The Effect of Ultraviolet Ray Exposure, Intensity, and Sunscreen Protection on the Growth of Escherichia coli

When people spend excessive lengths of time out in the sun, exposure to ultraviolet rays can be damaging to skin cells and their growth. The experiment tested the effects of UV exposure and intensity, as well as sunscreen protection, on the growth of Escherichia coli (E. coli). The experiment was intended to find individual effects of these factors as well as how they interacted with each other. The growth of E. coli represented skin cells, and how, if left exposed for too long, they could be damaged enough to stop growth. Half of each Petri dish with bacteria was covered with a layer of sunscreen of a certain Sun Protection Factor (SPF) depending on the trial performed. The dishes were then placed underneath a UV lamp set at the corresponding height, and left for the allotted exposure time. After being removed from under the lamp, the dishes were placed in an incubator for 24 hours, and the colonies of bacteria on the dishes were counted afterwards. After running a three-factor design of experiment (DOE), it was determined that the effects of significance were exposure, the interaction between exposure and intensity, and the interaction between exposure and sunscreen SPF.

Research Conducted By:

Emily Chapman
Warren Woods Tower High School

Teresa Satawa
Warren Woods Tower High School