Question

Particulates of ___ size pose greatest risk to human health

• A. Less than 7.5 micrometers in diameter
• B. Less than 2.5 micrometers in diameter
• C. Less than 4.5 micrometers in diameter
• D. Less than 3.5 micrometers in diameter

Answer 1

The Correct Option is B

Particulates of less than 2.5 micrometers in diameter (commonly referred to as PM2.5) pose the greatest risk to human health.

Why PM2.5 is Dangerous:

These fine particles are small enough to be inhaled deeply into the lungs and can even enter the bloodstream.

They can cause or exacerbate respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), and cardiovascular diseases.

PM2.5 particles can also carry toxic substances like heavy metals and carcinogens, which increase their harmful effects on health.

Because of their small size and ability to penetrate deep into the body, PM2.5 is a major concern in urban air pollution and is associated with increased mortality rates from cardiovascular and respiratory diseases.

Answer 2

The size of particulate matter (PM) is a critical factor in determining its impact on human health. Smaller particles are more dangerous because they can penetrate deeper into the respiratory system.

Here's why:

• Larger Particles: Larger particles are often trapped in the upper respiratory tract (nose and throat) and can be expelled through coughing or sneezing.
• Smaller Particles: Smaller particles can bypass these defenses and travel deeper into the lungs, reaching the bronchioles and alveoli (air sacs). From there, they can enter the bloodstream and cause systemic effects.

The most dangerous particulate matter is categorized as PM2.5, which refers to particulate matter with a diameter of 2.5 micrometers or less. These particles pose the greatest risk because they can be inhaled deeply into the lungs and enter the bloodstream.

Therefore, the answer is: Less than 2.5 micrometers in diameter