What is PM2.5, and why is it concerning?

PM2.5 refers to particulate matter that is 2.5 micrometers in diameter or smaller. This size is particularly concerning because these fine particles can penetrate deep into the respiratory system and reach the lungs, and even enter the bloodstream. When inhaled, PM2.5 can cause various health problems, including cardiovascular and respiratory issues, as well as exacerbate pre-existing conditions like asthma and bronchitis.

Additionally, exposure to PM2.5 is associated with increased morbidity and mortality rates, making it a significant public health concern. It is often a byproduct of combustion processes, such as vehicle emissions, industrial activities, and residential heating, which makes it crucial for air quality monitoring and regulation.

The other options do not accurately depict PM2.5; it is not larger in size, nor is it a gaseous pollutant or specifically related to ozone at ground level, which further emphasizes the significance of understanding the characteristics of PM2.5 in the realm of air pollution.