Even the poorest handheld umbrellas can block UV rays
Josette R. McMichael, M.D., from Emory University in Atlanta, and colleagues used a meter at 11 a.m. on a sunny April day (UV index 8) to measure UVR (both UV-A and UV-B) in microwatts per square centimeter. Measurements were taken without an umbrella three times and twice for each of 23 handheld unbrellas. Measurements were taken holding the meter aimed toward the sun both holding the meter 1 cm beneath the umbrella fabric and holding the meter approximately 1 cm from the researcher's nose.
The researchers found that the majority of umbrella canopies had a diameter between 81 and 99 cm, and 14 of the 23 were black. Without an umbrella, the UVR measurements were 6,563, 6,783, and 6,913 µW/cm². For UVR readings taken from 1 cm under the umbrella fabric, measurements ranged from 26 to 1,714 µW/cm². For measurements taken 1 cm from the researcher's nose while holding the umbrella overhead, UVR ranged from 67 to 1,256 µW/cm². The umbrellas blocked between 77 percent (white Totes) and 99 percent (silver Coolibar) of UVR.
"The poorest performing umbrella still blocked an average of 77 percent of UVR," the authors write.