsidies

Heavy use of fossil fuels (key dependency)

What limits expansion of farmland?

What inputs are used to increase yields?

Most high-quality farmland already in use --> expansion harms forests/wetlands

Yield increases rely on:

Fertilizers (add nutrients like N, P, K)

Pesticides (control pests)

Irrigation (water supply)

What was the Green Revolution?

Technology Increases Crop Production • Expanded Food Production • Yields Increased without New Land • More Research is Continuing • Each Technology Has External Costs - $ 6 -17 Billion / yr

• High Yield Crops are Hard to Grow • Need Fertilizer, Pesticides, Irrigation, Machines • Monocultures • Loss of Heirloom Crops & Heritage Breeds • Loss of Taste

How does livestock production impact food systems and the environment?

33% of cropland used to feed livestock (inefficient energy transfer)

CAFOs = Confined Animal Feeding Operations (large-scale animal farming)

~50% of U.S. livestock

Issues: waste pollution, disease spread, ethical concerns

Livestock produce ~14% of global greenhouse gases

Heavy antibiotic use -->antibiotic resistance + zoonotic diseases

What are biofuels and what is their main controversy?

Fuels made from crops (corn ethanol, sugarcane)

Controversy: compete with food production, potentially increasing food prices

What are transgenic / genetically modified (GM) crops?

Transgenic crops with altered DNA for desired traits

~433 million acres planted globally

Benefits:

Higher yields

Reduced pesticide use

Concerns:

Herbicide-resistant weeds

Environmental and safety uncertainties

Ongoing debate --> requires regulation (EPA, USDA, FDA)

What is the Cartagena Protocol

Cartagena Protocol = international agreement on safe handling of GM organisms

Requires labeling and science-based decisions

Precautionary principle = don't proceed unless proven safe

Not all countries (e.g., U.S.) adopted it. Only 147 Nations Ratified the Cartagena Protocol.

How has food distribution changed over time?

Shift from local self-sufficiency --> global food trade. Famine, death, and disaster used to be local.

Agriculture trade ≈ $1.3 trillion globally

Industrial revolution intensified trade, and there was a reduced need for self-sufficiency.

What is food security?

Food security = reliable access to sufficient, safe, nutritious food

Responsibility at 3 levels: family, nation, global

How is food need met at different levels?

Family: grow/buy food

Government: safety nets (food programs) at the local, state, and national level

Global: food aid + development for many different nations

What global issues affect food distribution?

Food aid flows from rich nations to poor nations, which leads to trade imbalances.

Developing nations still import and pay for food.

Developed nations use tariffs and subsidies to protect agriculture

Debt limits poor countries' access

What is the difference between hunger, malnutrition, and overnourishment?

Hunger = lack of enough calories

Malnutrition = lack of proper nutrients (even if calories are enough)

Overnourishment = excess calorie intake (obesity)

MDG's Goal of Reducing Hunger by 50% by 2015 was Met

What is the main cause of hunger?

Root cause = poverty, not lack of food globally

What is famine and what causes it?

How is food insecurity monitored and addressed?

Famine = severe food shortage causing widespread death

Causes: drought, conflict, political failure

Monitoring systems:

Global information and early warning system GIEWS (UN)

Famine Early warning system networkFEWS NET (USAID)

Aid exists from organizations like UN's World Food Program (WFP), but often arrives too late

High cost of shipping/storage (billions spent)

How can we feed more people in the future?

Increase yields

Reduce livestock/feed crops

Urban agriculture

Diet changes (less resource-intensive foods)

What is the "doubly green revolution"?

Doubly green revolution = increase production AND sustainability

What alternative food sources could help feed the future?

Options: insects (entomophagy), lab-grown meat, algae

Why are insects considered efficient food?

Insects require far less feed:

~1.7 kg feed per kg vs beef ~10 kg (from chart on page 32)

Much more efficient protein source

How can current food production be used more efficiently?

