2024 · Q7
Which one of the following statements correctly defines PM1 particles in air?
general-sciencebiotech-environment-science
- AThese are suspended particles of diameter more than 10 micron
- BThese are the particles that are filtered by the nose during respiration
- CThese are extremely fine particles of diameter less than 1 micron
- DThese are coarse particles that penetrate directly through the lungs into the bloodstream
Explanation
PM1 denotes particulate matter with an aerodynamic diameter of less than 1 micron (1000 nm) — extremely fine particles that can penetrate deep into the lungs and even enter the bloodstream. They are far smaller than PM10 (up to 10 microns) and PM2.5 (up to 2.5 microns). Options A and D describe coarse particles, and option B describes larger particles trapped by nasal filtration, not PM1. Hence option C is correct.