An Analysis of the Protection of Different SPF Levels in Sunscreen

Becca GleesonGrade 9

Problem Is there a limit to the maximum amount of

protection you can get from UV radiation by increasing the SPF of sunscreen?

My experimentation could help fair skinned people decide whether it is beneficial to buy a high SPF of sunscreen.

Research There are three different types of ultraviolet

(UV) radiation from the sun: UVA, UVB, and UVC.

UVA and UVB radiation can cause skin cancer.Broad Spectrum sunscreens are designed to

block UVA and UVB rays.The UV lamps that were used radiated UVA and

UVB rays. UV Fastcheck Strips® measure the energy

absorbed from the entire UV spectrum of radiation.

ResearchSPF stands for Sun Protection Factor.The SPF number multiplied by the time it

typically take a person to burn equals the length of time it takes to receive the same UV exposure as if no sunscreen was used.

As the SPF increases, the amount of additional protection gained decreases.

HypothesisH0: There will not be a statistically significant

difference between the amount of protection provided by the different SPFs of sunscreen.

HA: There will be a statistically significant difference between the amount of protection provided by the different SPFs of sunscreen.

If the UV protection provided by sunscreens of SPF 15, 30 and 50 is measured, then there will not be a statistically significant difference between the amount of energy absorbed when using SPF 30 or SPF 50.

Materials Sunscreen (SPF 15, 30 and 50)UV Fastcheck Strips® Comparative Dose Chart Glass microscope slidesUV radiating lampsBlocks Electronic BalanceTimer

ProcedureThe UV lamps were set up at a set distance from where the strips

were to be laid. Three of the UV Fastcheck Strips® were laid under the lamps.The sunscreen was added to two microscope slides (except for when

testing the control trials). One glass microscope slide was placed on top of two of the UV

Fastcheck Strips®. The other microscope slide was placed on top of the other strip.

The lamps were turned on.A timer was set for 900 seconds.The strips were checked every 900 seconds for a total of 5,400

seconds.When checked, the color of the strips was compared against the

Comparative Dose Chart.All of the steps were repeated for each SPF and the control.

ProcedureSteps for adding sunscreen:The glass microscope slide was placed on an

electronic balance.The electronic balance was zeroed.A one tenth gram of SPF 15 sunscreen was

added.All of these steps were repeated for the

second slide.All of the steps above were repeated for the

SPF 30 and 50 sunscreen trials.

VariablesIndependent variable: The SPF of Sunscreen Dependant variable: The amount of millijoules

of UV radiation absorbed by the UV Fastcheck Strips®

Control: The three trials without any sunscreen Constants: The UV lamps’ power, the amount

of sunscreen used, the brand and type of sunscreen, the distance from the lamp, the glass microscope slides, the time tested, the UV Fastcheck Strips® and Comparative Dose Chart

Time (seconds) Trial 1 Trial 2 Trial 3 AverageStandard Deviation

900 0.0 30.0 30.0 30.0 0.01800 50.0 50.0 50.0 50.0 0.02700 62.5 62.5 62.5 62.5 0.03600 75.0 75.0 75.0 75.0 0.04500 75.0 87.5 87.5 83.3 5.95400 87.5 100.0 100.0 95.8 5.9

Data Amount of UV Radiation Absorbed (mJ per cm2) Control

Time (seconds) Trial 1 Trial 2 Trial 3 AverageStandard

Deviation900 15.0 15.0 15.0 15.0 0.0

1800 30.0 30.0 30.0 30.0 0.02700 30.0 42.5 42.5 38.3 5.93600 50.0 75.0 75.0 66.7 11.84500 75.0 100.0 100.0 91.7 11.85400 75.0 100.0 100.0 91.7 11.8

Amount of UV Radiation Absorbed (mJ per cm2) SPF 15

DataTime (seconds) Trial 1 Trial 2 Trial 3 Average

Standard Deviation

900 15.0 15.0 15.0 15.0 0.01800 30.0 30.0 30.0 30.0 0.02700 42.5 42.5 42.5 42.5 0.03600 50.0 50.0 50.0 50.0 0.04500 62.5 62.5 62.5 62.5 0.05400 62.5 75.0 75.0 70.8 5.9

Time (seconds) Trial 1 Trial 2 Trial 3 AverageStandard

Deviation900 15.0 15.0 15.0 15.0 0.0

1800 30.0 30.0 30.0 30.0 0.02700 42.5 42.5 42.5 42.5 0.03600 50.0 50.0 50.0 50.0 0.04500 62.5 62.5 62.5 62.5 0.05400 75.0 75.0 75.0 75.0 0.0

Amount of UV Radiation Absorbed (mJ per cm2) SPF 50

Amount of UV Radiation Absorbed (mJ per cm2) SPF 30

Data

Data

Data

Control Average SPF 15 Average SPF 30 Average SPF 50 Averagey = 0.014x + 21.944 y = 0.0189x - 4.1111 y = 0.0122x + 6.7222 y = 0.0129x + 5.3333

R² = 0.9827 R² = 0.9549 R² = 0.99 R² = 0.9936

ConclusionHypothesis was supported. There was a significant difference between the control

and SPF 15 compared to SPF 30 and 50.There was not a significant difference between the

protection given by SPF 30 and 50. This shows that after a certain SPF, the protection

provided does not significantly differ.Further experimentation could include testing for

longer periods of time or with higher SPFs of sunscreen.

Sources of Error may include the position of the lamps and not checking the strips at exactly the right time.

Thank You!Thank you for listening to my experiment and

presentation!At this time, I would like to invite any

questions about my experiment.

Sources Bhanu, Ish B. "Blocking" Ultraviolet Light: Do Sunscreens and

Sunglasses Block UV. Research rept. no. SO501. N.p.: n.p., 2005. University of Southern California. Web. 31 Jan. 2013. <http://www.usc.edu/CSSF/History/2005/Projects/S05.pdf>.

Boyles, Salynn. "High-SPF Sunscreens: Are They Better?" WebMD. WebMD, 2013. Web. 31 Jan. 2013. <http://www.webmd.com/healthy-beauty/features/high-spf-sunscreens-are-they-better>.

Fung, Brian. "What SPF Does and Doesn't Tell You About Your Sunscreen." The Atlantic. Atlantic Media, 15 Aug. 2012. Web. 31 Jan. 2013. <http://www.theatlantic.com/health/archive/2012/08/what-spf-does-and-doesnt-tell-you-about-your-sunscreen/261180>.

"Sun Care FAQs." Banana Boat. Sun Pharmaceuticals, 2012. Web. 31 Jan. 2013. <http://www.bananaboat.com/sun/faq.aspx>.

"UV Fastcheck Strips." UV Process Supply, Inc. UV Process Supply, Inc., 2011. Web. 31 Jan. 2013. <http://www.uvps.com/product.asp?code=INTS+LBL+B>.