HWE Exam III

Lectures 19, 20, 21, and 22

Regions of the atmosphere (2)

Mesosphere, stratosphere, troposphere

Meso has most UV rays and IR radiation, trop has some IR radiation emitted from surface

Our greenhouse keeps us at 59F (2)

Sunlight goes through atmosphere, warms surface, then radiated back to space

Most outgoing heat is absorbed by GHGs and re-emitted in all directions, warming surface/lower atmosphere

Harms from depletion of ozone layer (4)

Average temperature of Earth’s surface will gradually increase

Increased amount of UV radiation will reach Earth’s surface

The oxygen content of the atmosphere will decrease

There is no harm, ozone is a toxic air pollutant (crucial to know: only at ground levels! Beneficial in atmosphere)

Attenuation of incoming solar radiation in Earth’s atmosphere (3)

Infared, visible, and UV: wavelength greater than 330 nm, penetration to Earth’s surface

UV: wavelength from 320 to 330 nm, 50 km in atmosphere

High energy: wavelength less than 100 nm, 200 km in atmosphere

UV rays and their effect on skin (3)

UVA rays: Longest rays (320-400 nm), penetrate deep into skin surface and cause DNA damage, result in skin cancers

UVB rays: Mid-length rays (290-320 nm), reach skin surface, cause tanning, burning, and signs of age

UVC rays: Shortest rays (100-290 nm), usually do not penetrate Earth’s ozone layer

Composition of unpolluted air (4)

Nitrogen: 756,000 ppm

Oxygen: ~203,000 ppm

Water: ~31,000 ppm

CO2: 400+ ppm

Atmosphere (4, 3)

Troposphere: 90% of all air molecules, 10% of ozone (“bad ozone”), 17 km above sea level at equator, 8 km over poles

Stratosphere: 10% of all air molecules, 90% of all ozone (ozone layer: found naturally), 30 km in depth

History of the atmosphere (4)

Initially no oxygen in the atmosphere

Around 2.3-2.7 bya, photosynthesizing cyanobacteria began adding oxygen to the troposphere, formation of protective ozone layer

Stratospheric ozone is essential to existence and most life on Earth

Tropospheric ozone is harmful to respiratory system and plants

Ozone cycle in the atmosphere (4)

1. O2 molecules are photolyzed, yielding 2 O atoms (slow process)

2. O3 molecules and O atoms are continuously being interconverted as solar UV breaks O3 into O2, and the O2 molecule quickly reacts with another O atom to yield O3 (fast process); (this interconversion process converts UV radiation into thermal energy, heating the atmosphere)

3. O3 is LOST by a reaction of the O atom or the O3 molecule with each other (O2 + O = O3) OR some other trace gas such as Cl2 (slow process)

Measuring ozone concentrations: The Dobson Unit (DU) (4)

The number of ozone molecules in a 0.01 mm layer of pure ozone OR

2.69 × 10^16 ozone molecules in a 1 cm² column of the atmosphere

Ozone hole average: 100 DU = 1 mm (thickness of a dime)

Global average ozone: 300 DU = 3 mm

Attacking ozone: A brief history (7)

Refrigeration: Food safety, Air conditioning; First refrigerants were toxic, flammable, and explosive (e.g. SO2, NH3)

Non-toxic alternatives (1928): Chlorofluorocarbons (e.g. Freon), Halons (contain bromine, fire-fighting chemicals)

Ozone-depleting pollutants: CFCs and halons (4)

Water-insoluble: Don’t “run out”

Persist up to 200 years: More stable than PCBs and polychlorinated pesticides

“Heavy”, but can move into stratosphere

Ozone hole over Antarctica (1)

Ozone hole: <220 DU

History of the ozone hole (3)

1960s: About 300 DU

Sharp decline from 1980s-1990s (about 285 to 150 DU)

Gradual recovery

Why is the ozone hole over Antarctica (7)

Chlorine: Normally stored as HCl and chlorine nitrate

Antarctic winter atmospheric conditions:

• Polar vortex (swirling whirlpool of stratospheric winds) - Isolates air in vortex

