Final answer:
Particles less than 1 micrometer can affect the deepest parts of the respiratory system, with the potential to cause serious health issues such as emphysema and lung cancer. The body's protective mechanisms may not be fully effective against these small particles, which can penetrate deeply into the lungs.
Step-by-step explanation:
Particles less than 1 micrometre (mcm), often referred to as PM1, have the potential to affect the deepest parts of the respiratory system, including the alveoli. Particulate matter such as PM2.5 and PM10 are already known to penetrate deeply into the lungs and cause various respiratory diseases like pneumonia, bronchitis, and asthma. The body does have protective mechanisms against these small particles, such as the nasal cavity hairs and mucus that trap particles, and the mucociliary escalator that helps sweep debris away from the lungs. Despite these mechanisms, very small particulates can still reach the alveolar region, potentially causing serious health issues such as emphysema and lung cancer, apart from worsening conditions like asthma and chronic bronchitis.