Eat less meat

Eat locally (reduce transport energy)

Reduce food waste

~40% of U.S. food is wasted -->major opportunity to reduce hunger

How do U.S. farm policies affect sustainability?

Subsidies favor large industrial farms

Encourage overproduction and environmental harm

Make sustainable practices harder to implement

Soil Importance & Degradation

90% of food comes from land-based agriculture

25% of cropland is degraded

Major causes: erosion, salinization, pollution, deforestation

Soil is critical for:

Food production

Ecosystem stability

Increasing pressure due to population growth

Soil Functions

Soil is a mix of geological and biological materials

Key functions:

Supports plant growth

Filters and stores water

Drives biogeochemical cycles (nutrients like C, N)

Exchanges gases (CO₂, O₂)

Habitat for ~25% of all species

Soil Formation & Texture

Soil forms through interactions of:

Parent material (rock source)

Weathering (physical + chemical breakdown)

Organic matter (detritus + organisms)

Soil texture = particle size distribution

Clay < 0.002 mm

Silt 0.002-0.05 mm

Sand 0.05-2.0 mm

Gravel

Cobbles

Boulders

Soil Texture & Properties

Most soils are mixtures of sand, silt, and clay

Loam (ideal soil):

~40% sand, 40% silt, 20% clay

Balances water retention and drainage

Texture affects:

Water infiltration

Nutrient holding capacity

Aeration (oxygen availability)

Workability (ease of farming)

Soil Profile & Horizons

Soil profile = vertical layers (horizons)

O horizon:

Organic layer, decomposing material (humus)

A horizon (topsoil):

Rich in organic matter, roots, microbes

Most important for plant growth

E horizon:

Zone of eluviation (leaching of minerals downward)

B horizon (subsoil):

Accumulation of minerals/clays from above

C horizon:

Weathered parent material

Soil Classification

Soil classification hierarchy:

Order, suborder, group, subgroup, family, class

4 key soil orders for agriculture:

Mollisols

Alfisols

Oxisols

Aridisols

Hydric soils indicate wetlands (important for environmental regulation)

Major Soil Orders

Mollisols

Fertile, Dark Soils of Temperate Grasslands • Best Agricultural Soils • Deep A Horizon; Rich in Humus & Minerals • With Less Precipitation Minerals Don't Leach Downward • Midwest US, Ukraine, Mongolia, Argentina

• Alfisols

Widespread, Moderately Weathered Soils in Moist Temperate Forests • Well-Developed O, A, E, & B Horizons • Suitable for Agriculture if Fertilized

Oxisols

Tropical & Subtropical Rain Forests • B Horizon Has Layer of Iron & Aluminum Oxides • Little O Horizon - Rapid Decomposition of Vegetation • Limited Agriculture - Minerals in Living Plants ONLY • Leached Minerals Form a Hardpan Resisting Cultivation

Aridisols

Soils of Drylands: Semiarid, Deserts, & Seasonally Dry Areas • Unstructured - Lack of Vegetation & Precipitation • Thin, Lightly Colored • Some May Support Livestock on Rangeland • Irrigation Leads to Salinization

Hydric Soils & Special Cases

Indicate a Wetland or Aquatic Site • Not a Soil Classification; Belong to Other Orders • Used to Delineate Wetland Boundaries for Development or Protection

Histosols:

Organic-rich soils (peat)

Gelisols:

Permafrost soils

Thawing releases greenhouse gases (climate impact)

Plant Growth Requirements

Nutrients (N, P, K)

Water

Oxygen (affected by soil compaction)

Proper pH (most near neutral ~7)

Low salinity

High salinity prevents water uptake (osmotic stress)

Irrigation can increase salinity over time

Nutrient Cycling & Fertilizers

Nutrient mining:

Nutrients removed when crops are harvested

Fertilizers replenish nutrients:

Organic (manure, compost)

Inorganic (synthetic, high concentration)

