Most of the toxicology studies of inhaled nanoparticles havefocused on its harmful effects on the lung. However, nasal toxicityof nanoparticles has not been previously examined, the researcherssaid.

"This study was the first to show that inhaled nanoparticless ofany sort can cause nasal pathology such as rhinitis, epithelial cellinjury and remodeling of the nasal mucous membranes that maycompromise its function for smell and for defending the lung fromharmful airborne agents," Harkema said.

In the laboratory, carbon black nanoparticles often are used assurrogates for other CDNPs – such as those found in dieselexhaust – to identify which physical or chemical features ofextremely small particles are most responsible for their toxiceffects to cells and tissues in the nose and lungs. This knowledge isimportant for setting occupational and environmental exposure limitsto maintain air quality and protect human health.

The fact that the nasal passages could be susceptible to thedangers of such nanoparticles is alarming because the nose, inaddition to its smelling duties, serves to not only humidify and warminhaled air, but also filter it, the researchers said.

"It basically acts as a scrubbing tower, removing inhaled gases,vapors and small airborne particles – including nanoparticles– that may be harmful to the lung," he said. "It turns out,nasal airways may also be targets of toxicity caused by inhalednanoparticles."

To look into the potential toxicity of these carbon blacknanoparticles, Harkema and colleagues exposed laboratory rodents tohigh levels of the material. They found that rats developed a numberof lesions on the surface epithelium, or the lining, of the nasalairways, as well as rhinitis, an inflammation of the mucous membranesof the nasal airways.

Mice had similar but less severe rhinitis and epithelial lesions,while hamsters did not develop rhinitis at all and only minimalalterations to the nasal epithelium. Why one rodent species is moresusceptible to nasal injury than another is not yet known.

Although the effects of inhaled nanoparticles on humans have yetto be determined, "these initial findings in laboratory rodentssuggest that our nose, like our lungs, is a potential target organfor toxicity of inhaled nanoparticles," Harkema said.

This is cache, read story here