1. Sunscreen's Effects on UV Attenuation Chase McCorkle 9 th grade Central Catholic High School

2. Ultraviolet Light Electromagnetic radiation The wavelength is shorter than that of visible light The shorter wavelength has greater energy The sun produces UV light Responsible for sunburn and some cancers Alters and damages DNA Three types; UVA, UVB, UVC

3. Sunscreen Commonly used topical ointment for help to prevent sunburn Prevents sunburn by reflecting or absorbing ultraviolet radiation from the sun Uses organic particulates to reflect or scatter UV light

4. Sunscreen (continued) Non-mineral sunscreen uses harmful ingredients Mineral sunscreen uses environmentally safe ingredients Sun protection factor (SPF) – the measurement of protection

5. Microbial Flora Comprised of all the microorganisms that reside in or on the human body (examples: skin, saliva, gut) Most species are non-pathogenic microorganisms that either have no effect on the host or offer some benefit

6. Skin Flora Comprised of all microorganisms of the human flora that live on the skin Trillions of bacteria live on or in the skin of an average human Stimulates the skin's immune system by the prevention of colonization by pathogenic microorganisms

7. Saccharomyces Cerevisiae Yeast Unicellular, eukaryotic microorganism 3–4 µm diameter The most studied cellular model in research Cell cycle is similar to human cells Comparable DNA replication, recombination, cell division and metabolism

8. Purpose To find if mineral sunscreen and non-mineral sunscreen vary significantly in the remediation of UV light’s effects on yeast cells

9. Hypothesis Null – there will be no significant effect of the sunscreen Alternative – Both sunscreens will have protective effect on UV exposed yeast survivorship

10. Materials 48 YEPD agar plates Spreader bars Ethanol Bunsen burner Vortex Saccharomyces Cerevisiae Yeast Mineral sunscreen SPF 60 Non-mineral sunscreen SPF 60 Wax paper 254 nanometer LabConco UV hood light with a UVC bulb 20- 40 micro watts per square centimeter 0.7-0.9 micro watts per square centimeter at the working surface Incubator Tape Micro pipettes Sterile solution Klet spectrophotometer

11. Procedure 1. Saccharomyces cerevisiae was grown overnight in sterilized YEPD media 2. A sample of the overnight cultures was added to fresh media in a sterile sidearm flask 3. The culture of yeast was incubated at 30°C until a density of 50 Klett spectrophotometer units was reached. This represents a cell density of 10^7 cells per mL 4. The culture was diluted in sterile dilution fluid to a concentration of approximately 10^5 cells per mL

12. Procedure (continued) 5.Measured out 0.1 grams of mineral sunscreen on wax paper 6.Spread in a circular motion using a sterilized spreader bar 7.Created 16 pieces for mineral and 16 non-mineral 8.Used sterile pipette to add 0.1 mL of yeast (10^3 cells per mL) to the YEPD plate 9.Attached the wax paper covered with sunscreen as a replacement lid for the plate

13. Procedure (continued) 10. Attached wax paper with nothing on it to create a control 11. Exposed plates to UV light at the time of 0, 60, 120, 360, and 720 seconds 12. When finished, took off the wax paper and put on the lids 13. Incubated at 38 degrees c for 48 hours 14. Measured the survivorship by counting the colonies of yeast 15. Took plates to lab at Carnegie Mellon University to be autoclaved

14. Sunscreen effects on UV exposed survivorship P-Value: 0.00039111 UV exposure (seconds) Yeast colonies

15. P- Values Time060120360720 P-value00.96571.19E-0.60.002050.03998

16. Analysis Dunnett’s Test T-Value 3.03

17. Analysis Dunnett’s Test T-value 3.03

18. Results Does UV light have a significant effect on yeast survivorship? Yes: P-Value 0.00039111 Is there significant variation between mineral and non-mineral sunscreen? Yes: T-Crit is greater than 3.03 at 60, 120, and 360 seconds but not at 720 seconds

19. Conclusion Null – UV light will not have a significant effect on yeast survivorship Reject the null Alternative – Both sunscreens will have protective effect on UV exposed yeast survivorship Reject the alternative

20. Limitations and extensions Plate lids were replaced which could lead to possible contamination Hard to insure even spread Only UVC light used Use different brands Use shorter exposure time intervals Use other types of exposure Use other means of spreading Try different microbial model Test growth/help

21. Works cited 1. "Effects of UV Radiation on You." Student's Guide -. N.p., n.d. Web. 16 Dec. 2014. 2. HowStuffWorks. HowStuffWorks.com, n.d. Web. 20 Dec. 2014. 3. "Natural vs. Chemical Sunscreen - Goddess Garden." Goddess Garden Natural vs Chemical Sunscreen Comments. N.p., 18 Mar. 2012. Web. 03 Dec. 2014. 4. "OCTINOXATE." || Skin Deep® Cosmetics Database. N.p., n.d. Web. 10 Dec. 2014. 5. "OXYBENZONE." || Skin Deep® Cosmetics Database. N.p., n.d. Web. 11 Dec. 2014. 6. "What Is SPF Sunscreen?" - Sun Protection Factor Explained by Badger. N.p., n.d. Web. 17 Dec. 2014.

22. Anova (all) Anova: Single Factor SUMMARY GroupsCountSumAverageVariance Column 12061530.751566.618 Column 220135667.81587.747 Column 32044722.35730.2395 ANOVA Source of VariationSSdfMSFP-valueF crit Between Groups23393.1211696.559.0330030.0003913.158843 Within Groups73807.5571294.868 Total97200.659