Transcript What Is The Deal With Ozone

“The World We Create”
NATS 101
Section 6
Next homework
available in D2L!
02/18
UNIT 2:
Environmental changes,
Natural or Man-Made?
The World We Create
Our actions can have a very large impact on the
environment. To illustrate these effects, in this
unit we will analyze three major phenomena:
Ozone
Depletion
Global
Warming
Water
Acidification
Why Should you Care?
Let’s first talk about SKIN CANCER:
DID YOU KNOW THAT….?
“Skin cancer is the most common form of
cancer in the United States.”
75% deaths
“1 in 5 Americans
will develop skin
cancer in the
course of a
lifetime.”
Did you know that?
Melanoma rates have tripled for men over the past 30
years and more than doubled for women.
Melanoma is the most common cancer in the young
population (20 – 39 age group).
Generate Hypothesis
What causes skin cancer?
Why is the rate of skin cancer increasing?
Why is it different for males than females?
How do you explain the different death rates from
Melanoma shown in the map?
Increase
What causes skin cancer?
Ultraviolet
radiation (UV)
from the sun is
the main cause of
all forms of skin
cancer.
THREE
MAIN TYPES
OF UV
UV-A
(lower energy)
Wrinkling and aging.
Melanoma.
UV- B
(mid energy)
Tanning and sunburn.
BCC.
UV-C
(high energy)
Extremely harmful.
Direct damage DNA
Why are rates different?
 Amount of UV exposure (natural and artificial) ;
 Personal background (genetics);
 Ethnicity (skin color);
Melanoma Incidence
Melanoma
Incidence
Rates
per year
Reasons: Tanning bed use, hiking, skiing,
skin color, age, sunscreen use.
Natural Protection
How does it work?
UVB light stimulates melanocytes to produce a pigment
called melanin.
Melanin is oxidized by UVA light, darkening the skin.
(Melanin absorbs UV and transforms it into heat)
FACTS:
 Nearly 30 million people tan indoors in the U.S. every
year;
 On an average day, more than one million Americans use
tanning salons;
 71% of tanning salon patrons
are girls and women aged 16-29;
 First exposure to tanning beds in youth
increases melanoma risk by 75%;
Sunscreens
Sunburn/BCC
Two types:
Organic
Transform UV into IR
radiation
(like Melanin)
Inorganic
Made of substances that
scatter/reflect UV
Aging/Melanoma
Sun Protection Factor
The SPF rating is calculated by comparing the
amount of time needed to produce a sunburn on
protected skin to the amount of time needed to
cause a sunburn on unprotected skin
(Measure of UVB protection only).
How do you measure SPF?
Burn Rate
(Without
Sunscreen)
10 minutes
10 minutes
10 minutes
SPF Number
Time it takes
to burn
2
(50 % UVB)
20 minutes
15
(93.3 % UVB)
30
(96.7% UVB)
150 minutes
300 minutes
However, the actual “burning time” depends
on many factors…
UV Exposure
We used the UV INDEX as a measure of the intensity of
UV radiation in the sunlight that reaches the Earth
(at solar noon).
UV
Index
Exposure
Level
Damage to lighterto Level
UV IndexDamage
Exposure
skinned
darker-skinned
0-2
0-2
Minimal
30 min
3-5
3-4
5-6
Low
Moderate
15-20 min
10-12 min
7-9
High
7-8.5 min
10-15
Very High
4-6 min
6-7
Low
> 120 min
Moderate
75-90
High
50-60
8 - 10
Very High
33-44
11
Extreme
20-30
UV Index
In your groups…
• Decide which of these factors may have a influence
on the actual UV index value on a given day:
Cloud Coverage
Elevation
Latitude
Concentration of ozone in the atmosphere
Day of year Time of day
Arrange the relevant factors from most to least
important.
You have 5 minutes
Factors that influence UV index:
Time of day, day of year, ozone concentration,
latitude, elevation, cloud coverage.
What is Ozone?
O3
Ozone (O3) is a gas made
of molecules with three
oxygen atoms.
O2
It differs from Oxygen (O2), the
gas that we need to survive.
For every 10 million air molecules,
about 2 million are OXYGEN
and only 3 are OZONE!
Bonds between the atoms in O3 are weaker than
the bonds between atoms in O2.
That makes ozone more “reactive.”
Where is Ozone?
Stratosphere
• 17-50km above the Earth
• 90% of atmospheric ozone
• Shields us from UV
radiation
Troposphere
• 0-17km above the Earth
• 10% of atmospheric ozone
• Toxic effects on humans
and vegetation
• “Smog”
How does O3 protect us?
Ozone’s Lifecycle: Destruction
BONDS BREAK
UV-B light
NET EFFECT:
2 O3 + UV-B  3 O2
(UV-B is Absorbed)
COLLISION
OXYGEN FORMATION
How does O3 protect us?
Ozone’s Lifecycle: Creation
BONDS BREAK
UV-C light
NET EFFECT:
3 O2 + UV-C  2 O3
COLLISION
(UV-C is Absorbed)
OZONE FORMATION
Ozone Cycle Recap.
Natural destruction of Ozone: UVB absorbed!
UVB
O3
O + O2
Natural formation of Ozone: UVC absorbed!
O + O2
UVC
O3
Every day, 300 million tons of O3 form and
an equal mass decomposes.
1% decrease in ozone
may result in a 2%
increase in solar
ultraviolet, UV-B.
95%
penetrates
5%
penetrates
0%
penetrates