1. Which Fabrics Best Block UV Rays? Kris Sabatini CCHS, Grade 9 2 nd Year in PJAS

2. Ultraviolet Rays - Ultraviolet (UV) rays are light waves that have shorter wavelengths than visible light. They range from 400nm to 10nm. - Given off from the sun but most are absorbed by the ozone layer. - The waves that reach Earth can lead to many problems in humans caused by DNA damage: skin burn, sun poisoning, skin irritation, redness, photo- aging, nausea, and possibly skin cancer. - The FDA Protection methods include sun screen, hats, and radiation-blocking clothing when outside for long periods of time.

3. Electro-magnetic spectrum

4. Fabrics Cotton - Common naturally grown fabric - Past Experiments show it to be effective at blocking UV rays Polyester - Manmade fabric made from fossil-fuels - Contains trace amounts of zinc-oxide, a UV inhibiter Nylon - Manmade fabric made from plastic fibers - Past experiments show it to be ineffective at blocking UV rays Wool - Natural fabric made of the hair of sheep - Very densely woven together making harder for UV rays to penetrate

5. Yeast Most studied cell in the world Easy to grow and culture Similar cell cycle, biochemistry and genetics to other eukaryotic cells, like those in human skin Saccharomyces cerevisiae

6. Objective/Purpose - To determine the fabric among four common types that is most effective at blocking UV rays

7. Hypothesis - The fabrics will not vary significantly in blocking UV light, yielding statistically similar yeast survivorship.

8. Materials 60 YEPD agar plates(1% yeast extract, 2% peptone, 2% dextrose, 1.5% agar) Sterile dilution fluid [SDF] (10mM KH2PO4, 10mM K2HPO4, 1mM MgSO4,.1mM CaCl2, 100mM NaCl) Klett spectrophotometer Sterile pipette tips and Micropipettors Vortex Sidearm flask Spreader bar Ethanol Micro burner Saccharomyces cerevisiae (yeast) UV Hood Rubber Gloves Test tubes Test Tube Rack SDF Test Tubes Autoclave 4 white fabrics, nylon, cotton, polyester and wool, cut into squares of 80 x 80 mm

9. Procedure 1.Sterilized Fabrics by autoclave. 2. Saccharomyces cerevisiae was grown overnight in sterilized YEPD media. 3.A sample of the overnight culture was added to YEPD in a sterile sidearm flask. 4. The culture was incubated at 30°C until a density of 50 Klett spectrophotometer units was reached. This represents a cell density of approximately and 10 7 cells per mL. 5. The cultures were diluted in sterile dilution fluid to a concentration of approximately 10 3 cells per mL. 6. 0.1 mL aliquots were spread onto the YEPD agar plates. 7. Sterilized hands by washing, putting on rubber gloves, and rubbing with ethanol. 8.Sterilized UV hood by rubbing with ethanol. 9.Placed agar plates in UV hood.

10. 10.Uncovered agar plates. 11.Placed sterile fabrics over uncovered yeast plates. 12.Exposed to UV rays (for 0,1, and 4 minutes). 13.Removed fabrics for agar plates. 14.Recovered the agar plates with its lid. 15. Removed from UV hood. 16. Repeated for each exposure time period. 17. Incubated for 48 hours at 30C. 18. The resulting colonies were counted and recorded.

11. Averages of Surviving Colonies 92 93 89 36 70 0 92 89 70 87 38 0 20 40 60 80 100 CottonPolyesterNylonWool Fabrics Number of Surviving Colonies 0 min 1 min 4 mins

12. P=.99509P=8.8E-09 P= 1.34 E-10 T= 2E-10

13. Conclusion The null Hypothesis was rejected. In the experiment, cotton was the most effective fabric at inhibiting ultraviolent rays which is supported a Dunnett’s Test preformed between Polyester and Cotton. The experiment also supports past studies that show nylon to be relatively ineffective at blocking UV rays. Polyester appeared to be the best synthetic fabric at inhibiting the UV rays.

14. Limitations -Due to slight differences in positioning in the UV hood, the cultures may have received slight differences in the amount of exposure to the ultra-violent rays. - Fabrics may have touched the growing cultures during UV exposure (Not a contamination risk, but might inhibit growth or remove cells from the cultures.)

15. Further Testing Different Fabrics Different UV exposure length Different model Varying growth times Photometer to measure UV penetration

16. Sources www.FDA.com http://www.uvguide.co.uk/ http://www.fabrics.net/ http://www.lumen- associates.com/UVlight.htm http://www.lumen- associates.com/UVlight.htm http://www.medgadget.com/