ITHACA, N.Y. - Billions of engineered nanoparticles in foods and pharmaceuticals are ingested by humans daily, and new Cornell research warns they may be more harmful to health than previously thought.

A research collaboration led by Michael Shuler, a professor of Chemical Engineering and chair of Biomedical Engineering at Cornell University, studied how large doses of polystyrene nanoparticles - a common, FDA-approved substance found in substances ranging from food additives to vitamins - affected how well chickens absorbed iron, an essential nutrient, into their cells.

The results were reported online Feb. 12 in the journal Nature Nanotechnology.

According to the study, high-intensity, short-term exposure to the particles initially blocked iron absorption, whereas longer-term exposure caused intestinal cell structures to change, allowing for a compensating uptick in iron absorption.

The researchers tested both acute and chronic nanoparticle exposure using human gut cells in petri dishes as well as live chickens and reported matching results. They chose chickens because these animals absorb iron into their bodies similarly to humans, and they are similarly sensitive to micronutrient deficiencies.

Shuler said the research serves to underscore how such particles, which have been widely studied and considered safe, cause barely detectable changes that could lead to, for example, over-absorption of other, harmful compounds.

Human exposure to nanoparticles is only increasing, Shuler said.

"Nanoparticles are entering our environment in many different ways," Shuler said. "We have some assurance that at a gross level they are not harmful, but there may be more subtle effects that we need to worry about."

The work was supported by the National Science Foundation, New York State Office of Science, Technology and Academic Research, Army Corp of Engineers and U.S. Department of Agriculture.

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