• Polar stratospheric clouds - Dark winters, Low temps, Cloud particles (water. ice, or nitric acid), Reaction of particles form chlorine gas (Cl2)

Polar stratospheric clouds (1)

Polar stratospheric clouds containing frozen crystals provide a reaction surface for the formation of chlorine in the Antarctic stratosphere

Why is the ozone hole over Antarctica (cont…) (6)

Sunlight in early spring (October):

• UV light breaks Cl-Cl bonds

• Cl atoms destroy ozone (catalytic reaction)

Warmer temperatures weaken polar vortex weaker

• Dispersal of chlorine by air from the surrounding latitudes

• Ozone layer stabilizes (until next spring)

Ozone destruction by chlorine atoms (3)

(Right to left):

O3 and Cl react, forming O2 and ClO (O3 destruction)

ClO and O react, forming O2 and Cl (O2 generation)

Net reaction: O + O3 → 2 O2 (Cl used as a catalyst)

UV Index Scale (2)

UV radiation reaching Earth changes O3 depletion and weather conditions

UV index published by EPA ranged from 1 to 11+

Health effects of UV radiation (5)

Human effects:

• Sunburn, accelerated skin aging, skin cancer

• Impaired immunological responses

• Eye inflammation (can lead to cataracts)

Effects on animal and plant life as well

Stochastic health effects of radiation (4)

Associated with CHRONIC exposure to radiation

SEVERITY of stochastic effects are INDEPENDENT of dose (i.e. think of cancer)

PROBABILITY of having the effect IS dose-dependent: At the highest dose: Effect may OR may not occur (no “safe” exposure)

Linear, no threshold, dose response relationship (LNT)

Incidence of BCCs in males 45-59 at locations varying in average daily ambient UVR (2)

Graph displays stochastic effect, shows no safe “threshold” of exposure

The radiation doesn’t determine how severe the cancer is, but rather how likely it is to happen

Schematic diagram of the relation between UVR exposure and the burden of disease (1)

Minimum risk of disease requires optimal exposure to UVR (means getting enough UVR, not too high OR too low)

The 1987 Montreal Protocol was signed for which of the following reasons? (1)

To phase out the use of CFC's causing depletion of the ozone layer

Atmospheric lifetime and ozone depleting potential of selected gases (8)

Cl2 gases:

• Freon (CFC-12): Atmospheric lifetime of 100 years, 1 ODP

• CFC-11: Atmospheric lifetime of 11 years, 1 ODP

• CCl4: Atmospheric lifetime of 26 years, 0.73 ODP

Br2 gases:

• Halon-1301: Atmospheric lifetime of 65 years, 16 ODP

• Halon-16: Atmospheric lifetime of 16 years, 7.1 ODP

• Methyl bromide (natural!): Atmospheric lifetime of 0.7 years, 0.51 ODP

National and international regulations (7)

U.S.

• CFCs in aerosol spray cans banned in 1977

• CFC and halon manufacture ceased by 1995

International: Montreal (1987) and Copenhagen Protocol (1992)

• First global environmental protection treaty

• Ratified by 190 nations

• Considered to be successful

Projected concentration of ozone-depleting chemicals in stratosphere (3)

No protocol: Highest

Only 1987 Montreal Protocol: Second highest (similar concentration to no protocol by 2100, just slower rise with Montreal implemented)

With 1992 Copenhagen Protocol: Significantly lower (big impact!)

How to reduce atmospheric levels of ozone-depleting substances (6)

Phase out of old appliances and collect CFCs

Assisting less-developed countries in phase out

• Grace period in phase out: China banned CFCs and halons in 2007

• Money for 3rd world manufactures to eliminate the product (like agricultural subsidies in U.S.)

Development of substitutes

Finding substitutes: EPAs Significant New Alternatives Policy (SNAP) Program (6)

Refrigeration and air conditioning

Fire suppression and explosion control

• Fire-fighting halons work very well, alternatives are costly or toxic

Sterilants

• Farmers “like” fumigant methyl bromide

Substitution of ozone-depleting substances: HFCs (6)

Manmade chemicals:

• They do not deplete ozone layer, but are potent GHGs

Uses: Refrigerants, aerosol propellants, solvents, fire retardants

Atmospheric sources: Leaks, servicing, equipment disposal

American Innovation and Manufacturing (AIM) Act of 2020: Directs EPA to address HFCs!