Issues:

Runoff causes water pollution (eutrophication)

Fertilizer production emits greenhouse gases

Disrupts natural nutrient cycles

Soil Degradation & Erosion

Soil degradation = loss of productivity and function

Erosion is most severe form

Causes:

Deforestation

Overgrazing of livestock

Agriculture

Vegetation prevents erosion by:

Reducing raindrop impact

Increasing water infiltration

Slowing runoff and wind

Water Use & Salinization

Irrigation methods:

Flood, center pivot, drip (most efficient)

1/6 of US crops are irrigated

Salinization:

Salt buildup from irrigation

Reduces yields (up to 60%)

Major contributor to desertification

Lost 42 million acres of croplands to salinizatiion and waterlogging between 1995 and 2013

Can reduce crop yields by up to 60%

Leaching & Soil Biota

leaching:

Loss of nutrients due to water movement

Can release toxins and alter soil chemistry

Soil biota:

Microorganisms maintain fertility

Help nutrient cycling and plant growth

Threats:

Erosion, salinity, acid rain, pollution

Emerging concern: nanoparticles (unknown effects)

Soil Conservation

Requires multi-level action (farmers, policy, society)

Example failure: Dust Bowl (poor practices + drought)

Conservation methods:

Contour plowing (follow land shape)

Strip farming

Terracing

Ground cover (reduces erosion)

Perennials (deep roots stabilize soil)

IPM (reduce pesticide use)

Sustainable Agriculture & Consumer Role

Low-input sustainable agriculture:

Small-scale, minimal synthetic chemicals

Lower yields but lower costs and environmental impact

Consumer impact:

Eat less meat (reduces land/water use)

Alternative proteins (fish, insects)

Organic and local foods reduce environmental impact

Reducing soil degradation supports long-term food production

Health, Epidemiology, and Disease Metrics

Health: complete physical, mental, and social well-being

Environmental health: how environment impacts human health

Epidemiology: study of disease patterns in populations

Morbidity: illness/disease rate

Mortality: death rate

Life expectancy increasing as infant mortality decreases

DALY (Disability Adjusted Life Years) = YLD (years lived with disability) + YLL (years of life lost)

Communicable diseases still cause millions of child deaths

Shift occurring: chronic diseases (diet, age) increasing, especially in low-income countries

Environmental Health, Risk, and Hazards

~4.8 million children under 5 died in 2023 (~13,100/day)

Two key components:

Environment

Hazards

Risk = Hazard × Vulnerability

Hazard: potential danger

Vulnerability: likelihood of being affected

Types of hazards:

Chemical

Physical

Biological

Cultural

Chemical Hazards and Toxicology

Inhalation, ingestion, injection, absorption

Types of toxic effects:

Mutagens: cause DNA mutations

Teratogens: disrupt development (fetuses most vulnerable)

Carcinogens: cause cancer

Water-soluble: excreted more easily

Fat-soluble: stored in body tissues (more dangerous long-term)

Toxic thresholds vary by age and individual

Heavy Metals: Lead and Mercury

Lead:

Damages brain and kidneys

Impairs mental development (especially children)

Former sources: paint, gasoline, pipes

Lead Contamination Control Act (1988) reduced exposure

Mercury (Hg):

Causes nerve damage, developmental issues, death

Fetuses and children most vulnerable

Major source: gold mining

Methylmercury accumulates in fish

Regulated by EPA

Environmental Toxins Concepts

Bioaccumulation: buildup of toxins in one organism over time

Biomagnification / Bioamplification: toxin concentration increases up food chain

Persistence: how long a chemical remains in environment

Synergistic effects: combined chemicals increase toxicity

Breakdown products can be more toxic than original substance

Detoxification:

Liver = main detox organ

Kidneys = excrete toxins

Biological Hazards, Disease, and Toxins

Biological hazards cause >20% of deaths globally

Pathogen: disease-causing organism

Disease: body's physiological response

Deadliest: respiratory and bloodstream infections

Disproportionately affect poor populations

Venom vs Poison:

