According to cell toxicity studies conducted by Professor Yinfa Ma and graduate student Qingbo Yang from the Missouri University of Science and Technology, zinc oxide nanoparticles, a common ingredient used in sunscreens, may increase risk of skin cancer.
From the studies, the research team found that zinc oxide nanoparticles may generate free radicals by undergoing a chemical reaction during their exposure to sunlight. These free radicals hold potential to cause damage to human cells and their DNAs, thus increasing the risk of skin cancer. The team also discovered that the longer exposure of zinc oxide to sunlight can destroy more human cells.
During the study, the research team suspended human lung cells in a zinc oxide nanoparticle solution and exposed them to various kinds of light over different time frames. The team then compared the results with the cells that were not submerged in the zinc oxide solution. What the team discovered was cells immersed in zinc oxide solution destroyed more quickly than those not submerged in the solution.
Lung cells submerged in zinc oxide solution deteriorated even during their exposure to visible light. Their rate of deterioration was much higher during their exposure to ultraviolet long-wave light. Ma suspected that when exposed to ultraviolet rays, the zinc oxide nanoparticles absorb the rays and release electrons due to a chemical reaction. These electrons may generate unstable free radicals, which behave as parasites when they bonded with other molecules, thus causing damage to those molecules.
Ma’s cell toxicity study of zinc oxide nanoparticles is in its initial stages. More research is still needed to draw conclusion about the toxicity of zinc oxide nanoparticles in sunscreens. For example, Ma plans to confirm whether free radicals are generated by zinc oxide nanoparticles using electron spin resonance tests. Moreover, clinical studies will be required to validate his study results.