What can I do to protect the ozone layer: EPA home appliance tips (7)

Repair air conditioners

• Prevents ozone-depleting refrigerants from escaping

• Make certain refrigerant is recovered before servicing

Remove refrigerant from equipment before disposal

Use EPA certified technician

Work with local officials: Help start a refrigerant recovery/recycling program

Man charged with sneaking banned GHGs into U.S. (1)

Damn thats crazy tho!

Composition of unpolluted air (again) (3)

CO2: 400+ ppm → latest figures (July 2024): 425.55 ppm

N2O (Nitrous oxide): 0.49 ppm

Air pollution kills people (7)

Established risk factors for adverse health effects

Especially dangerous for susceptible populations

Can cause: Severe respiratory problems, res. failure, CVD, cancer, impact fetuses

What is air pollution (13)

Ambient air pollution

• Air around us, ground-levels, tropospheric

Criteria air pollutants

• Criteria comes from the 1970 CAA

• 6 pollutants conformed to the definition (PM10, SO2, NOx, CO, O3, Pb)

National Ambient Air Quality Standards (NAAQS) (1)

Check out the link on slide 8: Includes pollutant, Primary/Secondary, Averaging Time, Level, Form

Primary vs. Secondary standards under the CAA (2)

Primary standards: Provide PH protection, including protecting the health of “sensitive” populations, such as asthmatics, children, and elderly

Secondary standards: Provide public welfare protection, including protection against decreased visibility, damage to animals/crops/vegetation/buildings

Important air pollutants (8)

Volatile organic pollutants (VOCs)

• Group emitted in large amounts

• Sometimes considered along with criteria pollutants

• Major precursors of O3 (with NOx → nitrogen oxides)

Hazardous air pollutants (HAPs)

• Organic (e.g. benzene)

• Inorganic (e.g. asbestos, heavy metals)

Mobile sources (vehicles) in the U.S. (5)

290 million light duty vehicles

3+ trillion miles driven annually

Motor vehicles: About 50% of air pollution

Metropolitan areas: Over 50%

Sources of CO2, NOx, CO, O3, PM10, VOCs

Multipollutant emissions comparison (4)

NH3: Agricultural sources

PM10/2.5: Dust

SO2: Fuel combustion

VOCs: Varied, mostly mobile, then solvent, then industrial

CO (5)

Represents 50% of air pollution by weight nationwide and worldwide

Decrease since 1970s in US/Europe

• Half of motor vehicle CO from only 10% of vehicles in US

• Open burning bans

• Adding oxygen containing fuel additives reduce CO in winter

CO health effects (5)

Causes 11% of hospital admissions for congestive heart failure in the elderly

Affects the brain, causing headaches, dizziness, fatigue, and drowsiness

Coma and death in confined places

• Garage: Suicide

• Bedroom: Malfunction of heating system (Important indoor air pollutant!)

CO sources: Incomplete combustion of carbon-containing fuels (6)

Urban traffic up to 80% of CO

Stalled traffic

Cigarette smoke (and e-cigs)

Coal burning (historical issue)

Biomass burned for cooking and heating

Atmospheric oxidation of methane gas (CH4)

Best time to jog and avoid CO pollution (2)

Go for a jog at 3 AM (daily variation of CO levels)

Winter has highest peaks, spring has lowest

Lead (Pb) (8)

Toxic heavy metal: Children are a susceptible population

Sources of lead in air

• Lead additive in gasoline (still used in some countries)

• Coal burning power plants, old water pipes

Other sources: Lead paint, solder, roadside soil, leaded tableware

Recycling lead-acid batteries: Occupational exposure

Lead air quality (1980-2012) (2)

Annual maximum 3 month average based on 13 sites

1980-2012: 91% decrease in national average!

