1. “The World We Create” NATS 101 Section 6
Next homework available in D2L!
02/18

2. UNIT 2: Environmental changes, Natural or Man-Made?

3. 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
Water Acidification
Global Warming

4. Let’s first talk about SKIN CANCER:
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.”
“1 in 5 Americans will develop skin cancer in the course of a lifetime.”
75% deaths

5. 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).

6. 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

7. What causes skin cancer?
Ultraviolet radiation (UV) from the sun is the main cause of all forms of skin cancer.
UV-A (lower energy) Wrinkling and aging. Melanoma.
UV- B (mid energy) Tanning and sunburn. BCC.
THREE MAIN TYPES OF UV
UV-C (high energy)
Extremely harmful. Direct damage DNA

8. Why are rates different?
Amount of UV exposure (natural and artificial) ;
Personal background (genetics);
Ethnicity (skin color);
Melanoma Incidence

9. Melanoma Incidence Rates per year
Reasons: Tanning bed use, hiking, skiing, skin color, age, sunscreen use.

10. Natural Protection

11. UVB light stimulates melanocytes to produce a pigment called melanin.
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%;

12. Sunscreens
Two types:
Sunburn/BCC
Aging/Melanoma
Organic Transform UV into IR radiation (like Melanin)
Inorganic Made of substances that scatter/reflect UV

13. 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).

14. How do you measure SPF? Burn Rate (Without Sunscreen) SPF Number
Time it takes to burn
10 minutes
2 (50 % UVB)
20 minutes
15 (93.3 % UVB)
150 minutes
30 (96.7% UVB)
300 minutes
However, the actual “burning time” depends on many factors…

15. Damage to lighter-skinned Damage to darker-skinned
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 lighter-skinned
Damage to darker-skinned
0-2
Minimal
30 min
> 120 min
3-4
Low
15-20 min
75-90
5-6
Moderate
10-12 min
50-60
7-9
High
7-8.5 min
33-44
10-15
Very High
4-6 min
20-30
UV Index 
Exposure Level
0 - 2 
Low 
3 - 5 
Moderate 
6 - 7 
High 
8 - 10 
Very High 
11 
Extreme 

16. 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

17. Factors that influence UV index:
Time of day, day of year, ozone concentration, latitude, elevation, cloud coverage.

18. Ozone (O3) is a gas made of molecules with three oxygen atoms.
What is Ozone?
Ozone (O3) is a gas made of molecules with three oxygen atoms. O3 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.”

19. 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”

20. How does O3 protect us? Ozone’s Lifecycle: Destruction
BONDS BREAK
NET EFFECT:
2 O3 + UV-B  3 O2 (UV-B is Absorbed)
UV-B light
COLLISION
OXYGEN FORMATION

21. How does O3 protect us? Ozone’s Lifecycle: Creation
UV-C light
BONDS BREAK
NET EFFECT:
3 O2 + UV-C  2 O3 (UV-C is Absorbed)
COLLISION
OZONE FORMATION

22. Every day, 300 million tons of O3 form and an equal mass decomposes.
Ozone Cycle Recap.
Natural destruction of Ozone: UVB absorbed!
O O + O2
UVB
Natural formation of Ozone: UVC absorbed!
UVC
O + O O3
Every day, 300 million tons of O3 form and an equal mass decomposes.

23. 95% penetrates 5% penetrates 0% penetrates
1% decrease in ozone may result in a 2% increase in solar ultraviolet, UV-B.
95% penetrates
5% penetrates 0%
penetrates