Chronic and acute oral exposure to polystyrene nanoparticles can affect iron uptake and transport in a model of human intestinal lining cells cultured in the laboratory and in a live chicken intestinal model reports a paper this week in Nature Nanotechnology. The models created in this study may provide a low-cost and high-throughput screening tool for future nanoparticle toxicity research. Because of their unique physical and chemical properties, engineered nanoparticles are used in a variety of applications, including the food industry and for drug delivery. In addition, it has been estimated that the average person in a developed country consumes over a trillion man-made fine to ultrafine particles every day. Some features of nanoparticles may, however, lead to harmful interactions with cellular material, but no studies have yet addressed the chronic effects of nanoparticle exposure on the normal function of the intestinal lining, known as the epithelium. Michael Shuler and colleagues show in cell culture and a chicken model - whose gastrointestinal tract has features similar to those of the human tract - that acute oral exposure to polystyrene nanoparticles can decrease iron uptake and transportation. They also show that chronic exposure can cause remodelling of the intestinal villi, and this increases the surface area available for iron absorption. The authors suggest that the polystyrene particles used in these experiments are generally considered to be non-toxic, but their interaction with a normal physiological process suggests a potential mechanism for a chronic, harmful, more subtle response. They note, however, that many of the consequences of oral nanoparticle exposure remain unknown, and therefore more studies are needed, especially looking at the effects of nanoparticles on nutrient absorption.