Sources of SO2 (4)

#1: Coal fired power plants

Cars are a minor source

Volcanoes are big natural sources, 1991 eruption of Mt. Pinatubo cooled Earth for a few years

Second to CO as most common urban air pollutant

SO2: Why we care (6)

SO2 gas irritates the lungs, damages plants and trees

SO2 converted to aerosols:

• Acid particulates are part of acid deposition

• Cooling effect on the climate

Reactions can occur on particle surfaces: Contribute to destruction of stratospheric ozone

Nitric oxide (NOx) (4)

Various NOs

NAAQS (2010) based on NO2

Adversely affects respiratory system

EPA: No area of the country uncompliant with current NO2 standards!

NOx sources (4)

Mostly mobile, then fuel combustion, then industry

Burning fuel at high temperature: Reaction between atmospheric N2 and O2

BUT: High temperatures promote efficient combustion

• Lower emissions of CO, PAHs, and other things at high temps

NOx vs SO2 (7)

NOx are precursors of ground level ozone (NOT SO2)

Like SO2:

• Cooling effect on Earth as aerosols (nitrate/nitric acid)

• Potent GHG

Unlike SO2:

• Nitrate is a major plant nutrient

• Important, toxic water pollutant from fertilizers

PM (3)

Tiny particles and liquid droplets

No fixed composition, size, and shape

EPA regulates PM10 and the MORE dangerous PM2.5

Why care about PM (2)

PM2.5 linked to increase in heart/lung disease, cancer

Don’t know about “bad actors” (sulfate, nitrate, elemental C, C compounds, metal oxides

Sources of PM (2)

PM10 sources: Farms, mines, roads, pollen, only 6% from fossil fuels

PM2.5 sources: Diesel motor vehicles, electric power plants, steel mills

Primary vs. secondary aerosols (8)

Primary aerosol particles:

• Industrial/vehicle exhaust emissions

• Wind-blown dust

• Salt from dried sea spray

Secondary aerosol particles:

• Gaseous pollutants in exhaust emissions

• Emissions from land vegetation and marine organisms

• Produced by photochemical processes in urban smog and higher atmosphere

Atmospheric particles have many effects (8)

Ozone depletion in stratosphere

Acid deposition

Fine aerosol particles:

• Affect human health, reduce visability

• Influence climate both directly and indirectly

Aircraft emissions have disproportionate effect

Sea-salt aerosols are fairly large (generally not transported far above surface)

Atmospheric aerosols (image on slides)

Refer to image

Effects on ozone are location-dependent (1)

Ozone in stratosphere protects Earth, but is harmful in the troposphere

Ozone is NOT a primary pollutant, it is formed from precursors (NOx and VOCs) (6)

NOx + VOC + Heat and Sunlight → O3

Ground level “bad” ozone not emitted directly into the air, but is created through chemical reactions between NOx and VOCs in the presence of sunlight

Major sources of NOx and VOCs:

• Emissions from industrial facilities and electric utilities

• Motor vehicle exhaust

• Gasoline vapors, chemical solvents

“Bad” ozone: Why we care (4)

Serious and persistent air quality problem

US Department of Agriculture: Ground level ozone causes more damage to plants than all other pollutants combined

EPA standard: 75 ppb

Many urban areas DON’T meet this standard

Epidemiologic triangle (3)

Three vertices: Agent (energy), Host (injured person), and Environment (physical and social)

Vehicle vectors connect these three points

Injury: External transfer of energy to human tissues in amounts that damage the cellular structure, tissues, blood vessels, or other structures

Types of energy (6)

Mechanical/Kinetic: Injuries from transfer of physical force (motor vehicle crashes, falls)

Thermal: Injuries from heat/cold exposure

Electrical: Injuries from electrical current

Chemical: Injuries from toxic/corrosive substances (OD)

Radiant: Injuries from radiation

Oxygen depravation (non-energy mechanism): Injuries from lack of oxygen

Classification of injuries (5)

Internal Classification of Diseases (ICD) injury matrices:

• Organizes injury data into helpful groupings to make national and international comparisons

• Classifies two dimensions: External cause (crash) and nature of injury (fracture)

Additional terms to know (2)

