Sunscreen's Effects on UV Attenuation

Chase McCorkle 9th grade Central Catholic High School

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

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

Sunscreen (continued)

• Non-mineral sunscreen uses harmful ingredients

• Mineral sunscreen uses environmentally safe ingredients

• Sun protection factor (SPF) – the measurement of protection

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

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

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

Purpose

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

Hypothesis

• Null –there will be no significant effect of the sunscreen

• Alternative – Both sunscreens will have protective effect on UV exposed yeast survivorship

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

Procedure1. 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

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

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

Sunscreen effects on UV exposed survivorship

P-Value: 0.00039111

UV exposure (seconds)

0 60 120 360 7200

30

60

90

120

88.2

51.5

4.31.3 0.8

88.2

109

73.5

32.5

17.8

88.2

42.5

61 0

Control

Non Mineral

Mineral

Yeast

colo

nie

s

P- Values

Time 0 60 120 360 720

P-value 0 0.9657 1.19E-0.6

0.00205 0.03998

Analysis Dunnett’s TestT-Value 3.03

Time 0 Sec 60 sec 120 sec 360 sec 720 sec

Mineral T-Value

0Insignificant

1.334Insignificant

0.295Insignificant

0.035Insignificant

0.114Insignificant

Non-Mineral T-Value

0 Insignificant

8.524Significant

11.689Significant

4.449Significant

2.596Insignificant

Analysis Dunnett’s Test

T-value 3.03

Time 0 sec 60 sec 120 sec 360 sec 720 sec

Mineral T-Value

0Insignificant

9.852Significant

11.393Significant

4.485Significant

2.711Insignificant

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

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

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

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.

Anova (all)Anova: Single Factor

SUMMARYGroups Count Sum Average Variance

Column 1 20 615 30.75 1566.618Column 2 20 1356 67.8 1587.747Column 3 20 447 22.35 730.2395

ANOVASource of Variation SS df MS F P-value F crit

Between Groups 23393.1 2 11696.55 9.033003 0.000391 3.158843Within Groups 73807.5 57 1294.868

Total 97200.6 59