Inhaled particulate matter (PM) is responsible for human morbidity and mortality. The coarser particles tend to act more superficially in the pulmonary system and result in morbidity. Fine particles penetrate deeper, and ultrafine particles (less than 0.1 μm or 100 nm) can enter cells and even pass the blood-brain barrier. The fine and ultrafine categories are likely responsible for some instances of major diseases of the lung, heart, and brain, the last including Alzheimer’s, and Parkinson’s. Episodic and diurnal emissions require study because their measurement and amelioration differ from those of continuous emissions. Growing children are more affected than adults by PM emissions.
Particulates Matter, 2021, Pages 77-91,