Intent of injury: Whether an injury was caused by an act carried out on person by oneself or another person with the goal of injuring or killing

Intentional injury: Injuries that result from self harm, legal intervention, interpersonal actions, and acts of war

Unintentional injury (5)

Damage or harm that is caused by external factors without intent or purpose

Important to note:

• The term unintentional is preferred to accident (unless referring to motor vehicle injuries)

• Accident implies a random event that cannot be prevented

Most unintentional injuries are preventable

Leading causes of death from injury (6)

Unintentional injuries:

• Unintentional poisoning (OD)

• Fall

• Motor vehicle crash

Suicide, homicide

Death by age group (5)

Unintentional poisoning (OD) is the leading cause of injury deaths across ALL age groups

Infants <12 months: Suffocation

Children to young adults (5-24 y.o.): Motor vehicle injuries OR firearm

Adults 35-64: Unintentional poisonings (OD)

Older adults: Falls

Leading cause of death by year age 1-44 (4)

Poisoning (exponential increase 2015-2020) > Motor vehicle traffic > Drowning/Falls > Other unintentional

Injury surveillance (1)

Ongoing, systemic collection, analysis, interpretation, and dissemination of data regarding a health-related event

Where to find injury/violence stats (1)

FARS, SUDORS, NVDRS, WISQARS (national electronic injury surveillance system all injury program)

Non-fatal injury, 2023 (2)

Fall, struck by/against, motor vehicle occupant, poisoning

Total: 26.7 million

Haddon Matrix (7)

Left rows include: Pre-event, Event, Post-event

Top columns include: Host (victim), Agent (energy), Vector (animate), Vehicle (inanimate); Physical environments, and Social environments

SOII Data (7)

Survey of Occupational Injury and Illness (SOII)

• Weighted sample of about 230,000 establishments

• Bureau of Labor statistics

Use of data from injury and illness record keeping forms: OSHA 300 or internal tracking

Excludes federal employees, self-employed, farms with <10 employees

High risk industries: OSHA requires tracking (external vis OSHA 300)

Low risk industries: Internal tracking still required, but not by OSHA

Recordable injury/illness (4)

Any work-related fatality (in COFI)

Any work-related injury or illness that results in loss of consciousness, days away from work, restricted work, or transfer to another job

Any work-related injury or illness requiring medical treatment BEYOND first aid (miss minor injuries)

Any work-related diagnosed case of cancer, chronic irreversible damage, fractured/cracked bones or teeth, and punctured eardrums

Magnitude of nonfatal workplace injuries, private industry 2024 (3)

Estimated number of nonfatal occupational injuries/illnesses: 2.5 million

Nonfatal occupational injuries: 2.34 million (94%)

National occupational illnesses: 150,000 (6%)

Injury by event or exposure, private industry 2023 and 2024 (2)

DART (days away from work, restriction, or transfer) = DAFW (days away from work) + DJTR (days of job transfer or restriction)

About 1.46 million DART injuries per year

Hierarchy of controls (6)

(Most effective)

Elimination: Physically remove hazard

Substitution: Replace hazard

Engineering controls: Isolate people from hazard

Administrative controls: Change how people work

PPE: Protect workers with PPE

(Least effective - requires employees to protect themselves from hazards)

Hierarchy of fall protection (6)

Hazard elimination

Passive fall protection (engineering)

Fall restraint systems (PPE)

Fall arrest systems (PPE)

Controlled access zones (No good admin control for fall protection)

Increasingly less effective from elimination to controlled access

Census of fatal occupational injuries

An event or exposure in the work environment that causes or contributes to a death

5000 deaths compared to 2.5 non-fatal injuries

Leading causes: Transportation, falls, contact incidents, violent acts

What is the difference between the epidemiology of fatal injuries and fatal occupational injuries? (2)

The epidemiology of fatal occupational injuries focuses exclusively on deaths occurring while working, often due to acute, preventable events, using surveillance like CFOI

In contrast, general fatal injuries cover all fatal events, including unintentional injuries (such as road traffic)

Regulations (5)

The National Labor Relations Act (1935): Doesn’t include agricultural workers in its protections

• United Farm Workers 1966: Cesar Chaves and Dolores Huerta

The Labor Standards Act (1938): Exempted small farms from the minimum wage

Minimum age of 14 (not 16), for family farms, can begin working at 12!

