Effects of Sunscreen and tanning lotion on yeast cells exposed to UV light

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Husanpreet Kaur Lab Partners: Chelsea Roundtree L113 Section 1365 Effects of Sunscreen and tanning lotion on yeast cells exposed to UV light Introduction: UV radiation is a type of radiation that is emitted from the sun and other artificial sources. UV radiation is classified into three primary types: ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC) (“UV Radiation | NCEH Environmental Health Features”). For UVA the wavelengths range from 315-399 nm, for UVB the wavelengths range from 280-314 nm, and for UVC the wavelengths range from 100-279 nm. Most of the UV radiation that reaches the earth is UVA although some forms of UVB also reach earth. But UVA is the most constant presence and has the biggest effect on the human skin. The wavelengths from the UVB region are absorbed into the skin and cause the skin to produce erythema, burns, and then finally skin cancer (“Sun Safety | Skin Cancer | CDC”). Even though UVA is the one that is most frequently exposed to the earth it only really causes the skin to age and wrinkle while being weakly carcinogenic (Matsumura). Most skin cancers are caused by too much exposure to UV lights, so it is imperative to use UV protectants (“Sun Safety | Skin Cancer | CDC”). Two such protectants are sunscreens and tanning lotions. Sunscreens block UV radiations from being absorbed by the skin. Sunscreens have a sun protection factor (SPF) on their labels which tells you how well the sunscreen protects the skin. As the SPF value increases so does the sunburn protection factor. But no sunscreen can block all UV rays, some still manage to make it through the barrier (“Sunscreens: Protect Your Skin - Health Encyclopedia”). Tanning lotions on the

other hand are created to provide accelerated tanning with very little SPF (“What is the Difference Between Sun Tan Lotion and Sunscreen? – Tanning Lotion Warehouse Blog”). The purpose of this lab is to see which of two UV protectants (sunscreen and tanning lotion) has a better chance of providing protection from UV radiation. In this experiment the hypothesis that will be tested is whether not sunscreen will have a better/higher rate protection for the survivability of yeast as compared to tanning lotion. It is predicted that sunscreen will be a better protectant due to sunscreen having a broad spectrum of protection and higher range of SPF. Methods First serial dilutions were performed, in which the Saccharomyces cerevisiae wild-type strain was obtained from an Eppendorf tube. The Saccharomyces cerevisiae was placed in Yeast Peptone Dextrose broth (YPD) which is a 24-hour overnight enrichment media. The culture was then prepared at 30˚Celcius. The Saccharomyces cerevisiae was diluted to 10^-4 dilution. Then 100 µl of yeast were plated onto the yeast synthetic complete (SC) agar plates. Next 1 mL of Hawaiian Tropic Everyday Active SPF 15 sunscreen was taken and spread onto 12 of the 24 plates. The other 12 plates were coated in 1 mL of Hawaiian Tropic Island Tanning Dry Spray Oil SPF 15 tanning lotion. Then 3 plates of sunscreen, and 3 plates of tanning lotion were irradiated under a UVG-54 lamp, 254nM, 6 watts (UV light) for 0 seconds (control group). 3 sunscreen plates and 3 tanning lotion plates were irradiated under UV light for 40 seconds, another 6 plates were irradiated for 80 seconds, and the remaining 6 were irradiated for 120 seconds. These plates were then incubated at 30˚C for 2 days and refrigerated. After refrigeration, the number of colonies on each plate were counted. Results

0 20 40 60 80 100 120 140 155 160 165 170 175 180 Number of yeast colonies found after application of sunscreen Time (secs) Number of Colonies Figure 1: The number of yeast colonies found in the plate started off at about 177 colonies after 0 seconds of UV irradiation, before drastically dropping to 163 colonies at 60 seconds and then shooting up to 174 colonies at 80 seconds and then finally spiking up to 178 colonies at 120 seconds. 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 160 Number of yeast colonies found after application of tanning lotion Time (secs) Number of Colonies Figure 2: The number of yeast colonies found in the plate started off at about 140 colonies after 0 seconds of UV irradiation, before dropping to about 90 colonies at 60 seconds and then shooting up to about 130 colonies at 80 seconds and staying the same up to 120 seconds.

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60 secs 80 secs 120 secs 86.00% 88.00% 90.00% 92.00% 94.00% 96.00% 98.00% 100.00% 102.00% Average percent survivability of yeast after application of sunscreen Time (seconds) Percen Survivability Figure 3: The average percent survivability of yeast after the application of sunscreen increases drastically from 60 seconds to 80 seconds at about 92% to about 98.5%, and then it increases again from 80 seconds to 120 seconds at 98.5% to 100%. 60 secs 80 secs 120 secs 0.00% 20.00% 40.00% 60.00% 80.00% 100.00% 120.00% Average percent survivability of yeast after application of tanning lotion Time (seconds) Percen Survivability Figure 4: The average percent survivability of yeast after the application of tanning lotions increases from 60 seconds to 80 seconds at about 65% to about 95%, and then it stays at 95% from 80 seconds to 120 seconds.

