“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 Water Acidification Global Warming

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

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. 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

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

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%;

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

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) 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…

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 

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.

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.”

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 NET EFFECT: 2 O3 + UV-B  3 O2 (UV-B is Absorbed) UV-B light COLLISION OXYGEN FORMATION

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

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

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