Hazardous tasks can be performed at 16 (not 18)

Percent working in agriculture (5)

26% of global population

2% of U.S. population

1900: 40% of U.S. → 1930: 21% of U.S.

Trends: Number of farms is decreasing, Average farm size is increasing, Land in farms roughly same

U.S. farms and their value of production by farm type (2)

Highest number of farms are small, but their production value is small

Large-scale farms make up only 5% of farms but about 50% of production

Median income of U.S. farm households by income/farm type (3)

Small farms make most of their income from off-farm sources

Midsize farms make about half of their income from farming

Large-scale farms make TONS of income, almost completely from farming

Farm workers and managers are different populations (4)

ACS Data:

Farmworkers: 26% female, 63% hispanic, 56% are U.S. citizens

Farm manager/supervisor: 17% female, 29% hispanic, 83% are U.S. citizens

Farmer/producer: 36% female, 3% hispanic

Occupations with high fatal work injury rates (2)

Fishery/logging workers, aircraft pilots, and recyclable material collectors all have high fatal work injury rates

Occupations with high NUMBER of fatal work injuries are driver workers/truck drivers and farmers/ranchers

Fatal injury ranking by occupation (8)

Farmer:

1. Transportation

2. Falls

3. Violence

Farmworker:

1. Transportation

2. Contact with the machine/object

3. Exposure to harmful substances/environments (electric current, confined space)

Number of fatal injuries in agriculture, Illinois (2)

By far, most from tractors, then roadway-related

Grain bins and farm equipment

Acute injuries (3)

Tractor rollovers account for 50% of farm-related fatalities

Roll-over protective structures (ROPS) help prevent

Less than 60% of tractors have ROPS

Challenges in quantifying non-fatal injuries (4)

BLS does not count as self-employed

SOII excludes <11 employees

Underreporting of injuries

Total number of workers difficult to count

Farm related counts and injury severity by injury cases (2)

Highest amount from falls, significant amount are moderate/severe

Then natural, machinery, and motor vehicle non-traffic

Injury diagnosis for farm-related injuries (2)

Over half are fractures

Then, open wound, superficial injury, and internal organ

Distribution of injuries from transportation sources (3)

Vehicle traffic and vehicle non-traffic

Ag. vehicle non-traffic

Riding animal, ATV non-traffic

Special hazards of livestock farming (8)

Contact with animal: 5% of fatal deaths

Acute and chronic respiratory hazards:

• Gases - H2S, NH3

• Organic dust exposures

Zoonoses

Noise

Livestock insecticides

Low back and upper extremity MSD among dairy farmers

Special hazards of crop farming (5)

Injury: Heavy machinery (high risk for injury), Grain storage

Illness: Pesticides/agricultural chemicals, Grain dusts (Organic Dust Toxic Syndrome)

• Specifically, Farmer’s Lung (allergic reaction to mold spores)

Ergonomic exposures (vibration)

UV radiation

Pesticide exposure (3)

Organophosphates:

Symptoms: Unconsciousness, constriction of pupil, muscle twitches, secretions from nose and mouth, breathing difficulty

Mechanism of Action: Blocks enzyme that breaks down acetylcholine

Grain engulfment and entrapment (2)

After 4 seconds: Sink knee-deep in the suction of flowing grain, cannot be freed without help

After 20 seconds: Buried (engulfed), mostly fatal

Describe Flowing grain, Bridged grain, and Vertical grain wall avalanche (3)

Flowing grain: Sink down into grain that is flowing out of storage

Bridged grain: Thin grain bridge with large hole underneath, likely to collapse and then entrap

Vertical grain wall avalanche: Huge wall of grain crashes down, buried underneath

Lifelife system stet-up

Research, is it PPE or engineering controls to protect against falling into grain?

Musculoskeletal disorders (2)

Hazard: Heavy lifting; Repetitive movements during planting, pruning, and harvesting

Control: Proper fit tool, Job rotation