Following a major reactor accident there is a probability that plutonium would be released into the environment as a polydisperse aerosol. Therefore a major route of intake is likely to be inhalation. Studies on the rat have shown that plutonium associated with particles greater than 25nm in diameter does not translocate from lungs to blood. Gel filtration, ultrafiltration and electron microscopy show that in the fraction less than 25 nm in diameter plutonium is only associated with particles of 1 nm in diameter. A principal factor influencing the movement of 239Pu and 238Pu from lungs to blood is the presence of these 1 nm particles. The present work considers the reactions occurring between 1 nm particles of 238PuO2 and lung fluid with a view to elucidating the transport mechanisms.