Slather on the Sunscreen

Skin cancer development may be accelerated with zinc oxide

(RxWiki News) For years now we've been told to use sunscreen to protect ourselves from too much sun and most importantly skin cancer. Well it turns out one of the ingredients in those lotions could actually be increasing the risk of developing skin cancer. Uh oh.

Zinc oxide is found in sunscreen and a number of other products. When it's exposed to sunlight, zinc oxide releases free radicals that can damage cells or DNA in the cells.

And this process could up the risk of skin cancer.

"Ask your doctor or pharmacist for a sunscreen recommendation."

Researchers at Missouri Science and Technology, led by Teaching Professor of Chemistry, Dr. Yinfa Ma, found that the longer zinc oxide is exposed to sun, the more damage it could cause to human cells.

“Zinc oxide may generate free radicals when exposed to UV (ultraviolet) sunlight,” Ma says, “and those free radicals can kill cells.”

Ma and his colleagues studied the reaction of human lung cells when they were placed in a solution containing zinc oxide and exposed to various kinds of light for different lengths of time. Cells that weren't immersed in zinc oxide served as a comparison control group.

Here's how the cells in the zinc oxide solution responded to various types of light.

  • Cells deteriorated when exposed to visible light.
  • When exposed to UV (sun) light, the “cell viability decreases dramatically," according to Ma.
  • After exposure to ultraviolet A (UVA) for three hours, half the cells died; after 12 hours 90 percent had died.

Ma found that the zinc oxide particles absorb the UV rays, which causes a chemical reaction that may produce unstable free radicals in the solution. 

The free radicals latch onto the other molecules and suck the life out of them.

Ma has been working in this area for several years now, and he cautions against drawing conclusions on the safety or dangers of sunscreen based on these preliminary research. These are very early findings. 

“More extensive study is still needed,” Ma says. “This is just the first step.”

“I still would advise people to wear sunscreen. Sunscreen is better than no protection at all,” Ma said.

Along with sunscreen, zinc oxide is found in a range of other products including paints, plastics, ointments and sealants. 

Ma's latest research will be published in the journal Toxicology and Applied Pharmacology.

Review Date: 
May 8, 2012