From Figures 1 and 2 it was seen that on average a higher number of colonies were found on the plates that were irradiated after the application of sunscreen in comparison to the plates that had been irradiated after the application of tanning lotion. In Figures 3 and 4, the plates that used sunscreen had a higher percent survivability as compared to the plates that used tanning lotion. Discussion: In this lab it was tested to see if whether not sunscreen would have a higher rate of protection for the survivability of yeast in comparison to tanning lotion. From the data it can be inferred that the sunscreen has a higher survivability rate for the yeast cells than tanning lotion because the number of colonies present in the dishes plated with sunscreen was higher than those plated with tanning lotion. The uses and properties of sunscreen and tanning lotion could be seen in the experiment as both plates had a substantially high percent of survivability for the yeast cells meaning that both applications were fairly successful in blocking out the UV radiation from affecting the cells. In another experiment done by Noorah Saleh Al-Sowayan and Tomather Alhamdy, the effects of different pieces of cloth versus sunscreen from UV radiation was tested on yeast cells. In this experiment they tested sunscreen with SPF 50, a cotton cloth, and a polyester cloth. From their results they concluded that the sunscreen was a better protectant than cloth as the number of yeast cells found in the sunscreen petri dish were 60, in comparison to the 25 found in the dish covered with a cotton cloth and the dish covered and 15 found in the dish covered with polyester. In the control the number of yeast cells that were found were 75. This shows that sunscreen had a higher rate of efficiency in protecting the yeast cells from UV radiation which is consistent with the results found in our experiment.

Within the data sets many differences could be spotted between those done individually and those of the group. Some significant errors could be seen in at the 60 second mark of irradiation for both the individual and the group data. It was expected that the number of yeast colonies would either stay around the same range or be more as compared to the yeast colonies at 80 and 120 secs, but from the data it could be seen that there was a drastic drop in the number of colonies at 60 seconds as compared to those a 0, 80, and 120 seconds. This error was seen in the plates for sunscreen and for tanning lotion. But this also may not have been an error as it was consistent throughout the different trials. A reasoning behind this data could be that for the 60 second plates the sunscreen and tanning lotions on their respective lates had not yet taken effect on the yeast and within that time frame instead of keeping yeast cells alive, the lack of effect and the irradiation caused the yeast cells to die out. Some other sources of error that could have occurred were inaccuracy in applying the tanning sunscreen. During the process of application, there may have been an inconsistent amount spread across the plates and there may have been an inconsistency in the amount of sunscreen applied onto the different plate. Other errors may have occurred when plating the yeast cells, some examples could be an inconsistent amount were plated or the spreader may have been too hot when being used to spread the yeast cells. For future studies it would be recommended to use a sunscreen and tanning lotion brand that does not have a spray applicator to have as accurate of a result as possible. In the future it would also be interesting to see how different brands of sunscreen vary from each other and seeing what is it that makes them so different from each other. This could be done with tanning lotion as well. The effects of water-resistant sunscreen and tanning lotion could also be tested for accuracy and effectiveness.

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Works Cited Matsumura, Yasuhiro. “Toxic effects of ultraviolet radiation on the skin.” Science Direct , 6 May 2021, https://www.sciencedirect.com/science/article/pii/S0041008X03004952. Accessed 25 February 2024. “Sun Safety | Skin Cancer | CDC.” Centers for Disease Control and Prevention , https://www.cdc.gov/cancer/skin/basic_info/sun-safety.htm. Accessed 25 February 2024. “Sunscreens: Protect Your Skin - Health Encyclopedia.” University of Rochester Medical Center , https://www.urmc.rochester.edu/encyclopedia/content.aspx? contenttypeid=85&contentid=P01351. Accessed 25 February 2024. “UV Radiation | NCEH Environmental Health Features.” Centers for Disease Control and Prevention , 3 July 2023, https://www.cdc.gov/nceh/features/uv-radiation-safety/index.html. Accessed 25 February 2024. “What is the Difference Between Sun Tan Lotion and Sunscreen? – Tanning Lotion Warehouse Blog.” Tanning Lotion Warehouse , 29 October 2021, https://www.tanninglotionwarehouse.com/blog/difference-between-sun-tan-lotion-and- sunscreen/. Accessed 25 February 2024.

Effects of Sunscreen and tanning lotion on yeast cells exposed to UV light

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