Lung particle overload: old school –new insights?

It is more than 25 years ago that the late Paul Morrow published his paper entitled "Possible mechanisms to explain dust overloading of the lungs" [1]. The paper had a major impact on our thinking on the retained dose and clearance upon inhalation of respirable dust. We have to realize that in those years' asbestos, man-made mineral fibres and coal-mine dust induced pulmonary diseases dominated the publications. Particle and Fibre Toxicology was not yet started, and fundamental discussions on general particle paradigms were disseminated through