What is a natural source of particulate matter?

Explanation

### Step-by-Step Text Solution:

1. **Understanding Particulate Matter**: Particulate matter (PM) refers to tiny particles or droplets in the air that can be inhaled and may cause health problems. They can originate from both natural and human-made sources.

2. **Identifying Natural Sources**: To answer the question, we need to identify what constitutes a natural source of particulate matter. Natural sources are those that occur without human intervention.

3. **Volcanic Eruptions**: One of the major natural sources of particulate matter is volcanic eruptions. When a volcano erupts, it releases gases and ash into the atmosphere, which are considered particulate matter.

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