Venom: injected (bite/sting)

Poison: ingested/absorbed

Both are toxic chemicals

Vaccination and Controversy

Based on germ theory (disease caused by microorganisms)

Edward Jenner (1796): first vaccine (smallpox from cowpox)

Vaccines undergo extensive safety testing

Wakefield study (MMR-autism) was fraudulent and retracted

Example of cherry-picking fallacy (selective evidence)

Physical and Cultural Hazards

Physical hazards:

Natural disasters

Ionizing radiation (high energy, DNA damage)

Non-ionizing radiation

Falls are the 2nd leading cause of death worldwide according to textbook

Car accidents

Cultural hazards:

Lifestyle choices (smoking, drug use, obesity)

Not always voluntary (poverty, environment)

Pollution and Public Health Systems

Pollutant: causes undesirable environmental change

Can be direct or indirect, local or global

Major organizations:

CDC: disease control

FDA: food safety

EPA: environmental regulation

WHO (est. 1948): global disease monitoring

Only ~1% of chemicals fully tested for safety

Public health limited by funding and information

Risk Perception and Tropical Risks

Small number of risks cause most deaths

Risk perception often irrational (ex: still driving despite risk)

Tropical regions:

Warm, wet climates → ideal for disease vectors

Vector: organism that transmits disease (ex: mosquito)

Mosquito = deadliest animal (implied from slide context)

Zoonotic diseases: transmitted from animals to humans

Air Pollution and Health

Humans breathe ~30 lbs of air per day

~800,000 deaths/year from air pollution (slide stat)

Indoor air often more dangerous than outdoor

Hygiene hypothesis: too clean environments may weaken immune system

Poverty increases risk:

More exposure to hazards

Less access to healthcare

Wealthier countries:

Longer life expectancy

Die more from chronic diseases

Risk Assessment

Used to evaluate hazards for policy decisions

4 steps:

Hazard identification

Dose-response assessment

Exposure assessment

Risk characterization

Key metrics:

LD50: dose that kills 50%

ED50: dose that affects 50%

Public Health Principles

Public health = preventing disease, prolonging life, promoting health

Involves science + politics

3 P's:

Prevention

Protection

Promotion

Challenging due to competing priorities and limited resources

Energy, Work, and Usage

Work = force applied over a distance

Energy = ability to do work

Power = rate of energy use (Watt)

Units:

Newton (force)

Joule (energy)

Watt (power)

Average U.S. home uses ~11,000 kWh/year

Fossil fuels supply ~80% of global energy

Major uses:

Electricity production (largest)

Transportation

Industry

Residential

Electricity is an energy carrier, not a primary energy source

Energy Consumption Patterns

• Richest Countries Use 80% of Energy with 20% of Population • Do Not Necessarily Have to Give Up Standard of Living to Use Less • Electricity Production is #1 Use • Transportation & Industry Close Behind • >80% of US Energy from Fossil Fuels • Nuclear & Renewable Sources Each >8%

Electricity Production and Efficiency

Most fossil fuel energy used to generate electricity

Coal used to be #1, now natural gas is #1

Generators convert heat → mechanical → electrical energy

Thermodynamics:

~3 units of fuel → 1 unit electricity (~30-35% efficiency)

1 MW powers ~800 homes

Electricity demand:

Baseload: constant supply (coal, nuclear)

Intermediate and peak: added as demand increases

Electricity Demand and Grid

Peak demand typically in evening and during heat waves

Utilities connected via power grid

Must balance supply and demand in real time

Aging infrastructure is a major issue

Smart grid proposed to improve efficiency and prevent outages

Peak demand typically in evening and during heat waves

Utilities connected via power grid

Must balance supply and demand in real time

Aging infrastructure is a major issue

Smart grid proposed to improve efficiency and prevent outages

Electricity use produces no pollution directly

Production (especially fossil fuels) creates pollution

Efficiency only ~30-35% due to:

