Although mechanisms regarding harmful action of inhaled ultrafine particles are becoming better understood, a major knowledge gap is the question of whether there is direct impact from inhaled nanoparticle translocation into the bloodstream.

A recent study by researchers at the University of Edinburgh and colleagues in the Netherlands has shown unequivocally that inhaled gold particles of sizes 30 nm and under can pass directly into the bloodstream in healthy and clinical patient volunteers and in vivo models, with the smallest particles (under 10 nm in size) showing higher rates of translocation. Gold was detected in blood and urine 15 minutes, 24 hours and even 3 months after inhalation exposure, and accumulated at sites showing inflammation damage, providing a possible mechanistic link between the particles and disease causation.

Gold nanoparticles may behave differently to, for example, traffic exhaust ultrafine particles of similar primary size but different chemical composition. However, if these were also shown to exhibit translocation behaviour, there would be hugely significant health implications from both acute and chronic exposures.

For further comment see The Independent online