In a new report, scientists have determined that nanoparticles in cosmetics, sunscreens, and hundreds of other personal care products may be harmful to the environment.
Their report was part of symposia that included almost two dozen papers at the 237th National Meeting of the American Chemical Society where scientists grappled to understand the environmental and human health effects of nanotechnology.
Hundreds of products utilizing these microscopic particles - 1/5,000th the diameter of a human hair - already are on the market.
With many more poised for debut, scientists are seeking to avoid unwanted health and environmental effects in advance.
The study by Cyndee Gruden, from the University of Toledo and Olga Mileyeva-Biebesheimer focused on nano-titanium dioxide (nano-TiO2) particles found in cosmetics, sunscreens, and other personal care products.
The particles are added to those products for their highly beneficial effects in blocking ultraviolet light in sunlight.
Excess exposure can cause premature aging of the skin and skin cancer.
According to Gruden, the particles are washed down the drain in homes as people bathe and end up in municipal sewage treatment plants.
From there, they can enter lakes, rivers, and other water sources where microorganisms serve essential roles in maintaining a healthy environment.
Gruden studied survival of Escherichia coli (E. coli) bacteria when exposed in laboratory cultures to various amounts of nano-TiO2.
She found surprisingly large reductions in survival in samples exposed to small concentrations of the nanoparticles for less than an hour.
"How fast the impact was surprised me," she said.
The findings open the door to future research, including studies to determine whether the same effects occur in the natural environment.
Gruden's method for pinpointing damage from nanoparticles uses fluorescence to identify when the cell membrane in microbes undergo damage.
When membranes - a crucial part of the microbe - are damaged, the cells emit a faint red glow.
"Methods based upon fluorescence allow us to obtain results faster, maybe with greater sensitivity," Gruden said, adding that this approach could speed scientific efforts to understand the threshold at which nanoparticles become toxic to microbes.