Conversion losses

Transmission losses

Thermal pollution: waste heat released into environment

Fossil Fuels and Coal

Fossil fuels:

Ancient solar energy stored as chemical energy

Nonrenewable (takes millions of years)

High energy density but polluting

Coal:

Most abundant fossil fuel (10× more than oil + gas combined)

Formed from plant material ~Carboniferous Period 286-360 million years ago

Impacts:

Mining dangerous (black lung disease)

Strip mining/mountaintop removal harm ecosystems

Burning releases:

CO₂ (climate change)

SO₂, NOx (acid rain)

Particulates (air pollution)

Toxic metals and coal ash

Clean Coal and Petroleum

Clean coal:

Carbon Capture and Storage (CCS)

CO₂ captured and stored underground

Currently uneconomical

Petroleum (oil):

Mixture of hydrocarbons

Must be refined via distillation

Products by weight:

Light: gasoline, kerosene

Medium: diesel

Heavy: wax, asphalt

Oil Production and History

1 barrel = 42 gallons

Recovery methods:

Primary: ~25%

Secondary: 25-40%

Tertiary: 30-60%+

Hubbert Peak:

When ~50% of oil is used, production declines

1970s oil crisis:

OPEC reduced supply, prices increased 4x

Caused inflation, unemployment, recession

U.S. Oil Dependence

U.S. response:

Alaskan pipeline

Strategic oil reserve (~37 days supply)

Problems with dependence:

Cost (e.g., $329 billion imports in 2000)

Supply disruption risk

Limited resources

Political and military involvement in oil regions

Oil imports contributed ~2/3 of trade deficit

Oil Resource Limitations

North America is the Most Explored Landmass • Offshore Oil = 30% of Domestic Production • How

Oil Availability and Alternatives

Global use: ~100.2 million barrels/day

Proven reserves: ~1.57 trillion barrels

~50 years of supply remaining (estimate)

Offshore drilling = ~30% of U.S. production

Alternatives:

Oil sands (bitumen): environmentally damaging

Oil shale (kerogen): ~800 billion barrels but not economically viable

Natural Gas

Mainly methane (CH₄)

Cleaner than coal/oil but still fossil fuel

~52 years of proven reserves

Fracking:

Increased production ~20%

Lowered cost

Causes water contamination, air pollution, earthquakes

Recently surpassed coal as main electricity source in U.S.

How Nuclear Energy Works

Controlled fission releases heat

Heat → steam → turbine → electricity

Baseload source (runs continuously)

Fission:

Splitting atoms (U-235)

Fusion:

Combining atoms (not yet practical)

Mass-energy conversion:

Lost mass → energy (Einstein concept)

Chain reaction:

Neutrons split atoms → release more neutrons

Nuclear Fuel and Reactor Operation

Uranium Ore is Mined • Milled Into Yellowcake - 80% UO2 • Purified & Enriched - Separate U235 from U238 • 3-5% U235 • Technical Difficulties Make it Difficult for Less Developed Countries • Control Rods Absorb Extra Neutrons Helping Control Reaction

• When U235 is Highly Enriched Fission Triggers a Self-Amplifying Reaction • Nuclear Weapons Have Small Amounts of Pure U235 or Other Material • The Whole Mass Undergoes Fission in a Fraction of a Second • Releasing All the Energy in A Single Large Explosion • Nuclear Power Plant Fuel Does NOT Require The Same Refinement • Nuclear Fuel is Safer

Nuclear Reactors Have Continuous Chain Reactions Using U235 • Uranium Refined to 3-5% U235 • Faster Neutrons Absorbed by U238 Convert it to Pu239 • Plutonium Undergoes Fission & Releases Energy • Moderators Surround the Enriched Uranium • Slow Down Neutrons & Also Gain HeatNuclear Reactors Have Continuous Chain Reactions Using U235 • Uranium Refined to 3-5% U235 • Faster Neutrons Absorbed by U238 Convert it to Pu239 • Plutonium Undergoes Fission & Releases Energy • Moderators Surround the Enriched Uranium • Slow Down Neutrons & Also Gain Heat

