Q.Even though RSPM ($\text{PM}_{10}$) makes up a smaller mass of total particulate matter than coarser SPM, it is considered more dangerous to health. Explain why, and name two natural and two anthropogenic (human-made) sources of atmospheric particulate matter.

RSPM is more dangerous than coarser SPM, mass for mass, because of where it ends up in the body rather than how much of it there is. Coarser SPM particles are heavy enough to be trapped by the nose and upper airway's natural filtering (nasal hair and mucus), where the body can deal with them fairly effectively. RSPM particles, being below about $10~\mu\text{m}$, are small enough to slip past that filtering entirely and travel deep into the bronchioles and alveoli of the lungs, where they can lodge and cause long-term damage -- so even a smaller total mass of RSPM can cause proportionally more harm than a larger mass of coarse SPM. Natural sources of particulate matter include windblown dust and sea-salt spray; anthropogenic sources include vehicle exh …

Explain the danger in terms of where the particle physically ends up in the respiratory system, then separately list natu …

Assuming 'more dangerous' must mean 'more mass' -- RSPM is more dangerous per unit mass specifically because …