1. Volcanoes: Volcanoes release large amounts of harmful gases and particles into the atmosphere during volcanic eruptions. These include sulfur dioxide, ash, and particulate matter, which can cause respiratory problems and contribute to climate change.

2. Forest fires: Forest fires emit a range of pollutants, including carbon monoxide, nitrogen oxides, and particulate matter. These emissions can affect air quality in the immediate area and can also be transported over long distances, impacting ecosystems and human health.

3. Dust storms: Dust storms can release large amounts of dust and other particles into the air, reducing visibility and causing respiratory problems. Dust storms are often caused by natural factors such as droughts and high winds, but can also be exacerbated by human activities such as land clearing and agriculture.