Light-Water Reactors LWRs - Use a Near Pure Water Moderator • Enriched U is Arranged in a Geometric Pattern Surrounded by Moderator • Fuel Rods = Uranium Dioxide Pellets Loaded into Long Metal Tubes • Fuel Rods Placed Close Together to Form a Reactor Core • Core Kept Inside a Reactor Vessel with Both Moderator & Coolant • Control Rods of Neutron Absorbing Material Inserted Between Fuel Rods

Control Rods Absorb Neutrons & Slow Chain Reaction • Chain Reaction Started & Controlled by Withdrawing & Inserting Control Rods • As Control Rods are Removed Fuel Rods & Moderator Heat Up

Nuclear Reactor Types and Risks

Types:

Boiling water reactor

Pressurized water reactor (~65% of U.S.)

Major risks:

LOCA (Loss of Coolant Accident), does not stop radioactive decay

Meltdown (core overheats and melts) enough heat released to melt materials at core

Safety:

Backup cooling systems

Concrete containment structures

Radiation and Radioactive Materials

Fission creates radioisotopes, unstable atoms that emit radiation

Radiation types include gamma rays and X-rays, high energy and penetrating

Radioactive emissions include both particles and radiation

Curie measures radioactivity

Sievert measures biological impact of radiation dose

Absorbed dose measured in joules per kilogram

1 rem equals 0.01 sieverts

Ionizing radiation removes electrons from atoms, creating ions and damaging tissues

Indirect Products of Fission - Become Radioactive by Absorbing Neutrons • Radioactive Wastes - Direct & Indirect Products of Fission • High-Level Wastes - Direct Products of Fission are Highly Radioactive • Low-Level Wastes - Indirect Products are Less Radioactive

Effects of Ionizing Radiation

Ionizing radiation:

Breaks chemical bonds

Alters molecular structure

Cannot be seen or felt at low doses

High doses:

Prevent cell division

Cause radiation sickness at exposures greater than 1 sievert

Damage blood, skin, and tissue repair systems

Low doses:

Damage DNA

Lead to cancer, leukemia, birth defects

Effects can take 10 to 40 years to appear

Additional effects:

Weakened immune system

Mental retardation

Cataracts

Radiation Exposure Levels and Risk

No safe level of radiation according to National Research Council

100 to 500 millisieverts increases cancer risk

Federal maximum exposure standard is 1.7 millisieverts per year

Average U.S. exposure is about 3.6 millisieverts per year

Sources include natural background radiation, not just nuclear energy

Nuclear power contributes less than 1% of total exposure

Radioactive Waste Characteristics

Radioactive waste includes direct and indirect products of fission

High-level waste:

Direct fission products

Highly radioactive

Low-level waste:

Indirect products

Less radioactive

Half-life:

Time required for half of material to decay

One nuclear plant produces about 20 tons of spent fuel per year

Worldwide accumulation approximately 71,780 tons over 40 years

Even low-level waste can take decades to become safe

Radioactive Waste Disposal Challenges

No permanent, fully implemented disposal solution exists

Geological burial considered safest long-term option

Requires:

Short-term containment

Long-term isolation from environment

Challenges:

Finding safe and stable locations

Public opposition, NIMBY

Legal and political barriers

Many countries have not identified suitable disposal sites

Short-Term Nuclear Waste Storage

Spent fuel stored in deep water pools:

Removes heat

Shields radiation

After several years transferred to dry casks:

Air-cooled

More stable storage

By 2015, storage pools nearly full

About 72 storage facilities in the U.S.

Intended as temporary until long-term solution is developed